### Get Domain Details with go-qemu

Source: https://github.com/digitalocean/go-qemu/blob/master/examples/README.md

Demonstrates connecting to a hypervisor host using qmp.NewLibvirtRPCMonitor and retrieving details for a specified domain. Supports local or remote connections.

```bash
go get github.com/digitalocean/go-qemu/...
   $ go run examples/domain_details/main.go
   or
   $ go run examples/domain_details/main.go -network=tcp \
              -address="hypervisorhost:16509" -domainName="ubuntu14.04"
```

```bash
Connecting to Connecting to unix:///var/run/libvirt/libvirt-sock

Version: 1.5.3

Status: running

[ PCIDevices ]
======================================
      [ID]        [Description]
======================================
[          ] [         Host bridge]
[          ] [          ISA bridge]
[          ] [      IDE controller]
[          ] [              Bridge]
[          ] [      VGA controller]
[      net0] [ Ethernet controller]
[    sound0] [    Audio controller]
[virtio-serial0] [                    ]
[          ] [      USB controller]
[          ] [      USB controller]
[          ] [      USB controller]
[       usb] [      USB controller]
[virtio-disk0] [     SCSI controller]
[  balloon0] [                    ]

[ BlockDevices ]
========================================================================
              Device   Driver                           File
========================================================================
  drive-virtio-disk0    qcow2 /var/lib/libvirt/images/ubuntu14.04.qcow2
      drive-ide0-0-0                                        
```

--------------------------------

### Install go-qemu Packages

Source: https://github.com/digitalocean/go-qemu/blob/master/README.md

Installs all packages within the go-qemu repository using the go get command. This is the standard method for retrieving Go dependencies.

```shell
$ go get github.com/digitalocean/go-qemu/...
```

--------------------------------

### List Domains using go-qemu Hypervisor

Source: https://github.com/digitalocean/go-qemu/blob/master/examples/README.md

Demonstrates using the go-qemu/hypervisor package to list domains from a connected hypervisor. The returned list is of type go-qemu/Domain. Requires libvirtd group membership or remote TCP connection.

```bash
go get github.com/digitalocean/go-qemu/...
   $ go run examples/hypervisor_domain_list/main.go -network=tcp \
                                          -address="hypervisorhost:16509"
```

```bash
Connecting to unix:///var/run/libvirt/libvirt-sock

**********Domains**********
centos7
ubuntu14.04
debian8

***************************
```

--------------------------------

### Shut Down Domain using go-qemu Hypervisor

Source: https://github.com/digitalocean/go-qemu/blob/master/examples/README.md

Demonstrates using the go-qemu/hypervisor package to shut off a specified domain. Supports local or remote connections.

```bash
go get github.com/digitalocean/go-qemu/...
   $ go run examples/domain_system_powerdown/main.go -domainName="ubuntu14.04"
   or
   $ go run examples/domain_system_powerdown/main.go -network=tcp \
    -address="hypervisorhost:16509"  -domainName="ubuntu14.04"
```

```bash
Connecting to unix:///var/run/libvirt/libvirt-sock
Domain should be shut off now
```

--------------------------------

### Parse QAPI Schema in Go

Source: https://github.com/digitalocean/go-qemu/blob/master/qapi-schema/README.md

Demonstrates how to use the `qapischema.Parse` function to parse a QAPI schema string into a `*qapischema.Tree` structure. It shows a basic example of a QAPI struct definition.

```go
input := `{ 'struct': 'DiskThing',
            'data': { 
                'diskname': { 
                    'type':'str',
                    'if':'DISKS_HAVE_NAMES' } } }`
schema, _ := qapischema.Parse(input)
```

--------------------------------

### go-qemu Package Overview

Source: https://github.com/digitalocean/go-qemu/blob/master/README.md

Provides a summary of the top-level packages in go-qemu and their intended uses. The 'hypervisor' package manages groups of VMs, 'qemu' interacts with single instances, and 'qmp' handles QEMU Machine Protocol communication.

```go
// Package hypervisor provides management facilities for one or
// more QEMU virtual machines on a hypervisor.
// Provides easier access for managing groups of VMs than the `qemu` package.
// Provides access to individual `qemu.Domain` types.

// Package qemu provides an interface for interacting with running QEMU instances.
// Typically used for managing a single VM.
// Good for quick experiments.

// Package qmp enables interaction with QEMU instances via the QEMU Machine
// Protocol (QMP).
// Typically not used by consumers outside of this repository.
// Wraps code-generated types with friendlier APIs.
```

