Logging

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.

Tip

NOT at the beginning of a log line means NOTICE.

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.