Logstasher provides logstash-friendly logging interface for Go. It wraps any writer and writes logstash events to it.

This is how output lines look like:

{"@timestamp":"2015-03-22T13:34:43.973174775Z","@version":1,"message":"hello","shards":[1,2,3],"tags":["wow","such"]}

f := map[string]interface{}{
    "app":    "myapp",
    "things": []string{"something", "another"},
}

w := logstasher.NewWriter(os.Stdout, f)

log.SetFlags(0)
log.SetOutput(w)

log.Println("hey, logstash!")

Logstasher provides command logstasher that can be used in unix pipes. It reads lines from stdin, turns them into json events and writes to stdout:

λ echo reporting from $(hostname -s) | logstasher -fields '{"app":"myapp","pi":3.14}'
{"@timestamp":"2015-03-22T13:33:42.344282854Z","@version":1,"app":"myapp","message":"reporting from hyperion","pi":3.14}

You can also pass -out option with filename to write and logstasher would happily write to that file, detecting log rotation and removal.

You can use minimal (8mb) docker image bobrik/logstasher to run logstasher:

# docker run --rm -it bobrik/logstasher -fields '{"from":"docker"}'
hey
{"@timestamp":"2015-03-23T15:48:02.543517666Z","@version":1,"from":"docker","message":"hey"}

or to install logstasher binary to your host:

# docker run --rm -v /usr/bin:/target bobrik/logstasher
installing logstaher in /target
# which logstasher
/usr/bin/logstasher

MIT