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Logging practices

Published February 7, 2023Last updated June 14, 20242 min read

This post covers some logging practices for the back-end (Node.js) apps.

  • Avoid putting unique identifiers (e.g., user id) within the message. A unique id will produce a lot of different messages with the same context. Use it as a message parameter.

  • Use the appropriate log level for the message. There are multiple log levels

    • info - app behavior, don't log every single step
    • error - app processing failure, something that needs to be fixed
    • debug - additional logs needed for troubleshooting
    • warning - something unexpected happened (e.g., third-party API fails)
    • fatal - app crash, needs to be fixed as soon as possible

Don't use the debug logs on production. Put log level as an environment variable.

  • Stream logs to the standard output in JSON format so logging aggregators (Graylog, e.g.) can collect and adequately parse them

  • Avoid logging any credentials, like passwords, auth tokens, etc.

  • Put correlation ID as a message parameter for tracing related logs.

  • Use a configurable logger like pino

const pino = require('pino');
const logger = pino({
level: process.env.LOG_LEVEL || 'info',
redact: {
paths: ['token'],
remove: true,
},
});
logger.info({ someId: 'id' }, 'Started the app...');
const correlationId = request.headers['correlation-id'] || uuid.v4();
logger.debug({ data: 'some data useful for debugging', correlationId }, 'Sending the request...');

Boilerplate

Here is the link to the boilerplate I use for the development.