pn-lambda-logger

A nodejs logger for AWS Lambda

• Writes logs to stdout using console.log
• Logs in JSON format
• Supports log levels: DEBUG, INFO, WARN, ERROR and OFF
• Defaults to log level INFO
• Built using typescript and includes types

Basic example:

import { APIGatewayEvent } from 'aws-lambda';
import { log } from 'pn-lambda-logger';
import { ok } from '../aws/response';

export const healthCheck = async (event: APIGatewayEvent, context: AWSLambda.Context, cb: AWSLambda.Callback) => {

// A standard INFO log message
log.info({ message: 'Message' });

}

  // Output
  {
    "@timestamp": 1541421856289,
    "level": "INFO",
    "message": "Message"
  }

Context and meta data

import { APIGatewayEvent } from 'aws-lambda';
import { log } from 'pn-lambda-logger';
import { ok } from '../aws/response';

export const healthCheck = async (event: APIGatewayEvent, context: AWSLambda.Context, cb: AWSLambda.Callback) => {

  // Setup so that the AWS Lambda meta data will be added to log output
  log.setup({ context, host: event.headers['Host'], verb: event.httpMethod, useragent: event.headers['User-Agent'], query: event.queryStringParameters, path: event.path, xRequestId: event.headers['X-REQUEST-ID'] });

  // A standard INFO log message
  log.info({ message: 'Message' });

  cb(null, ok({ status: 'UP' }));
};

{
  "@timestamp": 1541460988579,
  "level": "INFO",
  "message": "Message",
  "host": "abc123.execute-api.eu-west-1.amazonaws.com",
  "verb": "GET",
  "path": "/manage/health",
  "useragent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.77 Safari/537.36",
  "query": {
    "hello": "world"
  },
  "awsRequestId": "asdas-adsas-asdasdas-asdasda-adss",
  "functionName": "hello",
  "invokedFunctionArn": "arn:cccccc",
  "memoryLimitInMB": 1024,
  "remainingTime": 11147
}

Log Levels

The default log level is INFO log.level = LogLevels.INFO;.
To show debug messages you need to explicitly set the log.level to DEBUG like this:

// Set loglevel
log.level = LogLevels.DEBUG;
// Write debug log
log.debug({ message: 'message' });

{
  "@timestamp": 1541421856291,
  "level": "DEBUG",
  "message": "Message",
}

Logging extra data

You can add any number of extra properties to the object when logging, like this:

// Setup so that the AWS Lambda meta data will be added to log output
  log.setup({ context, host: event.headers['Host'], verb: event.httpMethod, useragent: event.headers['User-Agent'], query: event.queryStringParameters, path: event.path, xRequestId: event.headers['X-REQUEST-ID'] });

// Write debug log
log.info({ message: 'Message', myProp: 'hello', myNestedProp: {subProp: 'something'} });

{
stdoutHijacker.ts:12
  "@timestamp": 1541429192677,
  "level": "INFO",
  "message": "Message",
  "host": "abc123.execute-api.eu-west-1.amazonaws.com",
  "verb": "GET",
  "path": "/manage/health",
  "useragent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.77 Safari/537.36",
  "query": {
    "hello": "world"
  },
  "awsRequestId": "a3de505e-f16b-42f4-b3e6-bcd2e4a73903",
  "functionName": "ExampleCloudFormationStackName-ExampleLambdaFunctionResourceName-AULC3LB8Q02F",
  "functionVersion": "$LATEST",
  "invokedFunctionArn": "arn:aws:lambda:us-west-2:123456789012:function:ExampleCloudFormationStackName-ExampleLambdaFunctionResourceName-AULC3LB8Q02F",
  "memoryLimitInMB": 128,
  "remainingTime": 3,
  "myProp": "hello",
  "myNestedProp": {
    "subProp": "something"
  }
}

Mute all logs:

  log.level = LogLevels.OFF;

Set log level with environment variable

You can easily set the initial log level by setting the environment variable PN_LOG_LEVEL. This can be useful for setting different log levels in different environments TEST|PROD etc. Use 'OFF', 'DEBUG', 'INFO', 'WARN' or 'ERROR', like this:

PN_LOG_LEVEL: 'DEBUG'