Simple logging library for node projects

Main purpose for this library is having streamlined logging logic, like in production output would be in JSON and while developing it's output is simpler with better readability (default winston console). Library has two main components, logger and loggerExpress (express' middleware, which is easy to plug in).

Environment variables

• LOG_SERIALIZATION = json | text - when json is set, log output will be json serialized, text otherwise
• NODE_ENV = production | development - when production is set only info, warn and error levels are logged and for loggerExpress only erroneous response codes (>400) will be logged.
• LOG_LEVEL = debug | info | warn | error - set log level without having to change NODE_ENV of your application
• LOG_SANITIZATION = true - if not specified, sanitization depends on NODE_ENV: disabled for development, enabled for production. Setting this to true forces sanitization on in non-production environments. Production sanitization is always on and cannot be disabled via this flag.
• LOG_SANITIZE_CUSTOM_FIELDS = field1,field2,field3 - sanitize additional fields (when sanitization is enabled), defined as a comma-separated list of field names

logger

Logger adds metadata for instance (like host), replaces sensitive meta fields (like password) with asterisk.

Usage

It has typical logging functions like:

logger.init({ prefix: 'myProject' }); // All the meta info will be prefixed with this key

logger.debug('This is verbose debugging message', { someMetaData: 'Like so', user: { username: 'someuser' } });
logger.info('This is informational', { someMetaData: 'Like so', username: 'something', password: 'secret123' });
logger.warn('This warns about something', { someMetaData: 'Like so' });
logger.error('Some kind of error, things went bad', { someMetaData: 'Like so', username: 'something', password: 'secret123' });

loggerExpress

It adds metadata for:

• instance's hostname (os.hostname()) as host
• request
  • request.headers[x-forwarded-for] as meta.request.xForwardedFor
  • request.headers.authorization without signature as meta.request.authorization
  • req.connection.remoteAddres as meta.request.remoteAddress
  • body content (for debugging when error occur)),
• response
  • response.headers[content-length] as meta.response.contentLength
  • time duration how long does the serving took as meta.response.timeMs

Usage

As it's just express middleware you can simply import and use:

expressServer.use(loggerExpress);

Example json output

From express

{
  "timestamp": "2017-09-20T10:36:10.110Z",
  "level": "error",
  "host": "fdd9bb5a29dd",
  "method": "POST",
  "url": "\/graphql",
  "status": 400,
  "meta": {
    "request": {
      "xForwardedFor": "213.219.106.114, 172.68.182.194, 10.0.2.164",
      "body": {
        "id": "q7",
        "query": "query ...",
        "variables": {

        }
      }
    },
    "response": {
      "contentLength": 132,
      "timeMs": 8.024
    }
  }
}

From logger

{
  "@timestamp": "2017-09-20T10:36:10.110Z",
  "level": "error",
  "meta": {
    "stack": "GraphQLError: Cannot query field \"someRandomField\" on type \"SomeRandomType\".\n    at Object.Field (\/...\/FieldsOnCorrectType.js:66:31)\n    at Object.enter (\/...\/visitor.js:297:29)\n",
    "nodes": [
      {
        "selectionSet": null,
        "loc": {
          "start": 694,
          "end": 707
        },
        "directives": [

        ],
        "kind": "Field",
        "name": {
          "loc": {
            "start": 694,
            "end": 707
          },
          "kind": "Name",
          "value": "someRandomField"
        },
        "alias": null,
        "arguments": [

        ]
      }
    ],
    "locations": [
      {
        "line": 1,
        "column": 695
      }
    ],
    "positions": [
      694
    ],
    "source": {
      "name": "GraphQL request",
      "body": "query Application {...."
    },
    "message": "Cannot query field \"someRandomField\" on type \"SomeRandomType\"."
  },
  "host": "fdd9bb5a29dd",
  "message": "",
  "type": "live"
}