More sensible container names for Mesos/Marathon (#1316)

* Collect container environment variales (close #1314)

* Containers managed by Marathon can have meaningful names (close #1309)

* Make linter happy and fix tests

probe/docker/container.go

@@ -377,6 +377,7 @@ func (c *container) GetNode(hostID string, localAddrs []net.IP) report.Node {
 	}
 
 	result = AddLabels(result, c.container.Config.Labels)
+	result = AddEnv(result, c.container.Config.Env)
 	result = result.WithMetrics(c.metrics())
 	return result
 }

probe/docker/env.go

@@ -0,0 +1,39 @@
+package docker
+
+import (
+	"strings"
+
+	"github.com/weaveworks/scope/report"
+)
+
+// EnvPrefix is the key prefix used for Docker environment variables in Node
+// (e.g. "TERM=vt200" will get encoded as "docker_env_TERM"="vt200" in the
+// metadata)
+const EnvPrefix = "docker_env_"
+
+// AddEnv appends Docker environment variables to the Node from a topology.
+func AddEnv(node report.Node, env []string) report.Node {
+	node = node.Copy()
+	for _, value := range env {
+		v := strings.SplitN(value, "=", 2)
+		if len(v) == 2 {
+			key, value := v[0], v[1]
+			node = node.WithLatests(map[string]string{
+				EnvPrefix + key: value,
+			})
+		}
+	}
+	return node
+}
+
+// ExtractEnv returns the list of Docker environment variables given a Node from a topology.
+func ExtractEnv(node report.Node) map[string]string {
+	result := map[string]string{}
+	node.Latest.ForEach(func(key, value string) {
+		if strings.HasPrefix(key, EnvPrefix) {
+			env := key[len(EnvPrefix):]
+			result[env] = value
+		}
+	})
+	return result
+}

probe/docker/env_test.go

@@ -0,0 +1,38 @@
+package docker_test
+
+import (
+	"testing"
+
+	"github.com/weaveworks/scope/probe/docker"
+	"github.com/weaveworks/scope/report"
+	_ "github.com/weaveworks/scope/test"
+)
+
+func TestEnv(t *testing.T) {
+	given := []string{
+		"TERM=vt200",
+		"SHELL=/bin/ksh",
+		"FOO1=\"foo=bar\"",
+		"FOO2",
+	}
+	nmd := report.MakeNode()
+
+	nmd = docker.AddEnv(nmd, given)
+	have := docker.ExtractEnv(nmd)
+
+	if "vt200" != have["TERM"] {
+		t.Errorf("Expected \"vt200\", got \"%s\"", have["TERM"])
+	}
+
+	if "/bin/ksh" != have["SHELL"] {
+		t.Errorf("Expected \"/bin/ksh\", got \"%s\"", have["SHELL"])
+	}
+
+	if "\"foo=bar\"" != have["FOO1"] {
+		t.Errorf("Expected \"\"foo=bar\"\", got \"%s\"", have["FOO1"])
+	}
+
+	if len(have) != 3 {
+		t.Errorf("Expected only 3 items, got %d", len(have))
+	}
+}

render/detailed/summary.go

@@ -26,6 +26,7 @@ const (
 	// Keys we use to render container names
 	AmazonECSContainerNameLabel  = "com.amazonaws.ecs.container-name"
 	KubernetesContainerNameLabel = "io.kubernetes.container.name"
+	MarathonAppIDEnv             = "MARATHON_APP_ID"
 )
 
 // NodeSummaryGroup is a topology-typed group of children for a Node.
@@ -370,6 +371,9 @@ func getRenderableContainerName(nmd report.Node) string {
 		// is only provided by Kubernetes versions >= 1.2 (see
 		// https://github.com/kubernetes/kubernetes/pull/17234/ )
 		docker.LabelPrefix + KubernetesContainerNameLabel,
+		// Marathon doesn't set any Docker labels and this is the only meaningful
+		// attribute we can find to make Scope useful without Mesos plugin
+		docker.EnvPrefix + MarathonAppIDEnv,
 		docker.ContainerName,
 		docker.ContainerHostname,
 	} {