ExamplesCommon patterns and examples using LambdaLog.

To help jump start development with LambdaLog and some of the features/patterns, there are a handful of different examples that have been used in the real-world.

Tag log messages per file

A good use case for global tags is by labeling your log messages with the file the log is coming from. You will need to create a new instance of LambdaLog for each of your files instead of using the default instance.

 1// index.js
 2 
 3const { LambdaLog } = require('lambda-log'); 
 4 
 5exports.handler = async function handler(event) {
 6  // Require other files within the handler to prevent caching issues.
 7  const api = require('./api');
 8  const log = new LambdaLog({ 
 9    tags: ['index']
10  });
11 
12  log.info('Starting process'); 
    // => { "_logLevel": "info", "msg": "Starting process", "_tags": ["index"] } 
13 
14  // ...
15 
16  try {
17    if(api.isValidId(event.id)) {
18      const result = await api.getData(event);
19 
20      return result;
21    }
22 
23    return false;
24  } catch(error) {
25    log.error(error).throw; 
      // => { "_logLevel": "error", "msg": "...", "name": "Error", "stack": "...", "_tags": ["index"] } 
26  }
27};

All logs will contain ["index"] as their tag.

 1// api.js
 2 
 3const { LambdaLog } = require('lambda-log'); 
 4const log = new LambdaLog({
 5  tags: ['api']
 6});
 7 
 8module.exports = {
 9  getData: async function getData(event) {
10    log.info('Calling API with event data', { event }); 
      // => { "_logLevel": "info", "msg": "Calling API with event data", "event": { ... }, "_tags": ["api"] } 
11 
12    // ..get data
13 
14    return data;
15  },
16 
17  isValidId(id) {
18    if(/^[0-9a-z]{10}/.test(id)) {
19      return true;
20    }
21 
22    log.warn(`Invalid ID provided`, { id }, ['isValidId']); 
      // => { "_logLevel": "warn", "msg": "Invalid ID provided", "id": "...", "_tags": ["api", "isValidId"] } 
23    return false;
24  }
25};

All logs will contain ["api"] as their tag. The last log.warn() also has local tags as well which will yield ["api", "isValidId"] as its tags.

Include Lambda Function Name/Invocation ID in the log messages

You can add additional information from the Lambda Context Object into the global metadata of your logs.

 1// index.js
 2 
 3exports.handler = async function handler(event, context) {
 4  // Require inside the handler to prevent caching issues on subsequent executions
 5  const log = require('lambda-log'); 
 6  log.options.meta = {
 7    functionName: context.functionName,
 8    requestId: context.awsRequestId
 9  };
10 
11  log.info('Starting process'); 
    // => { "_logLevel": "info", "msg": "Starting process", "functionName": "my-lambda-function", "requestId": "xxx", "_tags": [] } 
12 
13  // ...
14 
15  return true;
16};

 1// index.js
 2 
 3const { LambdaLog } = require('lambda-log'); 
 4 
 5exports.handler = async function handler(event, context) {
 6  const log = new LambdaLog({ 
 7    meta: {
 8      functionName: context.functionName,
 9      requestId: context.awsRequestId
10    }
11  });
12 
13  log.info('Starting process'); 
    // => { "_logLevel": "info", "msg": "Starting process", "functionName": "my-lambda-function", "requestId": "xxx", "_tags": [] } 
14 
15  // ...
16 
17  return true;
18};