fn: async wait bugfix and low mem warnings (#649)

*) fix async high water mark logic
*) warning on 256 mem for async and async+sync pools

api/agent/resource.go

@@ -16,6 +16,11 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
+const (
+	Mem1MB = 1024 * 1024
+	Mem1GB = 1024 * 1024 * 1024
+)
+
 // A simple resource (memory, cpu, disk, etc.) tracker for scheduling.
 // TODO: add cpu, disk, network IO for future
 type ResourceTracker interface {
@@ -89,7 +94,7 @@ func (a *resourceTracker) isResourcePossible(memory uint64, isAsync bool) bool {
 // will close this token (i.e. the receiver should not call Close)
 func (a *resourceTracker) GetResourceToken(ctx context.Context, memory uint64, isAsync bool) <-chan ResourceToken {
 
-	memory = memory * 1024 * 1024
+	memory = memory * Mem1MB
 
 	c := a.cond
 	ch := make(chan ResourceToken)
@@ -162,7 +167,7 @@ func (a *resourceTracker) WaitAsyncResource() chan struct{} {
 	c := a.cond
 	go func() {
 		c.L.Lock()
-		for a.ramSyncUsed >= a.ramAsyncHWMark {
+		for a.ramAsyncUsed >= a.ramAsyncHWMark {
 			c.Wait()
 		}
 		c.L.Unlock()
@@ -236,9 +241,9 @@ func (a *resourceTracker) initializeMemory() {
 
 	} else {
 		// non-linux: assume 512MB sync only memory and 1.5GB async + sync memory
-		maxSyncMemory = 512 * 1024 * 1024
-		maxAsyncMemory = (1024 + 512) * 1024 * 1024
-		ramAsyncHWMark = 1024 * 1024 * 1024
+		maxSyncMemory = 512 * Mem1MB
+		maxAsyncMemory = (1024 + 512) * Mem1MB
+		ramAsyncHWMark = 1024 * Mem1MB
 	}
 
 	// For non-linux OS, we expect these (or their defaults) properly configured from command-line/env
@@ -252,6 +257,12 @@ func (a *resourceTracker) initializeMemory() {
 		logrus.Fatal("Cannot get the proper memory pool information to size server")
 	}
 
+	if maxSyncMemory+maxAsyncMemory < 256*Mem1MB {
+		logrus.Warn("Severaly Limited memory: ramSync + ramAsync < 256MB")
+	} else if maxAsyncMemory < 256*Mem1MB {
+		logrus.Warn("Severaly Limited memory: ramAsync < 256MB")
+	}
+
 	a.ramAsyncHWMark = ramAsyncHWMark
 	a.ramSyncTotal = maxSyncMemory
 	a.ramAsyncTotal = maxAsyncMemory
@@ -264,8 +275,8 @@ func getMemoryHeadRoom(usableMemory uint64) (uint64, error) {
 	headRoom := uint64(usableMemory / 10)
 
 	// clamp this with 256MB min -- 5GB max
-	maxHeadRoom := uint64(5 * 1024 * 1024 * 1024)
-	minHeadRoom := uint64(256 * 1024 * 1024)
+	maxHeadRoom := uint64(5 * Mem1GB)
+	minHeadRoom := uint64(256 * Mem1MB)
 
 	if minHeadRoom >= usableMemory {
 		return 0, fmt.Errorf("Not enough memory: %v", usableMemory)

api/agent/resource_test.go

@@ -0,0 +1,83 @@
+package agent
+
+import (
+	"testing"
+	"time"
+)
+
+func setTrackerTestVals(tr *resourceTracker, vals *trackerVals) {
+	tr.cond.L.Lock()
+
+	tr.ramSyncTotal = vals.st
+	tr.ramSyncUsed = vals.su
+	tr.ramAsyncTotal = vals.at
+	tr.ramAsyncUsed = vals.au
+	tr.ramAsyncHWMark = vals.am
+
+	tr.cond.L.Unlock()
+	tr.cond.Broadcast()
+}
+
+func getTrackerTestVals(tr *resourceTracker, vals *trackerVals) {
+
+	tr.cond.L.Lock()
+
+	vals.st = tr.ramSyncTotal
+	vals.su = tr.ramSyncUsed
+	vals.at = tr.ramAsyncTotal
+	vals.au = tr.ramAsyncUsed
+	vals.am = tr.ramAsyncHWMark
+
+	tr.cond.L.Unlock()
+}
+
+type trackerVals struct {
+	st uint64
+	su uint64
+	at uint64
+	au uint64
+	am uint64
+}
+
+func TestResourceAsyncMem(t *testing.T) {
+
+	var vals trackerVals
+
+	trI := NewResourceTracker()
+
+	tr := trI.(*resourceTracker)
+
+	getTrackerTestVals(tr, &vals)
+	if vals.st <= 0 || vals.su != 0 || vals.at <= 0 || vals.au != 0 || vals.am <= 0 {
+		t.Fatalf("faulty init %#v", vals)
+	}
+
+	// set set these to known vals
+	vals.st = 1 * 1024 * 1024
+	vals.su = 0
+	vals.at = 2 * 1024 * 1024
+	vals.au = 0
+	vals.am = 1 * 1024 * 1024
+
+	// should block & wait
+	vals.au = vals.am
+	setTrackerTestVals(tr, &vals)
+	ch := tr.WaitAsyncResource()
+
+	select {
+	case <-ch:
+		t.Fatal("high water mark over, should not trigger")
+	case <-time.After(time.Duration(500) * time.Millisecond):
+	}
+
+	// should not block & wait
+	vals.au = 0
+	setTrackerTestVals(tr, &vals)
+
+	select {
+	case <-ch:
+	case <-time.After(time.Duration(500) * time.Millisecond):
+		t.Fatal("high water mark not over, should trigger")
+	}
+
+}