The applicationMaster uses polling to apply for and receive resources from the ResourceManager through the RPC protocol.

Question

Options

• ATrue
• BFalse

• A
  75% (27)
• B
  25% (9)

Explanation

Option A is correct because in YARN, the ApplicationMaster communicates with the ResourceManager via the ApplicationMasterProtocol RPC interface, and this interaction is polling-based - the AM periodically calls allocate() on the RM to submit resource requests (ResourceRequest objects) and simultaneously receive any newly allocated containers in the response. This heartbeat-style polling serves a dual purpose: resource negotiation and liveness detection (the RM knows the AM is still alive as long as it keeps polling). Since this polling mechanism is the actual design of YARN's AM-RM protocol, option B (False) is incorrect - there is no push or callback model where the RM proactively notifies the AM of available resources.

Memory tip: Think of the AM as a job seeker who must keep calling the office (polling via RPC) to both submit applications and hear back - the office never calls you first.

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