Logging

All Moleculer’s core modules have a custom logger instance. They are inherited from the broker logger instance which can be configured in the broker options.

The v0.14 version contains breaking changes. This means that you can’t use the old way of configuring the logger. If you are using the built-in default console logger, this breaking change doesn’t affect you. For more info check the Migration Guide.

Built-in Loggers

Console (default)

This logger prints all log messages to the console. It supports several built-in formatters or you can use your custom formatter, as well.

Shorthand configuration with default options

// moleculer.config.js
module.exports = {
    logger: "Console",
};

// moleculer.config.js
module.exports = {
    // Enable console logger
    logger: true,
};

Full configuration

// moleculer.config.js
module.exports = {
    logger: {
        type: "Console",
        options: {
            // Logging level
            level: "info",
            // Using colors on the output
            colors: true,
            // Print module names with different colors (like docker-compose for containers)
            moduleColors: false,
            // Line formatter. It can be "json", "short", "simple", "full", a `Function` or a template string like "{timestamp} {level} {nodeID}/{mod}: {msg}"
            formatter: "full",
            // Custom object printer. If not defined, it uses the `util.inspect` method.
            objectPrinter: null,
            // Auto-padding the module name in order to messages begin at the same column.
            autoPadding: false
        }
    }
};

Formatters

full formatter (default)

// moleculer.config.js
module.exports = {
    logger: {
        type: "Console",
        options: {
            formatter: "full" // or `null`
        }
    }
};

Preview

short formatter

// moleculer.config.js
module.exports = {
    logger: {
        type: "Console",
        options: {
            formatter: "short"
        }
    }
};

Preview

simple formatter

// moleculer.config.js
module.exports = {
    logger: {
        type: "Console",
        options: {
            formatter: "simple"
        }
    }
};

Preview

json formatter

// moleculer.config.js
module.exports = {
    logger: {
        type: "Console",
        options: {
            formatter: "json"
        }
    }
};

Preview

Custom formatter

// moleculer.config.js
module.exports = {
    logger: {
        type: "Console",
        options: {
            formatter: (level, args, bindings) => [`[${level.toUpperCase()}]`, ...args]
        }
    }
};

Preview

File

This logger saves all log messages to file(s). It supports JSON & formatted text files or you can use your custom formatter, as well.

Shorthand configuration with default options

// moleculer.config.js
module.exports = {
    logger: "File",
};

It will save the log messages to the logs folder in the current directory with moleculer-{date}.log filename.

Full configuration

// moleculer.config.js
module.exports = {
    logger: {
        type: "File",
        options: {
            // Logging level
            level: "info",
            // Folder path to save files. You can use {nodeID} & {namespace} variables.
            folder: "./logs",
            // Filename template. You can use {date}, {nodeID} & {namespace} variables.
            filename: "moleculer-{date}.log",
            // Line formatter. It can be "json", "short", "simple", "full", a `Function` or a template string like "{timestamp} {level} {nodeID}/{mod}: {msg}"
            formatter: "json",
            // Custom object printer. If not defined, it uses the `util.inspect` method.
            objectPrinter: null,
            // End of line. Default values comes from the OS settings.
            eol: "\n",
            // File appending interval in milliseconds.
            interval: 1 * 1000
        }
    }
};

External Loggers

Pino

This logger uses the Pino logger.

Shorthand configuration with default options

// moleculer.config.js
module.exports = {
    logger: "Pino",
};

Full configuration

// moleculer.config.js
module.exports = {
    logger: {
        type: "Pino",
        options: {
            // Logging level
            level: "info",

            pino: {
                // More info: http://getpino.io/#/docs/api?id=options-object
                options: null,

                // More info: http://getpino.io/#/docs/api?id=destination-sonicboom-writablestream-string
                destination: "/logs/moleculer.log",
            }
        }
    }
};

To use this logger please install the pino module with npm install pino --save command.

Preview

Bunyan

This logger uses the Bunyan logger.

Shorthand configuration with default options

// moleculer.config.js
module.exports = {
    logger: "Bunyan",
};

Full configuration

// moleculer.config.js
module.exports = {
    logger: {
        type: "Bunyan",
        options: {
            // Logging level
            level: "info",

            bunyan: {
                // More settings: https://github.com/trentm/node-bunyan#constructor-api
                name: "moleculer"
            }
        }
    }
};

To use this logger please install the bunyan module with npm install bunyan --save command.

Preview

Winston

This logger uses the Winston logger.

Shorthand configuration with default options

// moleculer.config.js
module.exports = {
    logger: "Winston",
};

Full configuration

// moleculer.config.js
const winston = require("winston");

module.exports = {
    logger: {
        type: "Winston",
        options: {
            // Logging level
            level: "info",

            winston: {
                // More settings: https://github.com/winstonjs/winston#creating-your-own-logger
                transports: [
                    new winston.transports.Console(),
                    new winston.transports.File({ filename: "/logs/moleculer.log" })
                ]
            }
        }
    }
};

To use this logger please install the winston module with npm install winston --save command.

