logging.md

Logging

There are a few things to note about what Fn logs.

Logspout

We recommend using logspout to forward your logs to a log aggregator of your choice.

Format

All logs are emitted in logfmt format for easy parsing.

Each line contains timestamp, app id, and function id. Here's a sample:

2018-11-21T13:50:28-05:00 linuxkit-025000000001 app_id=01CV2SYZ9NNG8G00RZJ0000001,fn_id=01CWVSNBD0NG8G00RZJ00000 Caused by: java.lang.RuntimeException: Something went horribly wrong!

Remote syslog for functions

You may add a syslog url to any function application and all functions that exist under that application will ship all of their logs to it. You may provide a comma separated list, if desired. Currently, we support tcp, udp, and tcp+tls, and this will not work if behind a proxy [yet?] (this is my life now).

An example syslog url is:

tcp+tls://logs.papertrailapp.com:1

We log in a syslog format, with some variables added in logfmt format. If you find logfmt format offensive, please open an issue and we will consider adding more formats (or open a PR that does it, with tests, and you will receive 1 free cookie along with the feature you want). The logs from the functions themselves are not formatted, only our pre-amble, thus, if you'd like a fully logfmt line, you must use a logfmt logger to log from your function.

• All log lines are sent as level error w/ the current time and fnrunner as hostname.
• app_id will prefix every log line.

<11>2 1982-06-25T12:00:00Z fnrunner - - - - app_id=54321 this is your log line