org.axonframework.extensions.springcloud.commandhandling

Class SpringCloudCommandRouter

java.lang.Object

org.axonframework.extensions.springcloud.commandhandling.SpringCloudCommandRouter

All Implemented Interfaces:

org.axonframework.commandhandling.distributed.CommandRouter

Direct Known Subclasses:

SpringCloudHttpBackupCommandRouter

public class SpringCloudCommandRouter
extends Object
implements org.axonframework.commandhandling.distributed.CommandRouter

A CommandRouter implementation which uses Spring Cloud's DiscoveryClients to propagate its Command Message Routing Information, and to discover other Axon nodes and retrieve their Message Routing Information. It does so by utilizing the metadata contained in a ServiceInstance for storing the Message Routing Information in. Other nodes discovered through the DiscoveryClient system which do not contain any of the required Message Routing Information fields will be black listed, so not to perform any unneeded additional checks on that node.

The localServiceInstance is added for correct deviation between the local instance and the instances retrieved from the DiscoveryClient. A RoutingStrategy is in place to decide which instance will handle a given Command Message. Lastly, a Predicate of generic type ServiceInstance can be provided to filter out specific service instances which need to be disregarded, and a ConsistentHashChangeListener is configurable to notify if the memberships have been updated.

Since:

3.0

Author:

Steven van Beelen

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	SpringCloudCommandRouter.Builder Builder class to instantiate a SpringCloudCommandRouter.

Field Summary

Fields

Modifier and Type	Field and Description
protected org.axonframework.serialization.Serializer	serializer

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	SpringCloudCommandRouter(SpringCloudCommandRouter.Builder builder) Instantiate a SpringCloudCommandRouter based on the fields contained in the SpringCloudCommandRouter.Builder.

Method Summary

Modifier and Type	Method and Description
static SpringCloudCommandRouter.Builder	builder() Instantiate a Builder to be able to create a SpringCloudCommandRouter.
protected org.axonframework.commandhandling.distributed.Member	buildMember(org.springframework.cloud.client.ServiceInstance serviceInstance) Instantiate a Member of type URI based on the provided serviceInstance.
Optional<org.axonframework.commandhandling.distributed.Member>	findDestination(org.axonframework.commandhandling.CommandMessage<?> commandMessage)
void	resetLocalMembership(org.springframework.cloud.client.discovery.event.InstanceRegisteredEvent<?> event) Update the local member and all the other remote members known by the DiscoveryClient to be able to have an as up-to-date awareness of which actions which members can handle.
static boolean	serviceInstanceMetadataContainsMessageRoutingInformation(org.springframework.cloud.client.ServiceInstance serviceInstance) Deprecated. no current CapabilityDiscoveryMode bases itself on ServiceInstance.getMetadata() and as such this filter will be removed
void	updateMembership(int loadFactor, org.axonframework.commandhandling.distributed.CommandMessageFilter commandFilter)
void	updateMemberships(org.springframework.cloud.client.discovery.event.HeartbeatEvent event) Update the memberships of all nodes known by the DiscoveryClient to be able to have an as up-to-date awareness of which actions which members can handle.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

serializer

protected final org.axonframework.serialization.Serializer serializer

Constructor Detail

SpringCloudCommandRouter

protected SpringCloudCommandRouter(SpringCloudCommandRouter.Builder builder)

Instantiate a SpringCloudCommandRouter based on the fields contained in the SpringCloudCommandRouter.Builder.

Will assert that the DiscoveryClient, localServiceInstance of type Registration, RoutingStrategy and CapabilityDiscoveryMode are not null, and will throw an AxonConfigurationException if any of them is null.

Parameters:

builder - the SpringCloudCommandRouter.Builder used to instantiate a SpringCloudCommandRouter instance

Method Detail

builder

public static SpringCloudCommandRouter.Builder builder()

Instantiate a Builder to be able to create a SpringCloudCommandRouter.

The Serializer is defaulted to a XStreamSerializer, the serviceInstanceFilter to accept all instances, and the ConsistentHashChangeListener to a no-op solution. The DiscoveryClient, localServiceInstance of type Registration, the RoutingStrategy and the CapabilityDiscoveryMode are hard requirements and as such should be provided.

Returns:

a Builder to be able to create a SpringCloudCommandRouter

serviceInstanceMetadataContainsMessageRoutingInformation

@Deprecated
public static boolean serviceInstanceMetadataContainsMessageRoutingInformation(org.springframework.cloud.client.ServiceInstance serviceInstance)

Deprecated. no current CapabilityDiscoveryMode bases itself on ServiceInstance.getMetadata() and as such this filter will be removed

Boolean check if the metadata Map of the given ServiceInstance contains any of the expected message routing info keys.

Parameters:

serviceInstance - The ServiceInstance to check its metadata keys from

Returns:

true if the given serviceInstance contains all expected message routing info keys; false if one of the expected message routing info keys is missing.

findDestination

public Optional<org.axonframework.commandhandling.distributed.Member> findDestination(org.axonframework.commandhandling.CommandMessage<?> commandMessage)

Specified by:

findDestination in interface org.axonframework.commandhandling.distributed.CommandRouter

updateMembership

public void updateMembership(int loadFactor,
                             org.axonframework.commandhandling.distributed.CommandMessageFilter commandFilter)

Specified by:

updateMembership in interface org.axonframework.commandhandling.distributed.CommandRouter

resetLocalMembership

@EventListener
public void resetLocalMembership(org.springframework.cloud.client.discovery.event.InstanceRegisteredEvent<?> event)

Update the local member and all the other remote members known by the DiscoveryClient to be able to have an as up-to-date awareness of which actions which members can handle. This function is automatically triggered by an (unused) InstanceRegisteredEvent. Upon this event we may assume that the application has fully start up. Because of this we can update the local member with the correct name and URI, as initially these were not provided by the Registration yet.

Parameters:

event - an unused InstanceRegisteredEvent, serves as a trigger for this function

See Also:

buildMember(ServiceInstance)

updateMemberships

@EventListener
public void updateMemberships(org.springframework.cloud.client.discovery.event.HeartbeatEvent event)

Update the memberships of all nodes known by the DiscoveryClient to be able to have an as up-to-date awareness of which actions which members can handle. This function is automatically triggered by an (unused) HeartbeatEvent. The interval of this HeartbeatEvent thus specifies the speed within which cluster topologies, a.k.a. each nodes command handling capabilities, are propagated.

Parameters:

event - an unused HeartbeatEvent, serves as a trigger for this function

buildMember

protected org.axonframework.commandhandling.distributed.Member buildMember(org.springframework.cloud.client.ServiceInstance serviceInstance)

Instantiate a Member of type URI based on the provided serviceInstance. This Member is later used to send, for example, CommandMessages to.

A deviation is made between a local and a remote member, since if a local node is selected to handle the command, the local command bus may be leveraged. The check if a ServiceInstance is local is based on two potential situations:

1. The given serviceInstance is identical to the localServiceInstance thus making it local.
2. The URI of the given serviceInstance is identical to the URI of the localServiceInstance.

We take this route because we've identified that several Spring Cloud implementations do not contain any URI information during the start up phase and as a side effect will throw exception if the URI is requested from it. We thus return a simplified Member for the localServiceInstance to not trigger this exception.

Parameters:

serviceInstance - a ServiceInstance to build a Member for

Returns:

a Member based on the contents of the provided serviceInstance