Interface Definition Language(IDL)⌗

protocol buffers

Synchronous vs. asynchronous⌗

application-specific

RPC life cycle⌗

Unary RPC⌗

  1. client -> server
  • metadata
  • method name
  • deadline if applicable
  1. server -> client
  • send back its own initial metadata (which must be sent before any response) straight away
  • or wait for the client’s request message
  • which happens first, is application-specific
  • optional trailing metadata

Server streaming RPC⌗

like unary RPC

Client streaming RPC⌗

like unary RPC

Bidirectional streaming RPC⌗

  • the call is initiated by the client invoking the method and the server receiving the client metadata, method name, and deadline
  • server can choose to send back its initial metadata or wait for the client to start streaming messages
  • processing is application specific
  • two streams are independent

Deadlines/Timeouts⌗

  • clients to specify
  • server can query
  • specifying a deadline or timeout is language specific

RPC termination⌗

both the client and server make independent and local determinations of the success of the call, and their conclusions may not match

Cancelling an RPC⌗

  • client and server either can cancel at any time
  • changes made before a cancellation are not rolled back.

Metadata⌗

Channels⌗

  • clients can specify channel arguments to modify gRPC’s default behavior(such as message compression)
  • channels has state, including connected and idle
  • closing a channel is language dependent
  • Some languages also permit querying channel state