Service A invokes ServiceB. Service B invokes ServiceC. Service C invokes both Service D and Service

Question

Options

• AIn this runtime scenario, which services are acting as service consumers?
• BService A, Service B, Service C
• CService D, Service E
• DService A
• ENone, because a service cannot also be a service consumer.

• A
  78% (21)
• B
  4% (1)
• C
  4% (1)
• E
  15% (4)

Explanation

Option A (Service A, Service B, and Service C) is correct because a service consumer is any service that invokes another service at runtime. A invokes B, B invokes C, and C invokes both D and E - all three are making requests, so all three are consumers.

"Service D, Service E" is wrong because D and E are only receiving invocations, not making them. They act purely as service providers in this chain.

"Service A only" is wrong because it ignores that B and C are also issuing invocations further down the chain. Being invoked by something above you doesn't prevent you from also being a consumer of something below you.

"None, because a service cannot also be a service consumer" is wrong - this is a common misconception. In SOA, a service can simultaneously play both roles: provider to its caller and consumer of services it calls. B and C are perfect examples of this dual role.

Memory tip: Think of the direction of the request arrow. Whoever is sending the arrow (invoking) is the consumer; whoever is receiving it is the provider. If a service has at least one outgoing arrow, it's a consumer.

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