Failover and Upgrade
Failover procedures
Planned failover: During a failure or planned failover, the client must reconnect to the database. A planned failover is signaled to the client by the closing of the TCP connection on the server. The client must also close the connection and reconnect.
In the event of a failure, the connection might not be closed correctly. The new leader will send a gratuitous ARP packet to update the MAC address in the client's ARP table. Open TCP connections will be reset once the client sends a TCP packet. We recommend re-establishing a connection to the database by using an exponential back-off retry with an initial immediate retry.
Uncontrolled disconnection: Since we do not allow read connections to standby nodes, only primary disconnections are possible. However, uncontrolled disconnections can happen during maintenance windows, a cluster change, and during unexpected situations such as loss of storage disk space. Such disconnections are destructive for the ongoing transactions and also clients should reconnect.
If a node is disconnected from the cluster, then a new node will be created and provisioned. Losing a primary node leads to the same situation when a client should reconnect. Losing a replica is not noticeable to the customer.
PostgreSQL upgrades
IONOS Cloud updates and patches your database cluster to achieve high standards of functionality and security. This includes minor patches for PostgreSQL, as well as patches for the underlying OS. We try to make these updates unnoticeable to your operation. However, occasionally, we might have to restart your PostgreSQL instance to allow the changes to take effect. These interruptions will only occur during the maintenance window for your database, which is a weekly four-hour window.
When your cluster only contains one replica you might experience a short down-time during this maintenance window, while your database instance is being updated. In a replicated cluster, we only update standbys, but we might perform a switchover in order to change the leader node.
Considerations: Updates to a new minor version are always backward compatible. Such updates are done during the maintenance window with no additional actions from the user side.
Major Version Upgrades
Caution: Major changes of the PostgreSQL version are irreversible and can fail. You should read the official migration guide and test major version upgrades with an appropriate development cluster first.
Prerequisites:
Read the migration guide from Postgres (e.g. to version 13) and make sure your database cluster can be upgraded
Test the upgrade on development cluster with similar / the same data (you can create a new database cluster as a clone of your existing cluster)
Prepare for a downtime during the major version upgrade
Ensure the database cluster has enough available storage. While the upgrade is space-efficient (i.e. it does not copy the data directory), some temporary data is written to disk.
Before upgrading PostgreSQL major versions, customers should be aware that IONOS Cloud is not responsible for customer data or any utilized postgreSQL functionality. Hence, it is the responsibility of the customer to ensure that the migration to a new PostgreSQL major version does not impact their operations.
As per PostgreSQL official documentation: "New major versions also typically introduce some user-visible incompatibilities, so application programming changes might be required."
Supported Versions
Starting with version 10, PostgreSQL moved to a yearly release schedule, where each major version is supported for 5 years after initial release. You can find more details at https://www.postgresql.org/support/versioning/. We strive to support new versions as soon as possible.
When a major version approaches its end of life (EOL), we will announce the deprecation and removal of the version at least 3 months in advance. About 1 month before the EOL, no new database can be created with the deprecated version (the exact date will be part of the first announcement). When the EOL is reached, not yet upgraded databases will be upgraded in their next maintenance window.
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