Configuring Logging

This topic explains how to configure VMware Tanzu GemFire logging.

You configure logging in a member’s gemfire.properties or at startup with gfsh.

Before you begin, review VMware GemFire Basic Configuration and Programming.

Run a time synchronization service such as NTP on all Tanzu GemFire host machines. This is the only way to produce logs that are useful for troubleshooting. Synchronized time stamps ensure that log messages from different hosts can be merged to accurately reproduce a chronological history of a distributed run.
Use a sniffer to monitor your logs Look for new or unexpected warnings, errors, or severe messages. The logs output by your system have their own characteristics, indicative of your system configuration and of the particular behavior of your applications, so you must become familiar with your applications’ logs to use them effectively.
Configure member logging in each member’s gemfire.properties as needed:
```
# Default gemfire.properties log file settings
log-level=config
log-file=
log-file-size-limit=0
log-disk-space-limit=0
```
Note: You can also specify logging parameters when you start up members (either locators or servers) using the gfsh command-line utility. In addition, you can modify log file properties and log-level settings while a member is already running by using the alter runtime command.
1. Set log-level. Log levels are not case-sensitive. Options are:
  - none or off
  - severe or fatal (log messages with the highest level of importance)
  - error
  - warning or warn
  - info or config
  - fine or debug
  - finer or trace
  - finest or trace
  - all
  The more detailed levels (lower in this list) also include messages from all levels above them. For example, a warning log level shows warning, error, and severe messages. For general troubleshooting, we recommend setting the log level at config or higher on this list. The most detailed, lower levels in this list (all, finest, finer, fine) can quickly consume disk space and negatively impact system performance. Use these more detailed levels only when necessary.
2. Specify the log file name in log-file. This can be relative or absolute. If this property is not specified, the defaults are:
  - Standard output for applications
  - For servers, the default log file location is:
```
working-directory/server-name.log
```
    By default, when starting a server through gfsh, the working -directory corresponds to the directory (named after itself) that the cache server creates upon startup. Alternatively, you can specify a different working directory path when you start the cache server. The server-name corresponds to the name of the cache server provided upon startup.
  - For a standalone locator, the default log file location is:
```
working-directory/locator-name.log
```
    By default, when starting a locator through gfsh, the working -directory corresponds to the directory (named after itself) created when the locator starts up. Alternatively, you can specify a different working directory path when you start a locator. The locator-name corresponds to the name of the locator provided upon startup. If you are using a colocated or embedded locator, the locator logs will be part of the member’s log file.
  For the easiest logs examination and troubleshooting, send your logs to files instead of standard out. Note: Make sure each member logs to its own files. This makes the logs easier to decipher.
3. Set the maximum size of a single log file in log-file-size-limit. If not set, the single, main log file is used. If set, the metadata file, the main log, and rolled child logs are used.
4. Set the maximum size of all log files in log-disk-space-limit. If non-zero, this limits the combined size of all inactive log files, deleting oldest files first to stay under the limit. A zero setting indicates no limit.
If you are using the gfsh command-line interface, gfsh can create its own log file in the directory where you run the gfsh or gfsh.bat script. By default, gfsh does not generate log files for itself. To enable gfsh logs, set the following system property to the desired log level before starting gfsh:
```
export JAVA_ARGS=-Dgfsh.log-level=[severe|warning|info|config|fine|finer|finest]
```
gfsh log files are named gfsh-0_0.log.