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Stream.on()

Mon, 21 Sep 2026 15:16:28 +0000

Stream.on()

Set up handler functions for various events on the gRPC stream.

Parameter	Type	Description
event	string	The event name to define a handler for.
handler	`EventHandler`	The function to call when the event happens.

Possible events:

Event name	Description
data	Emitted when the server sends data.
error	Emitted when an error occurs. In case of the error, an `Error` object sends to the handler function.
end	Emitted when the server closes the incoming stream.

Note
When you enable the experimental async-metric-context feature flag, each Stream.on() handler captures the tags and metadata active when you register it. Metrics emitted by the handler use a copy of that context, and k6 restores the interrupted context after the handler returns or throws. Promise reactions and await continuations created by the handler keep its context.

Example

import { Client, Stream } from 'k6/net/grpc';
import { sleep } from 'k6';

const client = new Client();
client.load([], '../../grpc_server/route_guide.proto');

export default () => {
  if (__ITER == 0) {
    client.connect('127.0.0.1:10000', { plaintext: true });
  }

  const stream = new Stream(client, 'main.RouteGuide/RecordRoute');

  // sets up a handler for the data (server sends data) event
  stream.on('data', (stats) => {
    console.log('Finished trip with', stats.pointCount, 'points');
    console.log('Passed', stats.featureCount, 'features');
    console.log('Traveled', stats.distance, 'meters');
    console.log('It took', stats.elapsedTime, 'seconds');
  });

  // sets up a handler for the end event (stream closes)
  stream.on('end', function () {
    // The server has finished sending
    client.close();
    console.log('All done');
  });

  // sets up a handler for the error event (an error occurs)
  stream.on('error', function (e) {
    // An error has occurred and the stream has been closed.
    console.log('Error: ' + JSON.stringify(e));
  });

  sleep(1);
};

Error

Mon, 21 Sep 2026 15:16:28 +0000

Error

The error object is the object that is passed to the error event handler function.

Name	Type	Description
`Error.code`	number	A gRPC error code.
`Error.details`	array	A list of details attached to the error.
`Error.message`	string	An original error message.

Stream.end()

Mon, 21 Sep 2026 15:16:28 +0000

Stream.end()

Signals to the server that the client has finished sending messages.

Example

import { Client, Stream } from 'k6/net/grpc';
import { sleep } from 'k6';

const client = new Client();
client.load([], '../../grpc_server/route_guide.proto');

export default () => {
  if (__ITER == 0) {
    client.connect('127.0.0.1:10000', { plaintext: true });
  }

  const stream = new Stream(client, 'main.RouteGuide/RecordRoute');

  stream.on('data', (stats) => {
    console.log('Finished trip with', stats.pointCount, 'points');
    console.log('Passed', stats.featureCount, 'features');
    console.log('Traveled', stats.distance, 'meters');
    console.log('It took', stats.elapsedTime, 'seconds');
  });

  // send 2 items
  stream.write({ latitude: 406109563, longitude: -742186778 });
  stream.write({ latitude: 416802456, longitude: -742370183 });

  // send end-signal to the server
  stream.end();

  sleep(1);
};

Stream.write()

Mon, 21 Sep 2026 15:16:28 +0000

Stream.write()

Writes a message to the stream. The message is a canonical request object, as-per the Protobuf JSON Mapping.

Example

import { Client, Stream } from 'k6/net/grpc';
import { sleep } from 'k6';

const client = new Client();
client.load([], '../../grpc_server/route_guide.proto');

export default () => {
  if (__ITER == 0) {
    client.connect('127.0.0.1:10000', { plaintext: true });
  }

  const stream = new Stream(client, 'main.RouteGuide/RecordRoute');

  stream.on('data', (stats) => {
    console.log('Finished trip with', stats.pointCount, 'points');
  });

  // send an item
  stream.write({ latitude: 406109563, longitude: -742186778 });

  // send end-signal to the server
  stream.end();

  sleep(1);
};

Event Handler

Mon, 21 Sep 2026 15:16:28 +0000

Event Handler

The function to call for various events on the gRPC stream. It is set up using the stream.on() method.

Name	Type	Description
`data`	object or `Error`	It’s either object with the data from server (a message) or an error object, in case of `error` event
`metadata`	`Metadata`	The object that represents the gRPC stream’s message metadata.

Example

import { Client, Stream } from 'k6/net/grpc';
import { sleep } from 'k6';

const client = new Client();
client.load([], '../../grpc_server/route_guide.proto');

export default () => {
  if (__ITER == 0) {
    client.connect('127.0.0.1:10000', { plaintext: true });
  }

  const stream = new Stream(client, 'main.RouteGuide/RecordRoute');

  // sets up a handler for the data (server sends data) event
  stream.on('data', (stats, metadata) => {
    console.log('It took', stats.elapsedTime, 'seconds');
    console.log('This message has been received:', metadata.ts);
  });

  stream.on('end', function () {
    // The server has finished sending
    client.close();
  });

  sleep(1);
};

Metadata

Mon, 21 Sep 2026 15:16:28 +0000

Metadata

The Metadata is an object that represents the gRPC stream’s message.

Name	Type	Description
`Metadata.ts`	number	Contains the timestamp of the original event. For example, when a message has been received.

Example

import { Client, Stream } from 'k6/net/grpc';
import { sleep } from 'k6';

const client = new Client();
client.load([], '../../grpc_server/route_guide.proto');

export default () => {
  if (__ITER == 0) {
    client.connect('127.0.0.1:10000', { plaintext: true });
  }

  const stream = new Stream(client, 'main.RouteGuide/RecordRoute');

  // sets up a handler for the data (server sends data) event
  stream.on('data', (stats, metadata) => {
    console.log('It took', stats.elapsedTime, 'seconds');
    console.log('This message has been received:', metadata.ts);
  });

  stream.on('end', function () {
    // The server has finished sending
    client.close();
  });

  sleep(1);
};