Add file rotation based on file age to file output plugin

[flexd]

Required for all PRs:

• Signed CLA.
• Associated README.md updated.
• Has appropriate unit tests.
  I have not touched the unit tests at all (yet)

This replaces #3922

[flexd]

Err, there we go. Accidentally put in a older file_test.go and broke Write() a bit. This compiles for me, and appears to be working like it should. FYI: It's next to impossible to compile Telegraf with only 2GB ram :-(

[glinton]

Is there any way you can push these changes to the 3922 to preserve the history? Or is this a fundamentally different approach?

[flexd]

@glinton uh, I could in theory do that I guess? This is basically rotate.go from the other pull-request with a number of changes and then I added the rotate_max_age field to file.go, in the file plugin.

The other pull-request #3922 adds a whole new plugin rotatingfile that I would have to remove again, with a bunch of reverting commits or a force-push. Also I have deleted the local branch for that, but I guess it would be possible to get that back by pulling it from the pull-request.

Isn't history preserved enough by having the first pull-request saying this one takes over?

Edit: I'd say this is a fundamentally different approach.

[flexd]

Does the thumbs up mean everything is good? :-)

[danielnelson]

@flexd We added rotation based on this pull request to the agent logfile, I think we can update this pull request to use the rotating io.Writer now in https://github.com/influxdata/telegraf/tree/master/internal/rotate.

I'd like to include this in the 1.11 release, would you have time to update the pull request?

[flexd]

I will make the required changes :-) Very cool that my pull-request has lead to changes somewhere else!

[flexd]

Uh, that should do it! I think I might have messed up the rebase there with all these commits showing up :-/ Any suggestions?

[danielnelson]

I think you will need to do an interactive rebase git rebase -i master and then remove the unrelated commits keeping only your new changes.

[flexd]

That looks like it fixed it. :-)

[flexd]

That last check was leftover from before the io.MultiWriter was used I think :-) Used to be a slice of writers