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unary.md

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grpc.unary

grpc.unary allows making unary gRPC requests.

There is also grpc.invoke for making server-streaming requests and grpc.client for making bi-directional requests that will both work with unary methods.

API Docs:

grpc.unary(methodDescriptor: MethodDescriptor, props: UnaryRpcOptions): Request;

methodDescriptor is a generated method definition (see code generation for how to generate these).

UnaryRpcOptions:

  • host: string
    • The server address ("https://example.com:9100")
  • request: grpc.ProtobufMessage
    • The single request message to send to the server
  • metadata: grpc.Metadata
    • The metadata to send to the server
  • onEnd: (output: UnaryOutput<TResponse>) => void)
    • A callback for the end of the request and trailers being received
  • transport?: TransportConstructor
    • (optional) A function to build a Transport that will be used for the request. If no transport is specified then a browser-compatible transport will be used. See transport.
  • debug?: boolean
    • (optional) if true, debug information will be printed to the console

UnaryOutput

  • status: Code
  • statusMessage: string
  • headers: Metadata
    • The headers (Metadata) that the server sent
  • message: TResponse | null
    • The single message that the server sent in the response.
  • trailers: Metadata
    • The trailers (Metadata) that the server sent

Request:

// Close the connection to the server without waiting for any response
close(): void;

Lifecycle

A unary gRPC request goes through the following stages:

  • Request with optional metadata and a single message is sent to the server - unary()
  • Server sends headers (metadata)
  • Server responds with one message to the client
  • Server closes the request with status code and trailers (metadata) - onEnd callback called with the message and metadata that was received

Example:

const request = new QueryBooksRequest();
request.setAuthorPrefix("Geor");

const grpcRequest = grpc.unary(BookService.QueryBooks, {
  host: "https://example.com:9100",
  metadata: new grpc.Metadata({"HeaderTestKey1": "ClientValue1"}),
  onEnd: (({status, statusMessage, headers, message, trailers: string, trailers: grpc.Metadata}) => {
    console.log("onEnd", status, statusMessage, headers, message, trailers);
  },
});

grpcRequest.close();// Included as an example of how to close the request, but this usage would cancel the request immediately