fn: pre-fork pool for namespace/network speedup (#874)

* fn: pre-fork pool experimental implementation

api/agent/drivers/docker/docker_pool_test.go

@@ -0,0 +1,131 @@
+package docker
+
+import (
+	"testing"
+	"time"
+
+	"github.com/fnproject/fn/api/agent/drivers"
+)
+
+func TestRunnerDockerPool(t *testing.T) {
+
+	cfg := &drivers.Config{}
+
+	// shouldn't spin up a pool since cfg is empty
+	drv := NewDocker(*cfg)
+
+	cfg.PreForkPoolSize = 2
+	pool := NewDockerPool(*cfg, drv)
+
+	// primitive wait here
+	i := 0
+	for ; i < 10; i++ {
+		stats := pool.Usage()
+		if stats.free == 2 {
+			break
+		}
+
+		<-time.After(time.Duration(500) * time.Millisecond)
+	}
+	if i == 10 {
+		t.Fatalf("pool initialize timeout stats=%+v", pool.Usage())
+	}
+
+	id1, err := pool.AllocPoolId()
+	if err != nil {
+		t.Fatalf("pool AllocPoolId id1 err=%s", err.Error())
+	}
+	t.Logf("pool AllocPoolId id1=%s", id1)
+
+	id2, err := pool.AllocPoolId()
+	if err != nil {
+		t.Fatalf("pool AllocPoolId id2 err=%s", err.Error())
+	}
+	t.Logf("pool AllocPoolId id2=%s", id2)
+
+	id3, err := pool.AllocPoolId()
+	if err == nil {
+		t.Fatalf("pool AllocPoolId id3 should be err, but got id=%s", id3)
+	}
+	t.Logf("pool AllocPoolId id3=%s", id3)
+
+	pool.FreePoolId("nonsense")
+
+	id4, err := pool.AllocPoolId()
+	if err == nil {
+		t.Fatalf("pool AllocPoolId id4 should be err, but got id=%s", id3)
+	}
+	t.Logf("pool AllocPoolId id4=%s", id4)
+
+	pool.FreePoolId(id1)
+
+	id5, err := pool.AllocPoolId()
+	if err != nil {
+		t.Fatalf("pool AllocPoolId id5 err=%s", err.Error())
+	}
+	t.Logf("pool AllocPoolId id5=%s", id5)
+	if id5 != id1 {
+		t.Fatalf("pool AllocPoolId id5 != id1 (%s != %s)", id5, id1)
+	}
+
+	err = pool.Close()
+	if err != nil {
+		t.Fatalf("pool close err=%s", err.Error())
+	}
+
+	err = drv.Close()
+	if err != nil {
+		t.Fatalf("drv close err=%s", err.Error())
+	}
+
+	stats := pool.Usage()
+	if stats.free != 0 && stats.inuse != 0 {
+		t.Fatalf("pool shutdown timeout stats=%+v", stats)
+	}
+}
+
+func TestRunnerDockerPoolFaulty(t *testing.T) {
+
+	cfg := &drivers.Config{}
+
+	// shouldn't spin up a pool since cfg is empty
+	drv := NewDocker(*cfg)
+
+	cfg.PreForkPoolSize = 2
+	cfg.PreForkCmd = "sleep 0"
+
+	pool := NewDockerPool(*cfg, drv)
+
+	<-time.After(time.Duration(500) * time.Millisecond)
+
+	// Not much to see if pre-fork has exited, but let's close
+	// and wait at least to make sure we don't crash and burn.
+	id1, err := pool.AllocPoolId()
+	t.Logf("pool AllocPoolId id=%s err=%v", id1, err)
+	if id1 != "" {
+		pool.FreePoolId(id1)
+	}
+
+	<-time.After(time.Duration(500) * time.Millisecond)
+
+	id2, err := pool.AllocPoolId()
+	t.Logf("pool AllocPoolId id=%s err=%v", id2, err)
+	if id2 != "" {
+		pool.FreePoolId(id2)
+	}
+
+	err = pool.Close()
+	if err != nil {
+		t.Fatalf("pool close err=%s", err.Error())
+	}
+
+	err = drv.Close()
+	if err != nil {
+		t.Fatalf("drv close err=%s", err.Error())
+	}
+
+	stats := pool.Usage()
+	if stats.free != 0 && stats.inuse != 0 {
+		t.Fatalf("pool shutdown timeout stats=%+v", stats)
+	}
+}