zenoss / logri

Hierarchical, configurable, structured logging for Go

Logri

Logri is a wrapper for Logrus that provides hierarchical, configurable, structured logging.

Like Logrus, it's a drop-in replacement for Go's standard logging library, but it adds the ability to:

• Define loggers that inherit their log levels and output streams from parent loggers
• Configure loggers from a YAML file
• Update configuration on the fly
• Optionally watch a logging configuration file for changes

And, of course, it retains Logrus's excellent structured logging capabilities.

Usage

You can drop Logri in to replace logging or Logrus very simply:

package main


import (
        "github.com/Sirupsen/logrus"
    log "github.com/zenoss/logri"
)

func main() {

    log.Infof("Logri can replace the %s package", "logging")

    log.WithFields(logrus.Fields{
        "package": "logrus",
    }).Infof("Or another popular logging package")
}

Named loggers

The power of Logri comes in with named hierarchical loggers. Use logri.GetLogger(name) with a dotted name to return an individual logger that inherits its log level and outputs from its parent, but can add or override its own.

package main

import (
    "github.com/Sirupsen/logrus"
    "github.com/zenoss/logri"
)

var (
    pkglog = logri.GetLogger("package")
    cmplog = logri.GetLogger("package.component")
    subcmplog = logri.GetLogger("package.component.subcomponent")
)

func main() {

    pkglog.SetLevel(logrus.DebugLevel, true) // Second argument makes it inherited
    // package.component and package.component.subcomponent are also Debug level now

    // Quiet package.component down but leave subcomponent at debug
    cmplog.SetLevel(logrus.ErrorLevel, false) // Second argument false means
                                              // local to this logger only
}

Further calls to logri.GetLogger(name) will retrieve the same logger instance, so there's no need to jump through hoops exporting loggers to share them among packages.

Configuration via file

You can also configure Logri using a YAML file. Given a file /etc/logging.conf with these contents:

- logger: '*'
  level: debug
  out:
  - type: stderr
  - type: file
    options:
      file: /var/log/app.log
- logger: package
  level: warn
  local: true
  out:
  - type: file
    local: true
    options:
      file: /var/log/package.warn.log
- logger: package.component
  level: error
  out:
  - type: file
    options:
      file: /var/log/package.component.error.log

You can configure the loggers defined above very simply:

logri.ApplyConfigFromFile("/etc/logging.conf")

That can be called at any time, and it will reconfigure loggers to match the config at that time, with no need to restart or recreate loggers.

You can also watch that file for changes, rather than listening for a signal to reload logging config:

package main

import (
    "github.com/zenoss/logri"
)

func main() {

    // Start watching the logging config for changes
    go logri.WatchConfigFile("/etc/logging.conf")

    doStuff()
}