Greenplum® Command Center 4.16 Release Notes

About This Release

This document contains release information about Pivotal Greenplum Command Center 4.16. Greenplum Command Center 4.16 adds new features to Greenplum Command Center and resolves some issues.

Supported Platforms

Greenplum Command Center 4.16 is compatible with the following platforms.

Pivotal Greenplum Database 5.29.6 and above. (Greenplum Database 6 requires Command Center 6.x.) See Pivotal Greenplum Command Center Supported Platforms for the most current Greenplum Command Center and Greenplum Database compatibility information.
Red Hat Enterprise Linux 6.x¹ and 7.x
CentOS 6.x¹ and 7.x
SUSE Enterprise Linux 11 SP4²

¹If you use resource groups and workload management on Red Hat or CentOS 6.x, upgrade your kernel to 2.6.32-696 or higher to benefit from improvements in the Linux cgroups service.

²Greenplum Command Center workload management features are not supported on SUSE Enterprise Linux 11.

Enhancements and Changes in Greenplum Command Center 4.16

New and Changed Features

The default location of the gpmetrics directory is now $HOME – the home directory of the user who starts up Command Center – rather than $MASTER_DATA_DIRECTORY.

If you are upgrading from Command Center 4.15.x or earlier and a directory called gpmetrics does not already exist under $HOME, Command Center will migrate the gpcc.conf and gpcc-alert.yaml files from $MASTER_DATA_DIRECTORY/gpmetrics directory to $HOME/gpmetrics.

If a directory called gpmetrics does already exist under $HOME, you must copy the gpcc.conf and gpcc-alert.yaml files over manually before starting Command Center 4.16.0 for the first time.

To specify a default location different than $HOME for the gpmetrics directory, configure the gpmetrics_home parameter in the app.conf file. For more information, see the Command Center Console Parameters topic.

For more information, see Install the Greenplum Command Center Software.
A user can now configure Command Center to purge history data that exceeds the specified retention period. For more information, see the History Settings topic.
A user can now create Workload Management rules for logging queries that match a particular condition. For more information, see the Workload Management documentation page.
A user can now filter queries by by department name, using the Advanced Search tool in the Query Monitor dashboard. For more information, see the Query Monitor documentation page.
A user can now search query history by department name, using the Advanced Search tool in the History dashboard. For more information, see the History documentation page.
A user can now view the size of a table on the table detail page in the Table Browser.
The gpmetrics schema has the following changes:
- The gpmetrics.gpcc_queries_history table now has a column called access_tables_info, which stores the table OIDs of the tables the query accessed.
- The gpmetrics.gpcc_table_info and gpmetrics.gpcc_table_info_history tables now have a column called last_size_ts, which stores the time when the current table’s size column was last updated.
For more information, see the gpmetrics Schema Reference.
This Command Center release introduces a new gpmetrics configuration parameter – disable_size_check. When set to true, the Command Center table browser will not collect table size information, in order to prevent performance issues when there are a large number of tables. For more information, see the gpmetrics Configuration File Reference.
This Command Center release introduces a new console parameter – XSRFSecure – to protect the cookie Command Center uses. For more information, see the Command Center Console Parameters topic.

Resolved Issues

[32297] Resolved an issue where using “@” or “/” in the user field of the Command Center authentication screen resulted in an error.

Enhancements and Changes in Greenplum Command Center 4.15

New and Changed Features

A user can now create Workload Management rules based on CPU skew. For more information, see the Workload Management documentation page.
The realtime Query Details page now displays information about the queries being executed inside a function that a running query has called. For more information, see the Query Details documentation page.
The realtime Query Details page now displays a query’s Process ID. For more information, see the Query Details documentation page.
The Query History details page now displays a query’s peak memory. For more information, see the Query History Details documentation page.
A user can now search query history by query ID, using the Advanced Search tool in the History dashboard. For more information, see the History documentation page.
The Recommendations page now:
- includes an “Age Rank” report, which contains recommendations and information related to performing VACUUM FREEZE and VACUUM FULL on tables
- offers recommendations on which tables should have VACUUM FREEZE performed on them to reduce their age
- highlights which tables have had VACUUM FREEZE or VACUUM FULL performed on them
- allows users to export “Age Rank” from the Recommendations report page to identify which tables should have VACUUM FREEZE performed on them
For more information, see the Recommendations documentation page.
The gpmetrics configuration file (gpcc.conf) contains new sections and properties governing various aspects of Command Center behavior:
- A user can now specify the age a table must reach to prompt Command Center to issue a VACUUM FREEZE recommendation. This is configured with the new age_ratio parameter in the gpcc.conf configuration file.
- In a new section called pprof a user can configure various properties that govern how Command Center gathers performance data captured in the $GPCC_HOME/logs/*.prof files.
For more information, see the gpmetrics Configuration File Reference.
You can now turn off table statistics collection by setting the stats_check_interval configuration property to -1. For more information, see the gpmetrics Configuration File Reference.
Command Center now captures – in $GPCC_HOME/logs/*.prof files – backend performance data for use when troubleshooting heap- or CPU-related performance issues with VMware Support. For more information, see Administering Log Files, Work Files, and Performance Data.
The gpmetrics schema has a number of changes:
- The gpmetrics.gpcc_table_info and gpmetrics.gpcc_table_info_history tables now contain two new columns: age_percent column, which tracks information for calculating when a table should have VACUUM FREEZE run on it and last_vacuum_freeze, which records the last time that one of VACUUM FULL, VACUUM FREEZE and VACUUM FULL FREEZE was performed on the table. In addition, the last_vacuum_full column has been updated to record the last time VACUUM FULL FREEZE was performed on the table.
- The gpmetrics schema contains three new user-defined functions: gpcc_queries_top_10_memory_per_resgroup and gpcc_queries_top_10_cpu_per_resgroup – for retrieving by resource group the top ten queries utilitizing the most memory and CPU, respectively and gpcc_recommendations – which returns a list of tables in need of a vacuum-related action such as VACUUM, VACUUM FULL, ANALYZE, and VACUUM FREEZE.
- The gpmetrics.gpcc_wlm_rule table has two new columns: cpuskew_percent and cpuskew_duration_sec. If the CPU skew percent of a query is equal to or higher than cpuskew_percent during cpuskew_duration_sec seconds, Command Center executes this rule.
  
  For more information, see the gpmetrics Schema Reference.
There are three new server configuration parameters:
- gpcc.enable_save_full_query_text - When turned on, Command Center saves the full query text for queries whose text is longer than 100KB
- gpcc.enable_send_inner_query - When turned on, users can see the statements within functions that the query is calling when they click the Inner Queries tab in the query monitor’s Query Detail view.
- gpcc.enable_send_instrument - When turned off, Command Center does not display some query details – such as the visual query plan tree – and some statistics. This reduces Command Center’s memory consumption.
For more information, see the Server Configuration Parameters.

Resolved Issues

[32032] Resolved a memory issue caused by long query texts.

[32083] Resolved a crash issue caused by inner queries.

