Improvements to `docker-compose logs`

[dnephin]

This epic covers a bunch of improvements we'd like to make to the logs command.

• default to not following (similar to docker logs) (docker-compose logs behavior is different from docker logs #2187, Flush log buffer when printing logs #1549) in 1.7.0
• support -f, --follow (the current behaviour) to keep following log output in 1.7.0
• support --tail=<num> to only show a number of lines from the end of the log (Feature: Ability to clear log history #1083, limit fig log #265) in 1.7.0
• -t, --timestamp to add timestamps to the logs (Improvements to docker-compose logs #2227 (comment)) in 1.7.0
• if a new container is started while logs is running, logs for that container should start to show up in the log stream (''docker-compose logs'' does not show logs for new containers #1115) in 1.7.0
• if the log stream is done (the containers have stopped) logs should exit (logs doesn't exit if the container is already stopped #1866) in 1.7.0
• flush the buffer more frequently to deal with buffered output (container logs are missing when fig up by Webstorm  #1060, Flush log buffer when printing logs #1549) Fixed in 1.5.1
• continue printing logs after the first SIGINT until all containers exit (or we get another SIGINT) (Continue printing log output after Ctrl-C has been pressed #592)
• --json output the raw json lines (json-file logs are not valid JSON #2156)
  logs doesn't exit if the container is already stopped #1866 includes a proposal for how to support many of these features

[bkmeneguello]

My suggestion is to add to the --since= option the keyword "boot" to log only since boot time

[simonvanderveldt]

@dnephin Thanks for putting this on the radar. We've run into all of the listed issues except for the buffered output (though we might've missed it).
Especially the disparity between how docker logs and docker-compose logs work should be fixed.

[blah238]

I couldn't find it anywhere else, but can we also add a -t option for displaying timestamps (like docker's logs command)?

[dnephin]

Added it to the list

[gggeek]

+1 (I just finished adding "echo 'date'" lines to all my entrypoint scripts because of the lack of this feature!)