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:
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.
|
cas.ticket.registry.core.queue-identifier=
Identifier for this CAS server node that tags the sender/receiver in the queue and avoid processing of inbound calls. If left blank, an identifier is generated automatically and kept in memory.
|
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.
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.
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.
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:
1
2
3
4
@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.