How to send logs from Workflows in TypeScript

Logging in Workers and Clients

The Worker comes with a default logger which defaults to log any messages with level INFO and higher to STDERR using console.error. There are 5 levels in total:

• TRACE
• DEBUG
• INFO
• WARN
• ERROR

The reason we only offer a default logger is to minimize Worker dependencies and allow SDK users to bring their own logger.

Customizing the default logger

Temporal ships a DefaultLogger that implements the basic interface.

Set Default logger level

The following example creates a new logger that will log all messages with a level WARN and higher.

TypeScript

import { Runtime, DefaultLogger } from '@temporalio/worker';

// Creating a new logger that will log all messages with level WARN and higher.
const logger = new DefaultLogger('WARN', ({ level, message }) => {
  console.log(`Custom logger: ${level} — ${message}`);
});
Runtime.install({ logger });

JavaScript

import { Runtime, DefaultLogger } from '@temporalio/worker';

// Creating a new logger that will log all messages with level WARN and higher.
const logger = new DefaultLogger('WARN', ({ level, message }) => {
  console.log(`Custom logger: ${level} — ${message}`);
});
Runtime.install({ logger });

Example: Accumulate logs for testing/reporting

The following example creates a logger that will log all the messages to an array.

TypeScript

import { DefaultLogger, LogEntry } from '@temporalio/worker';

const logs: LogEntry[] = [];
const logger = new DefaultLogger('TRACE', (entry) => logs.push(entry));
log.debug('hey', { a: 1 });
log.info('ho');
log.warn('lets', { a: 1 });
log.error('go');

JavaScript

import { DefaultLogger } from '@temporalio/worker';

const logs = [];
const logger = new DefaultLogger('TRACE', (entry) => logs.push(entry));
log.debug('hey', { a: 1 });
log.info('ho');
log.warn('lets', { a: 1 });
log.error('go');

The log levels are listed here in increasing order of severity.