Enhancements and Changes in Greenplum Command Center 4.14

New and Changed Features

The realtime Query details and Query History details pages now display:
- the top 5 slices that consume the most CPU time
- the top 5 slices that consume the most memory
- the top 5 slices that use disk I/O
For more information, see the Query Details and Query History Details documentation pages.
A user can now exclude “idle in transaction” sessions when adding or editing an idle session killing rule. For more information, see the Workload Management documentation page.
The gpmetrics schema includes new and changed tables:
- gpmetrics.gpcc_resgroup_history, is a new table that stores the history of the resource consumption of each resource group on each segment
- gpmetrics.gpcc_department, is a new table that stores department information
- gpcc_role_department, is a new table that stores information about roles within department
- The gpmetrics.gpcc_queries_history table includes three new columns: slices_metrics, peak_memory and node_sliceid
- The gpmetrics.gpcc_plannode_history table’s sliceid column has been deprecated.
For more information, see the gpmetrics Schema Reference documentation page.
The gpmetrics schema now includes user-defined functions:
- gpcc_delete_department deletes a department name from the gpperfmon database.
- gpcc_queries_per_hour returns a variety of details about query activity per hour.
- gpcc_queries_per_user returns, for each user, the number of queries whose runtime is longer than the input interval, per hour, in the specified time range.
- gpcc_queries_per_user_max_and_total_spill_size returns, for each user, the total spill_size and maximum spill_size per query per hour.
- gpcc_queries_per_user_max_cpu returns, for each user, the query with the maximum segment and master cpu usage per hour, along with details about the query.
- gpcc_queries_per_user_max_run_time returns, for each user, the longest running query per hour, along with details about the query.
- gpcc_queries_per_user_max_skew returns, for each user, the query with the maximum amount of processing skew in the system (skew_cpu) per hour, along with details about the query.
- gpcc_queries_per_user_rows_out returns, for each user, the query with the maximum rows_out per hour, along with details about the query.
- gpcc_system_per_hour returns a variety of system information.
- gpcc_update_department renames a department.
For more information, see the gpmetrics Schema Reference documentation page.
A user can now monitor resource group system information, including:
- CPU utilization of selected resource groups
- CPU utilization of a specific resource group
- Memory utilization of selected resource groups
- Memory utilization of a specific resource group
- Concurrency status of selected resource groups
For more information, see the Managing Resource Groups documentation page.
Through a new user management interface, a user can now view information about departments and roles, manage and view permissions for roles, export usage information by role, rename a department name using a user-defined function, and delete unwanted departments from the gpperfmon database using a user-defined function. For more information, see the Managing Users documentation page.
Administrators now allow guest users to view the Query Monitor without logging in via the Settings view, rather than the now obsolete Permissions view. For more information, see the Settings documentation page.
Administrators now manage permissions via the new User Management view rather than the now obsolete Permissions view.
A user can now now determine the TLS cipher suites that Command Center accepts. For more information, see the Command Center Console Parameters documentation page.

Resolved Issues

[31132] - Command Center was failing to set up an email alert when the SMTP certificate was invalid, rather than issuing a message explaining to users how to proceed without a valid certificate. This has been resolved.
[31508] - Resolved an issue where Command Center was failing to save queries to the query history when there were CTAS queries inside a function.
[31531] - The Command Center was using a hard coded initial password for the gpmon role if the password was not created before the installer ran. It now uses a random string generated during installation instead.
[31781] - Resolved an issue where the accuracy and last_accuracy_ts fields in the gpmetrics.gpcc_table_info_history table were not being correctly populated when the planrows field in the gpmetrics.gpcc_plannode_history table had a very large value.
[31782] - Resolved a memory leak in the Command Center session monitor.
[31890] - Resolved an issue where, when users executed a query with an extremely long query text it could cause the query to fail, due to an invalid memory alloc request.
[31867] - Resolved an issue where the cpu_segment_percent column of the gpmetrics.gpcc_queries_now table was not matching the Host CPU Total.
[178957820] - Resolved an issue where the Query Monitor was refreshing a query list after returning from checking query details when paused.
[179418127] - Resolved an issue where Command Center was failing to send alert emails to all recipients if there was just one invalid recipient address.
[179666482] - Resolved an issue where Command Center was recording an incorrect spill file size in the gpmetrics.gpcc_queries_history table.

Enhancements and Changes in Greenplum Command Center 4.13

New and Changed Features

The Query Monitor page now filters displayed queries based on the query Status: Running, Queued, or Blocked. For more information, see the Query Monitor documentation page.
The Query Monitor page now contains an Advanced Search tool. The tool filters displayed queries based on query metrics such as query ID, database name, resource group, and more. For more information, see the Query Monitor documentation page.
A user can now pause the Query Monitor in order to view a snapshot of queries. For more information, see the Query Monitor documentation page.
The Query Monitor now displays session information, such as session status, associated users and databases, idle time, and associated queries. A user with Admin or Operator permission can see and cancel all users’ sessions, as well as export session details to a CSV file. For more information, see the Query Monitor documentation page.
A user can create a workload rule to terminate idle sessions and can examine rule logs of terminated sessions. For more information, see the Workload Management documentation page.
A user can create rules by spill file size. For more information, see the Workload Management documentation page.
The gpmetrics schema contains a new gpmetrics.gpcc_queries_now table that stores real-time query metrics data.
The gpcc_wlm_rule table has two additional rows: one for storing parameters for idle session kill rules, and one for storing spill file size.
For more information , see the gpmetrics Schema Reference documentation page.
Microsoft IE is no longer a supported browser for Command Center.

Resolved Issues

[176183074] - Resolved CORS security issues.
[31245] - The gpcc_queries_now table is now available as part of the gpmetrics schema. For more information , see the gpmetrics Schema Reference documentation page.
[31229] - Resolved an issue in which queries with long query text were blocking.
[31473] - Resolved an issue in which Command Center was sending alert emails too frequently.
[31443] - Resolved an issue in which Command Center reported blocked DDL queries as running.

Enhancements and Changes in Greenplum Command Center 4.12

New and Changed Features

The History page now contains a new Advanced Search tool. The tool allows users to search based on query metrics such as custom time range, query text, database name, user name, and more. Selecting “Custom” from the Time Range dropdown also displays the Advanced Search pop-up window. For more information see the Query History documentation page.
The Query details page now displays the query cost when clicking on the “+” sign next to the query Planner name. The submitted time now inludes a tooltip which displays the query’s submitted date. See Query History Metrics for more details.
Greenplum Command Center now supports IPV6. To install an IPV6-compatible version of Greenplum Command Center, pass the new -ipv6 parameter to the gpccinstall command.
The stats_check_interval parameter is now set in the gpcc.conf file rather than the app.conf file. If you currently have it set in app.conf, you must reset it in gpcc.conf; the value in app.conf will be ignored.
Command Centre now displays a Notifications label at login. Clicking on the label displays the Alerts window with alert history from the last 7 days. For more information, see the Alerts documentation page.
The Table Browser page has a new Advanced search link to allow administrators to filter their search based on table name, table size, or table owners. The results can be exported to a local file. See the Table Browser documentation page for more details.
The gpmetrics schema contains a new gpcc_export_log table that records the log notifications from the “EXPORT ALL” dropdown in the Query History or the Table Browser page.
The gpcc_alert_log table has been renamed to gpcc_alert_history and includes a new config column that records the alert history from the Notification Center or from email alerts.
The table gpcc_alert_rule has been discontinued.
For more information , see the gpmetrics Schema Reference documentation page.
The Command Center dashboard now displays a Feedback link, which displays a customer feedback form when clicked. Administrators can enter feedback for current Command Center features and experience. The form requires internet connectivity for the pop-up to appear.
Command Center now aggregates and displays a single alert notification when multiple segment failures occur at the same time.
Users can now customize security parameters in the app.conf file. For more details, see Setting Security Parameters.

