massh

Description

Go package for streaming Linux distributed shell commands via SSH.

What makes Massh special is it's ability to stream & process output concurrently. See _examples/example_streaming for some sample code.

Contribute

Have a question, idea, or something you think can be improved? Open an issue or PR and let's discuss it!

Example:

package main

import (
	"fmt"
	"github.com/discoriver/massh"
	"golang.org/x/crypto/ssh"
)

func main() {
	// Create pointers to config & job
	config := massh.NewConfig()

	job := &massh.Job{
		Command: "echo hello world",
	}

	config.SetHosts([]string{"192.168.1.118"})

	// Password auth
	config.SetPasswordAuth("u01", "password")

	// Key auth in same config. Auth will try all methods provided before failing.
	err := config.SetPrivateKeyAuth("~/.ssh/id_rsa", "")
	if err != nil {
		panic(err)
	}

	config.SetJob(job)
	config.SetWorkerPool(2)
	config.SetSSHHostKeyCallback(ssh.InsecureIgnoreHostKey())

	// Make sure config will run
	config.CheckSanity()

	res, err := config.Run()
	if err != nil {
		panic(err)
	}

	for i := range res {
		fmt.Printf("%s:\n \t OUT: %s \t ERR: %v\n", res[i].Host, res[i].Output, res[i].Error)
	}
}

More examples, including this one, are available in the examples directory.

Usage:

Get the massh package;

go get github.com/DiscoRiver/massh

Documentation

• GoDoc

Other

Bastion Host

Specify a bastion host and config with BastionHost and BastionHostSSHConfig in your massh.Config. You may leave BastionHostSSHConfig as nil, in which case SSHConfig will be used instead. The process is automatic, and if BastionHost is not nil, it will be used.

Streaming output

There is an example of streaming output in the direcotry _examples/example_streaming, which contains one method of reading from the results channel, and processing the output.

Running config.Stream() will populate the provided channel with results. Within this, there are two channels within each Result, StdOutStream and StdErrStream, which hold the stdout and stderr pipes respectively. Reading from these channels will give you the host's output/errors.

When a host has completed it's work and has exited, Result.DoneChannel will receive an empty struct. In my example, I use the following function to monitor this and report that a host has finished (see _examples/example_streaming for full program);

func readStream(res Result, wg *sync.WaitGroup) error {
	for {
		select {
		case d := <-res.StdOutStream:
			fmt.Printf("%s: %s", res.Host, d)
		case <-res.DoneChannel:
			fmt.Printf("%s: Finished\n", res.Host)
			wg.Done()
		}
	}
}

Unlike with Config.Run(), which returns a slice of Results when all hosts have exited, Config.Stream() requires some additional values to monitor host completion. For each individual host we have Result.DoneChannel, as explained above, but to detect when all hosts have finished, we have the variable NumberOfStreamingHostsCompleted, which will equal the length of Config.Hosts once everything has completed. Here is an example of what I'm using in _examples/example_streaming;

if NumberOfStreamingHostsCompleted == len(cfg.Hosts) {
		// We want to wait for all goroutines to complete before we declare that the work is finished, as
		// it's possible for us to execute this code before we've finished reading/processing all host output
		wg.Wait()

		fmt.Println("Everything returned.")
		return
}

Right now, the concurrency model used to read from the results channel is the responsibility of those using this package. An example of how this might be achieved can be found in the https://github.com/DiscoRiver/omnivore/tree/main/internal/ossh package, which is currently in development.