only set a single label for now

Other labels aren't strictly necessary here, and we may follow up with a
better way to customize.

drivers/docker/driver.go

@@ -67,10 +67,7 @@ var (
 )
 
 const (
-	dockerLabelTaskID   = "com.hashicorp.nomad.task_id"
-	dockerLabelTaskName = "com.hashicorp.nomad.task_name"
-	dockerLabelAllocID  = "com.hashicorp.nomad.alloc_id"
-	dockerLabelJobName  = "com.hashicorp.nomad.job_name"
+	dockerLabelAllocID = "com.hashicorp.nomad.alloc_id"
 )
 
 type Driver struct {
@@ -992,15 +989,12 @@ func (d *Driver) createContainerConfig(task *drivers.TaskConfig, driverConfig *T
 		config.Labels = driverConfig.Labels
 	}
 
-	config.Labels = map[string]string{
-		dockerLabelTaskID:   task.ID,
-		dockerLabelTaskName: task.Name,
-		dockerLabelAllocID:  task.AllocID,
-		dockerLabelJobName:  task.JobName,
-	}
+	labels := make(map[string]string, len(driverConfig.Labels)+1)
 	for k, v := range driverConfig.Labels {
-		config.Labels[k] = v
+		labels[k] = v
 	}
+	labels[dockerLabelAllocID] = task.AllocID
+	config.Labels = labels
 	logger.Debug("applied labels on the container", "labels", config.Labels)
 
 	config.Env = task.EnvList()

drivers/docker/driver_test.go

@@ -905,8 +905,8 @@ func TestDockerDriver_Labels(t *testing.T) {
 		t.Fatalf("err: %v", err)
 	}
 
-	// expect to see 4 additional standard labels
-	require.Equal(t, len(cfg.Labels)+4, len(container.Config.Labels))
+	// expect to see 1 additional standard labels
+	require.Equal(t, len(cfg.Labels)+1, len(container.Config.Labels))
 	for k, v := range cfg.Labels {
 		require.Equal(t, v, container.Config.Labels[k])
 	}
@@ -1018,6 +1018,10 @@ func TestDockerDriver_CreateContainerConfig_Labels(t *testing.T) {
 
 	cfg.Labels = map[string]string{
 		"user_label": "user_value",
+
+		// com.hashicorp.nomad. labels are reserved and
+		// cannot be overridden
+		"com.hashicorp.nomad.alloc_id": "bad_value",
 	}
 
 	require.NoError(t, task.EncodeConcreteDriverConfig(cfg))
@@ -1032,10 +1036,7 @@ func TestDockerDriver_CreateContainerConfig_Labels(t *testing.T) {
 		// user provided labels
 		"user_label": "user_value",
 		// default labels
-		"com.hashicorp.nomad.alloc_id":  task.AllocID,
-		"com.hashicorp.nomad.job_name":  "redis-demo-job",
-		"com.hashicorp.nomad.task_id":   task.ID,
-		"com.hashicorp.nomad.task_name": "redis-demo",
+		"com.hashicorp.nomad.alloc_id": task.AllocID,
 	}
 
 	require.Equal(t, expectedLabels, c.Config.Labels)