Resolved Issues

[31026] - Resolved an issue where Greenplum Command Center version 6.3.0 and 6.3.1 would not show a visual query plan in the query monitor in certain cases. Upgrade the metrics_collector if your Greenplum Database version is below 6.12.1.
[31061] - When a query ran less than 5 seconds, the CPU and Disk I/O were not captured. This issue has been resolved.

Release 4.11.1

Changes

The GPCC web server configuration has been altered to reject unsafe DES ciphers.

Resolved Issues

[30954] - During security scans, some SSL ciphers were highlighted as “medium strength”. This issue has been resolved. GPCC will now reject the unsafe ciphers.
[30939] - When a Greeplum Database query run a function with 0 arguments, the database crashed. This issue has been resolved.
[30956] - When exporting the queries history page to a CSV file, the Submitted field contained the time of the query but not the date. For example, in the GPCC UI, the Submitted field would show 2020-09-13 10:25:11 but the CSV file would only show 10:25:11. This issue has been resolved.
[174798424] - When creating a rule condition containing more than one slice, the rule condition was ignored, and the query ran normally. This issue has been resolved.
[174796107] - When updating the status of a workload management rule to inactive, when the rule condition was met, the rule remained active . This issue also appeared when deactivating multiple rules in a set, and when one rule of the set had been deleted but the rest remained in the inactive status. This issue has been resolved.
[174795058] - On the Query History Detail page, a query’s Submitted Time did not match the one displayed on the Query List page. This issue has been resolved.
[174983144] - On the Query Monitor page, when the query list extended further than the window size, the Workload dropdown column did not display correctly. This issue has been resolved.
[174922355] - When a partition’s root table appeared in the Accuracy % Rank list, the row count column incorrectly showed a 0 (nil) value. This issue has been resolved.
[174767109] - When creating a rule using the Planner Cost condition, and subsequently deleting that condition by reducing the planner cost to “0”, the updated rule still showed: “planner cost is greater than [0,0]”. This issue has been resolved.

Release 4.11.0

Workload Management

The Command Center interface for managing workload assignment rules has moved to a new page, Workload> Workload Mgmt. Resource group configuration and idle session management controls remain on the Workload> Resource Groups page. See Workload Management.
Workload management rules can now be assigned using any combination of resource group name (or all resource groups, by default), database role, and query tag identifiers.
Workload management rules can include one or more conditions that must be met before the rule action is performed. Conditions are triggered after configured maximum values for CPU time, Planner Cost, Running time, Slices, or Total Disk I/O are exceeded by a query.
For Greenplum 6.8 or later, you can configure workload management rules to automatically move queries to a specified resource group. These rules can be created on earlier Greenplum versions, but are immediately placed in the Inactive state.
Command Center automatically attempts to retry applying a failed rule action 2 times, after waiting a minimum of 15 seconds between retries. You can configure the time interval using the new configuration parameter, wlm_query_cooldown_time. See the gpmetrics Configuration file topic.
A new configuration parameter, wlm_short_query_threshold, can be used to ensure that Command Center only applies workload management rules after a query has run for at least the specified number of seconds. See the gpmetrics Configuration file topic.
Programmatically managing workload rules using the JSON object is no longer supported.
The new gpmetrics tables, gpcc_wlm_rule and gpcc_wlm_log_history, were introduced to store workload rule definitions and log history. See the gpmetrics Schema Reference.

Query Monitor

The Query Monitor page includes a new column, CPU Time, to show the amount of system CPU consumed by each query.
The Blocked By column is no longer displayed for active queries. To view information about blocking transactions, use the tooltip that is displayed when the query status is Blocked. See Query Monitor.

Permissions Changes

Only Operator and Admin users can move queries from the Query Monitor page.
Only Admin users can make changes to the Recommendations and Workload pages.
Basic users can now view the Table Browser page.

Fixed Issues

[30545] The metrics collection code was updated to resolve a buffer overflow condition that could cause Greenplum Database to crash when gp_enable_query_metrics was set to “on.”
[30812] Resolved a problem where the rows_out value displayed an incorrect number for certain queries.
[173978192] Resolved a problem where the web socket connection was not rebuilt after a user attempted to login to Command Center after a previous session timed out.
[174275398] Command Center will now fail to start if the web server port (28080) is being used by another program.
[174665588] Command Center now displays the correct value for Statement Memory for resource group entries.

Release 4.10

Command Center Installation Changes

Command Center directory names have changed to omit -web.

The Command Center installation directory name changed from greenplum-cc-web-<version> to greenplum-cc-<version>, for example /usr/local/greenplum-cc-4.9.0.
The Command Center installer creates a symbolic link greenplum-cc to the Command Center home directory if gpadmin has write permission in the installation directory. If the directory already exists, the link is recreated to link to the new Command Center installation directory. Use the link to access the gpcc_path.sh file in your shell startup script to ensure that you access the most recent installation. For example, add this line to your .bashrc or .bash_profile file:
```
source /usr/local/greenplum-cc/gpcc_path.sh
```
If the installation directory is not writable by the gpadmin user, you can create the directory and symbolic link and set the owner to gpadmin before you run gpccinstall.
You can run more than one Command Center instance on the same host. For example, if you run a Greenplum Database 5.x system and a Greenplum Database 6.x system on the same cluster, you can install Command Center instances for each system on the same master host. This feature is supported on Greenplum Database 5.28.0 or higher.

Before you run the installer, choose the Greenplum Database instance by sourcing the environment file (greenplum_path.sh). You must manually edit the $GPCC_HOME/app.conf file for each additional Command Center instance you want to run to choose different port numbers for the httpport, httpsport, rpcport, ws_perf_port, and agent_perf_port parameters.

Recommendations Feature

The new Recommendations feature helps to identify Greenplum Database tables that require maintenance to reduce bloat, improve accuracy of query plans, and reduce skew that affects query performance.

Schedule a table scan to run at a designated time and for a specified period of time. The scan can be scheduled to repeat daily or weekly on selected days of the week.
Command Center runs queries to collect information about tables, processing as many tables as it can during the scheduled period. The next scan resumes where the previous scan left off. Collected data is saved in the new gpmetrics.gpcc_table_info and [gpmetrics_table_info_history](../topics/ref-gpmetrics.html#gpcc_table_info_history] tables in the gpperfmon database.
The Recommendations page lists scanned tables in ranked order with recommendations to VACUUM, VACUUM FULL, ANALYZE, or redistribute tables.

See Recommendations for more information about the Recommendations feature.

I/O Wait Metrics

Command Center now collects CPU IOWait metrics. You can view IOWait metrics on the Host Metrics, Cluster Metrics, and History pages.

On the Host Metrics page, the CPU column value is the total of System, User, and IOWait percentages. The chart and pop-up box break out the System, User, IOWait, and Idle percentages separately.
On the Cluster Metrics and History pages, the CPU chart shows System and User percentages. The IOWait percentage is included in the System percentage, as in previous Command Center versions. The new IOWait chart shows just the percentage of CPU time spent in IOWait.

Workload Management Improvements

You can now set Memory Spill Ratio % for resource groups on the Workload Management page. Transactions spill to disk when they reach this threshold.

While editing resource group attributes, Command Center recalculates and displays Statement Memory, the amount of memory allocated to a query for each resource group.

See Workload Management for more information about these features.

gpcc stop Utility

If the Greenplum system is down, running the gpcc stop command will stop the Command Center agent and web server processes.

