Stop containers in parallel fashion

Prior, we were stopping containers serially.  So if a container had a default
timeout of 10 seconds and there were five containers being stopped, the operation
would take roughly 50 seconds.  If we stop these containers in parallel, the operation
should be roughly 10 seconds and change which is a significant speed up at scale.

Signed-off-by: baude <bbaude@redhat.com>

cmd/podman/stop.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"os"
+	rt "runtime"
 
 	"github.com/containers/libpod/cmd/podman/libpodruntime"
 	"github.com/containers/libpod/libpod"
@@ -98,21 +99,33 @@ func stopCmd(c *cli.Context) error {
 		}
 	}
 
+	var stopFuncs []workerInput
 	for _, ctr := range containers {
+		con := ctr
 		var stopTimeout uint
 		if c.IsSet("timeout") {
 			stopTimeout = c.Uint("timeout")
 		} else {
 			stopTimeout = ctr.StopTimeout()
 		}
-		if err := ctr.StopWithTimeout(stopTimeout); err != nil && err != libpod.ErrCtrStopped {
-			if lastError != nil {
-				fmt.Fprintln(os.Stderr, lastError)
-			}
-			lastError = errors.Wrapf(err, "failed to stop container %v", ctr.ID())
-		} else {
-			fmt.Println(ctr.ID())
+		f := func() error {
+			return con.StopWithTimeout(stopTimeout)
 		}
+		stopFuncs = append(stopFuncs, workerInput{
+			containerID:  con.ID(),
+			parallelFunc: f,
+		})
+	}
+
+	stopErrors := parallelExecuteWorkerPool(rt.NumCPU()*3, stopFuncs)
+
+	for cid, result := range stopErrors {
+		if result != nil && result != libpod.ErrCtrStopped {
+			fmt.Println(result.Error())
+			lastError = result
+			continue
+		}
+		fmt.Println(cid)
 	}
 	return lastError
 }

cmd/podman/utils.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"os"
 	gosignal "os/signal"
+	"sync"
 
 	"github.com/containers/libpod/libpod"
 	"github.com/docker/docker/pkg/signal"
@@ -215,3 +216,50 @@ func getPodsFromContext(c *cli.Context, r *libpod.Runtime) ([]*libpod.Pod, error
 	}
 	return pods, lastError
 }
+
+type pFunc func() error
+
+type workerInput struct {
+	containerID  string
+	parallelFunc pFunc
+}
+
+// worker is a "threaded" worker that takes jobs from the channel "queue"
+func worker(wg *sync.WaitGroup, jobs <-chan workerInput, results map[string]error) {
+	for j := range jobs {
+		err := j.parallelFunc()
+		results[j.containerID] = err
+		wg.Done()
+	}
+}
+
+// parallelExecuteWorkerPool takes container jobs and performs them in parallel.  The worker
+// int is determines how many workers/threads should be premade.
+func parallelExecuteWorkerPool(workers int, functions []workerInput) map[string]error {
+	var (
+		wg sync.WaitGroup
+	)
+	results := make(map[string]error)
+	paraJobs := make(chan workerInput, len(functions))
+
+	// If we have more workers than functions, match up the number of workers and functions
+	if workers > len(functions) {
+		workers = len(functions)
+	}
+
+	// Create the workers
+	for w := 1; w <= workers; w++ {
+		go worker(&wg, paraJobs, results)
+	}
+
+	// Add jobs to the workers
+	for _, j := range functions {
+		j := j
+		wg.Add(1)
+		paraJobs <- j
+	}
+
+	close(paraJobs)
+	wg.Wait()
+	return results
+}

vendor.conf

@@ -75,6 +75,7 @@ golang.org/x/net c427ad74c6d7a814201695e9ffde0c5d400a7674
 golang.org/x/sys master
 golang.org/x/text f72d8390a633d5dfb0cc84043294db9f6c935756
 golang.org/x/time f51c12702a4d776e4c1fa9b0fabab841babae631
+golang.org/x/sync master
 google.golang.org/grpc v1.0.4 https://github.com/grpc/grpc-go
 gopkg.in/cheggaaa/pb.v1 v1.0.7
 gopkg.in/inf.v0 v0.9.0