ECS Logging with Winstonedit

This Node.js package provides a formatter for the winston logger, compatible with Elastic Common Schema (ECS) logging. In combination with the Filebeat shipper, you can monitor all your logs in one place in the Elastic Stack.

Setupedit

Step 1: Installedit

$ npm install @elastic/ecs-winston-format

Step 2: Configureedit

const winston = require('winston')
const ecsFormat = require('@elastic/ecs-winston-format')

const logger = winston.createLogger({
  format: ecsFormat(), 
  transports: [
    new winston.transports.Console()
  ]
})

logger.info('hi')
logger.error('oops there is a problem', { err: new Error('boom') })

Step 3: Configure Filebeatedit

The best way to collect the logs once they are ECS-formatted is with Filebeat:

filebeat.inputs:
- type: log
  paths: /path/to/logs.json
  json.keys_under_root: true
  json.overwrite_keys: true
  json.add_error_key: true
  json.expand_keys: true

annotations:
  co.elastic.logs/json.keys_under_root: true
  co.elastic.logs/json.overwrite_keys: true
  co.elastic.logs/json.add_error_key: true
  co.elastic.logs/json.expand_keys: true

labels:
  co.elastic.logs/json.keys_under_root: true
  co.elastic.logs/json.overwrite_keys: true
  co.elastic.logs/json.add_error_key: true
  co.elastic.logs/json.expand_keys: true

For more information, see the Filebeat reference.

Usageedit

const winston = require('winston')
const ecsFormat = require('@elastic/ecs-winston-format')

const logger = winston.createLogger({
  level: 'info',
  format: ecsFormat(), 
  transports: [
    new winston.transports.Console()
  ]
})

logger.info('hi')
logger.error('oops there is a problem', { foo: 'bar' })

Running this script (available here) will produce log output similar to the following:

% node examples/basic.js
{"@timestamp":"2021-01-13T21:32:38.095Z","log.level":"info","message":"hi","ecs":{"version":"1.6.0"}}
{"@timestamp":"2021-01-13T21:32:38.096Z","log.level":"error","message":"oops there is a problem","ecs":{"version":"1.6.0"},"foo":"bar"}

The formatter handles serialization to JSON, so you don’t need to add the json formatter. As well, a timestamp is automatically generated by the formatter, so you don’t need to add the timestamp formatter.

Error loggingedit

By default, the formatter will convert an err meta field that is an Error instance to ECS Error fields. For example:

const winston = require('winston')
const ecsFormat = require('@elastic/ecs-winston-format')
const logger = winston.createLogger({
  format: ecsFormat(), 
  transports: [
    new winston.transports.Console()
  ]
})

const myErr = new Error('boom')
logger.info('oops', { err: myErr }) 

will yield (pretty-printed for readability):

% node examples/error.js | jq .
{
  "@timestamp": "2021-01-26T17:25:07.983Z",
  "log.level": "info",
  "message": "oops",
  "ecs": {
    "version": "1.6.0"
  },
  "error": {
    "type": "Error",
    "message": "boom",
    "stack_trace": "Error: boom\n    at Object.<anonymous> (..."
  }
}

Special handling of the err meta field can be disabled via the convertErr: false option:

...
const logger = winston.createLogger({
  format: ecsFormat({ convertErr: false }),
...

HTTP Request and Response Loggingedit

With the convertReqRes: true option, the formatter will automatically convert Node.js core request and response objects when passed as the req and res meta fields, respectively.

const http = require('http')
const winston = require('winston')
const ecsFormat = require('@elastic/ecs-winston-format')

const logger = winston.createLogger({
  level: 'info',
  format: ecsFormat({ convertReqRes: true }), 
  transports:
    new winston.transports.Console()
  ]
})

const server = http.createServer(handler)
server.listen(3000, () => {
  logger.info('listening at http://localhost:3000')
})

function handler (req, res) {
  res.setHeader('Foo', 'Bar')
  res.end('ok')
  logger.info('handled request', { req, res }) 
}

This will produce logs with request and response info using ECS HTTP fields. For example:

% node examples/http.js | jq .    # using jq for pretty printing
...                               # run 'curl http://localhost:3000/'
{
  "@timestamp": "2021-01-13T22:00:07.442Z",
  "log.level": "info",
  "message": "handled request",
  "ecs": {
    "version": "1.6.0"
  },
  "http": {
    "version": "1.1",
    "request": {
      "method": "GET",
      "headers": {
        "host": "localhost:3000",
        "accept": "*/*"
      }
    },
    "response": {
      "status_code": 200,
      "headers": {
        "foo": "Bar"
      }
    }
  },
  "url": {
    "path": "/",
    "full": "http://localhost:3000/"
  },
  "user_agent": {
    "original": "curl/7.64.1"
  }
}

Integration with APM Tracingedit

This ECS log formatter integrates with Elastic APM. If your Node app is using the Node.js Elastic APM Agent, then fields are added to log records that identify an active trace and the configured service name ("service.name" and "event.dataset"). These fields allow cross linking between traces and logs in Kibana and support log anomaly detection.

For example, running examples/http-with-elastic-apm.js and curl -i localhost:3000/ results in a log record with the following:

% node examples/http-with-elastic-apm.js | jq .
...
  "event": {
    "dataset": "http-with-elastic-apm.log"
  },
  "trace": {
    "id": "74631535a02bbe6a07c298b28c7443f4"
  },
  "transaction": {
    "id": "505400b77aba4d9a"
  },
  "service": {
    "name": "http-with-elastic-apm"
  }
...

These IDs match trace data reported by the APM agent.

Integration with Elastic APM can be explicitly disabled via the apmIntegration: false option, for example:

const logger = winston.createLogger({
  format: ecsFormat({ apmIntegration: false }),
  // ...
})