Namespace: activity

This library provides tools for authoring activities.

Import this module from Activity code - must not be used in Workflows.

Any function can be used as an Activity as long as its parameters and return value are serializable using a DataConverter.

Cancellation

Activities may be cancelled only if they emit heartbeats.
There are 2 ways to handle Activity cancellation:

1. await on Context.current().cancelled
2. Pass the context's abort signal at Context.current().cancellationSignal to a library that supports it

Examples

An Activity that fakes progress and can be cancelled

import { Context } from '@temporalio/activity';
import { CancelledFailure } from '@temporalio/common';

export async function fakeProgress(sleepIntervalMs = 1000): Promise<void> {
  try {
    // allow for resuming from heartbeat
    const startingPoint = Context.current().info.heartbeatDetails || 1;
    console.log('Starting activity at progress:', startingPoint);
    for (let progress = startingPoint; progress <= 100; ++progress) {
      // simple utility to sleep in activity for given interval or throw if Activity is cancelled
      // don't confuse with Workflow.sleep which is only used in Workflow functions!
      console.log('Progress:', progress);
      await Context.current().sleep(sleepIntervalMs);
      Context.current().heartbeat(progress);
    }
  } catch (err) {
    if (err instanceof CancelledFailure) {
      console.log('Fake progress activity cancelled');
      // Cleanup
    }
    throw err;
  }
}

An Activity that makes a cancellable HTTP request

import fetch from 'node-fetch';
import { Context } from '@temporalio/activity';

export async function cancellableFetch(url: string): Promise<Uint8Array> {
  const response = await fetch(url, { signal: Context.current().cancellationSignal });
  const contentLengthHeader = response.headers.get('Content-Length');
  if (contentLengthHeader === null) {
    throw new Error('expected Content-Length header to be set');
  }
  const contentLength = parseInt(contentLengthHeader);
  let bytesRead = 0;
  const chunks: Buffer[] = [];

  for await (const chunk of response.body) {
    if (!(chunk instanceof Buffer)) {
      throw new TypeError('Expected Buffer');
    }
    bytesRead += chunk.length;
    chunks.push(chunk);
    Context.current().heartbeat(bytesRead / contentLength);
  }
  return Buffer.concat(chunks);
}

Classes

• CompleteAsyncError
• Context
• IllegalStateError
• PayloadConverterError
• ValueError
• WorkflowExecutionAlreadyStartedError
• WorkflowNotFoundError

Interfaces

• Info

References

ActivityFunction

Re-exports ActivityFunction

---

ActivityInterface

Re-exports ActivityInterface

---

CancelledFailure

Re-exports CancelledFailure

Functions

errorCode

▸ errorCode(error): string | undefined

Get error code from an Error or return undefined

Parameters

Name	Type
error	unknown

Returns

string | undefined

---

errorMessage

▸ errorMessage(err): string | undefined

Get error message from an Error or string or return undefined

Parameters

Name	Type
err	unknown

Returns

string | undefined