fix: use dokku CONTAINER files for authoritative container ID lookup

Read container IDs from dokku's internal CONTAINER.process.N files
instead of filtering docker ps output. These files are the authoritative
source for current deployment containers and are properly updated when
scaling down (stale files are removed during deploy).

This avoids issues with orphaned containers from previous deployments
that may still be running but are no longer part of the current formation.

Author: josegonzalez

tasks/integration_test.go

@@ -116,51 +116,31 @@ func skipIfDockerLinkUnsupportedT(t *testing.T) {
 	}
 }
 
-// retireAndCleanupContainers forces dokku to retire old containers from
-// previous deploys and then cleans up stopped containers
-func retireAndCleanupContainers() {
-	subprocess.CallExecCommand(subprocess.ExecCommandInput{
-		Command: "dokku",
-		Args:    []string{"ps:retire"},
-	})
-	subprocess.CallExecCommand(subprocess.ExecCommandInput{
-		Command: "dokku",
-		Args:    []string{"cleanup"},
-	})
-}
-
-// getActiveContainers returns the IDs of running containers matching the given
-// app and process type, excluding retired containers (those renamed with a
-// timestamp suffix like "app.web.1.1640787924") and interim containers (those
-// with an ".upcoming-" suffix created during deployment).
-func getActiveContainers(appName, processType string) ([]string, error) {
-	result, err := subprocess.CallExecCommand(subprocess.ExecCommandInput{
-		Command: "docker",
-		Args:    []string{"ps", "--filter", fmt.Sprintf("label=com.dokku.app-name=%s", appName), "--filter", fmt.Sprintf("label=com.dokku.process-type=%s", processType), "--format", "{{.ID}}\t{{.Names}}"},
-	})
+// getCurrentContainerIDs reads the container IDs from dokku's internal
+// CONTAINER files (e.g., /home/dokku/APP/CONTAINER.web.1) which are the
+// authoritative source for the current deployment's containers.
+func getCurrentContainerIDs(appName, processType string) ([]string, error) {
+	scale, err := getPsScale(appName)
 	if err != nil {
 		return nil, err
 	}
-	output := strings.TrimSpace(result.StdoutContents())
-	if output == "" {
+	count, ok := scale[processType]
+	if !ok || count == 0 {
 		return nil, nil
 	}
 	var ids []string
-	for _, line := range strings.Split(output, "\n") {
-		parts := strings.SplitN(line, "\t", 2)
-		if len(parts) != 2 {
+	for i := 1; i <= count; i++ {
+		result, err := subprocess.CallExecCommand(subprocess.ExecCommandInput{
+			Command: "cat",
+			Args:    []string{fmt.Sprintf("/home/dokku/%s/CONTAINER.%s.%d", appName, processType, i)},
+		})
+		if err != nil {
 			continue
 		}
-		containerID := parts[0]
-		containerName := parts[1]
-		// skip retired containers (app.process.N.TIMESTAMP) and
-		// interim containers (app.process.N.upcoming-RANDOM)
-		// active containers have exactly 3 dot-separated segments: app.process.N
-		segments := strings.Split(containerName, ".")
-		if len(segments) != 3 {
-			continue
+		id := strings.TrimSpace(result.StdoutContents())
+		if id != "" {
+			ids = append(ids, id)
 		}
-		ids = append(ids, containerID)
 	}
 	return ids, nil
 }
@@ -1047,8 +1027,7 @@ func TestIntegrationPsScale(t *testing.T) {
 	}
 
 	// verify initial web container count is 1 via docker ps
-	retireAndCleanupContainers()
-	initialContainers, err := getActiveContainers(appName, "web")
+	initialContainers, err := getCurrentContainerIDs(appName, "web")
 	if err != nil {
 		t.Fatalf("failed to list containers: %v", err)
 	}
@@ -1086,8 +1065,7 @@ func TestIntegrationPsScale(t *testing.T) {
 	}
 
 	// clean up old containers and verify 2 web containers via docker ps
-	retireAndCleanupContainers()
-	scaledContainers, err := getActiveContainers(appName, "web")
+	scaledContainers, err := getCurrentContainerIDs(appName, "web")
 	if err != nil {
 		t.Fatalf("failed to list containers after scale: %v", err)
 	}
@@ -1133,8 +1111,7 @@ func TestIntegrationPsScale(t *testing.T) {
 	}
 
 	// clean up old containers and verify 1 web container after scale down
-	retireAndCleanupContainers()
-	finalContainers, err := getActiveContainers(appName, "web")
+	finalContainers, err := getCurrentContainerIDs(appName, "web")
 	if err != nil {
 		t.Fatalf("failed to list containers after scale down: %v", err)
 	}