[receiver/sqlserver] Add Always On Availability Group database replica metrics

[splunk-shanu]

Component(s)

receiver/sqlserver

Is your feature request related to a problem? Please describe.

Currently the sqlserver receiver does not expose any metrics for SQL Server Always On Availability Groups (AG). Operators running SQL Server with AG enabled have no way to monitor replica health —
specifically log send lag, redo queue backlog, and hardened latency — using the OpenTelemetry Collector. This forces them to rely on separate monitoring tools or custom queries to get visibility into
AG replica state.

Describe the solution you'd like

Add 4 new opt-in metrics to the sqlserver receiver sourced from sys.dm_hadr_database_replica_states:

• sqlserver.availability_group.database_replica.hardened_latency — time in seconds between a log record being generated on the primary and hardened to disk on the secondary (SQL Server 2016+)
• sqlserver.availability_group.database_replica.queue.size — amount of log data in the log send and redo queues (By), broken down by sqlserver.availability_group.queue.type attribute
• sqlserver.availability_group.database_replica.queue.rate — rate at which log data is being redone/sent on the secondary replica (By/s)

All metrics are enabled: false by default and require a direct connection to SQL Server with Always On Availability Groups enabled. Each metric carries sqlserver.availability_group.name,
db.namespace, and sqlserver.replica.name attributes for full context.

Describe alternatives you've considered

No response

Additional context

No response

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[github-actions]

Pinging code owners:

• receiver/sqlserver: @sincejune @crobert-1 @sv-splunk @ebrdarSplunk @XSAM @akshays-19 @splunk-shanu

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