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FAQ about Managed Service for PostgreSQL

Written by
Updated at December 24, 2024

General questions

Connection

Updating a cluster

Cluster configuration

Moving and restoring a cluster

Monitoring and logs

General questions

What is Managed Service for PostgreSQL?

Managed Service for PostgreSQL is a service that helps you create, operate, and scale PostgreSQL databases in a cloud infrastructure.

With Managed Service for PostgreSQL, you can:

  • Create a database with the required performance characteristics.
  • Scale processing power and storage dedicated for your databases as needed.
  • Get database logs.

Managed Service for PostgreSQL takes on time-consuming PostgreSQL infrastructure administration tasks:

  • Monitors resource usage.
  • Automatically creates DB backups.
  • Provides fault tolerance through automatic failover to backup replicas.
  • Keeps database software updated.

You interact with database clusters in Managed Service for PostgreSQL the same way you interact with regular databases in your local infrastructure. This allows you to manage internal database settings to meet your app requirements.

What part of database management and maintenance is Managed Service for PostgreSQL responsible for?

When you create clusters, Managed Service for PostgreSQL allocates resources, installs the DBMS, and creates databases.

For the created and running databases, Managed Service for PostgreSQL automatically creates backups and applies fixes and updates to the DBMS.

Managed Service for PostgreSQL also allows you to replicate data between database hosts (both within and across availability zones) and automatically routes the load to a backup replica in the event of a failure.

Which tasks are best addressed using Managed Service for PostgreSQL, and which using VMs with databases?

Yandex Cloud offers two ways to work with databases:

  • Managed Service for PostgreSQL allows you to operate template databases with no need to worry about administration.
  • Yandex Compute Cloud virtual machines allow you to create and configure your own databases. This approach allows you to use any database management systems, access databases via SSH, etc.

What is a database host and database cluster?

A database host is an isolated database environment in the cloud infrastructure with dedicated computing resources and reserved data storage.

A database cluster is one or more database hosts between which you can configure replication.

How do I get started with Managed Service for PostgreSQL?

Managed Service for PostgreSQL is available to any registered Yandex Cloud user.

To create a database cluster in Managed Service for PostgreSQL, you need to define its parameters:

  • Host class (performance characteristics, such as CPUs, RAM, etc.).
  • Storage size (reserved to the full extent when you create a cluster).
  • Network your cluster will be connected to.
  • Number of hosts for the cluster and the availability zone for each host.

For detailed instructions, see Getting started with Managed Service for PostgreSQL.

How many database hosts can there be in one cluster?

The minimum number of hosts depends on the selected type of storage:

  • A minimum of three hosts for these disks:

    • Local SSDs (local-ssd)
    • Non-replicated SSDs (network-ssd-nonreplicated)

  • A minimum of one host for these disks:

    • Network HDDs (network-hdd)
    • Network SSDs (network-ssd) * Ultra high-speed network SSDs with three replicas (network-ssd-io-m3)

The maximum number of hosts per cluster is subject to the limits in place.

For more information, see Quotas and limits in Managed Service for PostgreSQL.

How can I access a running DB host?

You can connect to Managed Service for PostgreSQL databases using standard DBMS methods.

Learn more about connecting to clusters.

How many clusters can I create within a single cloud?

MDB technical and organizational limits are given in Quotas and limits in Managed Service for PostgreSQL.

How are DB clusters maintained?

In Managed Service for PostgreSQL, maintenance implies:

  • Automatic installation of DBMS updates and revisions for DB hosts (including disabled clusters).
  • Changes to the host class and storage size.
  • Other Managed Service for PostgreSQL maintenance activities.

For more information, see Maintenance in Managed Service for PostgreSQL.

Which PostgreSQL version does Managed Service for PostgreSQL use?

Managed Service for PostgreSQL supports PostgreSQL 13, 14, 15, 16, and 17, as well as PostgreSQL 13, 14, 15, and 16 for 1C.

What happens when a new DBMS version is released?

The database software is updated when new minor versions are released. Owners of the affected DB clusters are notified of expected work times and DB availability in advance.

What happens when a DBMS version becomes deprecated?

One month after the database version becomes deprecated, Managed Service for PostgreSQL automatically sends email notifications to the owners of DB clusters created with this version.

New hosts can no longer be created using deprecated DBMS versions. Database clusters are automatically upgraded to the next supported version seven days after notification for minor versions and one month after notification for major versions. Deprecated major versions are going to be upgraded even if you have disabled automatic updates.

