Foglight queries read‑only user databases on SQL Server Always On replicas (4383831)

Foglight’s SQL Server cartridge discovers and runs per‑database collectors against databases the monitoring account can access. On Always On secondaries (read‑only replicas) this can result in Foglight querying read‑only user databases unless you explicitly restrict collection. This behavior is expected unless you change the instance configuration or credentials.

• Database discovery: The SQL Server cartridge enumerates databases visible to the monitoring login and runs database‑level collectors.
• Instance-level monitoring: If Foglight is pointed at a replica instance (or a credential has access on the replica), it will collect whatever databases that account can read.
• No automatic system‑DB only mode: There is no built‑in default that limits monitoring to system DBs on read‑only replicas; filtering must be configured.
• Permissions: The monitoring account’s permissions determine which databases Foglight can query.

Options

1. Recommended (best practice): Monitor each SQL Server instance/node directly (host/IP) as listener-based monitoring is not supported. This ensures accurate OS/DB correlation and correct failover detection. Avoid adding read‑only replicas unless you need their database‑level metrics. 
2. Use the Exclude Database filter in the Database agent Admin panel or in Agent Status Properties: Configure the Foglight instance’s database filters to allow only system DBs on replicas. Example include regex to allow only system databases. Knowledgabase article 4302274 explains how to exclude databases from being monitored.
3. Disable per‑database collectors: Turn off database‑level collections (database space/file/DB‑level metrics) for replica instances if you only need server OS metrics.
4. Remove/disable replica entries: If you do not need any metrics from that REPLICA, remove the agent from monitoring or disable monitoring for it. 
5. Use a restricted monitoring account: Create a monitoring login on replica servers that has only the minimal server‑level permissions (e.g., VIEW SERVER STATE) and no user‑DB mappings.
   1. Caveat: restricted creds may break DB‑level collectors. Test in staging.
6. Exclude updates (optional): If user databases are created often, schedule a maintenance task to add new user DBs to the exclude list.

Caveats

• Excluding databases or using restricted credentials reduces DB‑level visibility (index recommendations, per‑database waits, etc.). Always test changes in a non‑production environment first.