Apache Kafka Ticket Registry

The Apache Kafka ticket registry is very much an extension of the default ticket registry. The difference is that ticket operations applied to the registry are broadcasted using Kafka topics to other listening CAS nodes. Each node keeps copies of ticket state on its own and only instructs others to keep their copy accurate by broadcasting messages and data associated with each. Each message and ticket registry instance running inside a CAS node in the cluster is tagged with a unique identifier in order to avoid endless looping behavior and recursive needless inbound operations.

The broadcast and pub/sub mechanism is backed by Apache Kafka. Apache Kafka is a distributed event streaming platform designed for handling real-time data feeds. Kafka is highly scalable and fault-tolerant, making it ideal for building real-time data pipelines and streaming applications.

Key features of Apache Kafka include:

  • Message Broker: Kafka acts as a distributed messaging system that enables the publishing, storing, and processing of streams of data in real-time.
  • Producers and Consumers: Data is produced by producers and consumed by consumers in Kafka. Producers send messages to Kafka topics, and consumers read messages from these topics.
  • Topics: A topic is a category or stream name to which records are sent. Data is partitioned across multiple Kafka brokers based on topics.

Support is enabled by including the following dependency in the overlay:

1
2
3
4
5
<dependency>
    <groupId>org.apereo.cas</groupId>
    <artifactId>cas-server-support-kafka-ticket-registry</artifactId>
    <version>${cas.version}</version>
</dependency>
1
implementation "org.apereo.cas:cas-server-support-kafka-ticket-registry:${project.'cas.version'}"
1
2
3
4
5
6
7
8
9
dependencyManagement {
    imports {
        mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
    }
}

dependencies {
    implementation "org.apereo.cas:cas-server-support-kafka-ticket-registry"
}
1
2
3
4
5
6
7
8
9
10
dependencies {
    /*
        The following platform references are included automatically and are listed for reference only.

        implementation enforcedPlatform("org.apereo.cas:cas-server-support-bom:${project.'cas.version'}")
        implementation platform(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES)
        
    */
    implementation "org.apereo.cas:cas-server-support-kafka-ticket-registry"
}

CAS Configuration

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

cas.ticket.registry.in-memory.crypto.encryption.keyThe encryption key.
no default
Required

The encryption key. The encryption key by default and unless specified otherwise must be randomly-generated string whose length is defined by the encryption key size setting.

Type
String
Default
none
Defined by
EncryptionRandomizedCryptoProperties
cas.ticket.registry.in-memory.crypto.signing.keyThe signing key is a string whose length is defined by the signing key size setting.
no default
RequiredSpEL

The signing key is a string whose length is defined by the signing key size setting.

Type
String
Default
none
Defined by
SigningJwtCryptoProperties
Supports
Spring Expression Language
cas.ticket.registry.kafka.crypto.encryption.keyThe encryption key.
no default
Required

The encryption key. The encryption key by default and unless specified otherwise must be randomly-generated string whose length is defined by the encryption key size setting.

Type
String
Default
none
Defined by
EncryptionRandomizedCryptoProperties
cas.ticket.registry.kafka.crypto.signing.keyThe signing key is a string whose length is defined by the signing key size setting.
no default
RequiredSpEL

The signing key is a string whose length is defined by the signing key size setting.

Type
String
Default
none
Defined by
SigningJwtCryptoProperties
Supports
Spring Expression Language
cas.ticket.registry.in-memory.concurrencyThe estimated number of concurrently updating threads.
20

The estimated number of concurrently updating threads. The implementation performs internal sizing to try to accommodate this many threads.

Type
Integer
Default
20
Defined by
InMemoryTicketRegistryProperties
cas.ticket.registry.in-memory.crypto.algThe signing/encryption algorithm to use.
AES

The signing/encryption algorithm to use.

Type
String
Default
AES
Defined by
EncryptionRandomizedSigningJwtCryptographyProperties
cas.ticket.registry.in-memory.crypto.enabledWhether crypto operations are enabled.
true

Whether crypto operations are enabled.

Type
Boolean
Default
true
Defined by
EncryptionRandomizedSigningJwtCryptographyProperties
cas.ticket.registry.in-memory.crypto.encryption.key-sizeEncryption key size.
16

Encryption key size.

Type
Integer
Default
16
Defined by
EncryptionRandomizedCryptoProperties
cas.ticket.registry.in-memory.crypto.signing-enabledWhether signing encryption operations are enabled.
true

Whether signing encryption operations are enabled.

Type
Boolean
Default
true
Defined by
EncryptionRandomizedSigningJwtCryptographyProperties
cas.ticket.registry.in-memory.crypto.signing.key-sizeThe signing key size.
512

The signing key size.

Type
Integer
Default
512
Defined by
SigningJwtCryptoProperties
cas.ticket.registry.in-memory.initial-capacityThe initial capacity of the underlying memory store.
1000

The initial capacity of the underlying memory store. The implementation performs internal sizing to accommodate this many elements.

