This topic describes Command Center logging and log files, work files, and automatic collection of performance data for troubleshooting performance issues with VMware Support.
Logging and Log Files
The Command Center components—the backend server, agents, HTTP server, and the gpcc command-line utility—write messages to log files in the $GPCC_HOME/logs directory.
Log files rotate once per day or whenever the component starts or restarts. The current log file is saved to a file with a timestamp in its name and a new log file is started.
The log files can be useful for monitoring and troubleshooting, but you can delete them when you determine they are no longer useful. Remove older log files regularly to conserve disk space.
You can use a utility such as the Linux logrotate utility to manage archived log and data files.
Core Dump Files
Command Center has the capability of generating core dump files in the event of a crash. The mechanism for generating core files is enabled by the underlying operating system. See Core Dump in the VMware Greenplum documentation for instructions to enable core dumps on RHEL systems.
webserver.log
The Command Center backend web server writes to the webserver.log log file on the Command Center host in the $GPCC_HOME/logs directory on the host running Command Center. This is usually the coordinator host, but could also be the standby coordinator host. Messages in this log file describe start-up events, rpc request/response events with agents running on the VMware Greenplum segment hosts, and data loading from external tables to the gpmetrics tables in the gpperfmon database.
agent.log
A Command Center agent running on each VMware Greenplum host (including the segment and coordinator hosts) logs messages to the agent.log log file in the $GPCC_HOME/logs directory of the host machine. Agents log messages about connections to the Command Center rpc server, periodic data collection events, and metrics transmissions to the rpc port on the backend.
gpccws.log
The Command Center HTTP server writes messages to the gpccws.log file on the Command Center host in the $GPCC_HOME/logs directory. The messages in this log file include server start up messages and Websocket connection events with Command Center clients.
cli.log
The gpcc command-line utility writes messages to the cli.log file in the $GPCC_HOME/logs directory. Whenever the gpcc utility executes, it writes its output to the log file as well as the standard output. The log file is useful for auditing Command Center start and stop events. The cli.log file is not rotated and continues to grow until you archive or delete it manually.
Command Center Work Files
Command Center saves temporary data into files in the $GPCC_HOME/ccdata directory. These files 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). Each night, Command Center archives files in the $GPCC_HOME/ccdata directory that are more than two weeks old. The 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.
Automatic Collection of Performance Data
Command Center automatically collects performance data for the purpose of troubleshooting performance issues, in *.prof files in $GPCC_HOME/logs. Command Center implements Golang pprof runtime profiling described here.
This feature collects two types of benchmarking profile data: heap memory and CPU. Command Center saves the files hourly and overwites the data every 24 hours.
Using the properties in the [pprof] section of the gpmetrics configuration file, you can control:
- whether or not data collection is enabled (it is by default)
- the duration of the profiling interval
- the time duration of CPU profiling in each profiling interval
- the time-to-live (TTL) of profiling logs
- whether Command Center saves the heap memory profile, the CPU profile, or both.
For more details on the pprof-related configuration parameters, see the gpmetrics Configuration File Reference.
