chore(database_observability): Use Fanout, Consume and Drain

[kalleep]

Pull Request Details

We have added some shared functionallity for working with loki pipelines and should use them in our database_observability. This will make it easier in the future to start to migrate to new architecture for loki pipelines and avoid common pitfalls.

I did not review all collectors but just did a sample and e.g. explain_plan can cause a deadlock when component is stopping and in turn preventing alloy from stopping because nothing is consuming from handler.

Changes:

1. Use loki.Fanout - This is doing internal locking of logs receivers so components do not have to care about it. It will also stop forwarding when context is canceled.
2. Use loki.Consume - Runs the consume loop from a LogsReceiver and will exit when context is canceled.
3. Use loki.Drain - When components is stopping we need to still forward / drain to make sure collectors can stop. Since fix: Stop components in a deterministic order #5613 we have a deterministic order for stopping components so it is safe to forward to downstream components during stops but we still have a timeout after we would drain into nothing.
4. Use loki.NewEntry - This makes sure we set created timestramp of entries so they can be properly tracked by loki_write_entry_propagation_latency_seconds.

Issue(s) fixed by this Pull Request

Part of: #5826

Notes to the Reviewer

PR Checklist

• Documentation added
• Tests updated
• Config converters updated

[Copilot]

Pull request overview

This PR migrates database_observability (MySQL + Postgres) components to use the shared Loki pipeline helpers (Fanout, Consume, Drain, NewEntry) to reduce shutdown deadlocks and align with the repo’s evolving Loki pipeline architecture.

Changes:

• Replace manual receiver-forwarding loops with loki.Fanout + loki.Consume in MySQL/Postgres Run.
• Add loki.Drain(..., loki.DefaultDrainTimeout, ...) to ensure logs are drained/forwarded while collectors stop during shutdown.
• Switch BuildLokiEntryWithTimestamp to loki.NewEntry to ensure entry “created” timestamps are set; update affected tests for the new fanout field.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/component/database_observability/postgres/component.go	Use Fanout/Consume for forwarding and Drain during shutdown; add fanout field.
internal/component/database_observability/postgres/component_test.go	Update component construction to initialize fanout.
internal/component/database_observability/mysql/component.go	Use Fanout/Consume for forwarding and Drain during shutdown; add fanout field.
internal/component/database_observability/mysql/component_test.go	Update component construction to initialize fanout.
internal/component/database_observability/loki_entry.go	Build entries via loki.NewEntry to set internal created timestamp.

[kalleep]

Before both of these components stored both args and receivers but never actually updated the second one. So if a config change was made with new receivers that would not work and we would keep sending logs to the old receiver list causing all kinds of problems.

[matthewnolf]

LGTM 👍