Add UDP input back

[renan-strauss]

Hi there,

Seeing that my previous pull request is not likely to get merged because of the big refactoring going on, here's a PR to add UDP support back (not sure why it was removed) in alpha1. I hope this will be helpful, and I'm looking forward to the next release ! (got rc31 running in production and still seeing some issues as well as feeling the lack of CQs).

Keep up the good work,
Renan.

• CHANGELOG.md updated
• Rebased/mergable
• Tests pass
• Sign CLA (if not already signed)

[corylanou]

@renan- Thanks for the work. The reason we removed it was we are not going to support json on this endpoint. We are only going to support the new line protocol here likely. I'll get @pauldix to confirm though to be sure. Regardless, I imagine at the very least we would do something similar to the http endpoint and detect json vs. line protocol to support both.

[pauldix]

Yeah, I'd prefer to have UDP support only the line protocol. Which would mean it would need configuration options like the Graphite and CollectD input plugins. Set which database and retention policy you're writing into.

See #2696 for discussion on the merits of line protocol over JSON.

[renan-strauss]

Thanks for the quick answers guys ! I desperately need UDP support for my use case (to avoid any latency when writing data) so would you be interested in another PR supporting line protocol instead of JSON ?

[pauldix]

@renan- that would be great, we'd gladly take it. Going to cut RC32 tomorrow so if you can get it in time, it'll be included! Thanks again for helping out!

[pauldix]

@renan- oh, another thing to look at is to have it use the batcher that graphite and collectd now use.

[renan-strauss]

Thanks for the tip, starting to work on it.

[renan-strauss]

Updated the code, now waiting for your feedback.

[corylanou]

please add a test in config_test.go for this addition of the config.

[corylanou]

@renan- Thanks for the hard work! Certainly headed in the correct direction. Please let me know if you have any questions. I know not all of our services are in perfect shape yet either, but feel free to look at collectd to get an idea of some of the patterns we are currently using (I reference some as well in my comments).

[renan-strauss]

@corylanou You're welcome! I updated the PR once again based on your comments. I still wonder if the retention policy should be in config or always set to the default one. One more thing: what about ConsistencyLevel value when creating a WritePointsRequest ?

[corylanou]

We actually don't want to add these. This would enable the UDP endpoint for every test. We use this function to create a base config for the tests to use, and then turn on specific endpoints in the tests themselves. Simply revert the change to this file and we should be fine.

[renan-strauss]

Tests on CircleCI won't pass without these (panic because of the error returned by ListenAndServe when BindAddress or Database are empty)

[corylanou]

I think the real problem here is that the server isn't observing if UDP is enabled, and actually adding it to the services. I'm guessing a couple of our endpoints have that problem. I'll merge this, and then do another PR that fixes services starting that aren't enabled.

[corylanou]

@renan- Awesome! Thanks for all the work. Very much appreciated! Had one last minor comment. Looks like something changed that is preventing a merge so you'll have to rebase quick to make this mergeable.

For now let the default RP be used. It can be a feature we add in the future to specify an RP. If we do, all endpoints should likely support it as well.

Same with consistency level. feels like that should be a config option as well, but I'm fine with this PR not addressing it. Can be an easy feature to add.

Thanks again for the quick turn around. Hopefully we'll get this merged for tomorrow's RC.