Best practices for alerting on metrics with Azure Database for PostgreSQL monitoring

Whether you are a developer, database administrator, site reliability engineer, or a DevOps professional, monitoring databases is an important part of maintaining the reliability, availability, and performance of your PostgreSQL server. There are various metrics available for you in Microsoft Azure Database for PostgreSQL to get insights on the behavior of the server. You can also set alerts on these metrics using the Azure portal or Azure CLI.

With modern applications evolving from a traditional on-premises approach to becoming more hybrid or cloud-native, there is also a need to adopt some best practices for a successful monitoring strategy on a hybrid and public cloud. Here are some example best practices for using monitoring data on your PostgreSQL server, and areas you can consider improving based on these various metrics.

Active connections

Sample threshold (percentage or value): 80 percent of total connection limit for greater than or equal to 30 minutes, checked every five minutes.

Things to check:

• If you notice that active connections are at 80 percent of the total limit for the past half hour, verify if this is expected based on the workload.
• If you think the load is expected, active connections limit can be increased by upgrading the pricing tier or vCores. You can check active connection limits for each SKU.

Failed connections

Sample threshold (percentage or value): 10 failed connections in the last 30 minutes, checked every 5 minutes.

Things to check:

• If you see connection request failures over the last half hour, verify if this is expected by checking the logs for failure reasons.

• If this is a user error, take the appropriate action. For example, if there is an authentication failed error, check your username/password.
• If the error is SSL related, check that the SSL settings and input parameters are properly configured.
  • For Example: psql "sslmode=verify-ca sslrootcert=root.crt host=mydemoserver.postgres.database.azure.com dbname=postgres user=mylogin@mydemoserver"

CPU percent or memory percent

Sample threshold (percentage or value): 100 percent for 5 minutes or 95 percent for more than two hours.

Things to check:

• If you have hit 100 percent CPU or memory usage, check your application telemetry or logs to understand the impact of the errors.
• Review the number of active connections. Check for connection limits. If your application has exceeded the maximum connections or is reaching the limits, then consider scaling up computing.
• Another tool to help manage your application and optimize your workload is Query Performance Insights. Refer to the Query Store and its usage scenario.

IO percent

Sample threshold (percentage or value): 90 percent usage for greater than or equal to 60 minutes.

Things to check:

• If you see that IOPS is at 90 percent for one hour or more, verify if this is expected based on the application workload.
• If you expect a high load, then increase the IOPS limit by increasing storage. Storage to IOPS mapping is below for reference.

Storage

The storage you provision is the amount of storage capacity available to your Azure Database for PostgreSQL server. The storage is used for the database files, temporary files, transaction logs, and the PostgreSQL server logs. The total amount of storage you provision also defines the I/O capacity available to your server.

You can add additional storage capacity during and after the creation of the server. The Basic tier does not provide an IOPS guarantee. In the General purpose and Memory optimized pricing tiers, the IOPS scale with the provisioned storage size in a three to one ratio.

Storage percent

Sample threshold (percentage or value):

• Less than or equal to 10GB, 80 percent threshold.
• Less than or equal to 100GB, 90 percent threshold.
• Everything else, 95 percent threshold.

Things to check:

• If your server is reaching provisioned storage limits, it will soon be out of space and set to read-only.
• Monitor your usage and you can also provision for more storage to continue using the server without deleting any files, logs, and more.

If you have tried everything and none of the monitoring tips mentioned above lead you to a resolution, please don't hesitate to contact Microsoft Azure Support for assistance.

Acknowledgments

Special thanks to Anandsagar Kothapalli, Bassu Hiremath, Kalyan Sayyaparaju, Parikshit Savjani, and Praveen Barli for their contributions to this posting.