Ticket Registry Locking

A number of ticket registries support advanced distributed locking operations for highly concurrent requests. In scenarios where the CAS server is under very heavy load, it is possible for multiple requests to attempt to alter the server state at the same time. For example, you might consider service-ticket requests for two separate applications simultaneously where the resulting tickets and operations would end up changing the state of the single sign-on session, the linked ticket-granting ticket and how it tracks the two applications. In such scenarios, CAS may be configured to acquire and enforce locking operations such that the sequence of executions and requests is handled atomically and proper data and state is preserved such that concurrent requests would not lead to data loss and missing updates.

Locking strategies and options are by default available for the default ticket registry implementation. In the event that the ticket registry technology does support distributed locking, CAS would defer to the distributed lock implementation that is provided and supported by the ticket registry itself. As always, you may begin to design your own locking strategy if the registry technology of your choice does not yet support it.

CAS lock implementations are generally backed by Spring Integration, and its behavior can be controlled via CAS settings.

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.}

_{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. You should only include this field in your
configuration if you need to modify the default value.}

cas.ticket.registry.core.enable-locking=true

When set to true, registry operations will begin to support distributed locking for ticket operations. If the registry itself supports distributed locking, such as JDBC or Redis, then the lock implementation will defer to that option. Otherwise the default locking solution will be specific to a CAS server node, until replaced with a lock implementation or different locking option separate from the registry technology itself.

org.apereo.cas.configuration.model.core.ticket.registry.TicketRegistryCoreProperties.

_{How can I configure this property?}

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

:information_source: 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:

cas.ticket.registry.core.enable-locking=true

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: 
  ticket: 
    registry: 
      core: 
        enable-locking: "true"

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.ticket.registry.core.enable-locking="true" -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_TICKET_REGISTRY_CORE_ENABLE_LOCKING="true"

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.ticket.registry.core.enable-locking="true"

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.

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.

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. The validation process is on by default and can be skipped on startup using a special system property SKIP_CONFIG_VALIDATION that should be set to true. 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.

Default

The default lock implementation, generally suitable for single-node deployments, is one where the lock registry uses Masked Hashcode algorithm to obtain and store locks in JVM memory. The default mask is 0xFF which will create an array consisting of 1024 ReentrantLock instances. When the lock repository attempts to obtain a lock for a given lock key, (i.e. ticket id), the index of the Lock is determined by masking the object’s hash code and the Lock is returned.

Custom

To design your own locking implementation, you may inject the following @Bean into your CAS configuration:

@Bean
public LockRepository casTicketRegistryLockRepository() {
    return new MyLockRepository();
}

See this guide to learn more about how to register configurations into the CAS runtime.

Others

Distributed locking support is available for some, but not all, ticket registry implementations. Please refer to the documentation for each ticket registry implementation to learn whether support is available for distributed locking.