Decouple Scope lifecycle from Weave lifecycle

- Run the Weave integrations regardless of if weave is detected.
- Make everything backoff and not spam the logs.
- Add miekg dns to vendor.
- Have the app periodically register with weaveDNS, and the probe do lookups there.
- Decide what the local networks are at runtime, not once at startup.
- Correctly resolve app ids, fixes #825

app/weave.go

@@ -0,0 +1,149 @@
+package app
+
+import (
+	"fmt"
+	"net"
+	"strings"
+
+	fsouza "github.com/fsouza/go-dockerclient"
+
+	"github.com/weaveworks/scope/common/backoff"
+)
+
+// Default values for weave app integration
+const (
+	DefaultHostname       = "scope.weave.local."
+	DefaultWeaveURL       = "http://127.0.0.1:6784"
+	DefaultContainerName  = "weavescope"
+	DefaultDockerEndpoint = "unix:///var/run/docker.sock"
+)
+
+// WeavePublisher is a thing which periodically registers this app with WeaveDNS.
+type WeavePublisher struct {
+	containerName string
+	hostname      string
+	dockerClient  DockerClient
+	weaveClient   WeaveClient
+	backoff       backoff.Interface
+	interfaces    InterfaceFunc
+}
+
+// DockerClient is the little bit of the docker client we need.
+type DockerClient interface {
+	ListContainers(fsouza.ListContainersOptions) ([]fsouza.APIContainers, error)
+}
+
+// WeaveClient is the little bit of the weave clent we need.
+type WeaveClient interface {
+	AddDNSEntry(hostname, containerid string, ip net.IP) error
+	Expose() error
+}
+
+// Interface is because net.Interface isn't mockable.
+type Interface struct {
+	Name  string
+	Addrs []net.Addr
+}
+
+// InterfaceFunc is the type of Interfaces()
+type InterfaceFunc func() ([]Interface, error)
+
+// Interfaces returns the list of Interfaces on the machine.
+func Interfaces() ([]Interface, error) {
+	ifaces, err := net.Interfaces()
+	if err != nil {
+		return nil, err
+	}
+	result := []Interface{}
+	for _, i := range ifaces {
+		addrs, err := i.Addrs()
+		if err != nil {
+			continue
+		}
+		result = append(result, Interface{
+			Name:  i.Name,
+			Addrs: addrs,
+		})
+	}
+	return result, nil
+}
+
+// NewWeavePublisher makes a new Weave.
+func NewWeavePublisher(weaveClient WeaveClient, dockerClient DockerClient, interfaces InterfaceFunc, hostname, containerName string) *WeavePublisher {
+	w := &WeavePublisher{
+		containerName: containerName,
+		hostname:      hostname,
+		dockerClient:  dockerClient,
+		weaveClient:   weaveClient,
+		interfaces:    interfaces,
+	}
+	w.backoff = backoff.New(w.updateDNS, "updating weaveDNS")
+	go w.backoff.Start()
+	return w
+}
+
+// Stop the Weave.
+func (w *WeavePublisher) Stop() {
+	w.backoff.Stop()
+}
+
+func (w *WeavePublisher) updateDNS() (bool, error) {
+	// 0. expose this host
+	if err := w.weaveClient.Expose(); err != nil {
+		return false, err
+	}
+
+	// 1. work out my IP addresses
+	ifaces, err := w.interfaces()
+	if err != nil {
+		return false, err
+	}
+	ips := []net.IP{}
+	for _, i := range ifaces {
+		if strings.HasPrefix(i.Name, "lo") ||
+			strings.HasPrefix(i.Name, "docker") ||
+			strings.HasPrefix(i.Name, "veth") {
+			continue
+		}
+
+		for _, addr := range i.Addrs {
+			var ip net.IP
+			switch v := addr.(type) {
+			case *net.IPAddr:
+				ip = v.IP
+			case *net.IPNet:
+				ip = v.IP
+			}
+			if ip != nil && ip.To4() != nil {
+				ips = append(ips, ip)
+			}
+		}
+	}
+
+	// 2. work out my container name
+	containers, err := w.dockerClient.ListContainers(fsouza.ListContainersOptions{})
+	if err != nil {
+		return false, err
+	}
+	containerID := ""
+outer:
+	for _, container := range containers {
+		for _, name := range container.Names {
+			if name == "/"+w.containerName {
+				containerID = container.ID
+				break outer
+			}
+		}
+	}
+	if containerID == "" {
+		return false, fmt.Errorf("Container %s not found", w.containerName)
+	}
+
+	// 3. Register these with weave dns
+	for _, ip := range ips {
+		if err := w.weaveClient.AddDNSEntry(w.hostname, containerID, ip); err != nil {
+			return false, err
+		}
+	}
+	return false, nil
+}

