api: Windows MemorySwappiness Workaround

Abstracted platformHostConfigOverride in task_windows.go to another
method to clarify the intention of the override. Updated related
comments regarding injection point for HostConfig override values.

Commented on task_unix.go to explain the use of memorySwappinessDefault
constant.

Cleaned up extra lines in task_windows_test.go. Removed unneeded
properties in task object use in TestWindowsPlatformHostConfigOverride.

agent/api/task_unix.go

@@ -21,6 +21,9 @@ import (
 
 const (
 	portBindingHostIP = "0.0.0.0"
+
+	//memorySwappinessDefault is the expected default value for this platform. This is used in task_windows.go
+	//and is maintained here for unix default. Also used for testing
 	memorySwappinessDefault = 0
 )
 

agent/api/task_windows.go

@@ -24,6 +24,8 @@ import (
 
 const (
 	portBindingHostIP = ""
+
+	//memorySwappinessDefault is the expected default value for this platform
 	memorySwappinessDefault = -1
 )
 
@@ -54,13 +56,18 @@ func getCanonicalPath(path string) string {
 	return filepath.Clean(strings.ToLower(path))
 }
 
-// platformHostConfigOverride Sets up default HostConfig options to be passed to Docker API.
-// Docker for Windows treats some options different than Unix and some are not supported at all.
+// platformHostConfigOverride provides an entry point to set up default HostConfig options to be
+// passed to Docker API.
+func (task *Task) platformHostConfigOverride(hostConfig *docker.HostConfig) {
+	task.overrideDefaultMemorySwappiness(hostConfig);
+}
+
+// overrideDefaultMemorySwappiness Overrides the value of MemorySwappiness to -1
 // Version 1.12.x of Docker for Windows would ignore the unsupported option MemorySwappiness.
 // Version 17.03.x will cause an error if any value other than -1 is passed in for MemorySwappiness.
 // This bug is not noticed when no value is passed in. However, the go-dockerclient client version
 // we are using removed the json option omitempty causing this parameter to default to 0 if empty.
 // https://github.com/fsouza/go-dockerclient/commit/72342f96fabfa614a94b6ca57d987eccb8a836bf
-func (task *Task) platformHostConfigOverride(hostConfig *docker.HostConfig) {
+func (task *Task) overrideDefaultMemorySwappiness(hostConfig *docker.HostConfig) {
 	hostConfig.MemorySwappiness = memorySwappinessDefault
-}
+}

agent/api/task_windows_test.go

@@ -108,20 +108,9 @@ func TestWindowsPlatformHostConfigOverride(t *testing.T) {
 	// Testing Windows platform override for HostConfig.
 	// Expects MemorySwappiness option to be set to -1
 
-	task := &Task{
-		Arn:                 "myArn",
-		DesiredStatusUnsafe: TaskRunning,
-		Family:              "myFamily",
-		Version:             "1",
-		Containers: []*Container{
-			{
-				Name: "myName",
-			},
-		},
-	}
+	task := &Task{}
 
-	hostConfig := &docker.HostConfig{
-	}
+	hostConfig := &docker.HostConfig{}
 
 	task.platformHostConfigOverride(hostConfig)
 
@@ -131,8 +120,7 @@ func TestWindowsPlatformHostConfigOverride(t *testing.T) {
 
 func TestWindowsMemorySwappinessOption(t *testing.T) {
 	// Testing sending a task to windows overriding MemorySwappiness value
-	rawHostConfigInput := docker.HostConfig{
-	}
+	rawHostConfigInput := docker.HostConfig{}
 
 	rawHostConfig, err := json.Marshal(&rawHostConfigInput)
 	if err != nil {