Fixed Issues

When a query called a UDF that runs an inner query, the top level query could be missing in the Query Monitor view and in query history. This caused some columns in the Query Monitor view to display - instead of the correct value. This issue is fixed.
The disk IO read/write calculations in gpcc_system_history and the Cluster Metrics page included R/W rates for multiple devices on the same physical disk. This is fixed. The disk IO read/write rate calculations now exclude:
- partitions of disk
- dm (device-mapper)
- loop device
- md (multi-device such as raid)
The reported disk IO rate is now the same as the actual IO rate of the physical disk.
On the System ⟩ Storage page, values displayed as terrabytes (TB) were incorrectly converted from gigabytes (GB) by dividing by 1000. This is fixed. Values greater than 1024GB are correctly converted to TB by dividing by 1024.
Security vulnerability fixes have been added to prevent ClickJacking Attacks and to deny use of risky HTTP request methods.
The Running, Queued, and Blocked query counts on the Dashboard were misleading because they were not the current status at the time you were viewing the Dashboard, but the status about 15 seconds earlier. The numbers have been removed to avoid confusion. To view current numbers, go to the real-time Query Monitor by clicking the query graph from the Dashboard.
- A Disk Full alert was raised when the total disk space for all hosts in the cluster exceeded the threshold. Now an alert is raised if disk usage for any host exceeds the threshold. The alert email includes the name of the host that triggered the alert.
- The backend scan for the table browser periodically connected to the template1 database. This could prevent a user from creating a new database, because CREATE DATABASE is not allowed when there are any connections to the template1 database. This issue has been fixed. The template1 database is omitted from the backend scan.

Enhancements and Changes in Greenplum Command Center 4.9

Command Center Installation Changes

The Command Center release download file names have changed to include the Greenplum Database major version, for example greenplum-cc-web-4.9.0-gp5-rhel7-x86_64.zip.
The Command Center installer creates four entries in the pg_hba.conf authentication file for the gpmon role if there are no existing gpmon entries.
```
local      gpperfmon     gpmon                 md5
host       all           gpmon  127.0.0.1/28   md5
host       all           gpmon  ::1/128        md5
host       all           gpmon  samenet        md5
```
The samenet entry is new in this release, and the installer will add it to the pg_hba.conf file even when there are existing entries for the gpmon role.

Note that the Table Browser feature requires all in the database field of the host entries so that gpmon can retrieve table information from each database.

If you use an authentication method other than md5 for the gpmon user, such as LDAP or Kerberos, edit the pg_hba.conf file to enable connections from all hosts and access to all databases.

Command Center History Data Collection Changes

The Command Center version 4.9.0 installer enables History Data Collection.
If the gp_enable_gpperfmon Greenplum Database server configuration parameter is on, the Command Center installer sets it to off. You must restart Greenplum Database for this change to take effect.

Note: Pivotal recommends that you do not use the Greenplum Database gpperfmon service while running Greenplum Command Center because of its effects on Greenplum Database performance.
The history_enabled property in the $MASTER_DATA_DIRECTORY/gpmetrics/gpcc.conf file is deprecated and the installer will comment it out if it is present. A new property enable_history is added to the $GPCC_HOME/conf/app.conf configuration file. The default is true. If you disable history data collection on the Command Center Admin> Settings page, enable_history = false is written in the app.conf file.

New and Changed Features

A new Table Browser is added to allow administrators to see information about tables in Greenplum Databases. Tables displayed can be filtered by database, schema, owner, and size. The Command Center interface provides details about tables, including table storage types, distribution policies, partitions, sizes, and last access times. It lists recent queries that have accessed the table, with links into the Command Center query history. Notably, the Table Browser displays only metadata for tables; it does not provide access to data stored in tables.

Note: When you first start Command Center after installing this version, Command Center loads data into the new gpmetrics.gpcc_table_info table in the gpperfmon database. For databases with large numbers of tables, the initial load could take five minutes or longer. Table data will not be available in the Table Browser until it has been loaded.
The table browser uses two new tables in the gpmetrics schema: gpcc_table_info and gpcc_table_info_history. See gpmetrics Schema Reference for information about the contents of these tables.
The Command Center web server (gpccws) memory consumption is much improved compared to earlier Command Center versions.
On the History page, the count of running queries at any point on the Queries graph now includes queries that started and finished in the interval since the previous metrics sample. A new queries_finished column is added to the gpmetrics.gpcc_database_history table to record this count.
The metrics collector extension adds a new gpcc.enable_query_profiling server configuration parameter that can be enabled to help with performance troubleshooting. When off, the default, the metrics collector does not collect queries executed by the gpmon user in the gpperfmon database or plan node history for queries that run in less than ten seconds (or min_query_time, if it is set and greater than ten seconds). If you enable gpcc.enable_query_profiling in a session the metrics collector collects those queries. This parameter is introduced in the metrics collector extension included with Greenplum Database 5.24.0 and is not available in earlier Greenplum Database releases.
Each night, Command Center archives files in the $GPCC_HOME/ccdata directory that are more than two weeks old. The files in this directory include saved query text files (q*.txt), plan node files (gpccexec*.txt), and table size and statistics information files (gpcc_size_info.dat and gpcc_stat_info.dat). Archive files have names in the format archive_YYYYMMDD_YYYYMMDD.tar.gz, where the dates are the beginning and end dates of the week included in the archive. The archived files are no longer needed by Command Center but may be useful for troubleshooting; you can remove them manually if you do not want to save them.

Resolved Issues

[MPP-30259] The gpmetrics.gpcc_plannode_history table definition changed in Command Center 4.7. When upgrading from Command Center 4.4.x, 4.5.x, or 4.6.x to Command Center 4.7.x or 4.8.x, the installer did not upgrade the definition of the existing table. This resulted in a failure to harvest data to the gpcc_plannode_history table. This is fixed. Upgrading from a Command Center version earlier than 4.7 to Command Center 4.9 updates the gpcc_plannode_history table definition in the gpmetrics schema.
When a Command Center user signs out of Command Center, the Welcome page is displayed, but the message “Checking DB status…” is displayed for several seconds before the login form is presented. This is fixed. If there are no errors the login form is now displayed immediately.
The rightmost edge of system metrics graphs could drop to zero if the metrics data for that period was not yet available to display. This is fixed by cutting the time axis on the right edge of metrics graphs to the last period with available data. As a result of this fix, the time period displayed at the right edge of a graph can be slightly earlier than the last sync time displayed at the top of the page.
Users with self-only permissions could see other users’ query history. In Command Center 4.9 users with self-only permission have no access to the query history page, so they cannot see their own or others’ query history. Self-only users will be allowed access to their own query history in a future Command Center release.
The send_alert.sh script in the $MASTER_DATA_DIRECTORY/gpmetrics directory had a bug that caused some values to be incorrectly expanded when substituted into the template. This is fixed by replacing all occurrences of $ARGUMENT with ${ARGUMENT} in the script. You can implement the same fix if you have created a custom send_alert.sh script.
The Command Center Storage Status page did not display tablespaces with locations other than pg_default or pg_global. This is fixed. Expanding a hostname now shows each tablespace location. Hovering over the tablespace location displays a pop-up with a list of the data directories at that location. Data directories may not be displayed until Command Center has refreshed the Storage Status page, which occurs every four hours.
Transaction performance issues could occur when the workload manager gp_wlm extension was loaded in Greenplum Database and the Command Center workload management feature was not enabled. This is fixed in the gp_wlm extension included with Greenplum Database 5.24.0. For earlier versions of Greenplum Database, you can use one of the following methods to work around the problem:
- If you are using Greenplum Database resource groups, enable Workload Management in the Greenplum Command Center.
- If you are using Greenplum Database resource queues for workload management, remove the gp_wlm shared library from the shared_preload_libraries server configuration variable.
```
$ gpconfig -s shared_preload_libraries
```
```
Values on all segments are consistent
GUC          : shared_preload_libraries
Master  value: metrics_collector,$libdir/gp_wlm
Segment value: metrics_collector,$libdir/gp_wlm
```
```
$ gpconfig -c shared_preload_libraries -v 'metrics_collector'
$ gpstop -ar
```

