Apache Tomcat - Embedded Servlet Container Clustering

Enable in-memory session replication to replicate web application session deltas.

Clustering Type	Description
`DEFAULT`	Discovers cluster members via multicast discovery and optionally via staticly defined cluster members using the `clusterMembers`. SimpleTcpCluster with McastService
`CLOUD`	For use in Kubernetes where members are discovered via accessing the Kubernetes API or doing a DNS lookup of the members of a Kubernetes service. Documentation is currently light, see code for details.

Membership Providers	Description
`kubernetes`	Uses Kubernetes API to find other pods in a deployment. API is discovered and accessed via information in environment variables set in the container. The KUBERNETES_NAMESPACE environment variable is used to query the pods in the namespace and it will treat other pods in that namespace as potential cluster members but they can be filtered using the KUBERNETES_LABELS environment variable which are used as a label selector.
`dns`	Uses DNS lookups to find addresses of the cluster members behind a DNS name specified by DNS_MEMBERSHIP_SERVICE_NAME environment variable. Works in Kubernetes but doesn’t rely on Kubernetes.
`MembershipProvider` class	Use a membership provider implementation of your choice.

Most settings apply to the DEFAULT clustering type, which requires members to be defined via clusterMembers if multicast discovery doesn’t work. The cloudMembershipProvider setting applies to the CLOUD type.

The following settings and properties are available from the CAS configuration catalog:

_{The configuration settings listed below are tagged as Required in the CAS configuration metadata. This flag indicates that the presence of the setting may be needed to activate or affect the behavior of the CAS feature and generally should be reviewed, possibly owned and adjusted. If the setting is assigned a default value, you do not need to strictly put the setting in your copy of the configuration, but should review it nonetheless to make sure it matches your deployment expectations.}

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cas.server.tomcat.clustering.enabled=false

Enable tomcat session clustering.

org.apereo.cas.configuration.model.core.web.tomcat.CasEmbeddedApacheTomcatClusteringProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

Note

When possible, properties should be stored in lower-case kebab format, such as cas.property-name=value. The only possible exception to this rule is when naming actuator endpoints; The name of the actuator endpoints (i.e. ssoSessions) MUST remain in camelCase mode.

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:


1

cas.server.tomcat.clustering.enabled=...

This is the most common form of property configuration that is recognized by CAS, regardless of the actual property source, which might in fact be managed separately outside the CAS environment, by another system or cloud framework.

CAS properties can be specified using the YAML syntax:

cas: 
  server: 
    tomcat: 
      clustering: 
        enabled: "..."

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.server.tomcat.clustering.enabled="..." -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory. Note the placement of the system property which must be specified before the CAS web application is launched.

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_SERVER_TOMCAT_CLUSTERING_ENABLED="..."

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.server.tomcat.clustering.enabled="..."

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

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_{The configuration settings listed below are tagged as Optional in the CAS configuration metadata. This
flag indicates that the presence of the setting
is not immediately necessary in the end-user CAS configuration, because a default value is assigned or
the activation of the feature is not conditionally controlled by the setting value. In other words, you should only include this field in your
configuration if you need to modify the default value or if you need to turn on the feature controlled by the setting.}

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cas.server.tomcat.clustering.channel-send-options=8

This option is used to set the flag that all messages sent through the SimpleTcpCluster uses. The flag decides how the messages are sent, and is a simple logical OR.

2: SEND_OPTIONS_SYNCHRONIZED_ACK
4: SEND_OPTIONS_USE_ACK
8: SEND_OPTIONS_ASYNCHRONOUS

org.apereo.cas.configuration.model.core.web.tomcat.CasEmbeddedApacheTomcatClusteringProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

Note

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:


1

cas.server.tomcat.clustering.channel-send-options=8

CAS properties can be specified using the YAML syntax:

cas: 
  server: 
    tomcat: 
      clustering: 
        channel-send-options: "8"

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.server.tomcat.clustering.channel-send-options="8" -jar build/libs/cas.war

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_SERVER_TOMCAT_CLUSTERING_CHANNEL_SEND_OPTIONS="8"

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.server.tomcat.clustering.channel-send-options="8"

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

cas.server.tomcat.clustering.cloud-membership-provider=dns

Cloud membership provider, values are case sensitive and only used with clusteringType CLOUD. The different providers rely on environment variables to discover other members of cluster via DNS lookups of the service name or querying kubernetes API. See code or Tomcat documentation for the environment variables that are used.

