Heka by Mozilla is another alternative - http://hekad.readthedocs.org/en/latest/. I have been running in production to ship docker logs to our Elasticsearch cluster.
We (OVH) recently tried Heka to push syslog data into Kafka, but it eventually kept crashing under load. Other alternatives were way to slow for our needs.
So we ended up writing a simple tool, not as flexible as Heka but about 10 times faster https://github.com/jedisct1/flowgger