Preview

debug

This logger uses the debug logger.
To see messages you have to set the DEBUG environment variable to export DEBUG=moleculer:*.

Shorthand configuration with default options

// moleculer.config.js
module.exports = {
    logger: "Debug",
};

Full configuration

// moleculer.config.js
module.exports = {
    logger: {
        type: "Debug",
        options: {
            // Logging level
            level: "info",
        }
    }
};

To use this logger please install the debug module with npm install debug --save command.

Preview

Log4js

This logger uses the Log4js logger.

Shorthand configuration with default options

// moleculer.config.js
module.exports = {
    logger: "Log4js",
};

Full configuration

// moleculer.config.js
module.exports = {
    logger: {
        type: "Log4js",
        options: {
            // Logging level
            level: "info",
            
            log4js: {
                // More info: https://github.com/log4js-node/log4js-node#usage
                appenders: {
                    app: { type: "file", filename: "/logs/moleculer.log" }
                },
                categories: {
                    default: { appenders: [ "app" ], level: "debug" }
                }
            }
        }
    }
};

To use this logger please install the log4js module with npm install log4js --save command.

Preview

Datadog

This logger uploads log messages to the Datadog server.

Please note, this logger doesn’t print any messages to the console, just collects & uploads. Use it beside another logger which also prints the messages.

Shorthand configuration with default options

// moleculer.config.js
module.exports = {
    logger: "Datadog",
};

Full configuration

// moleculer.config.js
module.exports = {
    logger: {
        type: "Datadog",
        options: {
            // Logging level
            level: "info",
            // Datadog server endpoint. https://docs.datadoghq.com/api/?lang=bash#send-logs-over-http
            url: "https://http-intake.logs.datadoghq.com/v1/input/",
            // Datadog API key
            apiKey: process.env.DATADOG_API_KEY,
            // Datadog source variable
            ddSource: "moleculer",
            // Datadog env variable
            env: undefined,
            // Datadog hostname variable
            hostname: os.hostname(),
            // Custom object printer function for `Object` & `Ąrray`
            objectPrinter: null,
            // Data uploading interval
            interval: 10 * 1000
        }
    }
};

Preview

Multiple Loggers

This new logger configuration admits usage of multiple loggers even from the same logger type and different logging levels.

Define multiple loggers with different logging levels

// moleculer.config.js
module.exports = {
    logger: [
        {
            type: "Console",
            options: {
                level: "info",
            }
        },
        {            
            type: "File",
            options: {
                level: "info",
                folder: "/logs/moleculer",
                filename: "all-{date}.log",
                formatter: "{timestamp} {level} {nodeID}/{mod}: {msg}"
            }
        },
        {
            type: "File",
            options: {
                level: "error",
                folder: "/logs/moleculer",
                filename: "errors-{date}.json",
                formatter: "json"
            }
        }
    ]   
};

This example shows a configuration of Console logger, a File logger that saves all log messages in formatted text file and another File logger that only saves error messages in JSON format.

Filtering

You can configure your loggers to only log data of certain services or modules.
Example

// moleculer.config.js
module.exports = {
    logger: [
        // Shorthand `Console` logger configuration
        "Console",
        {            
            // This logger saves messages from all modules except "greeter" service.
            type: "File",
            options: {
                level: {
                    "GREETER": false,
                    "**": "info"
                },
                filename: "moleculer-{date}.log"
            }
        },
        {
            // This logger saves messages from only "greeter" service.
            type: "File",
            options: {
                level: {
                    "GREETER": "debug",
                    "**": false
                },
                filename: "greeter-{date}.log"
            }
        }
    ],

    logLevel: "info" // global log level. All loggers inherits it. 
};

Log Level Setting

To configure logging levels, you can use the well-known logLevel broker option which can be a String or an Object. However, it is also possible to overwrite it in all logger options with the level property.

Complex logging level configuration

// moleculer.config.js
module.exports = {
    logger: [
        // The console logger will use the `logLevel` global setting.
        "Console",
        {            
            type: "File",
            options: {
                // Overwrite the global setting.
                level: {
                    "GREETER": false,
                    "**": "warn"
                }
            }
        }
    ],
    logLevel: {
        "TRACING": "trace",
        "TRANS*": "warn",
        "GREETER": "debug",
        "**": "info",
    }
};

Custom logger

If you have your custom logger you should wrap it into a BaseLogger class and implement at least the getLogHandler method.

Using a custom logger

// moleculer.config.js
 const BaseLogger = require("moleculer").Loggers.Base;

class MyLogger extends BaseLogger {
    getLogHandler(bindings) {
        return (type, args) => console[type](`[MYLOG-${bindings.mod}]`, ...args);
    }
}

module.exports = {
    logger: new MyLogger()
};