kubernetes will use org.apache.catalina.tribes.KubernetesMembershipProvider
dns will use org.apache.catalina.tribes.DNSMembershipProvider
Class implementing org.apache.catalina.tribes.MembershipProvider

org.apereo.cas.configuration.model.core.web.tomcat.CasEmbeddedApacheTomcatClusteringProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

Note

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:


1

cas.server.tomcat.clustering.cloud-membership-provider=dns

CAS properties can be specified using the YAML syntax:

cas: 
  server: 
    tomcat: 
      clustering: 
        cloud-membership-provider: "dns"

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.server.tomcat.clustering.cloud-membership-provider="dns" -jar build/libs/cas.war

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_SERVER_TOMCAT_CLUSTERING_CLOUD_MEMBERSHIP_PROVIDER="dns"

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.server.tomcat.clustering.cloud-membership-provider="dns"

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

cas.server.tomcat.clustering.cluster-members=

Statically register members in the cluster. The syntax is: address:port:index

org.apereo.cas.configuration.model.core.web.tomcat.CasEmbeddedApacheTomcatClusteringProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

Note

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:


1

cas.server.tomcat.clustering.cluster-members=...

CAS properties can be specified using the YAML syntax:

cas: 
  server: 
    tomcat: 
      clustering: 
        cluster-members: "..."

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.server.tomcat.clustering.cluster-members="..." -jar build/libs/cas.war

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_SERVER_TOMCAT_CLUSTERING_CLUSTER_MEMBERS="..."

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.server.tomcat.clustering.cluster-members="..."

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

cas.server.tomcat.clustering.clustering-type=DEFAULT

Accepted values are: DEFAULT, CLOUD. Type of clustering to use, set to CLOUD if using CloudMembershipService.

org.apereo.cas.configuration.model.core.web.tomcat.CasEmbeddedApacheTomcatClusteringProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

Note

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:


1

cas.server.tomcat.clustering.clustering-type=DEFAULT

CAS properties can be specified using the YAML syntax:

cas: 
  server: 
    tomcat: 
      clustering: 
        clustering-type: "DEFAULT"

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.server.tomcat.clustering.clustering-type="DEFAULT" -jar build/libs/cas.war

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_SERVER_TOMCAT_CLUSTERING_CLUSTERING_TYPE="DEFAULT"

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.server.tomcat.clustering.clustering-type="DEFAULT"

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

cas.server.tomcat.clustering.expire-sessions-on-shutdown=false

When a web application is being shutdown, Tomcat issues an expire call to each session to notify all the listeners. If you wish for all sessions to expire on all nodes when a shutdown occurs on one node, set this value to true. Default value is false.

org.apereo.cas.configuration.model.core.web.tomcat.CasEmbeddedApacheTomcatClusteringProperties.

_{How can I configure this property?}

Configuration properties can be included and activated using the following strategies.

Note

CAS properties can be specified using the Java configuration property syntax in any and all .properties files:


1

cas.server.tomcat.clustering.expire-sessions-on-shutdown=...

CAS properties can be specified using the YAML syntax:

cas: 
  server: 
    tomcat: 
      clustering: 
        expire-sessions-on-shutdown: "..."

Note that YAML is very specific about structure and indentation. Be sure to verify the correctness of the final result with your YAML validator of choice.

CAS properties can be passed to the CAS web application as system properties, when the application is launched:

java -Dcas.server.tomcat.clustering.expire-sessions-on-shutdown="..." -jar build/libs/cas.war

CAS properties can specified as system environment variables before the CAS web application is launched:

export CAS_SERVER_TOMCAT_CLUSTERING_EXPIRE_SESSIONS_ON_SHUTDOWN="..."

java -jar build/libs/cas.war

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

CAS properties can be passed to the CAS web application as command-line arguments, when the application is launched:

java -jar build/libs/cas.war --cas.server.tomcat.clustering.expire-sessions-on-shutdown="..."

The above example assumes that the CAS web application is packaged as cas.war with an embedded server container and can be found in the build/libs directory.

