If you need to troubleshoot issues with your cluster, you can check a node's logs, which include details about certain node-level and range-level events, such as errors. For example, if CockroachDB crashes, it normally logs a stack trace to what caused the problem.
CockroachDB also generates secondary logs for queries being executed against your system. See SQL logging for details on obtaining these logs.
Details
When a node processes a cockroach command, it produces a stream of messages about the command's activities. Each message's body describes the activity, and its envelope contains metadata such as the message's severity level.
As a command generates messages, CockroachDB uses the command's logging flags and the message's severity level to determine the appropriate location for it.
Each node's logs detail only the internal activity of that node without visibility into the behavior of other nodes in the cluster. When troubleshooting, this means that you must identify the node where the problem occurred or collect the logs from all active nodes in your cluster.
Commands
All cockroach commands support logging. However, it's important to note:
cockroach startgenerates most messages related to the operation of your cluster.- Other commands do generate messages, but they're typically only interesting in troubleshooting scenarios.
Severity levels
CockroachDB identifies each message with a severity level, letting operators know if they need to intercede:
INFO(lowest severity; no action necessary)WARNINGERRORFATAL(highest severity; requires operator attention)
Default behavior by severity level
| Command | INFO messages |
WARNING and above messages |
|---|---|---|
cockroach start |
Write to file | Write to file |
| All other commands | Discard | Print to stderr |
Output locations
Based on the command's flags and the message's severity level, CockroachDB does one of the following:
Write to file
CockroachDB can write messages to log files. The files are named using the following format:
cockroach.[host].[user].[start timestamp in UTC].[process ID].log
For example:
cockroach.richards-mbp.rloveland.2018-03-15T15_24_10Z.024338.log
To make it easier to watch a log without knowing the full filename, a symlink with the short filename cockroach.log is also created. This symlink points to the most recent log.
All log file timestamps are in UTC because CockroachDB is designed to be deployed in a distributed cluster. Nodes may be located in different time zones, and using UTC makes it easy to correlate log messages from those nodes no matter where they are located.
| Property | cockroach start |
All other commands |
|---|---|---|
| Enabled by | Default1 | Explicit --log-dir flag |
| Default File Destination | [firststoredir]/logs |
N/A |
| Change File Destination | --log-dir=[destination] |
--log-dir=[destination] |
| Default Severity Level Threshold | INFO |
N/A |
| Change Severity Threshold | --log-file-verbosity=[severity level] |
--log-file-verbosity=[severity level] |
| Disabled by | --log-dir=1 |
Default |
1 If the cockroach process does not have access to on-disk storage, cockroach start does not write messages to log files; instead it prints all messages to stderr.
Log files can be accessed using the Admin UI, which displays them in JSON format.
Access the Admin UI and then click Advanced Debug in the left-hand navigation.
Under Raw Status Endpoints (JSON), click Log Files to view the JSON of all collected logs.
Copy one of the log filenames. Then click Specific Log File and replace the
cockroach.logplaceholder in the URL with the filename.
Print to stderr
CockroachDB can print messages to stderr, which normally prints them to the machine's terminal but does not store them.
| Property | cockroach start |
All other commands |
|---|---|---|
| Enabled by | Explicit --logtostderr flag2 |
Default |
| Default Severity Level Threshold | N/A | WARNING |
| Change Severity Threshold | --logtostderr=[severity level] |
--logtostderr=[severity level] |
| Disabled by | Default2 | --logtostderr=NONE |
cockroach start does not print any messages to stderr unless the cockroach process does not have access to on-disk storage, in which case it defaults to --logtostderr=INFO and prints all messages to stderr.Discard message
Messages with severity levels below the --logtostderr and --log-file-verbosity flag's values are neither written to files nor printed to stderr, so they are discarded.
By default, commands besides cockroach start discard messages with the INFO severity level.
Flags
These logging flags are used with cockroach commands.
| Flag | Description |
|---|---|
--log-dir |
Enable logging to files and write logs to the specified directory. Setting --log-dir to a blank directory (--log-dir=) disables logging to files. Do not use --log-dir=""; this creates a new directory named "" and stores log files in that directory. |
--log-dir-max-size |
After the log directory reaches the specified size, delete the oldest log file. The flag's argument takes standard file sizes, such as --log-dir-max-size=1GiB.Default: 100MiB |
--log-file-max-size |
After logs reach the specified size, begin writing logs to a new file. The flag's argument takes standard file sizes, such as --log-file-max-size=2MiB.Default: 10MiB |
--log-file-verbosity |
Only writes messages to log files if they are at or above the specified severity level, such as --log-file-verbosity=WARNING. Requires logging to files.Default: INFO |
--logtostderr |
Enable logging to stderr for messages at or above the specified severity level, such as --logtostderr=ERRORIf you use this flag without specifying the severity level (e.g., cockroach start --logtostderr), it prints messages of all severities to stderr.Setting --logtostderr=NONE disables logging to stderr. |
--no-color |
Do not colorize stderr. Possible values: true or false.When set to false, messages logged to stderr are colorized based on severity level. Default: false |
--sql-audit-dir |
If non-empty, create a SQL audit log in this directory. By default, SQL audit logs are written in the same directory as the other logs generated by CockroachDB. Note that enabling SQL audit logs can negatively impact performance. As a result, we recommend using SQL audit logs for security purposes only. For more information, see the EXPERIMENTAL_AUDIT reference page. |
See also
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