com.lightbend.lagom.javadsl.api

Interface ServiceLocator

All Known Implementing Classes:

AkkaDiscoveryServiceLocator, CircuitBreakingServiceLocator, ConfigurationServiceLocator, ConfigurationServiceLocator

public interface ServiceLocator

Locates services.

The service locator is responsible for two things, one is locating services according to the passed in name and service call information, the other is to implement circuit breaking functionality when doWithService(String, Descriptor.Call, Function) is invoked.

The reason circuit breaking is a service locator concern is that generally, the service locator will want to be aware of when a circuit breaker is open, and respond accordingly. For example, it may decide to pull that node from its routing pool, or it may decide to notify some up stream service registry that that node is no longer responding.

Method Summary

Modifier and Type	Method and Description
<T> CompletionStage<Optional<T>>	doWithService(String name, Descriptor.Call<?,?> serviceCall, Function<URI,CompletionStage<T>> block) Do the given action with the given service.
default CompletionStage<Optional<URI>>	locate(String name) Locate a service's URI for the given name.
CompletionStage<Optional<URI>>	locate(String name, Descriptor.Call<?,?> serviceCall) Locate a service's URI for the given name.
default CompletionStage<List<URI>>	locateAll(String name) Locate the service's URIs for the given name.
default CompletionStage<List<URI>>	locateAll(String name, Descriptor.Call<?,?> serviceCall) Locate the service's URIs for the given name.

Method Detail

locate

default CompletionStage<Optional<URI>> locate(String name)

Locate a service's URI for the given name.

Parameters:

name - The name of the service.

Returns:

The URI for that service, if it exists.

locateAll

default CompletionStage<List<URI>> locateAll(String name)

Locate the service's URIs for the given name.

Parameters:

name - The name of the service.

Returns:

One or more URIs for that service, otherwise an empty List if none is found.

Since:

1.4

locate

CompletionStage<Optional<URI>> locate(String name,
                                      Descriptor.Call<?,?> serviceCall)

Locate a service's URI for the given name.

Parameters:

name - The name of the service.

serviceCall - The service call descriptor that this lookup is for.

Returns:

The URI for that service, if it exists.

locateAll

default CompletionStage<List<URI>> locateAll(String name,
                                             Descriptor.Call<?,?> serviceCall)

Locate the service's URIs for the given name.

Parameters:

name - The name of the service.

serviceCall - The service call descriptor that this lookup is for.

Returns:

One or more URIs for that service, otherwise an empty List if none is found.

Since:

1.4

doWithService

<T> CompletionStage<Optional<T>> doWithService(String name,
                                               Descriptor.Call<?,?> serviceCall,
                                               Function<URI,CompletionStage<T>> block)

Do the given action with the given service.

This should be used in preference to locate(String, Descriptor.Call) when possible as it will allow the service locator to add in things like circuit breakers.

It is required that the service locator will, based on the service call circuit breaker configuration, wrap the invocation of the passed in block with a circuit breaker.

Parameters:

name - The name of the service.

serviceCall - The service call descriptor that this lookup is for.

block - A block of code that takes the URI for the service, and returns a future of some work done on the service. This will only be executed if the service was found.

Returns:

The result of the executed block, if the service was found.