[IGNITE-15572] Ability to set custom execution context for Ignite service. - ASF JIRA

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Details

Type: New Feature
Status: Resolved
Priority: Major
Resolution: Resolved
Affects Version/s: None
Fix Version/s: 2.13
Component/s: managed services
Labels:
- iep-79
- ise

Release Note:
Added a ServiceCallContext that allows implicitly pass additional parameters on every service call.
Ignite Flags:

Release Notes Required

Description

In traditional microservices, we have the ability to set a custom execution context. For example, a REST service may obtain the session ID from the request. We can say that each client request, in this case, has a set of explicit and implicit parameters. One of the implicit parameters is a session identifier that can be passed to the service using request headers. It would be nice to have a similar feature in Ignite services.

The basic idea behind the implementation:
1. Allow the user to bind the "execution context" to the service proxy object.
2. Pass this context as an additional implicit parameter each time the user service method is called.

API proposal (outdated, actual Java API in IGNITE-15794).

1. Using a custom annotation (ServiceRequestContextResource) and reading context attributes with a function.

MyService proxy = ignite.services().serviceProxy("svc", ... Collections.singletonMap("login", "user1"));

public class MyServiceImpl implements MyService {
    @ServiceRequestContextResource
    private Function<String, Object> ctxFunc;

    @Override public void serviceMethod() {
        String login = (String)ctxFunc.apply("login");
    }
    ...
}

2. Using a new method of the existing ServiceContext.

MyService proxy = ignite.services().serviceProxy("svc", ... Collections.singletonMap("login", "user1"));

public class MyServiceImpl implements MyService {
    private ServiceContext svcCtx;

    @Override public void init(ServiceContext svcCtx) {
        this.svcCtx = svcCtx;
    }

    @Override public void serviceMethod() {
        String user = svcCtx.attribute("login");
        // and/or
        String user = (String)svcCtx.attributes().get("login");
    }
    ... 
}

The next two options require wrapping Map<String, Object> into a new ServiceRequestContext class.

3. Read context "wrapper" using special annotation and supplier.

MyService proxy = ignite.services().serviceProxy("svc", ... new ServiceRequestContext("login", "user1"), 0);

public class MyServiceImpl implements MyService {
    @ServiceRequestContextResource
    Supplier<ServiceRequestContext> ctxSupplier;
	
    @Override public void serviceMethod() {
        String login = ctxSupplier.get().attribute("login");
    }
    ...
}

4. Using the special static method of the "wrapper" class.

MyService proxy = ignite.services().serviceProxy("svc", ... new ServiceRequestContext("login", "user1"), 0);

public class MyServiceImpl implements MyService {
    @Override public void serviceMethod() {		
        String login = ServiceRequestContext.current().attribute("login");
    }
    ...
}