ArangoDB Server Log Options

Log levels and topics

ArangoDB’s log output is grouped into topics. --log.level can be specified multiple times at startup, for as many topics as needed. The log verbosity and output files can be adjusted per log topic. For example

--log.level startup=trace --log.level queries=trace --log.level info

will log messages concerning startup at trace level, AQL queries at trace level and everything else at info level.

In a configuration file, it is written like this:

[log]
level = startup=trace
level = queries=trace
level = info

The available log levels are:

  • fatal: only logs fatal errors
  • error: only logs errors
  • warning: only logs warnings and errors
  • info: logs information messages, warnings and errors
  • debug: logs debug and information messages, warnings and errors
  • trace: logs trace, debug and information messages, warnings and errors

Note that levels debug and trace will be very verbose.

See Log Levels in the Monitoring chapter for a detailed description of the different levels.

Some relevant log topics available in ArangoDB 3 are:

  • agency: information about the agency
  • collector: information about the WAL collector’s state
  • compactor: information about the collection datafile compactor
  • datafiles: datafile-related operations
  • mmap: information about memory-mapping operations (including msync)
  • performance: performance-related messages
  • queries: executed AQL queries, slow queries
  • replication: replication-related info
  • requests: HTTP requests
  • startup: information about server startup and shutdown
  • threads: information about threads

See more log levels

Log outputs

The log option --log.output <definition> allows directing the global or per-topic log output to different outputs. The output definition <definition> can be one of

  • - for stdin
  • + for stderr
  • syslog://<syslog-facility>
  • syslog://<syslog-facility>/<application-name>
  • file://<relative-path>

The option can be specified multiple times in order to configure the output for different log topics. To set up a per-topic output configuration, use --log.output <topic>=<definition>, e.g.

queries=file://queries.txt

logs all queries to the file “queries.txt”.

The old option --log.file is still available in 3.0 for convenience reasons. In 3.0 it is a shortcut for the more general option --log.output file://filename.

The old option --log.requests-file is still available in 3.0. It is now a shortcut for the more general option --log.output requests=file://....

Using --log.output also allows directing log output to different files based on topics. For example, to log all AQL queries to a file “queries.log” one can use the options:

--log.level queries=trace --log.output queries=file:///path/to/queries.log

To additionally log HTTP request to a file named “requests.log” add the options:

--log.level requests=info --log.output requests=file:///path/to/requests.log

If you specify --log.file-mode octalvalue then any newly created log file will use “octalvalue” as file mode. Please note that the umask value will be applied as well.

If you specify --log.file-group name then any newly created log file will try to use “name” as group name. Please note that you have to be a member of that group. Otherwise the group ownership will not be changed. Please note that this option is only available under Linux and Mac. It is not available under Windows.

Forcing direct output

The option --log.force-direct can be used to disable logging in an extra logging thread. If set to true, any log messages are immediately printed in the thread that triggered the log message. This is non-optimal for performance but can aid debugging. If set to false, log messages are handed off to an extra logging thread, which asynchronously writes the log messages.

Time format

The option --log.time-format controls the time format used in log output. The possible values for this option are:

Format Example Description
timestamp 1553766923000 unix timestamps, in seconds
timestamp-millis 1553766923000.123 unix timestamps, in seconds, with millisecond precision
timestamp-micros 1553766923000.123456 unix timestamps, in seconds, with microsecond precision
uptime 987654 seconds since server start
uptime-millis 987654.123 seconds since server start, with millisecond precision
uptime-micros 987654.123456 seconds since server start, with microsecond precision
utc-datestring 2019-03-28T09:55:23Z UTC-based date and time in format YYYY-MM-DDTHH:MM:SSZ
utc-datestring-millis 2019-03-28T09:55:23.123Z like utc-datestring, but with millisecond precision
local-datestring 2019-03-28T10:55:23 local date and time in format YYYY-MM-DDTHH:MM:SS

Escaping

--log.escape value

This option toggles the escaping of log output.

If set to true, the following characters in the log output are escaped:

  • the carriage return character (hex 0d)
  • the newline character (hex 0a)
  • the tabstop character (hex 09)
  • any other characters with an ordinal value less than hex 20

If the option is set to false, no characters are escaped. Characters with an ordinal value less than hex 20 will not be printed in this mode but will be replaced with a space character (hex 20).

A side effect of turning off the escaping is that it will reduce the CPU overhead for the logging. However, this will only be noticeable when logging is set to a very verbose level (e.g. debug or trace).

The default value for this option is true.

Color logging

--log.color value

Logging to terminal output is by default colored. Colorful logging can be turned off by setting the value to false.

Source file and Line number

Log line number: --log.line-number

Normally, if an human readable fatal, error, warning or info message is logged, no information about the file and line number is provided. The file and line number is only logged for debug and trace message. This option can be use to always log these pieces of information.

Prefix

Log prefix: --log.prefix prefix

This option is used specify an prefix to logged text.

Threads

Log thread identifier: --log.thread true

Whenever log output is generated, the process ID is written as part of the log information. Setting this option appends the thread id of the calling thread to the process id. For example,

2010-09-20T13:04:01Z [19355] INFO ready for business

when no thread is logged and

2010-09-20T13:04:17Z [19371-18446744072487317056] ready for business

when this command line option is set.

To also log thread names, it is possible to set the --log.thread-name option. By default --log.thread-name is set to false.

Role

Log role: --log.role true

When set to true, this option will make the ArangoDB logger print a single character with the server’s role into each logged message. The roles are:

  • U: undefined/unclear (used at startup)
  • S: single server
  • C: coordinator
  • P: primary
  • A: agent

The default value for this option is false, so no roles will be logged.