Enhancements and Changes in Greenplum Command Center 4.8

New Features and Changes

The Enable GPCC history data collection option on the Admin> Settings page is now on by default. If you turned off this option in your current Command Center installation and you upgrade to Command Center 4.8.0, the option will remain off. Pivotal recommends that you turn it on.
Command Center can collect all metrics without the Greenplum Database gpperfmon service. For lower overhead, stop the gpperfmon service if it is running. Set the gp_enable_gpperfmon server configuration parameter to off and restart Greenplum Database.
If you include the -W option with the gpccinstall command, the installer prompts you to enter the password for the gpmon role. If the gpmon role does not already exist, the installer creates it with the password you specify. Without the -W option, the installer creates the gpmon role with the default password “changeme”.
The installer has a new -u (upgrade) option that installs Command Center using the configuration parameters from the current Command Center installation. You can use this option to reinstall the same version of Command Center or to upgrade to a newer version.
Japanese and Russian language options have been added to the Command Center installer.
When canceling one or more queries in the Command Center UI, a pop-up box prompts you to enter a message of up to 128 characters to add to the error message that is displayed to the user.
On the System> Storage Status view, when you expand a Hostname, the Data Directory column now lists the mount points of partitions on the segment host file system that contain Greenplum segment data directories. When you move your cursor over a mount point, a tooltip lists the data directories the partition contains.
History query search performance is greatly improved.
Newly created partitions for history tables in the gpmetrics schema will be created with RLE compression and the COMPRESSLEVEL=2 option, for improved compression/performance. Existing partitions are not changed.
The Command Center web server now supports only the TLSv1.2 protocol and above for secured connections.
Logging improvements. A new log_level parameter in the $GPCC_HOME/conf/app.conf configuration file determines the level of messages that will be logged. The parameter specifies which messages are added to these log files: gpccinstall.log, webserver.log, agent.log, and cli.log.

The parameter can be set to Debug, Info, or Error, where Debug is the most verbose and Error is the least verbose. The parameter values are not case-sensitive. The default is Info.

Fixed Issues

[#166658749] - If the MASTER_DATA_DIRECTORY environment variable is not set when gpcc start is run, the gpmetrics directory is created in the current directory. This issue is resolved. If the MASTER_DATA_DIRECTORY is not set, the gpcc start command will print a message and exit.
[#166346339] - If CPUSET is enabled for a resource group, the CPU% value is changed to -1. This value prevented editing resource groups in Command Center. Command Center now accepts a -1 value.
[#167156751] - Query text files in the $MASTER_DATA_DIRECTORY/gpmetrics/query_text directory were not cleaned up automatically. This issue is fixed.
[MPP-29944] - When Command Center is configured to use Kerberos authentication with the user id as the Command Center user, a query cancelled by the user was logged as cancelled by the gpmon user. This is fixed. If the optimizer is set to GPORCA, an extra message, “Feature not supported: SIRV functions”, is logged. This is a known issue.

Enhancements and Changes in Greenplum Command Center 4.7

Greenplum Command Center 4.7.0 contains the following new changes and features.

Command Center Installation New Features and Changes

The gpccinstall installation utility now writes details of the installation to the installation log file, gpccinstall.<timestamp>.log. Previously, the log contained a success message or any errors that prevented a successful message. The log now contains the values for the parameters used during the Command Center installation.
The gpccinstall utility must be run by the gpadmin user and the installation directory must be writable by the gpadmin user. The option to install Command Center as root and change ownership of the installed files to gpadmin is not supported because the root user cannot connect to Greenplum Database.
The new gpccinstall -auto option performs a non-interactive installation, using default values for all of the installation parameters.
Added the Korean language option for the Command Center User Interface.
It is now recommended to run Command Center on the master host, instead of the standby master host. Saving plan node history, a new feature in this Comand Center release, can generate a large number of messages between the agent running on the master host and the Command Center backend. Running Command Center on the master host keeps this traffic off of the LAN.

gpmetrics Schema Changes

When real-time metrics collection is enabled, Command Center saves execution plan node details to the gpmetrics.gpcc_plannode_history table in the gpperfmon database. Details are only saved for queries that execute for at least 10 seconds. The data in this table enable you to view visual query execution plan details when you select a query in the History view.

Query Monitor and History Changes

A Planner field is added to the Query Monitor Details view to identify the planner used to plan the query, either GPORCA or Legacy.
The detail for a query in the History view includes a visual query execution view that shows the actual rows returned for each plan node. History
The visual plan for a query in the Query Monitor shows the Estimated Progress for the query, a calculated percentage using the query plan’s cost estimate for each plan node and the actual rows vs. estimated rows for each node.

Alerts

When sending alert emails, Command Center can authenticate with the SMTP server using NONE, PLAIN, LOGIN, or CRAM-MD5 authentication.
The Username and Password fields in the Manage email configuration section of the Alerts page are now optional. These fields are only needed if the SMTP server requires them for authentication.

Logging Changes

Every hour, Command Center logs the number of queries that were not saved to the gpmetrics history in the previous hour because they completed in less time than than the threshhold time specified on the Admin> Settings page. The message is logged in the logs/webserver.log file in the Command Center installation directory.

Fixed Issues

165236914 - The gpcc command-line utility did not work with the -W option. This has been fixed. The gpcc command will use the gpmon password entered by the user when the -W option is supplied. If the -W option is not supplied, gpcc will use the PGPASSWORD environment variable, if set, or the .pgpass file in the gpadmin user’s home directory.
165111508 - LDAP authentication fails because Command Center improperly encodes the username in the Greenplum connection string. This is resolved. Command Center correctly escapes the username in the connection string.
164620455 - The Command Center agent memory usage and CPU usage grew very high when executing a query with an inner query. The inner query generated many small queries, sending a large number of packets to the metrics collector. This is fixed. Inner queries are marked so that metrics are not collected for them.
164818798 - When Workload Manager terminates an idle connection, a FATAL error and stack trace were logged. Now Workload Manager logs a WARNING message with no stack trace when an idle connection is terminated.
164263538, 164718926 - Command Center does not show query information for a COPY command, such as COPY <table> FROM STDIN;. The Command Center Query Monitor now displays available information for some COPY commands. A COPY command run by a non-superuser role can be controlled by a resource queue if the resource queue’s ACTIVE_STATEMENTS parameter specifies a maximum limit for the number of queries that can be executed by roles assigned to the queue. (Greenplum Database does not assign cost or memory values to COPY commands, so a COPY command with no ACTIVE_STATEMENTS parameter is not managed by a resource queue.) In Command Center, COPY commands managed by resource queues will now appear in the Query Monitor with available activity information. Command Center caches roles’ resource queue names and, for these commands, the resource queue name is displayed from the cache. If a role has been recently assigned a different resource queue, the cache may be out of date. See Known Issues for more information.

