Logger

This package can help you add some log to your application. We have four different levels of log, Debug, Info, Warn and Error, by default Debug will be discarded, Info and Warn will be redirect to Stdout and Error will be redirect to Stderr. Note Error Level will always be redirect to Stderr, and you cannot disable that.

This module have a default logger instance with empty Namespace to make easy you use it without any additional line, like we show below

package main

import log "github.com/NeowayLabs/logger"

func main() {
    log.Debug("number=%d string=%s...", 12, "test debug") // discarded
    log.Info("number=%d string=%s...", 10, "test info")   // [INFO] number=10 string=test info...
    log.Warn("number=%d string=%s...", 8, "test warn")    // [WARN] number=8 string=test warn...
    log.Error("number=%d string=%s...", 6, "test error")  // [ERROR] number=6 string=test error...
    // Fatal will abort program
    log.Fatal("number=%d string=%s...", 4, "test fatal")  // [FATAL] number=4 string=test error...
}

You can choose which level will be discarded or what will be shown calling SetLevel() passing logger.LevelDebug, logger.LevelInfo, logger.LevelWarn or logger.LevelError. You can create new instances with namespace if you want, to get new one call logger.Namespace("NAMESPACE).

You can use environment variable to set level instead call SetLevel manually, export LOGGER_LEVEL with debug, info, warn and error, this variable will set level to default namespace logger. To set only of specifc module you can export LOGGER_LEVEL_MY_MODULE, if you don't do that, the level of default will be used. NOTE: the module name will be replace "-" and "." to "_" and will be uppercase. If your module is: "vendor.my-module" your environment variable will be "LOGGER_LEVEL_VENDOR_MY_MODULE"

Take a look at following examples:

package main

import "github.com/NeowayLabs/logger"

func main() {
    // using default logger instance
    logger.Debug("number=%d string=%s...", 12, "test debug") // default debug is discarded
    logger.Warn("number=%d string=%s...", 8, "test warn")    // [WARN] number=8 string=test warn...

    // set level to show debug
    logger.SetLevel(logger.LevelDebug)
    logger.Debug("number=%d string=%s...", 12, "test debug") // [DEBUG] number=12 string=test debug...
    logger.Warn("number=%d string=%s...", 8, "test warn")    // [WARN] number=8 string=test warn...


    // getting new instance with namespace
    log := logger.Namespace("my-module")
    log.Debug("number=%d string=%s...", 12, "test debug") // default debug is discarded
    log.Warn("number=%d string=%s...", 8, "test warn")    // <my-module> [WARN] number=8 string=test warn...

    // set level to show debug
    log.SetLevel(logger.LevelDebug)
    log.Debug("number=%d string=%s...", 12, "test debug") // <my-module> [DEBUG] number=12 string=test debug...
    log.Warn("number=%d string=%s...", 8, "test warn")    // <my-module> [WARN] number=8 string=test warn...
}

Use new handlers

You can create new handler to log in the different ways, you can implement log handler to send any kind of alert, like send an email when error occour, or write warns to file. To do that you need implement at least of following interface. An example of our default implementation you found here

• Debug Interface
• Info Interface
• Warn Interface
• Error Interface
• Fatal Interface
• Init Interface this function will be called when you add your handler to logger instance and always setLevel was called

HTTP handler

To avoid you have to restart your app to change level of your logger, we develop a HTTP Handler to you control all the levels of your app, we have an usage example:

package main

import (
    "net/http"

    "github.com/NeowayLabs/logger"
)

func main() {
    log := logger.Namespace("TEST")

    http.Handle("/logger/", logger.HTTPHandler()) // handle /logger/NAMESPACE
    http.Handle("/logger", logger.HTTPHandler()) // handle /logger
    err := http.ListenAndServe(":8080", nil)
    if err != nil {
        log.Fatal("ListenAndServe: ", err)
    }
}

• You can get the list of all namespaces and its levels (key default is the empty namespace, default one)

curl http://localhost:8080/logger

• You can get the level of a specific namespace

curl http://localhost:8080/logger/test

• You can set the level of a specific namespace

curl -XPUT http://localhost:8080/logger --data '{"namespace": "", "level": "debug"}' # set level of default namespace (empty)
curl -XPUT http://localhost:8080/logger --data '{"namespace": "test", "level": "debug"}' # set level of test namespace
curl -XPUT http://localhost:8080/logger/test --data '{"level": "warn"}' # set level of test namespace

• You can set the level of all namespaces

curl -XPUT http://localhost:8080/logger/all --data '{"level": "debug"}' # set level of all namespaces