go-ethereum/p2p/adapters/docker.go
Lewis Marshall 5b4702304a p2p/adapters: Add "docker" node adapter
Signed-off-by: Lewis Marshall <lewis@lmars.net>
2017-05-06 14:23:39 +01:00

128 lines
3 KiB
Go

package adapters
import (
"fmt"
"io"
"io/ioutil"
"os"
"os/exec"
"path/filepath"
"runtime"
"sync"
"github.com/docker/docker/pkg/reexec"
"github.com/ethereum/go-ethereum/node"
)
// DockerNode is a NodeAdapter which wraps an ExecNode but exec's the current
// binary in a docker container rather than locally
type DockerNode struct {
ExecNode
}
// NewDockerNode creates a new DockerNode, building the docker image if
// necessary
func NewDockerNode(id *NodeId, service string) (*DockerNode, error) {
if runtime.GOOS != "linux" {
return nil, fmt.Errorf("NewDockerNode can only be used on Linux as it uses the current binary (which must be a Linux binary)")
}
if _, exists := serviceFuncs[service]; !exists {
return nil, fmt.Errorf("unknown node service %q", service)
}
// build the docker image
var err error
dockerOnce.Do(func() {
err = buildDockerImage()
})
if err != nil {
return nil, err
}
// generate the config
conf := node.DefaultConfig
conf.DataDir = "/data"
conf.P2P.NoDiscovery = true
conf.P2P.NAT = nil
node := &DockerNode{
ExecNode: ExecNode{
ID: id,
Service: service,
Config: &conf,
},
}
node.newCmd = node.dockerCommand
return node, nil
}
// dockerCommand returns a command which exec's the binary in a docker
// container.
//
// It uses a shell so that we can pass the _P2P_NODE_CONFIG environment
// variable to the container using the --env flag.
func (n *DockerNode) dockerCommand() *exec.Cmd {
return exec.Command(
"sh", "-c",
fmt.Sprintf(
`exec docker run --interactive --env _P2P_NODE_CONFIG="${_P2P_NODE_CONFIG}" %s p2p-node %s %s`,
dockerImage, n.Service, n.ID.String(),
),
)
}
// dockerImage is the name of the docker image
const dockerImage = "p2p-node"
// dockerOnce is used to build the docker image only once
var dockerOnce sync.Once
// buildDockerImage builds the docker image which is used to run devp2p nodes
// using docker.
//
// It adds the current binary as "p2p-node" so that it runs execP2PNode
// when executed.
func buildDockerImage() error {
// create a directory to use as the docker build context
dir, err := ioutil.TempDir("", "p2p-docker")
if err != nil {
return err
}
defer os.RemoveAll(dir)
// copy the current binary into the build context
bin, err := os.Open(reexec.Self())
if err != nil {
return err
}
defer bin.Close()
dst, err := os.OpenFile(filepath.Join(dir, "self.bin"), os.O_WRONLY|os.O_CREATE, 0755)
if err != nil {
return err
}
defer dst.Close()
if _, err := io.Copy(dst, bin); err != nil {
return err
}
// create the Dockerfile
dockerfile := []byte(`
FROM ubuntu:16.04
RUN mkdir /data
ADD self.bin /bin/p2p-node
`)
if err := ioutil.WriteFile(filepath.Join(dir, "Dockerfile"), dockerfile, 0644); err != nil {
return err
}
// run 'docker build'
cmd := exec.Command("docker", "build", "-t", dockerImage, dir)
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
if err := cmd.Run(); err != nil {
return fmt.Errorf("error building docker image: %s", err)
}
return nil
}