Merge pull request #781 from remind101/dedupe-describes

Reduce number of DescribeTaskDefinition calls.

CHANGELOG.md

@@ -18,6 +18,10 @@
 * `emp scale -l` now lists configured scale, not the running processes [#769](https://github.com/remind101/empire/pull/769)
 * Fixed a bug where it was previously possible to create a signed access token with an empty username [#780](https://github.com/remind101/empire/pull/780)
 
+**Performance**
+
+* `emp ps` should be significantly faster for services running a lot of processes [#781](https://github.com/remind101/empire/pull/781)
+
 **Security**
 
 * Empire is now built with Go 1.5.3 to address [CVE-2015-8618](https://groups.google.com/forum/#!topic/golang-announce/MEATuOi_ei4) [#737](https://github.com/remind101/empire/pull/737).

scheduler/ecs/ecs.go

@@ -238,20 +238,30 @@ func (m *Scheduler) Instances(ctx context.Context, appID string) ([]*scheduler.I
 		return instances, err
 	}
 
+	taskDefinitions := make(map[string]*ecs.TaskDefinition)
 	for _, t := range tasks {
-		resp, err := m.ecs.DescribeTaskDefinition(ctx, &ecs.DescribeTaskDefinitionInput{
-			TaskDefinition: t.TaskDefinitionArn,
-		})
-		if err != nil {
-			return instances, err
+		k := *t.TaskDefinitionArn
+
+		if _, ok := taskDefinitions[k]; !ok {
+			resp, err := m.ecs.DescribeTaskDefinition(ctx, &ecs.DescribeTaskDefinitionInput{
+				TaskDefinition: t.TaskDefinitionArn,
+			})
+			if err != nil {
+				return instances, err
+			}
+			taskDefinitions[k] = resp.TaskDefinition
 		}
+	}
+
+	for _, t := range tasks {
+		taskDefinition := taskDefinitions[*t.TaskDefinitionArn]
 
 		id, err := arn.ResourceID(*t.TaskArn)
 		if err != nil {
 			return instances, err
 		}
 
-		p, err := taskDefinitionToProcess(resp.TaskDefinition)
+		p, err := taskDefinitionToProcess(taskDefinition)
 		if err != nil {
 			return instances, err
 		}

scheduler/ecs/ecs_test.go

@@ -130,7 +130,7 @@ func TestScheduler_Instances(t *testing.T) {
 			},
 			Response: awsutil.Response{
 				StatusCode: 200,
-				Body:       `{"taskArns":["arn:aws:ecs:us-east-1:249285743859:task/ae69bb4c-3903-4844-82fe-548ac5b74570"]}`,
+				Body:       `{"taskArns":["arn:aws:ecs:us-east-1:249285743859:task/ae69bb4c-3903-4844-82fe-548ac5b74570","arn:aws:ecs:us-east-1:249285743859:task/ae69bb4c-3903-4844-82fe-548ac5b74571"]}`,
 			},
 		},
 
@@ -150,11 +150,11 @@ func TestScheduler_Instances(t *testing.T) {
 			Request: awsutil.Request{
 				RequestURI: "/",
 				Operation:  "AmazonEC2ContainerServiceV20141113.DescribeTasks",
-				Body:       `{"cluster":"empire","tasks":["arn:aws:ecs:us-east-1:249285743859:task/ae69bb4c-3903-4844-82fe-548ac5b74570"]}`,
+				Body:       `{"cluster":"empire","tasks":["arn:aws:ecs:us-east-1:249285743859:task/ae69bb4c-3903-4844-82fe-548ac5b74570","arn:aws:ecs:us-east-1:249285743859:task/ae69bb4c-3903-4844-82fe-548ac5b74571"]}`,
 			},
 			Response: awsutil.Response{
 				StatusCode: 200,
-				Body:       `{"tasks":[{"taskArn":"arn:aws:ecs:us-east-1:249285743859:task/ae69bb4c-3903-4844-82fe-548ac5b74570","taskDefinitionArn":"arn:aws:ecs:us-east-1:249285743859:task-definition/1234--web","lastStatus":"RUNNING","startedAt": 1448419193}]}`,
+				Body:       `{"tasks":[{"taskArn":"arn:aws:ecs:us-east-1:249285743859:task/ae69bb4c-3903-4844-82fe-548ac5b74570","taskDefinitionArn":"arn:aws:ecs:us-east-1:249285743859:task-definition/1234--web","lastStatus":"RUNNING","startedAt": 1448419193},{"taskArn":"arn:aws:ecs:us-east-1:249285743859:task/ae69bb4c-3903-4844-82fe-548ac5b74571","taskDefinitionArn":"arn:aws:ecs:us-east-1:249285743859:task-definition/1234--web","lastStatus":"RUNNING","startedAt": 1448419193}]}`,
 			},
 		},
 
@@ -178,8 +178,8 @@ func TestScheduler_Instances(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if len(instances) != 1 {
-		t.Fatal("expected 1 instance")
+	if len(instances) != 2 {
+		t.Fatal("expected 2 instances")
 	}
 
 	i := instances[0]