xlog

Install

go get github.com/rs/xlog

Copy Logger

You may want to get a copy of the current logger to pass a modified version to a function without touching the original:

l := xlog.FromContext(ctx)
l2 := xlog.Copy(l)
l2.SetField("foo", "bar")

Make sure you copy a request context logger if you plan to use it in a go routine that may still exist after the end of the current request. Contextual loggers are reused after each requests to lower the pressure on the garbage collector. If you would use such a logger in a go routine, you may end up using a logger from another request/context or worse, a nil pointer:

l := xlog.FromContext(ctx)
l2 := xlog.Copy(l)
go func() {
    // use the safe copy
    l2.Info("something")
}()

Configure Output

By default, output is setup to output debug and info message on STDOUT and warning and errors to STDERR. You can easily change this setup.

XLog output can be customized using composable output handlers. Thanks to the LevelOutput, MultiOutput and FilterOutput, it is easy to route messages precisely.

conf := xlog.Config{
    Output: xlog.NewOutputChannel(xlog.MultiOutput{
        // Send all logs with field type=mymodule to a remote syslog
        0: xlog.FilterOutput{
            Cond: func(fields map[string]interface{}) bool {
                return fields["type"] == "mymodule"
            },
            Output: xlog.NewSyslogOutput("tcp", "1.2.3.4:1234", "mymodule"),
        },
        // Setup different output per log level
        1: xlog.LevelOutput{
            // Send errors to the console
            Error: xlog.NewConsoleOutput(),
            // Send syslog output for error level
            Info: xlog.NewSyslogOutput("", "", ""),
        },
    }),
})

h = xlog.NewHandler(conf)

Third Party Extensions

Project	Author	Description
gRPClog	Hugo González Labrador	An adapter to use xlog as the logger for grpclog.
xlog-nsq	Olivier Poitrey	An xlog to NSQ output.
xlog-sentry	trong	An xlog to Sentry output.