164346696 - Command Center does not display more than one filespace per host. This has been fixed in Command Center.
165589279 - The Command Center Dashboard displayed UTC time when the Europe/Moscow timezone was set in the OS and Greenplum Database. The root cause of this issue is that Greenplum Database 5 does not handle the MSK time zone properly. This is fixed in Command Center and issue 7543 has been opened for Greenplum Database.

Enhancements and Changes in Greenplum Command Center 4.6

Greenplum Command Center 4.6.0 contains the following new features:

Display Language Selection

The Greenplum Command Center user interface has been updated with localization support. At installion time, you can choose the language to use in the Command Center user interface. Command Center currently supports English (default) and Chinese languages.

gpmetrics History Schema (Beta)

The Command Center history views currently draw data from the Greenplum Database gpperfmon database, which has a data collection process that is separate from the Command Center real-time metrics collection system.

In this release, you can enable saving data from the real-time metrics collection system to history tables in the gpmetrics schema. When you enable this feature, Command Center uses the gpmetrics history tables to display history data in the user interface. This is a new feature, currently considered experimental. In a future release, the gpmetrics tables will be the only source for history data and Command Center will no longer depend upon the gpperfmon database.

To enable gpmetrics history, visit the Admin> Settings view in Command Center. In addition to enabling history collection, you can set the minimum run-time for queries to be saved in history.

See the gpmetrics Schema Reference for information about the tables in the gpmetrics schema.

Enhancements and Changes in Greenplum Command Center 4.5

Greenplum Command Center 4.5.0 contains the following new features:

Alert Rules

On the new Admin> Alerts page, Command Center users with superuser permission can configure alert rules. When an alert rule is matched, a record is logged in the gpmetrics.gpcc_alert_log table and, optionally, an email is sent to a list of addresses you specify. You can also write a custom shell script to send alerts to other messaging systems.

Alert rules can detect the following events:

Segment failure
Out of memory errors
Average memory usage percentage of segment hosts exceeds a specified percentage for a specified number of minutes
Memory usage on the master host exceeds a specified percentage for a specified number of minutes
Total disk space used on all hosts exceeds a specified percentage
Number of Greenplum Database connections exceeds a specified percentage
Average CPU usage of segment hosts exceeds a specified percentage for a specified number of minutes
Spill files for an active query exceed a specified number of gigabytes
Runtime for a query exceeds a specified number of minutes
A query is blocked for more than a specified number of minutes

Query Text Download for Long Queries

On the Query Details page, if the query text is longer than 100K characters, Command Center only shows the first 100K characters and, when you click COPY, copies only the first 100K characters to the clipboard. When the query text is longer than 100K characters, Command Center adds a button, Retrieve full query text, which you can click to download a text file containing the entire text of the query. The file is available to download for 24 hours, or until the query is saved to history, when history collection is enabled.

Fixed Issues

161436520 - Panels displaying help text can now be scrolled vertically when the text does not fit in the window.
158278655 - The displayed metrics for a query could be inaccurate if Command Center received the query “done” status before the final metrics arrived. Now the final metrics are updated even when they arrive after the “done” status.
161074984 - Repeated assertion errors logged in the agent.log file caused log files to grow quickly and consume too much disk space. This is fixed. Each type of assertion error will be logged no more than once every 10 minutes.
162114428 - When a user visits Command Center with a browser, the Command Center web server (gpccws process) establishes a websocket connection and runs two goroutines to service the websocket. When the websocket closes, one of the goroutines does not exit. After many connections the gpccws process can occupy gigabytes of memory. This memory leak is fixed.

Enhancements and Changes in Greenplum Command Center 4.4.2

The Greenplum Database metrics collector extension is now enabled only when Command Center agents are running. Previously, if an agent process terminated, the metrics collector continued to collect and send data.

Greenplum Command Center 4.4.2 contains the following resolved issues:

160195564 - When Command Center is restarted after a user has submitted a query, and the user submits another query in the same session, the database name and user name are missing from the second query in the Command Center interface. This is fixed.
161077294 - The Authentication view now prevents the user from saving an undefined entry to the pg_hba.conf file.
161274227 - The Command Center installer, gpccinstall, no longer prints errors to the pg_log log file about missing iterators and emc_connect_history tables.
161273865 - The Query Monitor no longer shows runtimes flashing to 0 seconds when a query is cancelled through the user interface.

Enhancements and Changes in Greenplum Command Center 4.4.1

The Admin> Authorization view allows entering host names in the Address field.
On the visual query plan, a data motion showed a finished status when the send data operation completed. This is changed so that the node completes only after the corresponding data receive operation has also completed.
Enabled cross-site request forgery prevention during login.

Resolved Issues in Greenplum Command Center 4.4.1

160679694 - If Command Center is restarted while on the Query Monitor view and the browser is then refreshed, an extra web socket connection is created. This is fixed.
MPP-29539 - Command Center agent (ccagent) logging is disabled for a known issue with PL/pgSQL queries.

Enhancements and Changes in Greenplum Command Center 4.4.0

Greenplum Command Center 4.4.0 contains the following features and enhancements.

Workload Management

Command Center has a new user interface to assist administrators in enabling resource groups in Greenplum Database, importing existing resource queues to resource groups, and enabling workload management with Command Center. The option to import resource queues to resource groups is presented if no resource groups have been created (other than default_group and admin_group) and Greenplum Database has resource queues to convert (other than pg_default). Once the administrator has imported resource queues, or chosen to skip importing resource queues, the option to import queues is no longer presented.
The resource group list on the Workload Management view has a new column to show the minimum (fixed) amount of memory that will be allocated to a query for each resource group. This value is recalculated when you enter new values while editing resource groups.
Administrators can now define resource group assignment rules and idle session kill rules with an interactive interface. It is no longer necessary to edit the JSON document for workload management rules. The JSON text field is removed.
The Workload Management view changed to a light theme.

Permissions

Command Center users with the Self Only permission level can:
- see all queries on the query monitor, including queries owned by other users
- cancel their own queries
- access the query details view for their own queries
- hover on a query to see query text for their own queries
- hover on locking/blocking queries and access details of locking/blocking queries that do not belong to other users
Users with Self Only permission level cannot see query text or access the details views of others’ queries.
The Greenplum Database roles gpcc_basic, gpcc_operator, and gpcc_operator_basic are created during Command Center installation if they do not already exist.

Query Monitor

Fixed a bug where the database name and role name were missing from query details when queries are executed in a session after restarting Command Center.

Enhancements and Changes in Greenplum Command Center 4.3

Greenplum Command Center 4.3.0 contains the following enhancements.

Resource Group Management

The Admin>Workload Mgmt view has a new user interface you can use to add and remove resource groups and to change the Concurrency, CPU %, and Memory % attributes of resource groups.

Resource Group Role Assignments

The Admin>Workload Mgmt view has a new user interface you can use to view and change Greenplum Database roles’ default resource groups.

Details Added to Visual Query Plan Steps

The metrics collector extension in Greenplum Database release 5.9 is updated to submit additional information about each step in the query plan to the Command Center backend. Command Center displays this information in the visual query plan when you expand a step in the query plan. The new information displayed depends on the operation the step performs and includes details such as hash key, merge key, join condition, or filter condition. Previously, you could only see this information by generating the textual query plan.

Enhancements and Changes in Greenplum Command Center 4.2

Greenplum Command Center 4.2.0 contains the following enhancements.

Visual Query Plan

The Command Center Query Details view now includes a visual query plan.

