log-output.md

Log Output

The logs are generally printed using pino in NDJSON format.

Useful Commands

Running collect with pretty output (recommended only for development).

perfception collect --pretty

Filtering output by a log level. One of 'fatal', 'error', 'warn', 'info', 'debug', 'trace' or 'silent'.

perfception collect --level info

Collecting and outputting the logs to a file in addition to the STDOUT.

perfception collect 2>&1 | tee logs/collect`date '+%Y-%m-%d_%H-%M-%S'`.log

See jq, pino-tee and pino-pretty for more logging options.

For example the following command will create pretty output on stdout with a log level "info" or above but write a full blown NDJSON file with trace level logs in addition:

perfception collect 2>&1 | tee logs/collect-`date '+%Y-%m-%d_%H-%M-%S'`.log |  jq -c 'select(.level > 20)' | pino-pretty

You can now analyze the corresponding log if required with:

# replace the date and time in the file name and `.level > 0` with the level you want to work with (e.g. 30, 40, 50).
cat collect2020-05-16_17-40-14.log |  jq -c 'select(.level > 0)' | pino-pretty