Introducing gmx, runtime instrumentation for Go applications

What is gmx ?

gmx is an experimental package for instrumenting Go applications. gmx is similar to Java’s jmx and provides a simple method of querying the internal state of your Go application by invoking anonymous functions bound to published keys. Here is an example using the included client, gmxc.

% ./gmxc -p 16378 runtime.version runtime.numcpu os.args 
os.args: [./godoc -v -http=:8080]
runtime.numcpu: 4
runtime.version: weekly.2012-01-27 11688+

How can I use gmx in my applications ?

In the example above, a stock godoc was instrumented by importing the package into main.

package main

import _ ""

The runtime and os instruments are provided by default by gmx.

How can I export my own values via gmx ?

You can publish gmx instruments at any point in your application. The most logical place is inside your package’s init function.

package foo

import ""

var c1 = 1
var c2 = 2

func init() {
        // publish c1 via a closure
        gmx.Publish("c1", func() interface{} {
                return c1
        // publish c2 via a function
        gmx.Publish("c2", getC2)

func getC2() interface{} {
        return c2

Using gmxc the values can be queried at runtime:

./gmxc -p 16467 c1 c2
c2: 2
c1: 1

Who is gmx aimed at ?

If you are developing an application in Go, especially a daemon or some other long running process, then gmx may appeal to you. If you live on the other side of the DevOps table, gmx will hopfully allow you to gain a greater understanding of the internal workings of applications you have been charged with caring for.

If you find gmx useful for you, please let me know. I plan to continue to develop the default instrumentation bundled with gmx and am always open to pull requests for additional functionality.

You can find the source to gmx on github,