Initial discovery receiver skeleton

[rmfitzpatrick]

These changes introduce the initial Discovery receiver component methods and config validation (proposed readme: #1812).

[atoulme]

I don't mind if you want to use your own impl of LogRecord, but it might be easier to use plog.LogRecord if you want to access all the fields. For example, your LogRecord struct doesn't have SeverityText or SeverityNum. You would get that for free if you use plog.LogRecord.

[rmfitzpatrick]

The config log record is used to express the values that are desired in the actual plog.LogRecord item that's going to be produced by the receiver. I don't know if it's possible to use a plog.LogRecord in its place given the implementation is in "go.opentelemetry.io/collector/pdata/internal/data/protogen/logs/v1" and doesn't use mapstructure, but considering we only care about specific fields with more convenient accessors I don't think it's a concern.

Severity becomes SeverityText but since we may want to specify num as well I can update it.*

edit: updated

[atoulme]

Changes look ok:

• the receiver is not mapped to components, so this is not going to affect the collector yet.
• it would be good to have a README

[rmfitzpatrick]

• the receiver is not mapped to components, so this is not going to affect the collector yet.

I don't plan on adding this as a component until its initial functionality has been merged (observer event emitting and metrics/statement evaluation are next PRs). There are also some required upstream PRs for this to be fully functional:

open-telemetry/opentelemetry-collector-contrib#12801
open-telemetry/opentelemetry-collector-contrib#12670

• it would be good to have a README

This was the first PR and has landed: https://github.com/signalfx/splunk-otel-collector/blob/main/internal/receiver/discoveryreceiver/README.md

[atoulme]

• the receiver is not mapped to components, so this is not going to affect the collector yet.

I don't plan on adding this as a component until its initial functionality has been merged (observer event emitting and metrics/statement evaluation are next PRs). There are also some required upstream PRs for this to be fully functional:
No worries.

• it would be good to have a README

This was the first PR and has landed: https://github.com/signalfx/splunk-otel-collector/blob/main/internal/receiver/discoveryreceiver/README.md
I looked for it and missed it. Apologies!

[aurbiztondo-splunk]

Left a couple of comments!