bin/kc.[sh|bat] start --cache=ispnKeycloak is designed for high availability and multi-node clustered setups. The current distributed cache implementation is built on top of Infinispan, a high-performance, distributable in-memory data grid.
When you start Keycloak in production mode, by using the start command, caching is enabled and all Keycloak nodes in your network are discovered.
By default, caches are using a UDP transport stack so that nodes are discovered using IP multicast transport based on UDP. For most production environments, there are better discovery alternatives to UDP available. Keycloak allows you to either choose from a set of pre-defined default transport stacks, or to define your own custom stack, as you will see later in this guide.
To explicitly enable distributed infinispan caching, enter this command:
bin/kc.[sh|bat] start --cache=ispnWhen you start Keycloak in development mode, by using the start-dev command, Keycloak uses only local caches and distributed caches are completely disabled by implicitly setting the --cache=local option.
The local cache mode is intended only for development and testing purposes.
Keycloak provides a cache configuration file with sensible defaults located at conf/cache-ispn.xml.
The cache configuration is a regular Infinispan configuration file.
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 |
authenticationSessions |
Distributed |
Caches authentication sessions, created/destroyed/expired during the authentication process |
sessions |
Distributed |
Cache persisted user session data |
clientSessions |
Distributed |
Cache persisted client session data |
offlineSessions |
Distributed |
Cache persisted offline user session data |
offlineClientSessions |
Distributed |
Cache persisted offline client session data |
loginFailures |
Distributed |
keep track of failed logins, fraud detection |
actionTokens |
Distributed |
Caches action Tokens |
Keycloak caches persistent data locally to avoid unnecessary round-trips to the database.
The following data is kept local to each node in the cluster using local caches:
realms and related data like clients, roles, and groups.
users and related data like granted roles and group memberships.
authorization and related data like resources, permissions, and policies.
keys
Local caches for realms, users, and authorization are configured to hold up to 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.
In order to achieve an optimal runtime and avoid additional round-trips to the database you should consider looking at the configuration for each cache to make sure the maximum number of entries is aligned with the size of your database. More entries you can cache, less often the server needs to fetch data from the database. You should evaluate the trade-offs between memory utilization and performance.
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 a replicated cache and used for sending these invalidation messages. The entries/messages in this cache are very short-lived,
and you should not expect this cache growing in size over time.
Authentication sessions are created whenever a user tries to authenticate. They are automatically destroyed once the authentication process completes or due to reaching their expiration time.
The authenticationSessions distributed cache is used to store authentication sessions and any other data associated with it
during the authentication process.
By relying on a distributable cache, authentication sessions are available to any node in the cluster so that users can be redirected to any node without losing their authentication state. However, production-ready deployments should always consider session affinity and favor redirecting users to the node where their sessions were initially created. By doing that, you are going to avoid unnecessary state transfer between nodes and improve CPU, memory, and network utilization.
Once the user is authenticated, a user session is created. The user session tracks your active users and their state so that they can seamlessly authenticate to any application without being asked for their credentials again. For each application, the user authenticates with a client session, so that the server can track the applications the user is authenticated with and their state on a per-application basis.
User and client sessions are automatically destroyed whenever the user performs a logout, the client performs a token revocation, or due to reaching their expiration time.
The session data are stored in the database by default and loaded on-demand to the following caches:
sessions
clientSessions
By relying on a distributable cache, cached user and client sessions are available to any node in the cluster so that users can be redirected to any node without the need to load session data from the database. However, production-ready deployments should always consider session affinity and favor redirecting users to the node where their sessions were initially created. By doing that, you are going to avoid unnecessary state transfer between nodes and improve CPU, memory, and network utilization.
These in-memory caches for user sessions and client sessions are limited to, by default, 10000 entries per node which reduces the overall memory usage of Keycloak for larger installations.
The internal caches will run with only a single owner for each cache entry.
Consider trade-off between memory consumption and the database utilization and set different sizes for the caches, edit Keycloak’s cache config file (conf/cache-ispn.xml) to set a <memory max-count="..."/> for those caches.
By default, user sessions are stored in the database and loaded on-demand to the cache. It is possible to configure Keycloak to store user sessions in the cache only and minimize the database utilization.
Since all the sessions in this setup are stored in-memory, there are two side effects related to this:
Losing sessions on when all Keycloak nodes restart.
Increased memory consumption.
Follow these steps to enable this setup:
Since the cache is the only source of truth for user and client sessions, configure caches to not limit the number of entries and to replicate each entry to at least two nodes. To do so, edit Keycloak’s cache config file (conf/cache-ispn.xml) for caches sessions and clientSessions with the following update:
Remove the <memory max-count="..."/>
Change owners attribute of the distributed-cache tag to 2 or more
An example of the resulting configuration for the sessions cache would look as follows.
<distributed-cache name="sessions" owners="2">
<expiration lifespan="-1"/>
</distributed-cache>Disable persistent-user-sessions feature using the following command:
bin/kc.sh start --features-disabled=persistent-user-sessions ...
|
Disabling |
As an OpenID Connect Provider, the server is also capable of authenticating users and issuing offline tokens. Similarly to regular user and client sessions, when an offline token is issued by the server upon successful authentication, the server also creates an offline user session and an offline client session.
The following caches are used to store offline sessions:
offlineSessions
offlineClientSessions
Similarly to regular user and client sessions caches, also the offline user and client session caches are limited to 10000 entries per node by default. Items which are evicted from the memory will be loaded on-demand from the database when needed.
Consider trade-off between memory consumption and the database utilization and set different sizes for the caches, edit Keycloak’s cache config file (conf/cache-ispn.xml) to set a <memory max-count="..."/> for those caches.
