# Monitor High-Availability Clusters

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This guide explains how Datasentinel detects and manages HA clusters, how instances are grouped, and how to analyze workload and activity in highly available PostgreSQL environments.

## HA Cluster Detection

Datasentinel automatically detects the role of each PostgreSQL instance, identifying primary instances and read-only replicas based on runtime characteristics.

{% hint style="info" %}
If a failover occurs, Datasentinel updates instance roles automatically to reflect the new cluster topology.
{% endhint %}

## Using Tags with HA Clusters

[**Tags**](broken://pages/FO20mthj1Oz13rIFC3Hr) can be applied to PostgreSQL instances that belong to an HA cluster.

When instances share the same tag (for example, `ha_cluster=sales-app`), you can:

* Analyze the consolidated workload of the cluster
* Apply[ **role-based access control (RBAC)**](broken://pages/XpwouTmv9sm8pybTAScA) at the cluster level
* [**Filter dashboards**](broken://pages/FO20mthj1Oz13rIFC3Hr) and reports by cluster or application

Tags combined with HA awareness provide powerful grouping and access-control capabilities.

## Consolidated Cluster View

Datasentinel provides a **cluster-level view** that aggregates activity across all instances in the HA cluster.

This allows you to:

* Analyze total workload across the cluster
* Compare activity between primary and replicas
* Identify load distribution and imbalance

Cluster-level analysis removes the need to inspect each instance individually.

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## Workload Analysis Across HA Clusters

Using Datasentinel dashboards and analysis modules, you can:

* View [**Top Queries**](broken://pages/0z3m1C0QshZ1dCVZ6tw7) across the entire cluster
* Analyze [**Session Activity**](broken://pages/yUGnw5CyiREJgqkA9ALe) on primary and replicas
* Identify queries executed on replicas only
* Detect replication-aware workload patterns

This is particularly useful for understanding how applications leverage read replicas.

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## Viewing Replication Statistics

Datasentinel collects and logs replication statistics for PostgreSQL read replicas, providing clear visibility into replication health.

For each replica, Datasentinel allows you to:

* View the **WAL delta size**, representing the amount of data remaining to be replicated
* Monitor **replication delay**, indicating how far replicas lag behind the primary instance

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## Common Use Cases

Typical HA cluster monitoring scenarios include:

* Analyzing total workload across primary and replicas
* Verifying that read traffic is correctly routed to replicas
* Comparing query patterns between instances
* Monitoring cluster behavior during failover events

## Best Practices

* Use consistent tags across all instances in an HA cluster
* Combine cluster-level analysis with instance-level dashboards
* Review workload distribution regularly
* Use tags to control access to entire clusters via RBAC

{% hint style="info" %}
Datasentinel is compatible with read replicas from managed PostgreSQL services offered by major public cloud providers, including Amazon RDS, Microsoft Azure, and Google Cloud.
{% endhint %}

## Conclusion

Datasentinel provides clear visibility into high-availability PostgreSQL environments by automatically detecting primary and replica roles and enabling consolidated activity analysis across instances.


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