<#import "/templates/guide.adoc" as tmpl>
<#import "/templates/kc.adoc" as kc>
<#import "/templates/options.adoc" as opts>

<@tmpl.guide
title="Configuring distributed caches"
summary="Understand how to configure the caching layer"
includedOptions="cache cache-*">

Keycloak is designed for high availability and multi-node clustered setups.
The current distributed cache implementation is built on top of https://infinispan.org[Infinispan], a high-performance, distributable in-memory data grid.

All available cache options are build options, so they need to be applied to a `build` of Keycloak before starting.

== Enable distributed caching
When you start Keycloak in production mode, by using the `start` command, caching is enabled and all Keycloak nodes in your network are discovered.

To explicitly enable distributed infinispan caching, enter this command:

<@kc.build parameters="--cache=ispn"/>

When you start Keycloak in development mode, by using the `start-dev` command, Keycloak uses only local caches, applying the `--cache=local` option.
The `local` cache mode is intended only for development and testing purposes.

== Configuring caches
Keycloak provides a cache configuration file with sensible defaults located at `conf/cache-ispn.xml`.

The cache configuration is a regular https://infinispan.org/docs/stable/titles/configuring/configuring.html[Infinispan configuration file].

=== Cache types and defaults

.Local caches
Keycloak caches persistent data locally to avoid unnecessary database requests.
The following caches are used:

* realms
* users
* authorization
* keys

.Invalidation of local caches
Local caching improves performance, but adds a challenge in multi-node setups.
When one Keycloak node updates data in the shared database, all other nodes need to be aware of it, so they invalidate that data from their caches.
The `work` cache is used for sending these invalidation messages.

.Authentication sessions
Authentication sessions are started when an unauthenticated user or service tries to log in to Keycloak.
The `authenticationSessions` distributed cache is used to save data during authentication of a particular user.

.User sessions
The following are the distributed caches for sessions of authenticated users and services:

* sessions
* clientSessions
* offlineSessions
* offlineClientSessions

These caches are used to save data about user sessions and clients attached to the sessions.

.Password brute force detection
The `loginFailures` distributed cache is used to track data about failed login attempts.
This cache is needed for the Brute Force Protection feature to work in a multi-node Keycloak setup.

.Action tokens
Action tokens are used for scenarios when a user needs to confirm an action asynchronously, for example in the emails sent by the forgot password flow.
The `actionTokens` distributed cache is used to track metadata about action tokens.

The following table gives an overview of the specific caches Keycloak uses.
You configure these caches in `conf/cache-ispn.xml`:

|====
|Cache name|Cache Type|Description
|realms|Local|Cache persisted realm data
|users|Local|Cache persisted user data
|authorization|Local|Cache persisted authorization data
|keys|Local|Cache external public keys
|work|Replicated|Propagate invalidation messages across nodes
|sessions|Distributed|Caches user sessions, when user is authenticated
|authenticationSessions|Distributed|Caches authentication sessions, when user is authenticating
|offlineSessions|Distributed|Caches offline sessions
|clientSessions|Distributed|Caches sessions for each client a user is authenticated with
|offlineClientSessions|Distributed|Caches offline client sessions
|loginFailures|Distributed|keep track of failed logins, fraud detection
|actionTokens|Distributed|Caches action Tokens
|====

Local caches for realms, users, and authorization are configured to have 10,000 entries per default.
The local key cache can hold up to 1,000 entries per default and defaults to expire every one hour.
Therefore, keys are forced to be periodically downloaded from external clients or identity providers.

Each distributed cache has two owners per default, which means that two nodes have a copy of the specific cache entries.
Non-owner nodes query the owners of a specific cache to obtain data.
When both owner nodes are offline, all data is lost.
This situation usually leads to users being logged out at the next request and having to log in again.

=== Specify your own cache configuration file

To specify your own cache configuration file, enter this command:

<@kc.build parameters="--cache-config-file=my-cache-file.xml"/>

== Transport stacks
Transport stacks ensure that distributed cache nodes in a cluster communicate in a reliable fashion.
Keycloak supports a wide range of transport stacks:

<@opts.expectedValues option="cache-stack"/>

To apply a specific cache stack, enter this command:

<@kc.build parameters="--cache-stack=<stack>"/>

The default stack is set to `UDP` when distributed caches are enabled.

=== Available transport stacks
The following table shows transport stacks that are available without any further configuration than using the `--cache-stack` build option:
|===
|Stack name|Transport protocol|Discovery
|tcp|TCP|MPING (uses UDP multicast).
|udp|UDP|UDP multicast
|===

The following table shows transport stacks that are available using the `--cache-stack` build option and a minimum configuration:
|===
|Stack name|Transport protocol|Discovery
|kubernetes|TCP|DNS_PING (requires `-Djgroups.dns.query=<headless-service-FQDN>` to be added to JAVA_OPTS or JAVA_OPTS_APPEND environment variable).
|===

=== Additional transport stacks
The following table shows transport stacks that are supported by Keycloak, but need some extra steps to work.
Note that _none_  of these stacks are Kubernetes / OpenShift stacks, so no need exists to enable the "google" stack if you want to run Keycloak on top of the Google Kubernetes engine.
In that case, use the `kubernetes` stack.
Instead, when you have a distributed cache setup running on AWS EC2 instances, you would need to set the stack to `ec2`, because ec2 does not support a default discovery mechanism such as `UDP`.

|===
|Stack name|Transport protocol|Discovery
|ec2|TCP|NATIVE_S3_PING
|google|TCP|GOOGLE_PING2
|azure|TCP|AZURE_PING
|===

Cloud vendor specific stacks have additional dependencies for Keycloak.
For more information and links to repositories with these dependencies, see the https://infinispan.org/docs/dev/titles/embedding/embedding.html#jgroups-cloud-discovery-protocols_cluster-transport[Infinispan documentation].

To provide the dependencies to Keycloak, put the respective JAR in the `providers` directory and `build` Keycloak by entering this command:

<@kc.build parameters="--cache-stack=<ec2|google|azure>"/>

=== Securing cache communication
The current Infinispan cache implementation should be secured by various security measures such as RBAC, ACLs, and Transport stack encryption. For more information about securing cache communication, see the https://infinispan.org/docs/dev/titles/security/security.html#[Infinispan security guide].

</@tmpl.guide>
