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https://github.com/digitalocean/go-libvirt

Package libvirt provides a pure Go interface for interacting with Libvirt. Apache 2.0 Licensed.
https://github.com/digitalocean/go-libvirt

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Package libvirt provides a pure Go interface for interacting with Libvirt. Apache 2.0 Licensed.

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README 

        
libvirt

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====



Package `go-libvirt` provides a pure Go interface for interacting with libvirt.



Rather than using libvirt's C bindings, this package makes use of

libvirt's RPC interface, as documented [here](https://libvirt.org/kbase/internals/rpc.html).

Connections to the libvirt server may be local, or remote. RPC packets are encoded

using the XDR standard as defined by [RFC 4506](https://tools.ietf.org/html/rfc4506.html).



libvirt's RPC interface is quite extensive, and changes from one version to the

next, so this project uses a pair of code generators to build the go bindings.

The code generators should be run whenever you want to build go-libvirt for a

new version of libvirt. See the next section for directions on re-generating

go-libvirt.



[Pull requests are welcome](https://github.com/digitalocean/go-libvirt/blob/master/CONTRIBUTING.md)!



Feel free to join us in [`#go-libvirt` on libera chat](https://web.libera.chat/)

if you'd like to discuss the project.



Running the Code Generators

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



The code generator doesn't run automatically when you build go-libvirt. It's

meant to be run manually any time you change the version of libvirt you're

using. When you download go-libvirt it will come with generated files

corresponding to a particular version of libvirt. You can use the library as-is,

but the generated code may be missing libvirt functions, if you're using a newer

version of libvirt, or it may have extra functions that will return

'unimplemented' errors if you try to call them. If this is a problem, you should

re-run the code generator. To do this, follow these steps:



- First, download a copy of the libvirt sources corresponding to the version you

  want to use.

- Change directories into where you've unpacked your distribution of libvirt.

- The second step depends on the version of libvirt you'd like to build against.

  It's not necessary to actually build libvirt, but it is necessary to run libvirt's

  "configure" step because it generates required files.

  - For libvirt < v6.7.0:

    - `$ mkdir build; cd build`

    - `$ ../autogen.sh`

  - For libvirt >= v6.7.0:

    - `$ meson setup build`

- Finally, set the environment variable `LIBVIRT_SOURCE` to the directory you

  put libvirt into, and run `go generate ./...` from the go-libvirt directory.

  This runs both of the go-libvirt's code generators.



How to Use This Library

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



Once you've vendored go-libvirt into your project, you'll probably want to call

some libvirt functions. There's some example code below showing how to connect

to libvirt and make one such call, but once you get past the introduction you'll

next want to call some other libvirt functions. How do you find them?



Start with the [libvirt API reference](https://libvirt.org/html/index.html).

Let's say you want to gracefully shutdown a VM, and after reading through the

libvirt docs you determine that virDomainShutdown() is the function you want to

call to do that. Where's that function in go-libvirt? We transform the names

slightly when building the go bindings. There's no need for a global prefix like

"vir" in Go, since all our functions are inside the package namespace, so we

drop it. That means the Go function for `virDomainShutdown()` is just `DomainShutdown()`,

and sure enough, you can find the Go function `DomainShutdown()` in libvirt.gen.go,

with parameters and return values equivalent to those documented in the API

reference.



Suppose you then decide you need more control over your shutdown, so you switch

over to `virDomainShutdownFlags()`. As its name suggests, this function takes a

flag parameter which has possible values specified in an enum called

`virDomainShutdownFlagValues`. Flag types like this are a little tricky for the

code generator, because the C functions just take an integer type - only the

libvirt documentation actually ties the flags to the enum types. In most cases

though we're able to generate a wrapper function with a distinct flag type,

making it easier for Go tooling to suggest possible flag values while you're

working. Checking the documentation for this function:



`godoc github.com/digitalocean/go-libvirt DomainShutdownFlags`



returns this:



`func (l *Libvirt) DomainShutdownFlags(Dom Domain, Flags DomainShutdownFlagValues) (err error)`



If you want to see the possible flag values, `godoc` can help again:



```

$ godoc github.com/digitalocean/go-libvirt DomainShutdownFlagValues



type DomainShutdownFlagValues int32

    DomainShutdownFlagValues as declared in libvirt/libvirt-domain.h:1121



const (

    DomainShutdownDefault      DomainShutdownFlagValues = iota

    DomainShutdownAcpiPowerBtn DomainShutdownFlagValues = 1

    DomainShutdownGuestAgent   DomainShutdownFlagValues = 2

    DomainShutdownInitctl      DomainShutdownFlagValues = 4

    DomainShutdownSignal       DomainShutdownFlagValues = 8

    DomainShutdownParavirt     DomainShutdownFlagValues = 16

)

    DomainShutdownFlagValues enumeration from libvirt/libvirt-domain.h:1121

```



One other suggestion: most of the code in go-libvirt is now generated, but a few

hand-written routines still exist in libvirt.go, and wrap calls to the generated

code with slightly different parameters or return values. We suggest avoiding

these hand-written routines and calling the generated routines in libvirt.gen.go

instead. Over time these handwritten routines will be removed from go-libvirt.