Idle Session Kill Rules

Idle session kill rules can include optional exemptedRoles and message parameters.

The value of the exemptedRoles parameter is a list of Greenplum Database roles that are exempted from the rule. The list can include Posix regular expressions to match Greenplum Database role names.
The value of the message parameter is a string to include in the message that is displayed when a session is killed.

Command Center Can Run on the Master Host or Standby Master Host

The Greenplum Command Center web server and backend may now be executed on the master host or on the standby master host. Running GPCC on the standby master host is recommended to avoid adding load to the master server, but it is no longer a requirement. After the GPCC software is installed, log in to the host where you want to run GPCC, source the gpcc_path.sh file in the GPCC installation directory, and run the gpcc start command.

Enhancements and Changes in Greenplum Command Center 4.1

Greenplum Command Center 4.1.0 contains the following enhancements.

Command Center administrators can set permission levels for Command Center users. Permissions are enforced as described in the documentation.
On the Query Detail view, clicking Copy in the query text or query plan panel copies the text in the panel to the clipboard.
A help icon and in-app help have been added on the Query Monitor and Query Detail views.

The following workload management features, improvements, and bug fixes have been added in the workload management extension included with Greenplum Database 5.8.0.

On the Admin>Workload Mgmt view, you can add idle session kill rules for each resource group. When you add these rules, the Greenplum Database workload management extension kills a session after it has been idle for the number of seconds you specify. See Workload Management for syntax and examples.
Optimizations have been implemented to reduce the impact on Greenplum Database when the workload management extension is disabled.
The workload management extension takes advantage of resource group name-to-id caching added in Greenplum Database.
Fixed a bug in the workload management extension that caused errors to print to the psql prompt, even when the extension was disabled.

Greenplum Command Center 4.1.0 contains the following bug fixes.

<!— #156648869 —>

In the History Detail view, when either of the Disk R or Disk W metrics is 0, both are reported to be 0. This is fixed.

<!— #156749938 —>

When using the Kerberos gpmon-only authentication mode, generating an explain plan failed. This is fixed.

<!— #156298125 —>

The Command Center agent failed with the message “Error: can’t find gpcc.query_metrics_port, metrics_collector is not correctly installed.” This occurs when running Command Center on a Greenplum Database system that was upgraded from an earlier Greenplum Database 5.x release. The metrics_collector and gp_wlm extensions are installed with the upgrade, but the upgrade process does not perform the required configuration changes in the postgresql.conf configuration file. The Command Center installation instructions now include steps to manually configure and restart an upgraded Greenplum Database system.

<!— #156717637 —>

When Command Center starts, an error message is written in the Greenplum Database log file: “function gpcc_schema.read_pghba(unknown) does not exist.” This is fixed.

A change to time zone handling in Greenplum Database 5.7 can cause Greenplum Command Center 4.0.0 to display an incorrect time if the master host operating system time and Greenplum Database use different time zones. Now Command Center times are displayed using the time zone of the Greenplum Database master host operating system. The current time, last sync time, and timestamps in alert logs, cluster metrics, and query history are all displayed using the master host’s system time zone.

<!— #156717320 —>

On the Admin> Authorization view, when the authorization method is gss and the options field contains text, changing the method to trust does not clear the options field and it is not possible to save changes to the pg_hba.conf file.

<!— #157102375 —>

The Command Center web server, gpccws, spawns ssh processes but does not reap them in a timely manner, leading to many zombie processes. This is fixed.

<!— #157139648 —>

On the Admin> Authentication view, if the number of users listed in the user column is longer than can be displayed, Command Center truncates the list and adds ellipsis (...) to the end. Only administrators can view the complete value, by editing the field. Now any user with access to the view can see the full list of users by hovering over the field.

Enhancements and Changes in Greenplum Command Center 4.0

Command Center Installation Changes

Greenplum Command Center 4.x software, unlike previous releases, is installed on every host in the Greenplum Database cluster. The Command Center web server and backend run on the standby master, if your Greenplum Database cluster has a standby master. If there is no standby master, Command Center runs on the master host instead.

To modify the Command Center installation—for example to enable or disable SSL or install Command Center on new or replaced hosts—just re-execute the installer and restart Command Center. It is not necessary to uninstall Command Center before reinstalling.

There is one Command Center installation per Greenplum Database cluster. It is no longer necessary to create Command Center instances after installing the software.

The gpcmdr command-line utility is replaced with the new gpcc utility. Use the gpcc utility to start and stop Command Center and metrics collection agents, check Command Center status, and enable or disable Kerberos authentication.

In previous releases, the gpmon role required only local connections to databases on the Greenplum master host. In Greenplum Command Center 4.x, the gpmon user must be able to connect to databases from the host running the Command Center web server and backend, which requires adding a host entry to the pg_hba.conf authentication configuration file.

Real-time Query Metrics

Greenplum Command Center 4.0 introduces real-time query metrics for Pivotal Greenplum Database 5.7 and above. This new feature combines the following new features in Greenplum Database and Greenplum Command Center:

Greenplum Database saves query execution metrics in shared memory while queries execute.
A new Greenplum Database metrics collection extension, included with Pivotal Greenplum Database, emits the saved metrics as UDP datagrams.
A new Greenplum Command Center metrics collection agent running on each Greenplum Database host receives the datagrams and posts metrics to the Greenplum Command Center backend. The Command Center backend starts and manages the metrics collection agents.

The Command Center Query monitor view updates in real time so you can see queries that are waiting to execute and the current status and resource usage for queries that are running.

Metrics collection now includes lock and spill file information. On the Query Monitor, you can see which queries are blocked and which queries hold the locks blocking them. The Query Monitor shows the total size of spill files created on all segments for each query.

Installing the gpperfmon database remains a prerequisite for Command Center. The gpperfmon database is the source for query history displayed in the Command Center user interface. The new real-time metrics are not persisted and are not directly related to the metrics collected and persisted in the gpperfmon database.

Workload Management

Workload management is now an integrated Command Center feature rather than a separate product. Workload management is available in Command Center only after resource groups have been enabled in Greenplum Database by changing the gp_resource_manager server configuration parameter from 'queue' to 'group' and enabling Linux control groups (cgroups).

In Command Center 4.0, workload management allows you to assign transactions to Greenplum Database resource groups at execution time by evaluating the current database role and query tags against workload assignment filters you define in Command Center. Query tags are user-defined name=value parameters that you define in the gpcc.query_tags database session parameter. You can define multiple query tags separated by semicolons. Set query tags in a Greenplum Database session either as a parameter in the database connection URL or by executing SET gpcc.query_tags TO '<tag1>=<val1>;<tag2>=<val2>;...' in the database session.

When a transaction is about to execute, the current database role and query tags are compared to the workload assignment filters that you have created in Command Center. If a match is found, the transaction is assigned to a resource group according to the workload management filter. Otherwise, the transaction is assigned to the database user’s resource group, which is the default behavior when Command Center workload management is not enabled.

Workload management uses the gp_wlm database extension included with Pivotal Greenplum Database.

Unimplemented Features

Some features available in previous Greenplum Command Center releases have been removed or are not yet implemented in Command Center 4.x.

The ability for a Command Center admin to post a message to the Query Monitor view is not yet implemented.
The multi-cluster view has been removed.

Known Issues

The following are known issues in the current Greenplum Command Center release.

Command Center does not monitor FETCH queries.

Performance issues with a large query string

Submitting a large query string with psql -c or libraries causes Command Center performance issues.

