monitor_test.go

package qmp

import (
	"context"
	"fmt"
	"log"
	"time"
)

// This example shows how to use the Monitor to communicate with a QEMU instance via QMP.
func ExampleMonitor() {
	mon, err := NewMonitor("/var/run/qemu/alice.qmp", 60*time.Second)
	if err != nil {
		log.Fatalln(err)
	}
	defer mon.Close()

	done := make(chan struct{})
	go func() {
		ts := time.Now()
		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()
		got, err := mon.GetEvents(ctx, "SHUTDOWN", uint64(ts.Unix()))
		if err != nil {
			log.Printf("Timeout error (type=%T): %s\n", err, err)
		} else {
			log.Printf("OK, got a SHUTDOWN event: %#v\n", got)
		}
		close(done)
	}()

	log.Println("Sleeping for three seconds ...")

	time.Sleep(3 * time.Second)

	log.Println("... and sending a 'system_powerdown' command.")

	if err := mon.Run(Command{"system_powerdown", nil}, nil); err != nil {
		log.Fatalln(err)
	}

	<-done
}

// An example of executing a command via human monitor.
func ExampleMonitor_Run() {
	mon, err := NewMonitor("/var/run/qemu/alice.qmp", 60*time.Second)
	if err != nil {
		log.Fatalln(err)
	}

	var out string

	if err := mon.Run(Command{"human-monitor-command", &HumanCommand{"info vnc"}}, &out); err != nil {
		log.Fatalln(err)
	}

	fmt.Println(out)
}

// An example of removing a device from a guest.
// Completion of the process is signaled with a DEVICE_DELETED event.
func ExampleMonitor_WaitDeviceDeletedEvent() {
	mon, err := NewMonitor("/var/run/qemu/alice.qmp", 60*time.Second)
	if err != nil {
		log.Fatalln(err)
	}

	deviceID := struct {
		Id string `json:"id"`
	}{
		"blk_alice",
	}

	ts := time.Now()
	if err := mon.Run(Command{"device_del", &deviceID}, nil); err != nil {
		log.Fatalln("device_del error:", err)
	}

	// ... and wait until the operation is completed
	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
	defer cancel()

	switch _, err := mon.WaitDeviceDeletedEvent(ctx, "blk_alice", uint64(ts.Unix())); {
	case err == nil:
	case err == context.DeadlineExceeded:
		log.Fatalln("device_del timeout error: failed to complete within 60 seconds")
	default:
		log.Fatalln(err)
	}
}