refactor: hopefully more robust prune logic, docs

cli/app/undeploy.go

@@ -24,52 +24,53 @@ var pruneFlag = &cli.BoolFlag{
 	Usage:       "Prunes unused containers, networks, and dangling images for an app",
 }
 
-// pruneSystem runs the equivalent of a "docker system prune" after undeploying
-// in order to clean up left over state related to the deployment. We must run
-// this logic inside a loop as it may take some time for the undeployed to come
-// down.
+// pruneSystem runs the equivalent of a "docker system prune" after an undeploy
+// in order to clean up left over state related to the deployment. Volumes are
+// not pruned to avoid unwated data loss.
 func pruneSystem(c *cli.Context, cl *dockerClient.Client, app config.App) error {
+	stackName := app.StackName()
+	ctx := context.Background()
+
 	for {
-		if !prune {
-			return nil
-		}
+		logrus.Debugf("polling for %s stack, waiting to be undeployed...", stackName)
 
-		stackName := app.StackName()
-
-		ctx := context.Background()
-		pruneFilters := filters.NewArgs()
-		stackSearch := fmt.Sprintf("%s*", stackName)
-		pruneFilters.Add("label", stackSearch)
-		cr, err := cl.ContainersPrune(ctx, pruneFilters)
+		services, err := stack.GetStackServices(ctx, cl, stackName)
 		if err != nil {
-			logrus.Errorf(err.Error())
-			time.Sleep(time.Second)
-			continue
+			return err
 		}
 
-		logrus.Infof("containers deleted: %s; space reclaimed: %v", cr.ContainersDeleted, cr.SpaceReclaimed)
-
-		nr, err := cl.NetworksPrune(ctx, pruneFilters)
-		if err != nil {
-			logrus.Errorf(err.Error())
-			time.Sleep(time.Second)
-			continue
+		if len(services) == 0 {
+			logrus.Debugf("%s undeployed, moving on with pruning logic", stackName)
+			break
 		}
 
-		logrus.Infof("networks deleted %s", nr.NetworksDeleted)
-
-		ir, err := cl.ImagesPrune(ctx, pruneFilters)
-		if err != nil {
-			logrus.Errorf(err.Error())
-			time.Sleep(time.Second)
-			continue
-		}
-
-		logrus.Infof("images deleted: %s; space reclaimed: %v", ir.ImagesDeleted, ir.SpaceReclaimed)
-
-		break
+		time.Sleep(time.Second)
 	}
 
+	pruneFilters := filters.NewArgs()
+	stackSearch := fmt.Sprintf("%s*", stackName)
+	pruneFilters.Add("label", stackSearch)
+	cr, err := cl.ContainersPrune(ctx, pruneFilters)
+	if err != nil {
+		return err
+	}
+
+	logrus.Infof("containers deleted: %s; space reclaimed: %v", cr.ContainersDeleted, cr.SpaceReclaimed)
+
+	nr, err := cl.NetworksPrune(ctx, pruneFilters)
+	if err != nil {
+		return err
+	}
+
+	logrus.Infof("networks deleted %s", nr.NetworksDeleted)
+
+	ir, err := cl.ImagesPrune(ctx, pruneFilters)
+	if err != nil {
+		return err
+	}
+
+	logrus.Infof("images deleted: %s; space reclaimed: %v", ir.ImagesDeleted, ir.SpaceReclaimed)
+
 	return nil
 }
 
@@ -118,8 +119,10 @@ volumes as eligible for pruning once undeployed.
 			logrus.Fatal(err)
 		}
 
-		if err := pruneSystem(c, cl, app); err != nil {
-			logrus.Fatal(err)
+		if prune {
+			if err := pruneSystem(c, cl, app); err != nil {
+				logrus.Fatal(err)
+			}
 		}
 
 		return nil