org.axonframework.springcloud.commandhandling

Class SpringCloudCommandRouter

java.lang.Object

org.axonframework.springcloud.commandhandling.SpringCloudCommandRouter

All Implemented Interfaces:

CommandRouter

Direct Known Subclasses:

SpringCloudHttpBackupCommandRouter

public class SpringCloudCommandRouter
extends Object
implements CommandRouter

A CommandRouter implementation which uses Spring Cloud's DiscoveryClients to propagate its CommandMessage 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.

Author:

Steven van Beelen

Field Summary

Fields

Modifier and Type	Field and Description
protected XStreamSerializer	serializer

Constructor Summary

Constructors

Constructor and Description
SpringCloudCommandRouter(org.springframework.cloud.client.discovery.DiscoveryClient discoveryClient, org.springframework.cloud.client.serviceregistry.Registration localServiceInstance, RoutingStrategy routingStrategy) Initialize a CommandRouter with the given DiscoveryClient to update its own membership as a CommandRouter and to create its own awareness of available nodes to send commands to in a ConsistentHash.
SpringCloudCommandRouter(org.springframework.cloud.client.discovery.DiscoveryClient discoveryClient, org.springframework.cloud.client.serviceregistry.Registration localServiceInstance, RoutingStrategy routingStrategy, Predicate<org.springframework.cloud.client.ServiceInstance> serviceInstanceFilter) Initialize a CommandRouter with the given DiscoveryClient to update its own membership as a CommandRouter and to create its own awareness of available nodes to send commands to in a ConsistentHash.
SpringCloudCommandRouter(org.springframework.cloud.client.discovery.DiscoveryClient discoveryClient, org.springframework.cloud.client.serviceregistry.Registration localServiceInstance, RoutingStrategy routingStrategy, Predicate<org.springframework.cloud.client.ServiceInstance> serviceInstanceFilter, ConsistentHashChangeListener consistentHashChangeListener) Initialize a CommandRouter with the given DiscoveryClient to update its own membership as a CommandRouter and to create its own awareness of available nodes to send commands to in a ConsistentHash.

Method Summary

Modifier and Type	Method and Description
protected Member	buildMember(org.springframework.cloud.client.ServiceInstance serviceInstance) Instantiate a Member of type URI based on the provided serviceInstance.
Optional<Member>	findDestination(CommandMessage<?> commandMessage) Returns the member instance to which the given message should be routed.
protected Optional<MessageRoutingInformation>	getMessageRoutingInformation(org.springframework.cloud.client.ServiceInstance serviceInstance) Retrieve the MessageRoutingInformation of the provided serviceInstance.
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) Boolean check if the metadata Map of the given ServiceInstance contains any of the expected message routing info keys.
void	updateMembership(int loadFactor, Predicate<? super CommandMessage<?>> commandFilter) Updates the load factor and capabilities of this member representing the current endpoint if the implementation allows memberships to be updated dynamically.
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 XStreamSerializer serializer

Constructor Detail

SpringCloudCommandRouter

public SpringCloudCommandRouter(org.springframework.cloud.client.discovery.DiscoveryClient discoveryClient,
                                org.springframework.cloud.client.serviceregistry.Registration localServiceInstance,
                                RoutingStrategy routingStrategy)

Initialize a CommandRouter with the given DiscoveryClient to update its own membership as a CommandRouter and to create its own awareness of available nodes to send commands to in a ConsistentHash. The routingStrategy is used to define the key based on which Command Messages are routed to their respective handler nodes. Uses a default Predicate<ServiceInstance> filter function to remove any ServiceInstance which miss message routing information key-value pairs in their metadata. This is thus the serviceInstanceMetadataContainsMessageRoutingInformation(ServiceInstance serviceInstance) function.

