Postgres database agent support

[JayPolanco]

Description of the issue

Self-managed PostgreSQL monitoring on EC2 requires the CloudWatch Agent to collect counter metrics, DB Load (active session sampling at 1s), and Top SQL statistics. The upstream OTel PostgreSQL receiver (v0.150.0) provides the foundation but has gaps for these requirements.

Description of changes

Embedded upstream v0.150.0 postgresqlreceiver into receiver/postgresqlreceiver/ with adapted module paths and inlined internal/sqlquery dependency.

Registered new components in service/defaultcomponents/components.go:

• postgresqlreceiver
• signaltometricsconnector (converts log events → metrics)

Gap fixes on top of upstream (reviewer focus):

1. Independent query_sample collection_interval — Added CollectionInterval to QuerySampleCollection and separate ControllerConfig in createLogsReceiver. Allows 1s DB Load sampling without affecting 60s counter collection.

   • config.go:43 — CollectionInterval field
   • factory.go:85 — default value
   • factory.go:128-132 — logsControllerConfig override logic
   • factory.go:170 — passed to NewLogsController

2. postgresql.sessions metric — New gauge metric querying pg_stat_activity GROUP BY state for session state breakdown (active/idle/idle_in_transaction). Disabled by default via metrics config.

   • client.go:75 — interface method
   • client.go:709-729 — implementation
   • scraper.go:180 — call site
   • scraper.go:565-582 — collectSessionStates method

3. Top SQL local_blks columns — Added local_blks_hit, local_blks_read, local_blks_dirtied, local_blks_written to the top query SQL template.

   • topQueryTemplate.tmpl:8-11

4. Exclude receiver self-connection from DB Load — Added pid <> pg_backend_pid() filter to the query sample template to prevent the receiver's own database connection from inflating active session counts.

   • querySampleTemplate.tmpl:36

Updated components_test.go for new receiver and connector counts.

License

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Tests

• components_test.go updated and passing
• End-to-end validated on EC2 with PostgreSQL 16: counter metrics, Top SQL metrics, DB Load metrics, session states, and raw log events all flowing to CloudWatch

Requirements

1. Run make fmt and make fmt-sh
2. Run make lint

[JayPolanco]

Not needed