feat: (FOUNDENG-344) Change enroot to use /var/tmp as localTmp direct…

…ory (#631)

* use /var/tmp as tmpfs
Co-authored-by: Pankaj Mandal <[email protected]>

master/pkg/tasks/dispatcher_task.go

@@ -152,6 +152,10 @@ func (t *TaskSpec) ToDispatcherManifest(
 
 	mounts, userWantsDirMountedOnTmp := getDataVolumes(t.Mounts)
 
+	if containerRunType == enroot {
+		mounts = addTmpFs(mounts, "varTmp", varTmp)
+	}
+
 	/*
 	 * We need a per-container-private link directory to host /run/determined.
 	 * This is the target of a number of softlinks that are remapped to per-container
@@ -162,7 +166,7 @@ func (t *TaskSpec) ToDispatcherManifest(
 	 */
 	localTmp := "/"
 	if containerRunType == enroot {
-		localTmp = tmp
+		localTmp = varTmp
 	}
 
 	// Use the specified workDir if it is user-specified.
@@ -722,6 +726,21 @@ func getDataVolumes(mounts []mount.Mount) ([]launcher.Data, bool) {
 	return volumes, userWantsDirMountedOnTmp
 }
 
+// Used for creating a tmpfs mount type at the target location.
+func addTmpFs(volumes []launcher.Data, name string, target string) []launcher.Data {
+	volume := *launcher.NewData()
+	volume.SetName(name)
+	volume.SetSource("tmpfs")
+
+	/*
+	 * Set target and add a mount option to enable target directory creation,
+	 * if it did not exist
+	 */
+	volume.SetTarget(target + ":x-create=dir")
+	volumes = append(volumes, volume)
+	return volumes
+}
+
 // Create a softlink archive entry for the specified file name in the
 // '/run/determined' directory to the local container temp version.
 // Provide a localTmp directory to redirect it elsewhere (must end in /).

master/pkg/tasks/dispatcher_task_test.go

@@ -908,6 +908,18 @@ func Test_getDataVolumns(t *testing.T) {
 	}
 }
 
+func Test_addTmpFs(t *testing.T) {
+	arg := []mount.Mount{}
+	volumes, _ := getDataVolumes(arg)
+	name := "varTmp"
+	target := "/var/tmp"
+	volumes = addTmpFs(volumes, name, target)
+	v := volumes[0]
+	assert.Equal(t, *v.Name, "varTmp")
+	assert.Equal(t, *v.Source, "tmpfs")
+	assert.Equal(t, *v.Target, "/var/tmp:x-create=dir")
+}
+
 func Test_getPayloadName(t *testing.T) {
 	tests := []struct {
 		name string