Parameters:

discoveryClient - The DiscoveryClient used to discovery and notify other nodes

localServiceInstance - A Registration representing the local Service Instance of this application. Necessary to differentiate between other instances for correct message routing

routingStrategy - The strategy for routing Commands to a Node

SpringCloudCommandRouter

public SpringCloudCommandRouter(org.springframework.cloud.client.discovery.DiscoveryClient discoveryClient,
                                org.springframework.cloud.client.serviceregistry.Registration localServiceInstance,
                                RoutingStrategy routingStrategy,
                                Predicate<org.springframework.cloud.client.ServiceInstance> serviceInstanceFilter)

Initialize a CommandRouter with the given DiscoveryClient to update its own membership as a CommandRouter and to create its own awareness of available nodes to send commands to in a ConsistentHash. The routingStrategy is used to define the key based on which Command Messages are routed to their respective handler nodes. A Predicate<ServiceInstance> to filter a ServiceInstance from the membership update loop.

Parameters:

discoveryClient - The DiscoveryClient used to discovery and notify other nodes

localServiceInstance - A Registration representing the local Service Instance of this application. Necessary to differentiate between other instances for correct message routing

routingStrategy - The strategy for routing Commands to a Node

serviceInstanceFilter - The Predicate<ServiceInstance> used to filter ServiceInstance from the update membership loop.

SpringCloudCommandRouter

public SpringCloudCommandRouter(org.springframework.cloud.client.discovery.DiscoveryClient discoveryClient,
                                org.springframework.cloud.client.serviceregistry.Registration localServiceInstance,
                                RoutingStrategy routingStrategy,
                                Predicate<org.springframework.cloud.client.ServiceInstance> serviceInstanceFilter,
                                ConsistentHashChangeListener consistentHashChangeListener)

Initialize a CommandRouter with the given DiscoveryClient to update its own membership as a CommandRouter and to create its own awareness of available nodes to send commands to in a ConsistentHash. The given consistentHashChangeListener is notified about changes in membership that affect routing of messages. The routingStrategy is used to define the key based on which Command Messages are routed to their respective handler nodes. A Predicate<ServiceInstance> to filter a ServiceInstance from the membership update loop.

Parameters:

discoveryClient - The DiscoveryClient used to discovery and notify other nodes

localServiceInstance - A Registration representing the local Service Instance of this application. Necessary to differentiate between other instances for correct message routing

routingStrategy - The strategy for routing Commands to a Node

serviceInstanceFilter - The Predicate<ServiceInstance> used to filter ServiceInstance from the update membership loop.

consistentHashChangeListener - The callback to invoke when there is a change in the ConsistentHash

Method Detail

serviceInstanceMetadataContainsMessageRoutingInformation

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

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<Member> findDestination(CommandMessage<?> commandMessage)

Description copied from interface: CommandRouter

Returns the member instance to which the given message should be routed. If no suitable member could be found an empty Optional is returned.

Specified by:

findDestination in interface CommandRouter

Parameters:

commandMessage - the command message to find a member for

Returns:

the member that should handle the message or an empty Optional if no suitable member was found

updateMembership

public void updateMembership(int loadFactor,
                             Predicate<? super CommandMessage<?>> commandFilter)

Description copied from interface: CommandRouter

Updates the load factor and capabilities of this member representing the current endpoint if the implementation allows memberships to be updated dynamically.

Specified by:

updateMembership in interface CommandRouter

Parameters:

loadFactor - the new load factor of the member for this endpoint

commandFilter - the new capabilities of the member for this endpoint

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.

Parameters:

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

buildMember

protected 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, Command messages to.

A deviation is made between a local and a remote member, since if local is selected to handle the command, the local CommandBus 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 or 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 implementation 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

getMessageRoutingInformation

protected Optional<MessageRoutingInformation> getMessageRoutingInformation(org.springframework.cloud.client.ServiceInstance serviceInstance)

Retrieve the MessageRoutingInformation of the provided serviceInstance. If the MessageRoutingInformation could not be found, an Optional.empty() will be returned. Otherwise the MessageRoutingInformation will be contained in the Optional.

Parameters:

serviceInstance - A ServiceInstance to retrieve MessageRoutingInformation from.

Returns:

an Optional of type MessageRoutingInformation, containing the corresponding MessageRoutingInformation for the given serviceInstance if it could be retrieved.