06 Deadlines and run

A deadline tells gRPC how long the client is willing to wait for a response. If the call takes longer, gRPC cancels it on both sides and returns a DEADLINE_EXCEEDED error. Always set a deadline in production — an unresponsive server will otherwise block the client indefinitely.

Set a deadline on a unary call

const deadline = new Date(Date.now() + 5000); // 5 s from now
client.SayHello({ name: "Ada" }, { deadline }, (err, response) => {
  if (err) { console.error(`error ${err.code}: ${err.details}`); return; }
  console.log(response.message);
});

Pass the options object { deadline } as the second argument (between request and callback). deadline is a Date representing the absolute wall-clock expiry time.

What your project looks like now

greeter/
  greeter.proto       ← SayHello + SayHellos
  load.js             ← shared grpc + proto loader
  server.js           ← sayHello (validated) + sayHellos
  client.js           ← unary call with deadline
  stream-client.js    ← streaming call
  package.json
  node_modules/

Run the whole thing

Open two terminals in the greeter/ directory.

Terminal 1 — start the server:

node server.js
# Greeter listening on :50051

Terminal 2 — run the clients:

node client.js
# Hello, Ada

node stream-client.js
# Hello, Ada
# Hi, Ada
# Hey, Ada
# stream done

Test the deadline

Stop the server (Ctrl+C in terminal 1), then run the deadline'd client:

node client.js
# error 14: No connection established

With the server down the call fails within ~5 s (UNAVAILABLE; the TCP connect itself times out before the deadline, so you see code 14 rather than 4). Set a very short deadline (100 ms) against a slow server to observe DEADLINE_EXCEEDED (code 4).

What's next

• Add bidirectional streaming — the client and server both stream concurrently.
• Explore TLS credentials (grpc.credentials.createSsl(...)) to secure the channel.
• Try metadata — attach key/value pairs to calls (similar to HTTP headers).
• Use interceptors for cross-cutting concerns like logging and retry.