Logging

:warning: The logging options outlined here are based on a preview feature, and are subject to change

Nimbus offers several options for logging - by default, logs are written to stdout using the chronicles textlines format which is convenient to read and can be used with tooling for heroku/logfmt.

Change log level

You can customise Nimbus' verbosity with the --log-level option.

For example:

./run-mainnet-beacon-node.sh --log-level=WARN

The default value is INFO.

Possible values (in order of decreasing verbosity) are:

TRACE
DEBUG
INFO
NOTICE
WARN
ERROR
FATAL
NONE

Change logging style

Nimbus supports three log formats: colors, nocolors and json. In auto mode, logs will be printed using either colors or nocolors.

You can choose a log format with the --log-format option, which also understands auto and none:

./run-mainnet-beacon-node.sh --log-format=none # disable logging to std out
./run-mainnet-beacon-node.sh --log-format=json # print json logs, one line per item

Logging to a file

To send logs to a file, you can redirect the stdout logs:

# log json to filename.jsonl
./run-mainnet-beacon-node.sh --log-format=json > filename.jsonl

We recommend keeping an eye on the growth of this file with a log rotator. Logs are written in the "JSON Lines" format - one json entry per line.