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# This option is used to set the flag that all messages sent through the SimpleTcpCluster uses.
# cas.server.tomcat.clustering.channel-send-options=8

# Cloud membership provider, values are case sensitive and only used with clusteringType {@code CLOUD}.
# cas.server.tomcat.clustering.cloud-membership-provider=dns

# Statically register members in the cluster.
# cas.server.tomcat.clustering.cluster-members=

# Accepted values are: {@code DEFAULT, CLOUD}.
# cas.server.tomcat.clustering.clustering-type=DEFAULT

# When a web application is being shutdown, Tomcat issues an expire call to each session to notify all the listeners.
# cas.server.tomcat.clustering.expire-sessions-on-shutdown=false

# Accepted values are: {@code DELTA, BACKUP}.
# cas.server.tomcat.clustering.manager-type=DELTA

# Multicast address for membership.
# cas.server.tomcat.clustering.membership-address=228.0.0.4

# The membership component will time out members and notify the Channel if a member fails to send a heartbeat within a give time.
# cas.server.tomcat.clustering.membership-drop-time=3000

# The frequency in milliseconds in which heartbeats are sent out.
# cas.server.tomcat.clustering.membership-frequency=500

# Membership uses multicast, it will call java.net.MulticastSocket.setLoopbackMode(localLoopbackDisabled).
# cas.server.tomcat.clustering.membership-local-loopback-disabled=false

# Multicast port (the port and the address together determine cluster membership.
# cas.server.tomcat.clustering.membership-port=45564

# Membership uses multicast, it will call java.net.MulticastSocket.setLoopbackMode(localLoopbackDisabled).
# cas.server.tomcat.clustering.membership-recovery-counter=10

# In case of a network failure, Java multicast socket don't transparently fail over, instead the socket will continuously throw {@code IOException} upon each receive request.
# cas.server.tomcat.clustering.membership-recovery-enabled=true

# The address (network interface) to listen for incoming traffic.
# cas.server.tomcat.clustering.receiver-address=auto

# Default value is 100.
# cas.server.tomcat.clustering.receiver-auto-bind=100

# Maximum threads configured for the listener.
# cas.server.tomcat.clustering.receiver-max-threads=6

# The listen port for incoming data.
# cas.server.tomcat.clustering.receiver-port=4000

# Listener timeout.
# cas.server.tomcat.clustering.receiver-timeout=5000

Configuration Metadata

The collection of configuration properties listed in this section are automatically generated from the CAS source and components that contain the actual field definitions, types, descriptions, modules, etc. This metadata may not always be 100% accurate, or could be lacking details and sufficient explanations.

Be Selective

This section is meant as a guide only. Do NOT copy/paste the entire collection of settings into your CAS configuration; rather pick only the properties that you need. Do NOT enable settings unless you are certain of their purpose and do NOT copy settings into your configuration only to keep them as reference. All these ideas lead to upgrade headaches, maintenance nightmares and premature aging.

YAGNI

Note that for nearly ALL use cases, declaring and configuring properties listed here is sufficient. You should NOT have to explicitly massage a CAS XML/Java/etc configuration file to design an authentication handler, create attribute release policies, etc. CAS at runtime will auto-configure all required changes for you. If you are unsure about the meaning of a given CAS setting, do NOT turn it on without hesitation. Review the codebase or better yet, ask questions to clarify the intended behavior.

Naming Convention

Property names can be specified in very relaxed terms. For instance cas.someProperty, cas.some-property, cas.some_property are all valid names. While all forms are accepted by CAS, there are certain components (in CAS and other frameworks used) whose activation at runtime is conditional on a property value, where this property is required to have been specified in CAS configuration using kebab case. This is both true for properties that are owned by CAS as well as those that might be presented to the system via an external library or framework such as Spring Boot, etc.

Note

Settings and properties that are controlled by the CAS platform directly always begin with the prefix cas. All other settings are controlled and provided to CAS via other underlying frameworks and may have their own schemas and syntax. BE CAREFUL with the distinction. Unrecognized properties are rejected by CAS and/or frameworks upon which CAS depends. This means if you somehow misspell a property definition or fail to adhere to the dot-notation syntax and such, your setting is entirely refused by CAS and likely the feature it controls will never be activated in the way you intend.

Validation

Configuration properties are automatically validated on CAS startup to report issues with configuration binding, specially if defined CAS settings cannot be recognized or validated by the configuration schema. Additional validation processes are also handled via Configuration Metadata and property migrations applied automatically on startup by Spring Boot and family.

Indexed Settings

CAS settings able to accept multiple values are typically documented with an index, such as cas.some.setting[0]=value. The index [0] is meant to be incremented by the adopter to allow for distinct multiple configuration blocks.