e611a189cb
If a logdriver doesn't register a callback function to validate log options, it won't be usable. Fix the journald driver by adding a dummy validator. Teach the client and the daemon's "logs" logic that the server can also supply "logs" data via the "journald" driver. Update documentation and tests that depend on error messages. Add support for reading log data from the systemd journal to the journald log driver. The internal logic uses a goroutine to scan the journal for matching entries after any specified cutoff time, formats the messages from those entries as JSONLog messages, and stuffs the results down a pipe whose reading end we hand back to the caller. If we are missing any of the 'linux', 'cgo', or 'journald' build tags, however, we don't implement a reader, so the 'logs' endpoint will still return an error. Make the necessary changes to the build setup to ensure that support for reading container logs from the systemd journal is built. Rename the Jmap member of the journald logdriver's struct to "vars" to make it non-public, and to make it easier to tell that it's just there to hold additional variable values that we want journald to record along with log data that we're sending to it. In the client, don't assume that we know which logdrivers the server implements, and remove the check that looks at the server. It's redundant because the server already knows, and the check also makes using older clients with newer servers (which may have new logdrivers in them) unnecessarily hard. When we try to "logs" and have to report that the container's logdriver doesn't support reading, send the error message through the might-be-a-multiplexer so that clients which are expecting multiplexed data will be able to properly display the error, instead of tripping over the data and printing a less helpful "Unrecognized input header" error. Signed-off-by: Nalin Dahyabhai <nalin@redhat.com> (github: nalind)
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logs
Usage: docker logs [OPTIONS] CONTAINER
Fetch the logs of a container
-f, --follow=false Follow log output
--since="" Show logs since timestamp
-t, --timestamps=false Show timestamps
--tail="all" Number of lines to show from the end of the logs
NOTE: this command is available only for containers with json-file and
journald logging drivers.
The docker logs command batch-retrieves logs present at the time of execution.
The docker logs --follow command will continue streaming the new output from
the container's STDOUT and STDERR.
Passing a negative number or a non-integer to --tail is invalid and the
value is set to all in that case.
The docker logs --timestamp commands will add an RFC3339Nano
timestamp, for example 2014-09-16T06:17:46.000000000Z, to each
log entry. To ensure that the timestamps for are aligned the
nano-second part of the timestamp will be padded with zero when necessary.
The --since option shows only the container logs generated after
a given date. You can specify the date as an RFC 3339 date, a UNIX
timestamp, or a Go duration string (e.g. 1m30s, 3h). Docker computes
the date relative to the client machine’s time. You can combine
the --since option with either or both of the --follow or --tail options.