Chapter 8. Configuring distributed caches Red Hat build of Keycloak 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. 8.1. Enable distributed caching When you start Red Hat build of Keycloak in production mode, by using the start command, caching is enabled and all Red Hat build of 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. Red Hat build of 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 chapter. To explicitly enable distributed infinispan caching, enter this command: bin/kc.[sh|bat] build --cache=ispn When you start Red Hat build of Keycloak in development mode, by using the start-dev command, Red Hat build of 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. 8.2. Configuring caches Red Hat build of 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 Red Hat build of 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 Caches user sessions, created upon successful authentication and destroyed during logout, token revocation, or due to expiration clientSessions Distributed Caches client sessions, created upon successful authentication to a specific client and destroyed during logout, token revocation, or due to expiration offlineSessions Distributed Caches offline user sessions, created upon successful authentication and destroyed during logout, token revocation, or due to expiration offlineClientSessions Distributed Caches client sessions, created upon successful authentication to a specific client and destroyed during logout, token revocation, or due to expiration loginFailures Distributed keep track of failed logins, fraud detection actionTokens Distributed Caches action Tokens 8.2.1. Cache types and defaults Local caches Red Hat build of 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. Invalidation of local caches Local caching improves performance, but adds a challenge in multi-node setups. When one Red Hat build of 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 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. User sessions 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 is created too, 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 following caches are used to store both user and client sessions: sessions clientSessions By relying on a distributable cache, user and client sessions are available to any node in the cluster so that users can be redirected to any node without loosing their 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. 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 a user and client sessions. However, due to the nature of offline tokens, offline sessions are handled differently as they are long-lived and should survive a complete cluster shutdown. Because of that, they are also persisted to the database. The following caches are used to store offline sessions: offlineSessions offlineClientSessions Upon a cluster restart, offline sessions are lazily loaded from the database and kept in a shared cache using the two caches above. 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 Red Hat build of 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. 8.2.2. Configuring caches for availability Distributed caches replicate cache entries on a subset of nodes in a cluster and assigns entries to fixed owner nodes. 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 request and having to log in again. 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. 8.2.3. Specify your own cache configuration file To specify your own cache configuration file, enter this command: bin/kc.[sh|bat] build --cache-config-file=my-cache-file.xml The configuration file is relative to the conf/ directory. 8.3. Transport stacks Transport stacks ensure that distributed cache nodes in a cluster communicate in a reliable fashion. Red Hat build of Keycloak supports a wide range of transport stacks: tcp udp kubernetes ec2 azure google To apply a specific cache stack, enter this command: bin/kc.[sh|bat] build --cache-stack=<stack> The default stack is set to UDP when distributed caches are enabled. 8.3.1. 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). 8.3.2. Additional transport stacks The following table shows transport stacks that are supported by Red Hat build of 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 Red Hat build of 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 Red Hat build of Keycloak. For more information and links to repositories with these dependencies, see the Infinispan documentation . To provide the dependencies to Red Hat build of Keycloak, put the respective JAR in the providers directory and build Keycloak by entering this command: bin/kc.[sh|bat] build --cache-stack=<ec2|google|azure> 8.3.3. Custom transport stacks 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 . defining a custom transport stack 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. 8.4. 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 Infinispan security guide . 8.5. Exposing metrics from caches By default, metrics from caches are not automatically exposed when the metrics are enabled. For more details about how to enable metrics, see Enabling Red Hat build of Keycloak Metrics . To enable global metrics for all caches within the cache-container , you need to change your cache configuration file (e.g.: conf/cache-ispn.xml ) to enable statistics at the cache-container level as follows: enabling metrics for all caches Similarly, you can enable metrics individually for each cache by enabling statistics as follows: enabling metrics for a specific cache 8.6. Relevant options Value cache 🛠 Defines the cache mechanism for high-availability. By default in production mode, a ispn cache is used to create a cluster between multiple server nodes. By default in development mode, a local cache disables clustering and is intended for development and testing purposes. CLI: --cache Env: KC_CACHE ispn (default), local cache-config-file 🛠 Defines the file from which cache configuration should be loaded from. The configuration file is relative to the conf/ directory. CLI: --cache-config-file Env: KC_CACHE_CONFIG_FILE cache-stack 🛠 Define the default stack to use for cluster communication and node discovery. This option only takes effect if cache is set to ispn . Default: udp. CLI: --cache-stack Env: KC_CACHE_STACK tcp , udp , kubernetes , ec2 , azure , google

Commands:
bin/kc.[sh|bat] build --cache=ispn
bin/kc.[sh|bat] build --cache-config-file=my-cache-file.xml
bin/kc.[sh|bat] build --cache-stack=<stack>
bin/kc.[sh|bat] build --cache-stack=<ec2|google|azure>
<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>
<cache-container name="keycloak" statistics="true"> </cache-container>
<local-cache name="realms" statistics="true"> </local-cache>