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 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.
In order to reduce memory usage, it’s possible to place an upper bound on the number of entries which are stored in a given
cache. To specify an upper bound of on a cache, you must provide the following command line argument
--cache-embedded-${CACHE_NAME}-max-count=, with ${CACHE_NAME} replaced with the name of the cache you would like to
apply the upper bound to. For example, to apply an upper-bound of 1000 to the offlineSessions cache you would configure
--cache-embedded-offline-sessions-max-count=1000. An upper bound can not be defined on the following caches:
actionToken, authenticationSessions, loginFailures, work.
Distributed caches replicate cache entries on a subset of nodes in a cluster and assigns entries to fixed owner nodes.
Each distributed cache, that is a primary source of truth of the data (authenticationSessions, loginFailures and actionTokens) 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.
The default number of owners is enough to survive 1 node (owner) failure in a cluster setup with at least three nodes. You are free
to change the number of owners accordingly to better fit into your availability requirements. To change the number of owners, open conf/cache-ispn.xml and change the value for owners=<value> for the distributed caches to your desired value.
To specify your own cache configuration file, enter this command:
bin/kc.[sh|bat] start --cache-config-file=my-cache-file.xmlThe configuration file is relative to the conf/ directory.
For configuration of Keycloak server for high availability and multi-node clustered setup there was introduced following CLI options cache-remote-host, cache-remote-port, cache-remote-username and cache-remote-password simplifying configuration within the XML file.
Once any of declared CLI parameters are present, it is expected there is no configuration related to remote store present in the XML file.
| Disabling security is not recommended in production! |
In a development or test environment, it is easier to start an unsecured Infinispan server.
For these use case, the CLI options cache-remote-tls-enabled disables the encryption (TLS) between Keycloak and Infinispan.
Keycloak will fail to start if the Infinispan server is configured to accept only encrypted connections.
The CLI options cache-remote-username and cache-remote-password are optional and, if not set, Keycloak will connect to the Infinispan server without presenting any credentials.
If the Infinispan server has authentication enabled, Keycloak will fail to start.
Transport stacks ensure that distributed cache nodes in a cluster communicate in a reliable fashion. Keycloak supports a wide range of transport stacks:
tcp
udp
kubernetes
ec2
azure
To apply a specific cache stack, enter this command:
bin/kc.[sh|bat] start --cache-stack=<stack>The default stack is set to udp when distributed caches are enabled.
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 runtime option and a minimum configuration:
| Stack name | Transport protocol | Discovery |
|---|---|---|
kubernetes |
TCP |
DNS_PING (requires |
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 |
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 Infinispan documentation.
To provide the dependencies to Keycloak, put the respective JAR in the providers directory and build Keycloak by entering this command:
bin/kc.[sh|bat] start --cache-stack=<ec2|google|azure>If none of the available transport stacks are enough for your deployment, you are able to change your cache configuration file and define your own transport stack.
For more details, see Using inline JGroups stacks.
<jgroups>
<stack name="my-encrypt-udp" extends="udp">
<SSL_KEY_EXCHANGE keystore_name="server.jks"
keystore_password="password"
stack.combine="INSERT_AFTER"
stack.position="VERIFY_SUSPECT2"/>
<ASYM_ENCRYPT asym_keylength="2048"
asym_algorithm="RSA"
change_key_on_coord_leave = "false"
change_key_on_leave = "false"
use_external_key_exchange = "true"
stack.combine="INSERT_BEFORE"
stack.position="pbcast.NAKACK2"/>
</stack>
</jgroups>
<cache-container name="keycloak">
<transport lock-timeout="60000" stack="my-encrypt-udp"/>
...
</cache-container>By default, the value set to the cache-stack option has precedence over the transport stack you define in the cache configuration file.
If you are defining a custom stack, make sure the cache-stack option is not used for the custom changes to take effect.
The current Infinispan cache implementation should be secured by various security measures such as RBAC, ACLs, and transport stack encryption.
JGroups handles all the communication between Keycloak server, and it supports Java SSL sockets for TCP communication. Keycloak uses CLI options to configure the TLS communication without having to create a customized JGroups stack or modifying the cache XML file.
To enable TLS, cache-embedded-mtls-enabled must be set to true.
It requires a keystore with the certificate to use: cache-embedded-mtls-key-store-file sets the path to the keystore, and cache-embedded-mtls-key-store-password sets the password to decrypt it.
The truststore contains the valid certificates to accept connection from, and it can be configured with cache-embedded-mtls-trust-store-file (path to the truststore), and cache-embedded-mtls-trust-store-password (password to decrypt it).
To restrict unauthorized access, use a self-signed certificate for each Keycloak deployment.
For JGroups stacks with UDP or TCP_NIO2, see the JGroups Encryption documentation on how to set up the protocol stack.
For more information about securing cache communication, see the Infinispan security guide.
Metrics from caches are automatically exposed when the metrics are enabled.
To enable histograms for the cache metrics, set cache-metrics-histograms-enabled to true.
While these metrics provide more insights into the latency distribution, collecting them might have a performance impact, so you should be cautious to activate them in an already saturated system.
bin/kc.[sh|bat] start --metrics-enabled=true --cache-metrics-histograms-enabled=trueFor more details about how to enable metrics, see Enabling Keycloak Metrics.
| Value | |
|---|---|
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Available only when embedded Infinispan clusters configured |
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Available only when embedded Infinispan clusters configured |
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Available only when embedded Infinispan clusters configured |
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Available only when embedded Infinispan clusters configured |
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Available only when metrics are enabled |
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Available only when remote host is set |
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Available only when remote host is set |
(default) |
Available only when remote host is set |
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Available only when remote host is set |
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