Handle container links

Ensures that linked containers are restarted if any of their
dependencies are restarted -- and makes sure that everything happens in
the correct order.

docker/container.go

@@ -0,0 +1,103 @@
+package docker
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/samalba/dockerclient"
+)
+
+type Container struct {
+	Stale bool
+
+	containerInfo *dockerclient.ContainerInfo
+	imageInfo     *dockerclient.ImageInfo
+}
+
+func (c Container) Name() string {
+	return c.containerInfo.Name
+}
+
+func (c Container) Links() []string {
+	links := []string{}
+
+	if (c.containerInfo != nil) && (c.containerInfo.HostConfig != nil) {
+		for _, link := range c.containerInfo.HostConfig.Links {
+			name := strings.Split(link, ":")[0]
+			links = append(links, name)
+		}
+	}
+
+	return links
+}
+
+// Ideally, we'd just be able to take the ContainerConfig from the old container
+// and use it as the starting point for creating the new container; however,
+// the ContainerConfig that comes back from the Inspect call merges the default
+// configuration (the stuff specified in the metadata for the image itself)
+// with the overridden configuration (the stuff that you might specify as part
+// of the "docker run"). In order to avoid unintentionally overriding the
+// defaults in the new image we need to separate the override options from the
+// default options. To do this we have to compare the ContainerConfig for the
+// running container with the ContainerConfig from the image that container was
+// started from. This function returns a ContainerConfig which contains just
+// the options overridden at runtime.
+func (c Container) runtimeConfig() *dockerclient.ContainerConfig {
+	config := c.containerInfo.Config
+	imageConfig := c.imageInfo.Config
+
+	if config.WorkingDir == imageConfig.WorkingDir {
+		config.WorkingDir = ""
+	}
+
+	if config.User == imageConfig.User {
+		config.User = ""
+	}
+
+	if sliceEqual(config.Cmd, imageConfig.Cmd) {
+		config.Cmd = []string{}
+	}
+
+	if sliceEqual(config.Entrypoint, imageConfig.Entrypoint) {
+		config.Entrypoint = []string{}
+	}
+
+	config.Env = sliceSubtract(config.Env, imageConfig.Env)
+
+	config.Labels = stringMapSubtract(config.Labels, imageConfig.Labels)
+
+	config.Volumes = structMapSubtract(config.Volumes, imageConfig.Volumes)
+
+	config.ExposedPorts = structMapSubtract(config.ExposedPorts, imageConfig.ExposedPorts)
+	for p, _ := range c.containerInfo.HostConfig.PortBindings {
+		config.ExposedPorts[p] = struct{}{}
+	}
+
+	return config
+}
+
+// Any links in the HostConfig need to be re-written before they can be
+// re-submitted to the Docker create API.
+func (c Container) hostConfig() *dockerclient.HostConfig {
+	hostConfig := c.containerInfo.HostConfig
+
+	for i, link := range hostConfig.Links {
+		name := link[0:strings.Index(link, ":")]
+		alias := link[strings.LastIndex(link, "/"):]
+
+		hostConfig.Links[i] = fmt.Sprintf("%s:%s", name, alias)
+	}
+
+	return hostConfig
+}
+
+func NewTestContainer(name string, links []string) Container {
+	return Container{
+		containerInfo: &dockerclient.ContainerInfo{
+			Name: name,
+			HostConfig: &dockerclient.HostConfig{
+				Links: links,
+			},
+		},
+	}
+}