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Command-Line Options for Logging
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
Note that there must not be any whitespace around the second
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
trace will be very verbose.
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-releated 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
The log option
--log.output <definition> allows directing the global
or per-topic log output to different outputs. The output definition
can be one of
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.
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
The old option
--log.requests-file is still available in 3.0. It is now a shortcut
for the more general option
--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
--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
Forcing direct output
--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.
Log dates and times in local time zone:
If specified, all dates and times in log messages will use the server’s
local time-zone. If not specified, all dates and times in log messages
will be printed in UTC / Zulu time. The date and time format used in logs
YYYY-MM-DD HH:MM:SS, regardless of this setting. If UTC time
is used, a
Z will be appended to indicate Zulu time.
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.
This option is used specify an prefix to logged text.
Log thread identifier:
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  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.
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.