<a id=179572065">Incorrect query ID displayed on “Query is blocked for xxx minutes alert”

When the “Query is blocked for xxx minutes” alert is triggered, the query ID shown on the notification feed may be incorrect.

<a id=178295227">Query tags rule not enforced when query tags are surrounded by single quotes

Resource group assignment by a query tags rule has no effect if the query tags are defined by PGOPTIONS with single quotes.

Command Center requires restart after Daylight Savings Time

When Daylight Saving Time occurs, Command Center requires a restart to repopulate certain data metrics.

Last Accessed column affected by persistent table rebuild

When using the gppersistentrebuild utility, the Last Accessed column in the Table Browser view might be refreshed, although no queries accessed the tables.

Discrepancy in the Query Submitted Time

On the Query History Detail page, a query’s Submitted Time does not match the one displayed on the Query List page.

Limitation in Displaying Workload Group Drop Down Options

On the Query Monitor page, the last row (or the only row) of the query list doesn’t display the Workload column menu options correctly. As a workaround, scroll the page to show the Workload dropdown menu content.

Limitation in the Accuracy % Rank list

When a partition’s root table appears in the Accuracy % Rank list, the row count column incorrectly shows 0 (nil) value.

Limitation when a rule condition contains more than one slice

When you create a rule that contains more than one slice, the rule is ignored, the condition is not met, and the query runs normally.

Limitation for Defining Planner Cost in Workload Rules

When you define a workload management rule that uses the Planner Cost condition, the input field transforms your entry to a double datatype value. This can limit the ability to accurately define large planner costs that may be necessary for the GPORCA optimizer. For example, if you enter the GPORCA maximum cost value as 1457494496834852608, the actual value is converted to 1457494496834852600 for the rule. The value shown in the completed rule definition is the value that the rule enforces, and it may not be the exact value that you entered. Increase the cost value as necessary to cover the cost you want to set as the maximum.

External Updates to Workload Management Rules are Delayed

If you recreate the gp_wlm extension from outside of Command Center after you have already created workload management rules using the Command Center interface, the rules engine may not run for a period of roughly 1 hour. This behavior occurs because Command Center checks for the availability of the extension every hour. Any changes you make outside of Command Center in this situation will not be visible until Command Center checks for the extension, or until you login to Command Center and access the Workload> Workload Mgmt page.

Customized SSH Path Not Supported with the Upgrade (-u) Option

If you upgrade your Command Center installation using the gpccinstall -u option and you also specify an SSH program using the -ssh-path <path> option, the customized SSH path will not be used during the installation and the ssh_path parameter will not be set in the app.conf file.

Loading `gp_wlm` Extension Without Enabling Resource Groups Can Cause Performance Issues

A performance issue can occur if Workload Management is not enabled in Command Center and the gp_wlm.so library is included in the shared_reload_libraries system configuration parameter when Greenplum Database starts. The fix for this issue is in Greenplum Database 5.24.0.

If you cannot upgrade to Greenplum Database 5.24, you can prevent problems with one of these workarounds:
- If you are using resource group workload management in Greenplum Database, ensure that Workload Management is enabled in Command Center.
- If you are using resource queue workload management in Greenplum Database, remove gp_wlm from the shared_preload_libaries configuration parameter and restart Greenplum Database.

Calculated Root Table Size Inaccurate for Some Partitioned Tables

When viewing the Table Browser view, the calculated size for a partitioned table is incorrect if some child partitions are in different schemas than the root table.

Sorting Tables by Size on Partition List Page is Slow

If there are a large number of tables in a schema in a database, sorting the partition table list by size can take a long time to display.

Failure to Auto-Create Monthly Partitions in gpmetrics Schema

In time zones with daylight savings time (DST) ending in the month of October, Greenplum Command Center fails to create new October partitions for tables in the gpmetrics schema because it specifies the same start and end date for the partitions. The error does not occur in time zones that do not have DST, or in time zones with DST ending in November.

Workaround

Manually create partitions for October 2019.

psql -U gpmon gpperfmon

Enter the following commands to create the October 2019 partitions:

ALTER TABLE gpmetrics.gpcc_disk_history
      ADD PARTITION START (date '2019-10-01') INCLUSIVE END (date '2019-11-01') EXCLUSIVE
      WITH (APPENDONLY=true, ORIENTATION=column, COMPRESSTYPE=RLE_TYPE, COMPRESSLEVEL=2);

ALTER TABLE gpmetrics.gpcc_system_history
      ADD PARTITION START (date '2019-10-01') INCLUSIVE END (date '2019-11-01') EXCLUSIVE
      WITH (APPENDONLY=true, ORIENTATION=column, COMPRESSTYPE=RLE_TYPE, COMPRESSLEVEL=2);

ALTER TABLE gpmetrics.gpcc_queries_history
      ADD PARTITION START (date '2019-10-01') INCLUSIVE END (date '2019-11-01') EXCLUSIVE
      WITH (APPENDONLY=true, ORIENTATION=column, COMPRESSTYPE=RLE_TYPE, COMPRESSLEVEL=2);

ALTER TABLE gpmetrics.gpcc_plannode_history
      ADD PARTITION START (date '2019-10-01') INCLUSIVE END (date '2019-11-01') EXCLUSIVE
      WITH (APPENDONLY=true, ORIENTATION=column, COMPRESSTYPE=RLE_TYPE, COMPRESSLEVEL=2);

ALTER TABLE gpmetrics.gpcc_database_history
      ADD PARTITION START (date '2019-10-01') INCLUSIVE END (date '2019-11-01') EXCLUSIVE
      WITH (APPENDONLY=true, ORIENTATION=column, COMPRESSTYPE=RLE_TYPE, COMPRESSLEVEL=2);

ALTER TABLE gpmetrics.gpcc_alert_log
      ADD PARTITION START (date '2019-10-01') INCLUSIVE END (date '2019-11-01') EXCLUSIVE
      WITH (APPENDONLY=true, ORIENTATION=column, COMPRESSTYPE=RLE_TYPE, COMPRESSLEVEL=2);

ALTER TABLE gpmetrics.gpcc_pg_log_history
      SPLIT DEFAULT PARTITION START (date '2019-10-01') INCLUSIVE END (date '2019-11-01') EXCLUSIVE
      INTO(PARTITION t2019Oct, DEFAULT PARTITION);

Query Monitor is Empty When Using HTTP Proxy

When accessing the Command Center frontend or backend with an HTTP proxy in place, no query activity is displayed in the Query Monitor. To work around this issue, the proxy must be disabled for Command Center client browser connections and for ccagent processes connecting to the Command Center backend from the Greenplum master and segment hosts. See Using an HTTP Proxy Server with Command Center for more information about this issue.

Unable to View Real Time Queries After Upgrading From a Previous Command Center Release

If you install a new version of Greenplum Command Center using the same port number as the previous version, and you use the Chrome web browser, you may be unable to view real-time queries until after you clear the browser’s cache. See the note in Connecting to the Command Center Console for steps to clear the browser cache.

Resource Queue Name Incorrect for Some Queries

To display the resource queue name for queries in the Query Monitor, Command Center caches user IDs with resource queue names. The cache is updated when the Command Center backend receives a planned query from the metrics collector. Some utility commands are not planned, such as COPY commands that have no SELECT clause. These commands use a resource queue slot, but are not passed through an optimizer. If a user is assigned a different resource queue and then executes an unplanned command, the Command Center Query Monitor will display the resource queue name that was previously cached.