Engine versions and upgrading
ElastiCache (Redis OSS) versions are identified with a semantic version which comprise a MAJOR and MINOR component. For example, in Redis OSS 6.2, the major version is 6, and the minor version 2. When operating self-designed clusters, ElastiCache (Redis OSS) also exposes the PATCH component, e.g. Redis OSS 6.2.1, and the patch version is 1.
MAJOR versions are for API incompatible changes and MINOR versions are for new functionality added in a backwards-compatible way. PATCH versions are for backwards-compatible bug fixes and non-functional changes.
Version management for ElastiCache Serverless
ElastiCache Serverless automatically applies the latest MINOR and PATCH software version to your cache, without any impact or downtime to your application. No action is required on your end.
When a new MAJOR version is available, ElastiCache Serverless will send you a notification in the console and an event in EventBridge. You can choose to upgrade your cache to the latest major version by modifying your cache using the Console, CLI, or API and selecting the latest engine version.
Version management for self-designed ElastiCache clusters
When working with self-designed ElastiCache clusters, you can control when the software powering your cache cluster is upgraded to new versions that are supported by ElastiCache . You can control when to upgrade your cache to the latest available MAJOR, MINOR, and PATCH versions. You initiate engine version upgrades to your cluster or replication group by modifying it and specifying a new engine version.
You can control if and when the protocol-compliant software powering your cache cluster is upgraded to new versions that are supported by ElastiCache. This level of control enables you to maintain compatibility with specific versions, test new versions with your application before deploying in production, and perform version upgrades on your own terms and timelines.
Because version upgrades might involve some compatibility risk, they don't occur automatically. You must initiate them.
You initiate engine version upgrades to your cluster or replication group by modifying it and specifying a new engine version. For more information, see the following:
Upgrade considerations when working with self-designed clusters
Note
The following considerations only apply when upgrading self-designed clusters. They do not apply to ElastiCache Serverless.
When upgrading a self-designed cluster, consider the follwing
Engine version management is designed so that you can have as much control as possible over how patching occurs. However, ElastiCache reserves the right to patch your cluster on your behalf in the unlikely event of a critical security vulnerability in the system or cache software.
Beginning with Redis OSS 6.0, ElastiCache (Redis OSS) will offer a single version for each Redis OSS minor release, rather than offering multiple patch versions.
Starting with Redis OSS engine version 5.0.6, you can upgrade your cluster version with minimal downtime. The cluster is available for reads during the entire upgrade and is available for writes for most of the upgrade duration, except during the failover operation which lasts a few seconds.
You can also upgrade your ElastiCache clusters with versions earlier than 5.0.6. The process involved is the same but may incur longer failover time during DNS propagation (30s-1m).
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Beginning with Redis OSS 7, ElastiCache (Redis OSS) supports switching between Redis OSS (cluster mode disabled) and Redis OSS (cluster mode enabled).
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The Amazon ElastiCache (Redis OSS) engine upgrade process is designed to make a best effort to retain your existing data and requires successful Redis OSS replication.
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When upgrading the engine, ElastiCache (Redis OSS) will terminate existing client connections. To minimize downtime during engine upgrades, we recommend you implement best practices for Redis OSS clients with error retries and exponential backoff and the best practices for minimizing downtime during maintenance.
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You can't upgrade directly from Redis OSS (cluster mode disabled) to Redis OSS (cluster mode enabled) when you upgrade your engine. The following procedure shows you how to upgrade from Redis OSS (cluster mode disabled) to Redis OSS (cluster mode enabled).
To upgrade from a Redis OSS (cluster mode disabled) to Redis OSS (cluster mode enabled) engine version
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Make a backup of your Redis OSS (cluster mode disabled) cluster or replication group. For more information, see Taking manual backups.
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Use the backup to create and seed a Redis OSS (cluster mode enabled) cluster with one shard (node group). Specify the new engine version and enable cluster mode when creating the cluster or replication group. For more information, see Seeding a new self-designed cluster with an externally created backup.
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Delete the old Redis OSS (cluster mode disabled) cluster or replication group. For more information, see Deleting a cluster or Deleting a replication group.
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Scale the new Redis OSS (cluster mode enabled) cluster or replication group to the number of shards (node groups) that you need. For more information, see Scaling clusters in Redis OSS (Cluster Mode Enabled)
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When upgrading major engine versions, for example from 5.0.6 to 6.0, you need to also choose a new parameter group that is compatible with the new engine version.
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For single Redis OSS clusters and clusters with Multi-AZ disabled, we recommend that sufficient memory be made available to Redis OSS as described in Ensuring that you have enough memory to create a Redis OSS snapshot. In these cases, the primary is unavailable to service requests during the upgrade process.
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For Redis OSS clusters with Multi-AZ enabled, we also recommend that you schedule engine upgrades during periods of low incoming write traffic. When upgrading to Redis OSS 5.0.6 or above, the primary cluster continues to be available to service requests during the upgrade process.
Clusters and replication groups with multiple shards are processed and patched as follows:
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All shards are processed in parallel. Only one upgrade operation is performed on a shard at any time.
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In each shard, all replicas are processed before the primary is processed. If there are fewer replicas in a shard, the primary in that shard might be processed before the replicas in other shards are finished processing.
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Across all the shards, primary nodes are processed in series. Only one primary node is upgraded at a time.
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If encryption is enabled on your current cluster or replication group, you cannot upgrade to an engine version that does not support encryption, such as from 3.2.6 to 3.2.10.
How to upgrade engine versions
You initiate version upgrades to your cluster or replication group by modifying it using the ElastiCache console, the Amazon CLI, or the ElastiCache API and specifying a newer engine version. For more information, see the following topics.
| How to modify clusters and replication groups | |
|---|---|
| Clusters | Replication groups |
| Using the Amazon Web Services Management Console | Using the Amazon Web Services Management Console |
| Using the Amazon CLI | Using the Amazon CLI |
| Using the ElastiCache API | Using the ElastiCache API |
Resolving blocked Redis OSS engine upgrades
As shown in the following table, your Redis OSS engine upgrade operation is blocked if you have a pending scale up operation.
| Pending operations | Blocked operations |
|---|---|
| Scale up | Immediate engine upgrade |
| Engine upgrade | Immediate scale up |
| Scale up and engine upgrade | Immediate scale up |
| Immediate engine upgrade |
To resolve a blocked Redis OSS engine upgrade
Do one of the following:
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Schedule your Redis OSS engine upgrade operation for the next maintenance window by clearing the Apply immediately check box.
With the CLI, use
--no-apply-immediately. With the API, useApplyImmediately=false. -
Wait until your next maintenance window (or after) to perform your Redis OSS engine upgrade operation.
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Add the Redis OSS scale up operation to this cluster modification with the Apply Immediately check box chosen.
With the CLI, use
--apply-immediately. With the API, useApplyImmediately=true.This approach effectively cancels the engine upgrade during the next maintenance window by performing it immediately.
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