Warning

License: Pro - Requires a Pro or Enterprise license.

Overview

The SQL Server AlwaysOn probe monitors the health of SQL Server AlwaysOn Availability Groups through the SQL Server Dynamic Management Views (DMVs). It reports per-replica role, synchronization health and connectivity, and per-database lag, queue sizes and throughput rates. One probe instance monitors one SQL Server instance; add more instances for additional servers.

Collected data:

• Server reachability
• Per-replica role (primary / secondary), synchronization health and connectivity
• Per-database secondary lag
• Per-database log-send and redo queue sizes
• Per-database log-send and redo throughput rates

All metrics are emitted under the senhub.mssql_ha.* namespace. Replica series carry an availability-group and replica attribute; database series carry an availability-group and database attribute. These attributes also act as filters in the Sensor URLs tab of the console.

The probe also emits a db entity for the monitored SQL Server instance so that the topology view can build a node from it — surfaced even when the server is unreachable or has no Availability Group configured.

Quick Start

Basic Configuration

# probes.d/20-mssql_ha.yaml — each file under probes.d/ is a YAML array of probes
- name: mssql-ha-prod
  type: mssql_ha
  params:
    host: sqlnode1.example.com
    port: 1433
    username: monitoring
    password: "${secret:mssql-ha-prod.password}"   # OS secret store; inline plaintext is auto-sealed on install
    encrypt: "true"
    trust_server_cert: false
    interval: 60

The ${secret:...} reference resolves the password from the OS-native secret store (see Configuration).

Multiple Instances

Monitor several SQL Server instances with separate probe instances:

# probes.d/20-mssql_ha.yaml
- name: mssql-ha-dc1
  type: mssql_ha
  params:
    host: sqlnode1.example.com
    username: monitoring
    password: "${secret:mssql-ha-dc1.password}"

- name: mssql-ha-dc2
  type: mssql_ha
  params:
    host: sqlnode2.example.com
    username: monitoring
    password: "${secret:mssql-ha-dc2.password}"
    encrypt: "disable"   # test/lab instance with no TLS

Configuration Parameters

Parameter	Must set	Default	Description
host	Yes	-	SQL Server hostname or address; host\Instance for a named instance. Example: sql01.example.com
port	No	1433	SQL Server TCP port
username	Yes	-	SQL login with read access to the AlwaysOn DMVs
password	In practice	-	Password of the SQL login; empty for an unauthenticated login. A secret: reference it with ${secret:…}, ${env:…} or ${file:…} rather than writing it in the file
encrypt	No	true	TLS negotiation with the server (go-mssqldb convention). One of true, false, disable
trust_server_cert	No	false	Accept the server certificate without validating it
interval	No	60	Seconds between collections
timeout	No	30	Connection and query timeout per cycle, in seconds

Metrics Collected

Overview

Metric	Unit	Description
senhub.mssql_ha.up	1	1 when the last ping reached the server this cycle, else 0

Replicas

Each replica series carries an ag.name (availability group) and replica.name attribute.

Metric	Unit	Description
senhub.mssql_ha.replica.role	1	Replica role (Primary=1, Secondary=0)
senhub.mssql_ha.replica.health	1	Synchronization health (Healthy=1, otherwise 0)
senhub.mssql_ha.replica.connected	1	Connectivity state (Connected=1, Disconnected=0)

Databases

Each database series carries an ag.name (availability group) and database.name attribute.

Metric	Unit	Description
senhub.mssql_ha.database.lag	s	Estimated secondary-replica lag behind the primary
senhub.mssql_ha.log_send_queue	By	Log records on the primary not yet sent to the secondary
senhub.mssql_ha.redo_queue	By	Log records received by the secondary not yet redone
senhub.mssql_ha.log_send_rate	By/s	Rate at which log is sent from the primary to the secondary
senhub.mssql_ha.redo_rate	By/s	Rate at which received log is redone on the secondary

Filtering (Sensor URLs tab of the console)

The Sensor URLs tab of the console exposes filters for this probe:

• Metric Type (category) — overview, replicas, databases
• Availability Group — pick a specific AG
• Replica — pick a specific replica
• Database — pick a specific availability database

Requirements

• SQL Server with AlwaysOn Availability Groups enabled and reachable from the agent host (default TCP port 1433).
• A SQL Server login with permission to read the AlwaysOn DMVs — VIEW SERVER STATE is sufficient. A minimal-privilege account is recommended over sa.
• The probe reads sys.dm_hadr_availability_replica_states, sys.availability_replicas, sys.availability_groups and sys.dm_hadr_database_replica_states.

AlwaysOn required

This probe reports Availability Group replication health only. For general SQL Server health and throughput (batch/transaction rates, buffer cache, per-database I/O), use the SQL Server probe — the two are complementary and can run side by side against the same instance.

Outputs

SQL Server AlwaysOn metrics are available through every configured output — OTLP, Prometheus, and the pull formats (PRTG, Nagios, Web UI). For PRTG and Nagios, query the probe by its configured name:

curl "http://localhost:8080/api/{agentkey}/prtg/metrics/mssql-ha-prod"
curl "http://localhost:8080/api/{agentkey}/nagios/metrics/mssql-ha-prod"

Metric reference

Every metric this probe can emit. Metric is the OpenTelemetry name the OTLP, Prometheus and Zabbix outputs derive theirs from. Name is what a Nagios check and the API metrics= filter match. PRTG channel is the label PRTG shows, placeholders filled from the series' tags.

Metric	Name	PRTG channel	Unit	Description
senhub.mssql_ha.up	mssql_ha_up	Server Reachable	#	1 when the last ping reached the SQL Server this cycle, else 0
senhub.mssql_ha.replica.role	mssql_ha_replica_role	Replica Role ({ag_name}/{replica})	#	Availability-group replica role (Primary=1, Secondary=0)
senhub.mssql_ha.replica.health	mssql_ha_replica_health	Replica Sync Health ({ag_name}/{replica})	#	Replica synchronization health (Healthy=1, otherwise 0)
senhub.mssql_ha.replica.connected	mssql_ha_replica_connected	Replica Connected ({ag_name}/{replica})	#	Replica connectivity state (Connected=1, Disconnected=0)
senhub.mssql_ha.database.lag	mssql_ha_database_lag	Secondary Lag ({ag_name}/{database})	s	Estimated secondary-replica lag behind the primary
senhub.mssql_ha.log_send_queue	mssql_ha_log_send_queue	Log Send Queue ({ag_name}/{database})	Bytes	Log records on the primary not yet sent to the secondary
senhub.mssql_ha.redo_queue	mssql_ha_redo_queue	Redo Queue ({ag_name}/{database})	Bytes	Log records received by the secondary not yet redone
senhub.mssql_ha.log_send_rate	mssql_ha_log_send_rate	Log Send Rate ({ag_name}/{database})	Bytes/s	Rate at which log is sent from the primary to the secondary
senhub.mssql_ha.redo_rate	mssql_ha_redo_rate	Redo Rate ({ag_name}/{database})	Bytes/s	Rate at which received log is redone on the secondary