Warning

-------



While these package are reasonably well-tested and have seen some use inside of

DigitalOcean, there may be subtle bugs which could cause the packages to act

in unexpected ways.  Use at your own risk!



In addition, the API is not considered stable at this time.  If you would like

to include package `libvirt` in a project, we highly recommend vendoring it into

your project.



Example

-------



```go

package main



import (

	"fmt"

	"log"

	"net/url"



	"github.com/digitalocean/go-libvirt"

)



func main() {

	uri, _ := url.Parse(string(libvirt.QEMUSystem))

	l, err := libvirt.ConnectToURI(uri)

	if err != nil {

		log.Fatalf("failed to connect: %v", err)

	}



	v, err := l.ConnectGetLibVersion()

	if err != nil {

		log.Fatalf("failed to retrieve libvirt version: %v", err)

	}

	fmt.Println("Version:", v)



	flags := libvirt.ConnectListDomainsActive | libvirt.ConnectListDomainsInactive

	domains, _, err := l.ConnectListAllDomains(1, flags)

	if err != nil {

		log.Fatalf("failed to retrieve domains: %v", err)

	}



	fmt.Println("ID\tName\t\tUUID")

	fmt.Printf("--------------------------------------------------------\n")

	for _, d := range domains {

		fmt.Printf("%d\t%s\t%x\n", d.ID, d.Name, d.UUID)

	}



	if err = l.Disconnect(); err != nil {

		log.Fatalf("failed to disconnect: %v", err)

	}

}



```



```

Version: 1.3.4

ID	Name		UUID

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

1	Test-1		dc329f87d4de47198cfd2e21c6105b01

2	Test-2		dc229f87d4de47198cfd2e21c6105b01

```



Example (Connect to libvirt via TLS over TCP)

-------



```go

package main



import (

        "crypto/tls"

        "crypto/x509"



        "fmt"

        "io/ioutil"

        "log"



        "github.com/digitalocean/go-libvirt"

        "github.com/digitalocean/go-libvirt/socket/dialers"

)



func main() {

        // This dials libvirt on the local machine

        // It connects to libvirt via TLS over TCP

        // To connect to a remote machine, you need to have the ca/cert/key of it.

        // The private key is at ~/.pki/libvirt/clientkey.pem

        // or /etc/pki/libvirt/private/clientkey.pem

        // The Client Cert is at ~/.pki/libvirt/clientcert.pem

        // or /etc/pki/libvirt/clientcert.pem

        // The CA Cert is at ~/.pki/libvirt/cacert.pem

        // or /etc/pki/CA/cacert.pem



        // Use host name or IP which is valid in certificate

        addr := "10.10.10.10"



        l := libvirt.NewWithDialer(dialers.NewTLS(addr))

        if err := l.Connect(); err != nil {

                log.Fatalf("failed to connect: %v", err)

        }



        v, err := l.Version()

        if err != nil {

                log.Fatalf("failed to retrieve libvirt version: %v", err)

        }

        fmt.Println("Version:", v)



        // Return both running and stopped VMs

        flags := libvirt.ConnectListDomainsActive | libvirt.ConnectListDomainsInactive

        domains, _, err := l.ConnectListAllDomains(1, flags)

        if err != nil {

                log.Fatalf("failed to retrieve domains: %v", err)

        }



        fmt.Println("ID\tName\t\tUUID")

        fmt.Println("--------------------------------------------------------")

        for _, d := range domains {

                fmt.Printf("%d\t%s\t%x\n", d.ID, d.Name, d.UUID)

        }



        if err := l.Disconnect(); err != nil {

                log.Fatalf("failed to disconnect: %v", err)

        }

}

```



Running the Integration Tests

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



GitHub actions workflows are defined in [.github/workflows](.github/workflows)

and can be triggered manually in the GitHub UI after pushing a branch. There

are not currently convenient scripts for setting up and running integration tests

locally, but installing libvirt and defining only the artifacts described by the

files in testdata should be sufficient to be able to run the integration test file

against.