etcdctlv3: Add option to defrag a data directory directly

[jpbetz]

We've run into a number of cases where it would be helpful to be able to defrag when etcd is not running. @heyitsanthony Is this an appropriate place to add such a command, or would it be better if I put it elsewhere? Maybe bbolt's CLI?

[xiang90]

@jpbetz this seems fine to me.

@heyitsanthony opinions?

[heyitsanthony]

Looks OK in general, but probably needs something like https://github.com/coreos/etcd/blob/master/etcdctl/ctlv3/command/migrate_command.go#L105-L117 so it won't hang without any kind of message if running on a data dir in use by an active etcd process.

[jpbetz]

Thanks @heyitsanthony,

Added the "file locked" message--

waiting for etcd to close and release its lock on "default.etcd/member/snap/db". To defrag a running etcd instance, omit --data-dir.

[heyitsanthony]

lgtm thanks

[xiang90]

@jpbetz Can you also update the documentation for etcdctl? Then it is good to go.

[jpbetz]

@xiang90 I've added a section to op-guide/maintenance page.

[xiang90]

@jpbetz

https://github.com/coreos/etcd/tree/master/etcdctl#defrag also needs to be updated.

[jpbetz]

Thanks @xiang90. Updated the readme as well.

[xiang90]

we need to mention the new option into the readme. example: https://github.com/coreos/etcd/tree/master/etcdctl#get-options-key-range_end

[jpbetz]

Added the Options section and updated command to DEFRAG [options].

[heyitsanthony]

@jpbetz it's queued

[xiang90]

lgtm

[jpbetz]

@etcd-bot please retest this

[heyitsanthony]

failures unrelated; merging

[xiang90]

@jpbetz I am going to merge this regardless the CI. Thanks for the contribution!

[xiang90]

@jpbetz @heyitsanthony is faster...

[jpbetz]

Excellent. Thanks!