How do you calculate usage cost for a database host?

In Managed Service for PostgreSQL, the usage cost is calculated based on the following parameters:

  • Selected host class.
  • Size of the storage reserved for the database host.
  • Size of the database cluster backups. Backup size equal to the storage size is free of charge. Backup storage that exceeds this size is charged at special rates.
  • Number of hours of database host operation. Partial hours are rounded to an integer value. To find out the cost per hour of operation for each host class, see Managed Service for PostgreSQL pricing policy.

How can I change the computing resources and storage size for a database cluster?

You can change computing resources and storage size in the management console. All you need to do is choose a different host class for the required cluster.

The cluster characteristics change within 30 minutes. During this period, other maintenance activities may also be enabled for the cluster, such as installing updates.

Can I configure auto increase of cluster storage size?

Yes, you can set up automatic increase of the storage size when creating or updating a cluster.

Is database host backup enabled by default?

Yes, backup is enabled by default. For PostgreSQL, a full backup takes place once a day and saves all DB cluster transaction logs. This allows you to restore the cluster state to any point in time during the backup storage period, except for the last 30 seconds.

By default, backups are stored for seven days.

When are backups performed? Is a database cluster available during backup?

The backup window is an interval during which a full daily backup of the DB cluster is performed. The backup window is from 01:00 to 05:00 (UTC+3).

Clusters remain fully accessible during the backup window.

Are PostgreSQL DB cluster connections encrypted?

Connections between a database cluster and an application are always encrypted using SSL. You cannot disable cluster connection encryption.

What is a read-only replica in PostgreSQL?

A read-only replica is a PostgreSQL DB cluster host available only for reads. Its data is synced with the master host (applies only if the cluster has more than 1 host). You can use a read-only replica to reduce the load on the DB master host with a large number of read requests.

What metrics and processes can be tracked using monitoring?

For all DBMS types, you can track:

  • CPU, memory, network, or disk usage, in absolute terms.
  • Amount of data in the DB cluster and the remaining free space in the data storage.

For DB hosts, you can track metrics specific to the corresponding type of DBMS. For example, for PostgreSQL, you can track:

  • Average query execution time.
  • Number of queries per second.
  • Number of errors in logs, etc.

Monitoring can be performed with a minimum granularity of 5 seconds.

Can I get logs of my operations with services?

Yes, you can request log records about your resources from Yandex Cloud services. For more information, see Data requests.

What limitations are imposed on PostgreSQL database clusters?

For more information about Managed Service for PostgreSQL limitations, see Quotas and limits in Managed Service for PostgreSQL. Characteristics of clusters that can be created using Managed Service for PostgreSQL are given in PostgreSQL host classes.

What PostgreSQL extensions are supported in Managed Service for PostgreSQL?

The list of supported PostgreSQL extensions is provided in Managing extensions.

Which data center stores PostgreSQL cluster backups?

Cluster backups are stored and available in all three data centers.

Does the service meet the requirements under Russian Federation Federal Law No. 152-FZ on Personal Data?

Yes, it does. You can read the full security audit conclusion.

Can I get superuser privileges in PostgreSQL?

Yes, you can. To do this, assign the mdb_superuser role to the user.

Can I copy data from a Managed Service for PostgreSQL table to a local file? Can I populate a table with data from a local file?

Yes, you can both copy data from a table to a local file and populate a table with data from a local file. For more information, see Copying and populating a table from a local machine.

Are there any special aspects or restrictions on the use of a garbage collector in Managed Service for PostgreSQL clusters?

Managed Service for PostgreSQL clusters support all parameters of the VACUUM command. However, you should consider the following specifics when using them:

  • To run VACUUM FULL, the user must have the mdb_admin role. The VACUUM FULL command does not affect system views.
  • In PostgreSQL version 14, the INDEX_CLEANUP parameter functionality has been enhanced: it now has the AUTO value by default. This means the VACUUM command skips index cleaning if it considers it unnecessary. To ensure backward compatibility with the previous PostgreSQL versions, set INDEX_CLEANUP to ON.

Why is the cluster slow even though the computing resources are not used fully?

Perhaps, the maximum storage IOPS and bandwidth values are insufficient for processing the current number of requests. In this case, throttling is triggered and the performance of the entire cluster degrades.

