Understand Debug & Error Logs

Understand Debug & Error Logs

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.

Tip:

For detailed information about queries being executed against your system, see SQL Audit Logging.

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 start generates 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)
WARNING
ERROR
FATAL (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

Note:
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

Note:
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.

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`

Note:
² 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

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.
`—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=ERROR`If 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`	New in v2.0: 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. For more information, see SQL Audit Logging.

Understand Debug Logs