Monitoring and logs in Managed Service for PostgreSQL

• Where can I track my use of disk space to avoid exceeding the 95% read-only limit?

• Are logs stored on the same disk as PostgreSQL data? How are they charged?

• What are WALs and what are they used for?

• What does the Cached parameter mean for PostgreSQL cluster host RAM monitoring?

• How do I get alerts on critical PostgreSQL cluster parameters?

• How do I set up an alert that triggers as soon as a certain percentage of disk space has been used up?

Where can I track my use of disk space to avoid exceeding the 95% read-only limit?Where can I track my use of disk space to avoid exceeding the 95% read-only limit?

You can track your disk space:

• In the management console using cluster status monitoring tools.
• In Yandex Monitoring that allows you to set up alerts for specified metrics.

Are logs stored on the same disk as PostgreSQL data? How are they charged?Are logs stored on the same disk as PostgreSQL data? How are they charged?

Logs are stored on different disks than data and rotated automatically. You can view log information using the CLI command below:

yc managed-postgresql cluster list-logs <cluster_ID>

Cluster log storage is free of charge.

What is the retention period for logs?What is the retention period for logs?

Cluster logs are stored for 30 days.

What are WALs and what are they used for?What are WALs and what are they used for?

Write-Ahead Logs are used for writing data to the disk and for data replication. They are created with write requests and take up disk space until log data is written out to host disks to ensure DBMS reliability and fault tolerance.

For more information about PostgreSQL, see the official documentation.

What does the Cached parameter mean for PostgreSQL cluster host RAM monitoring?What does the Cached parameter mean for PostgreSQL cluster host RAM monitoring?

Cached stores cached data. Most operations are performed in random-access memory, since this is where all database information is stored. Caching is applied both to databases and to disks, which may cause the amount of cached data to exceed the storage size.

If the amount of RAM used by applications increases, some of the cache memory may be released.

For more information about caching disk data in Linux, see the documentation.

How do I get alerts on critical PostgreSQL cluster parameters?How do I get alerts on critical PostgreSQL cluster parameters?

Use Yandex Monitoring and set up alerts for the parameters critical for you.

How do I set up an alert that triggers as soon as a certain percentage of disk space has been used up?How do I set up an alert that triggers as soon as a certain percentage of disk space has been used up?

Create an alert with the disk.used_bytes metric in Yandex Monitoring. This metric shows the disk space usage in the Managed Service for PostgreSQL cluster.

For disk.used_bytes, use notification thresholds. The recommended values are as follows:

• Alarm: 90% of the disk space
• Warning: 80% of the disk space

Thresholds are set in bytes only. For example, the recommended values for a 100 GB disk are as follows:

• Alarm: 96636764160 bytes (90%)
• Warning: 85899345920 bytes (80%)