[receiver/elasticsearch] Request to enable more metrics by default

[crobert-1]

Component(s)

receiver/elasticsearch

Describe the issue you're reporting

This is a request to enable a few existing metrics by default, that are currently disabled by default.

Requested metrics

Here's the list of metrics:

elasticsearch.index.documents: The number of documents for an index
elasticsearch.index.operations.merge.current: The number of currently active segment merges
elasticsearch.index.segments.count: Number of segments of an index.

Justification

These metrics are all important in understanding the current status of an Elasticsearch index.

The count of documents in an index is helpful in understanding the size and contents of an index.

The current merge count is also important to see the state of the cluster due to the potential performance impacts of the ongoing index merges.

The segment count of an index is also important to understand the current state of an index, and potential performance impacts of how many segments are in it (more segments can result in longer search times).

Counter-point to Justification

This component is marked as beta stability, and enabling metrics by default is considered a breaking change. Breaking changes are allowed, but should be minimized, according to the stability definition referenced.

Discussion is welcome, I can open a PR if this is acceptable to code owners.

[github-actions]

Pinging code owners:

• receiver/elasticsearch: @djaglowski @BinaryFissionGames

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[crobert-1]

Removing needs triage as a code owner has responded with a 👍. I'll post a PR.