Sql/metrics input in Elastic Agent not returning data (v8.14.3, PostgreSQL 17.2)

Elastic Stack Elastic Agent
1

Hi,
I'm using Elastic Agent in standalone mode (without Fleet) on RHEL 9, version 8.14.3. I aim to collect the max_connections value from pg_settings in PostgreSQL 17.2 and correlate it with the number of active connections from pg_stat_activity.

Setup:

  • Elastic Agent: 8.14.3 (standalone mode)
  • PostgreSQL: 17.2 (server and client)
  • Elastic Stack: 8.14.3
  • OS: RHEL 9

Configuration:

- type: sql/metrics
  id: sql-postgres-max-connections-my_app
  data_stream.namespace: my_app
  streams:
    - data_stream.dataset: sql.postgresql_custom
      driver: "postgres"
      hosts:
        - postgres://postgres@localhost:5432/?sslmode=disable
      metricsets:
        - query
      period: 1m
      result:
        format: table
      result_column_name: max_connections
      sql_query: >
        SELECT setting::int AS max_connections FROM pg_settings WHERE name = 'max_connections';

Issue:
Despite the configuration, no data is ingested into Elasticsearch. The index .ds-metrics-sql.postgresql_custom-* is created, but documents only contain the SQL query string without any result fields.

Troubleshooting Steps Taken:

  • Verified PostgreSQL connectivity and authentication.
  • Executed the SQL query manually via psql successfully.
  • Tried both format: table and format: document in the result section.
  • Tested with a simple query: SELECT 42 AS test_value; — same issue.
  • Enabled debug logging with selectors: ["*"] — no relevant errors or warnings.
  • Checked the components directory: postgresql module is present, but no sql module found.
  • Attempted to run the agent with --dev flag — not supported.

Questions:

  1. Is the sql/metrics input officially supported in Elastic Agent 8.14.3 standalone mode?
  2. Are there known issues or limitations with this input in the specified version?
  3. Should the result of the SQL query appear directly in the _source of the document?
  4. Is there an internal component or module required for sql/metrics that might be missing?
  5. Would upgrading to Elastic Agent 8.15 or 9.0 resolve this issue, even if the Elastic Stack remains at 8.14.3?

Any insights or assistance would be greatly appreciated - thanks a lot in advance.