Metrics missing due to tag-based execution constraints

Collectors with tag constraints (cluster, primary, standby, dbname:, extension:, etc.) will not execute when tags don't match. For example, collectors tagged 'primary' will skip execution on standby servers, and collectors tagged 'extension:pg_stat_statements' will skip when extension is not installed.

Verify exporter tags with pg_exporter --tag='production,critical' startup flags. Check server role (primary vs standby) with SELECT pg_is_in_recovery(). Verify extensions with SELECT * FROM pg_extension. Use pg_exporter --explain to see which collectors match current tags. Add appropriate tags to enable collectors or remove tag constraints if needed.