Type
Integer
Default
1000
Defined by
InMemoryTicketRegistryProperties
cas.ticket.registry.in-memory.load-factorThe load factor threshold, used to control resizing.
1

The load factor threshold, used to control resizing. Resizing may be performed when the average number of elements per bin exceeds this threshold.

Type
Integer
Default
1
Defined by
InMemoryTicketRegistryProperties
cas.ticket.registry.in-memory.propertiesFree-form key-value pairs to configure the specific registry with custom settings.
no default

Free-form key-value pairs to configure the specific registry with custom settings.

Type
Map<String,String>
Default
none
Defined by
InMemoryTicketRegistryProperties
cas.ticket.registry.kafka.auto-create-topicsWhether the registry should auto-create topics.
true

Whether the registry should auto-create topics.

Type
Boolean
Default
true
Defined by
KafkaTicketRegistryProperties
cas.ticket.registry.kafka.bootstrap-addressKafka bootstrapping server address (i.e. localhost:9092).
no default

Kafka bootstrapping server address (i.e. localhost:9092).

Type
String
Default
none
Defined by
KafkaTicketRegistryProperties
cas.ticket.registry.kafka.concurrencyThe concurrency level in ConcurrentMessageListenerContainer determines the number of concurrent threads that will be used to process messages.
no default

The concurrency level in ConcurrentMessageListenerContainer determines the number of concurrent threads that will be used to process messages. This allows you to parallelize message consumption, which can improve throughput and performance. By default, this is the number of available processors (CPU cores) to the Java virtual machine.

Type
Integer
Default
none
Defined by
KafkaTicketRegistryProperties
cas.ticket.registry.kafka.crypto.algThe signing/encryption algorithm to use.
AES

The signing/encryption algorithm to use.

Type
String
Default
AES
Defined by
EncryptionRandomizedSigningJwtCryptographyProperties
cas.ticket.registry.kafka.crypto.enabledWhether crypto operations are enabled.
true

Whether crypto operations are enabled.

Type
Boolean
Default
true
Defined by
EncryptionRandomizedSigningJwtCryptographyProperties
cas.ticket.registry.kafka.crypto.encryption.key-sizeEncryption key size.
16

Encryption key size.

Type
Integer
Default
16
Defined by
EncryptionRandomizedCryptoProperties
cas.ticket.registry.kafka.crypto.signing-enabledWhether signing encryption operations are enabled.
true

Whether signing encryption operations are enabled.

Type
Boolean
Default
true
Defined by
EncryptionRandomizedSigningJwtCryptographyProperties
cas.ticket.registry.kafka.crypto.signing.key-sizeThe signing key size.
512

The signing key size.

Type
Integer
Default
512
Defined by
SigningJwtCryptoProperties
cas.ticket.registry.kafka.group-idPrefix of the consumer group each CAS node uses to consume ticket registry messages.
cas-ticket-registry

Prefix of the consumer group each CAS node uses to consume ticket registry messages. Every node keeps its own copy of the registry and must receive every change, so the group is completed with the node's queue identifier (cas.ticket.registry.core.queue-identifier, or a random value when that is not set) and no two nodes share a group. Nodes that share a group split the topic partitions between them, so each change would reach only one of them. Setting the queue identifier keeps a node's group, and its committed offsets, stable across restarts.

Type
String
Default
cas-ticket-registry
Defined by
KafkaTicketRegistryProperties

Required settings may be needed to activate or affect the feature; review them even when they have a default. Optional settings only need to be set to change a default or to turn on the behavior they control. Third party settings belong to libraries such as Spring Boot that CAS builds on; their own documentation may have more detail.

Signing & encryption

This CAS feature is able to accept signing and encryption crypto keys. In most scenarios if keys are not provided, CAS will auto-generate them. The following instructions apply if you wish to manually and beforehand create the signing and encryption keys.

Note that if you are asked to create a JWK of a certain size for the key, you are to use the following set of commands to generate the token:

1
2
wget https://raw.githubusercontent.com/apereo/cas/master/etc/jwk-gen.jar
java -jar jwk-gen.jar -t oct -s [size]

The outcome would be similar to:

1
2
3
4
5
{
  "kty": "oct",
  "kid": "...",
  "k": "..."
}

The generated value for k needs to be assigned to the relevant CAS settings. Note that keys generated via the above algorithm are processed by CAS using the Advanced Encryption Standard (AES) algorithm which is a specification for the encryption of electronic data established by the U.S. National Institute of Standards and Technology.


Notes on configuration

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.

: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.

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, especially 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.

Troubleshooting

To enable additional logging, configure the log4j configuration file to add the following levels:

1
2
3
4
5
6
...
<Logger name="org.apache.kafka" level="debug" additivity="false">
    <AppenderRef ref="casConsole"/>
    <AppenderRef ref="casFile"/>
</Logger>
...