@commercetools-backend/loggers

Opinionated JSON loggers for HTTP server applications.

Install

$ npm install --save @commercetools-backend/loggers

Middlewares

Access logger

Creates a logger to be used for HTTP requests access logs.

const {
  createAccessLoggerMiddleware,
} = require('@commercetools-backend/loggers');

app.use(createAccessLoggerMiddleware());

Options

• level (string): The log level to be used. Default: info
• silent (boolean): In case logs should be skipped. Default: false
• json (boolean): To use the JSON formatter, otherwise falls back to CLI format. It's recommended to use the JSON formatter on production.
• formatters (Array of Winston formatters): In case you want to pass additional Winston formatters.
• ignoreUrls (Array of string): A list of URL paths to be ignored from being logged.

Application logger

Creates a logger to be used programmatically in the application code.

const { createApplicationLogger } = require('@commercetools-backend/loggers');

const app = createApplicationLogger();

app.info('Hey there', { meta: { name: 'Tom' } });

Options

• level (string): The log level to be used. Default: info
• silent (boolean): In case logs should be skipped. Default: false
• json (boolean): To use the JSON formatter, otherwise falls back to CLI format. It's recommended to use the JSON formatter on production.
• formatters (Array of Winston formatters): In case you want to pass additional Winston formatters.

Formatters

The package provides some come Winston formatters that can be passed to the given loggers.

Rewrite fields

This formatter allows to rewrite fields from the JSON logger. It can be useful for redacting insecure information, or to map certain fields to a specific format (for example for Kibana).

const {
  createAccessLoggerMiddleware,
  rewriteFieldsFormatter,
} = require('@commercetools-backend/loggers');

app.use(
  createAccessLoggerMiddleware({
    formatters: [
      rewriteFieldsFormatter({
        fields: [
          { from: 'level', to: 'logLevel' },
          { from: 'meta.error.message', to: 'meta.errorMessage' },
          {
            from: 'meta.error',
            to: 'meta.errorJsonString',
            replaceValue: (value) => JSON.stringify(value),
          },
        ],
      }),
    ],
  })
);

Options

• fields (Array of RewriteField): A RewriteField is an object with the following properties:
  • from (string): A JSON path to one of the fields of the log information that needs to be rewritten. The field will be deleted.
  • to (string): A JSON path to the new field that should be created.
  • replaceValue (function): An optional function that takes the value from the original field and returns a new value for the field. It can be used for example to serialize the value with JSON.stringify.