app/weave_test.go

@@ -0,0 +1,103 @@
+package app_test
+
+import (
+	"net"
+	"sync"
+	"testing"
+	"time"
+
+	fsouza "github.com/fsouza/go-dockerclient"
+
+	"github.com/weaveworks/scope/app"
+	"github.com/weaveworks/scope/test"
+)
+
+type mockDockerClient struct{}
+
+func (mockDockerClient) ListContainers(fsouza.ListContainersOptions) ([]fsouza.APIContainers, error) {
+	return []fsouza.APIContainers{
+		{
+			Names: []string{"/" + containerName},
+			ID:    containerID,
+		},
+		{
+			Names: []string{"/notme"},
+			ID:    "1234abcd",
+		},
+	}, nil
+}
+
+type entry struct {
+	containerid string
+	ip          net.IP
+}
+
+type mockWeaveClient struct {
+	sync.Mutex
+	published map[string]entry
+}
+
+func (m *mockWeaveClient) AddDNSEntry(hostname, containerid string, ip net.IP) error {
+	m.Lock()
+	defer m.Unlock()
+	m.published[hostname] = entry{containerid, ip}
+	return nil
+}
+
+func (m *mockWeaveClient) Expose() error {
+	return nil
+}
+
+const (
+	hostname      = "foo.weave"
+	containerName = "bar"
+	containerID   = "a1b2c3d4"
+)
+
+var (
+	ip = net.ParseIP("1.2.3.4")
+)
+
+func TestWeave(t *testing.T) {
+	weaveClient := &mockWeaveClient{
+		published: map[string]entry{},
+	}
+	dockerClient := mockDockerClient{}
+	interfaces := func() ([]app.Interface, error) {
+		return []app.Interface{
+			{
+				Name: "eth0",
+				Addrs: []net.Addr{
+					&net.IPAddr{
+						IP: ip,
+					},
+				},
+			},
+			{
+				Name: "docker0",
+				Addrs: []net.Addr{
+					&net.IPAddr{
+						IP: net.ParseIP("4.3.2.1"),
+					},
+				},
+			},
+		}, nil
+	}
+	publisher := app.NewWeavePublisher(
+		weaveClient, dockerClient, interfaces,
+		hostname, containerName)
+	defer publisher.Stop()
+
+	want := map[string]entry{
+		hostname: {containerID, ip},
+	}
+	test.Poll(t, 100*time.Millisecond, want, func() interface{} {
+		weaveClient.Lock()
+		defer weaveClient.Unlock()
+		result := map[string]entry{}
+		for k, v := range weaveClient.published {
+			result[k] = v
+		}
+		return result
+	})
+}

common/backoff/backoff.go

@@ -0,0 +1,90 @@
+package backoff
+
+import (
+	"log"
+	"time"
+)
+
+type backoff struct {
+	f                          func() (bool, error)
+	quit, done                 chan struct{}
+	msg                        string
+	initialBackoff, maxBackoff time.Duration
+}
+
+// Interface does f in a loop, sleeping for initialBackoff between
+// each iterations.  If it hits an error, it exponentially backs
+// off to maxBackoff.  Backoff will log when it backs off, but
+// will stop logging when it reaches maxBackoff.  It will also
+// log on first success.
+type Interface interface {
+	Start()
+	Stop()
+	SetInitialBackoff(time.Duration)
+}
+
+// New makes a new Interface
+func New(f func() (bool, error), msg string) Interface {
+	return &backoff{
+		f:              f,
+		quit:           make(chan struct{}),
+		done:           make(chan struct{}),
+		msg:            msg,
+		initialBackoff: 10 * time.Second,
+		maxBackoff:     60 * time.Second,
+	}
+}
+
+func (b *backoff) SetInitialBackoff(d time.Duration) {
+	b.initialBackoff = d
+}
+
+// Stop the backoff, and waits for it to stop.
+func (b *backoff) Stop() {
+	close(b.quit)
+	<-b.done
+}
+
+// Start the backoff.  Can only be called once.
+func (b *backoff) Start() {
+	defer close(b.done)
+	backoff := b.initialBackoff
+	shouldLog := true
+
+	for {
+		done, err := b.f()
+		if done {
+			return
+		}
+
+		if err != nil {
+			backoff *= 2
+			if backoff > b.maxBackoff {
+				backoff = b.maxBackoff
+			}
+		} else if backoff > b.initialBackoff {
+			backoff = b.initialBackoff
+			shouldLog = true
+		}
+
+		if shouldLog {
+			if err != nil {
+				log.Printf("Error %s, backing off %s: %s",
+					b.msg, backoff, err)
+			} else {
+				log.Printf("Success %s", b.msg)
+			}
+		}
+
+		if backoff >= b.maxBackoff || err == nil {
+			shouldLog = false
+		}
+
+		select {
+		case <-time.After(backoff):
+		case <-b.quit:
+			return
+		}
+	}
+
+}

common/exec/exec.go

@@ -12,6 +12,8 @@ type Cmd interface {
 	Start() error
 	Wait() error
 	Kill() error
+	Output() ([]byte, error)
+	Run() error
 }
 
 // Command is a hook for mocking