The maximum IOPS and bandwidth values increase by a fixed value when the storage size increases by a certain step. The step and increment values depend on the disk type:

Disk type Step, GB Max IOPS increase (read/write) Max bandwidth increase (read/write), MB/s
network-hdd 256 300/300 30/30
network-ssd 32 1,000/1,000 15/15
network-ssd-nonreplicated 93 28,000/5,600 110/82

To increase the maximum IOPS and bandwidth values and make throttling less likely, increase the storage size when you update your cluster.

If you are using the network-hdd storage type, consider switching to network-ssd or network-ssd-nonreplicated by restoring the cluster from a backup.

Connection

Can I access a cluster from within Yandex Cloud?

You can connect to Managed Service for PostgreSQL cluster hosts:

  • Over the internet, if you configured public access for the appropriate host. You can only connect to such hosts over an SSL connection.
  • From Yandex Cloud virtual machines located in the same cloud network. If the host is not publicly accessible, there is no need to use SSL for connections from such virtual machines.
  • From a container in Yandex Serverless Containers. If the host is not publicly accessible, the container must be located in the same cloud network.

For more information, see the service documentation.

Can I connect to a cluster from a Docker container?

Yes, you can. To do this, configure the Dockerfile.

You can find an example of connection from a container in Yandex Serverless Containers in this tutorial.

How do I obtain an SSL certificate to connect to Managed Service for PostgreSQL on Windows?

You can obtain an SSL certificate using PowerShell:

mkdir $HOME\.postgresql; curl.exe --output $HOME\.postgresql\root.crt https://storage.yandexcloud.net/cloud-certs/CA.pem

The certificate will be saved to the $HOME\.postgresql\root.crt file.

For more information about obtaining a certificate and connecting to a database, see the service documentation.

What do I do if I get the revocation check error when using PowerShell to obtain an SSL certificate?

Here is the full text of the error:

curl: (35) schannel: next InitializeSecurityContext failed: Unknown error (0x80092012)
The revocation function was unable to check revocation for the certificate

This means, when connecting to the website, the service failed to check whether or not the website’s certificate is on the list of revoked certificates.

To fix this error:

  • Make sure the corporate network settings do not block the check.

  • Run the command with the --ssl-no-revoke parameter.

    mkdir $HOME\.postgresql; curl.exe --ssl-no-revoke -o $HOME\.postgresql\root.crt https://storage.yandexcloud.net/cloud-certs/CA.pem

How do I install an SSL certificate to connect Power BI to Managed Service for PostgreSQL via psql?

  1. Install Windows Subsystem for Linux (WSL) and run the following command in the terminal:

    mkdir /mnt/c/temp && \
curl "https://storage.yandexcloud.net/cloud-certs/CA.pem" --output /mnt/c/temp/CA.pem && \
openssl pkcs12 -export -out /mnt/c/temp/CA.pfx -nokeys -in /mnt/c/temp/CA.pem

    The certificate will be available at C:\temp\CA.pfx.

  2. Place the obtained certificate in the Windows certificate store.

What must I do if I get the SSL is required error when connecting?

The error occurs because you are trying to connect to the cluster with a public host. These hosts only support connections with an SSL certificate. You can:

Can I connect to cluster hosts over SSH?

You cannot connect to hosts via SSH. This is done for the sake of security and user cluster fault tolerance because direct changes inside a host can render it completely inoperable.

What is the maximum allowed number of concurrent connections to a single host in Managed Service for PostgreSQL?

The number of concurrent connections is specified at the cluster level in the Max connections setting. By default, the maximum value is set, which is calculated by the following formula:

200 × <number_of_vCPUs_per_host>

For information about how to update the PostgreSQL settings at the cluster level, see our documentation.

What is the allowed number of connections per user?

By default, a cluster reserves 50 connections to each host per user. You can change this number in the Conn limit setting.

If the connection limit per user is reached, any attempt to establish a new connection will fail with the following error:

too many active clients for user (pool_size for user <username> reached <limit_value>)

To learn how to update the PostgreSQL settings at the user level, see our documentation.

Why do I get an error when trying to connect to a database?

Connecting to a database may fail with an error like:

ERROR: odyssey: ce3ea075f4ffa: route for 'dbname.username' is not found

The error means that the connection parameters contain an invalid database name.

Why do I get an error when trying to connect to a database from Looker Studio?

To connect from Looker Studio, be sure to generate a client certificate file and a private key and specify them in the connection settings. For more information about how to do this, see Connecting from Looker Studio.

Why does a connection terminate with an error?