--------------------------------

### Libvirt RPC Driver Connection

Source: https://github.com/digitalocean/go-qemu/blob/master/qmp/README.md

Establishes a connection to a Libvirt daemon using the RPC driver for QMP interaction. Requires a running Libvirt daemon and specifies the connection details.

```go
conn, err := net.DialTimeout("tcp", "192.168.1.1:16509", 2*time.Second)
monitor := libvirtrpc.New("stage-lb-1", conn)
```

--------------------------------

### Direct Socket Connection

Source: https://github.com/digitalocean/go-qemu/blob/master/qmp/README.md

Connects directly to a QEMU instance's monitor socket when not managed by Libvirt. Requires the path to the UNIX socket and a timeout duration.

```go
monitor, err := qmp.NewSocketMonitor("unix", "/var/lib/qemu/example.monitor", 2*time.Second)
```

--------------------------------

### Execute QMP Command and Parse Status

Source: https://github.com/digitalocean/go-qemu/blob/master/qmp/README.md

Executes a QMP command ('query-status') against a QEMU instance and parses the JSON response to retrieve the VM's status. Includes a Go struct for the expected result.

```go
type StatusResult struct {
	ID     string `json:"id"`
	Return struct {
		Running    bool   `json:"running"`
		Singlestep bool   `json:"singlestep"`
		Status     string `json:"status"`
	} `json:"return"`
}

monitor.Connect()
defer monitor.Disconnect()

cmd := []byte(`{ "execute": "query-status" }`)
raw, _ := monitor.Run(cmd)

var result StatusResult
json.Unmarshal(raw, &result)

fmt.Println(result.Return.Status)
```

--------------------------------

### Libvirt virsh Driver Connection

Source: https://github.com/digitalocean/go-qemu/blob/master/qmp/README.md

Connects to a QEMU instance managed by Libvirt by proxying requests through the 'virsh' executable. This method uses a Libvirt URI to specify the connection.

```go
monitor, err := qmp.NewLibvirtMonitor("qemu:///system", "stage-lb-1")
```

--------------------------------

### Monitor QMP Events

Source: https://github.com/digitalocean/go-qemu/blob/master/qmp/README.md

Establishes a connection to a QEMU instance and streams QMP events. It iterates over the event stream and logs each received event, such as power state changes or resets.

```go
monitor.Connect()
def monitor.Disconnect()

stream, _ := monitor.Events()
for e := range stream {
	log.Printf("EVENT: %s", e.Event)
}
```

--------------------------------

### QAPI Schema Tree Structure

Source: https://github.com/digitalocean/go-qemu/blob/master/qapi-schema/README.md

Illustrates the resulting `*qapischema.Tree` structure after parsing a QAPI schema. This output format is useful for understanding the parsed schema's components, such as structs, members, and conditional types.

```txt
&qapischema.Tree{
  Node: qapischema.Root{  },
  Children: []*qapischema.Tree{
    {
      Node: &qapischema.Struct{
        Name: "DiskThing",
        Members: []qapischema.Member{
          {
            Name: "diskname",
            Type: qapischema.TypeRef{
              Type: "str",
            },
            If: &qapischema.Cond{
              If: &qapischema.CondIf("DISKS_HAVE_NAMES"),
            },
          },
        },
      },
    },
  },
}
```

--------------------------------

### Traverse Parsed QAPI Schema Tree

Source: https://github.com/digitalocean/go-qemu/blob/master/qapi-schema/README.md

Provides a Go function `visit` that recursively traverses the `*qapischema.Tree`. It uses a type switch to handle different QAPI node types (Root, Struct, Union, Event, Command, Alternate) and processes child nodes.

```go
func visit(tree *qapischema.Tree) {
	sswitch data := tree.Node.(type) {
	// Root node, no data, traverse the subtrees in the .Children field.
	case qapischema.Root:
	case qapischema.Include:
	case qapischema.Pragma:
	case *qapischema.Struct:
	case *qapischema.Union:
	case *qapischema.Event:
	case *qapischema.Command:
	case *qapischema.Alternate:
	}

	// Process the rest of the document
	for _, t := range tree.Children {
		visit(t)
	}
}

func main() {
	tree, _ := qapischema.Parse(input)

	visit(tree)
}
```

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