Support multiple HTTP inputs

[gunnaraasen]

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Adds support for multiple HTTP listeners. This is the last issue to completely fix #2785.

[gunnaraasen]

Looks like AppVeyor failed on an influx_stress test.

[e-dard]

LGTM 👍

[jwilder]

This is looks like a breaking change to the config file. Are there any other inputs that are limited to only one?

It would be nice to not have the config break. Can we keep the existing HTTP config option and add it to the slice for backwards compatibility?

[gunnaraasen]

@jwilder I'm planning to open another PR to do exactly that for all the listeners but haven't finished yet.

[jwilder]

@gunnaraasen What happens when you use an old config that still uses [http] and not [[http]]?

[jwilder]

Needs to be moved to next release.

[jwilder]

This needs to be updated to support [http] and log a deprecation warning similar to how we handled [collectd] and [opentsdb]. See: https://github.com/influxdata/influxdb/blob/master/cmd/influxd/run/config.go#L133

[jsternberg]

What's the rationale behind this change? Unlike the other configuration changes, I don't see much value to multiple HTTP listeners. There are some downsides though with the naming behind the environment variable overrides and the configuration file change. If someone needs multiple HTTP listeners, what can we do better that Nginx can't do? Otherwise, I think we should just advise people to install a proper web server without risking the breaking change.

[jwilder]

I agree w/ @jsternberg. I don't see the benefit of supporting this.

[gunnaraasen]

Mainly, the benefit would be the ability to set up an unauthenticated localhost listener for administrative access. It would also make this service consistent with the Graphite, OpenTSDB, UDP, and CollectD services.

I'm going to close this since it's a large change not necessary for 1.0.