Add Prometheus remote write exporter to collector default package

[markcartertm]

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We need to add a Prometheus exporter that can push prometheus data from the collector to a Prometheus remote write API endpoint.
A goal of the OpenTelemetry collector is to provide built in support for ingestion and export of Prometheus metrics. currently, OTEL collector includes a Prometheus exporter that exposes /metrics allowing a Prometheus server to scrape the collector. we currently do not have an exporter that allows the collector to push collected metrics to a remote write backend such as CorTex. if we were to add remote write support we can eliminate the need to run a Prometheus server in a Kubernetes cluster just to scrape the prometheus node exporters and send to a remote write API.
Describe the solution you'd like
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We need to add a new Prometheus exporter that can send data to a prometheus remote write backend such as Cortex,Thanos, Spanner, SignalFX, InffluxDB, Elasticsearch etc. such an exporter will be included in the default collector package. by adding Prometheus remote write exporter we will significantly increase the number of metric backends that OTEL collector can send metrics to by default.

Describe alternatives you've considered
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There really aren't any.
Additional context
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List of remote write destinations supported by Prometheus that will be enabled by adding remote write support in OTEL:
https://prometheus.io/docs/operating/integrations/

[markcartertm]

@alolita can we get an intern to drive a POC for this together with a mentor?

[alolita]

@markcartertm we've already assigned an intern to work on this. Thanks for filing an issue!

Following up on requesting a OTEL Collector mentor.

[jmacd]

Are you interested in support for receiving Prometheus push data, too?

[alolita]

Hi! @jmacd yes would definitely like to understand the requirements to build this out. Would you have some cycles to review our design and code?

[dabangarang]

Hi just to understand @alolita this is not the project that Yang and I are in charge of? I was under the impression that we will not make use of Prometheus remote write, but instead, create an exporter that ports directly to the backends of interest directly.

[jmacd]

I am happy to help, @alolita. I have read through the current otel-collector implementation of the Prometheus receiver and exporter, and I've also been working on specifying how Prometheus data transformation should work by default (open-telemetry/oteps#118).

[huyan0]

I am working on this issue.

[alolita]

HI @jmacd thanks for the offer :-) Two of our intern engineers @huyan0 and @danielbang907 (in the process of gaining membership) are working with me on this Prometheus read/write exporter. Please assign us - @alolita @huyan0 to this issue. Many thanks!

[morigs]

#1464 document seems detailed enough and ready for use. What are the plans for implementation? I need this exporter too and ready to contribute

[huyan0]

@morigs code PRs should be coming in this week. We will keep you updated : )

[alolita]

Hi @bogdandrutu can you assign this issue to me @alolita, @huyan0 and @danielbang907 - we are working on this implementation in #1464

[tigrannajaryan]

@alolita where are we with this? I see there is a related PR. Is there more work expected on this?

[alolita]

Hi @tigrannajaryan @bogdandrutu The Prometheus remote write exporter has been completed and merged. We will open separate PRs for SIGv4 support and compliance with latest OTLP changes. The core is complete and merged. This issue can be closed.

[tigrannajaryan]

Thanks @alolita

[PatrikSteuer]

Is there ongoing work to provide a remote write receiver as well? This would allow prometheus servers to push metrics to a remote collector.