A Managed Service for PostgreSQL cluster connection may be terminated with the following message:

FATAL: terminating connection due to administrator command

This message does not indicate an error, it means that the session/transaction duration has exceeded the Session duration timeout setting value (default value: 12 hours).

Updating a cluster

Why did the cluster change its status to Updating during an unscheduled backup?

The cluster changes its status to Updating right after the backup process is launched. You cannot cancel this operation. Wait for it to complete instead.

The time this operation is performed depends on a number of factors, such as DB size, cluster configuration, and the nature of data being stored. The average speed when recovering a cluster from a backup is about 100 Mbps.

Can I create two PostgreSQL databases at the same time?

You cannot apply multiple transactions to a cluster at the same time. It is an architectural feature of the technologies utilized by Yandex Cloud.

Can I change the number of connections available to a user?

Yes, you can. To do this, change the values of the relevant settings:

  • Conn limit: Maximum number of host connections per user. The default is 50. The minimum is 10.
  • Max connections: Maximum number of connections reserved for all users. The default value is 200 × <number_of_vCPUs_per_host>. You have to keep in mind that this number includes 15 service connections: for instance, if a cluster has "max_connections": 100, you are only able to reserve at most 85 connections per cluster host for users.

Can I change an existing host's class (standard, memory-optimized, burstable)?

Yes, you can by following the procedure in Changing cluster settings.

Can I change the disk type in an existing cluster?

Yes, you can. To do this, restore the cluster from a backup and specify the desired disk type when configuring the new cluster.

Can I manage a cluster using SQL commands?

There are some restrictions for cluster management using SQL commands. For more information, see SQL command limits.

Why cannot I stop a cluster?

Error message:

ERROR: rpc error: code = FailedPrecondition desc = Cluster has no backups

A cluster that has no backups cannot be stopped. To fix the error and stop the cluster, create its backup.

Cluster configuration

Is autovacuum enabled for all tables by default?

Yes, AUTOVACUUM is enabled for all tables by default.

Autovacuuming does not run at a specific time. Instead, it runs when a certain value specified in the settings is reached, for example, when the share of updated or deleted table records becomes equal to the Autovacuum vacuum scale factor.

For more information, see the PostgreSQL documentation.

Which LC_COLLATE and LC_CTYPE values are set for databases by default?

As databases are created, LC_CTYPE=C and LC_COLLATE=C are set by default. You can't change these settings for the database you create with clusters. However, you can create a new database and set the values you need for it.

Can I change the LC_COLLATE and LC_CTYPE values?

You cannot change locale settings after you create a database. You can:

  • Create a new database with the desired settings.
  • Set a sorting locale (LC_COLLATE) for elements of an existing database:
    • When calling a function: 
      SELECT lower(t1 COLLATE "ru_RU.utf8") FROM test;
    • When creating and updating a table: 
      CREATE TABLE test (t1 text COLLATE "ru_RU.utf8");

Can I change the DB owner?

Once you create a DB, you cannot change its owner. If you create a DB via Terraform and then change its owner in the owner parameter, this will recreate the DB and its data will be lost.

Moving and restoring a cluster

Can I restore a cluster backup to a running Managed Service for PostgreSQL instance in a different cloud network?

You can only recover a cluster from a backup within a single cloud network.

To migrate data between cloud networks, follow the migration guide.

Can I change the retention period of automatic backups?

When creating or modifying a cluster, you can set the retention period for automatic backups.

Do I need the wal2json plugin if data is only replicated but not copied?

Yes, you need the plugin even if you do not copy data.

Can I make a local dump of a database backup?

You cannot use the service to make a local dump of a DB backup from Yandex Cloud but you can use the pg_dump utility.

How do I move a local PostgreSQL database dump to Yandex Cloud?

Follow the steps described in Migrating databases.

Why does a data transfer through creating and restoring a logical dump fail with an error?

Restoring a logical dump may fail with one of the following errors:

  • ERROR: role "<source_username>" does not exist
  • ERROR: must be member of role "<source_username>"

The errors occur because the target cluster does not have the user (or the privileges of the user) who created the logical dump in the source cluster.

To resolve the errors:

  1. In the target cluster, add a user with access to the migrated database and the same name as the user who created the logical dump in the source cluster.
  2. Use this user to restore the logical dump or grant their privileges to the user who is restoring the logical dump.

Monitoring and logs

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

You can track your disk space:

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?

Cluster logs are stored for 30 days.

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?

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?

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?

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%)
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