Enable memory oversubscription (#102)

* Enable memory oversubscription

* Fix and add e2e test

.github/workflows/ci.yml

@@ -146,13 +146,15 @@ jobs:
           wget -q "https://releases.hashicorp.com/nomad/${NOMAD_VERSION}/nomad_${NOMAD_VERSION}_SHA256SUMS"
           grep "nomad_${NOMAD_VERSION}_linux_amd64.zip" nomad_${NOMAD_VERSION}_SHA256SUMS | sha256sum -c -
           unzip nomad_${NOMAD_VERSION}_linux_amd64.zip
+      - name: Set Nomad Config
+        run: echo "server { default_scheduler_config { memory_oversubscription_enabled = true } }" > e2e-config.hcl
       - name: Download Poseidon binary
         uses: actions/download-artifact@v2
         with:
           name: poseidon
       - name: Run e2e tests
         run: |
-          sudo ./nomad agent -dev -log-level=WARN &
+          sudo ./nomad agent -dev -log-level=WARN -config e2e-config.hcl &
           until curl -s --fail http://localhost:4646/v1/agent/health ; do sleep 1; done
           chmod +x ./poseidon
           ./poseidon &

api/swagger.yaml

@@ -27,7 +27,7 @@ components:
           type: number
           example: 100
         memoryLimit:
-          description: Memory limit for one runner in MB
+          description: Memory limit for one runner in MB. Exceeding the limit may result in termination of the runner.
           type: integer
           example: 256
         networkAccess:

docs/resources/server.example.hcl

@@ -10,5 +10,6 @@ server {
     # https://www.nomadproject.io/docs/configuration/server
     default_scheduler_config {
         scheduler_algorithm = "spread"
+        memory_oversubscription_enabled = true
     }
 }

internal/environment/nomad_environment.go

@@ -104,15 +104,20 @@ func (n *NomadEnvironment) SetCPULimit(limit uint) {
 func (n *NomadEnvironment) MemoryLimit() uint {
 	defaultTaskGroup := nomad.FindAndValidateDefaultTaskGroup(n.job)
 	defaultTask := nomad.FindAndValidateDefaultTask(defaultTaskGroup)
-	return uint(*defaultTask.Resources.MemoryMB)
+	maxMemoryLimit := defaultTask.Resources.MemoryMaxMB
+	if maxMemoryLimit != nil {
+		return uint(*maxMemoryLimit)
+	} else {
+		return 0
+	}
 }
 
 func (n *NomadEnvironment) SetMemoryLimit(limit uint) {
 	defaultTaskGroup := nomad.FindAndValidateDefaultTaskGroup(n.job)
 	defaultTask := nomad.FindAndValidateDefaultTask(defaultTaskGroup)
 
-	integerMemoryLimit := int(limit)
-	defaultTask.Resources.MemoryMB = &integerMemoryLimit
+	integerMemoryMaxLimit := int(limit)
+	defaultTask.Resources.MemoryMaxMB = &integerMemoryMaxLimit
 }
 
 func (n *NomadEnvironment) Image() string {

internal/environment/template-environment-job.hcl

@@ -42,7 +42,7 @@ job "template-0" {
 
       resources {
         cpu    = 40
-        memory = 40
+        memory = 16
       }
 
       restart {

tests/e2e/e2e_test.go

@@ -24,11 +24,12 @@ import (
  */
 
 var (
-	log             = logging.GetLogger("e2e")
-	testDockerImage = flag.String("dockerImage", "", "Docker image to use in E2E tests")
-	nomadClient     *nomadApi.Client
-	nomadNamespace  string
-	environmentIDs  []dto.EnvironmentID
+	log                     = logging.GetLogger("e2e")
+	testDockerImage         = flag.String("dockerImage", "", "Docker image to use in E2E tests")
+	nomadClient             *nomadApi.Client
+	nomadNamespace          string
+	environmentIDs          []dto.EnvironmentID
+	defaultNomadEnvironment dto.ExecutionEnvironmentRequest
 )
 
 type E2ETestSuite struct {
@@ -102,7 +103,7 @@ func createDefaultEnvironment() {
 
 	path := helpers.BuildURL(api.BasePath, api.EnvironmentsPath, tests.DefaultEnvironmentIDAsString)
 
-	request := dto.ExecutionEnvironmentRequest{
+	defaultNomadEnvironment = dto.ExecutionEnvironmentRequest{
 		PrewarmingPoolSize: 10,
 		CPULimit:           100,
 		MemoryLimit:        100,
@@ -111,7 +112,7 @@ func createDefaultEnvironment() {
 		ExposedPorts:       nil,
 	}
 
-	resp, err := helpers.HTTPPutJSON(path, request)
+	resp, err := helpers.HTTPPutJSON(path, defaultNomadEnvironment)
 	if err != nil || resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusNoContent {
 		log.WithError(err).Fatal("Couldn't create default environment for e2e tests")
 	}

tests/e2e/environments_test.go

@@ -364,7 +364,7 @@ func validateJob(t *testing.T, expected dto.ExecutionEnvironmentRequest) {
 
 	task := taskGroup.Tasks[0]
 	assertEqualValueIntPointer(t, int(expected.CPULimit), task.Resources.CPU)
-	assertEqualValueIntPointer(t, int(expected.MemoryLimit), task.Resources.MemoryMB)
+	assertEqualValueIntPointer(t, int(expected.MemoryLimit), task.Resources.MemoryMaxMB)
 	assert.Equal(t, expected.Image, task.Config["image"])
 
 	if expected.NetworkAccess {

tests/e2e/websocket_test.go

@@ -13,6 +13,7 @@ import (
 	"github.com/openHPI/poseidon/tests/helpers"
 	"github.com/stretchr/testify/suite"
 	"net/http"
+	"strconv"
 	"strings"
 	"time"
 )
@@ -175,6 +176,28 @@ func (s *E2ETestSuite) TestEchoEnvironment() {
 	}
 }
 
+func (s *E2ETestSuite) TestMemoryMaxLimit_Nomad() {
+	maxMemoryLimit := defaultNomadEnvironment.MemoryLimit
+	// The operating system is in charge to kill the process and sometimes tolerates small exceeding of the limit.
+	maxMemoryLimit = uint(1.1 * float64(maxMemoryLimit))
+	connection, err := ProvideWebSocketConnection(&s.Suite, tests.DefaultEnvironmentIDAsInteger, &dto.ExecutionRequest{
+		// This shell line tries to load maxMemoryLimit Bytes into the memory.
+		Command: "</dev/zero head -c " + strconv.Itoa(int(maxMemoryLimit)) + "MB | tail > /dev/null",
+	})
+	s.Require().NoError(err)
+
+	startMessage, err := helpers.ReceiveNextWebSocketMessage(connection)
+	s.Require().NoError(err)
+	s.Equal(dto.WebSocketMetaStart, startMessage.Type)
+
+	messages, err := helpers.ReceiveAllWebSocketMessages(connection)
+	s.Require().Error(err)
+	s.Equal(err, &websocket.CloseError{Code: websocket.CloseNormalClosure})
+	stdout, stderr, _ := helpers.WebSocketOutputMessages(messages)
+	s.Empty(stdout)
+	s.Contains(stderr, "Killed")
+}
+
 func (s *E2ETestSuite) TestNomadStderrFifoIsRemoved() {
 	runnerID, err := ProvideRunner(&dto.RunnerRequest{
 		ExecutionEnvironmentID: tests.DefaultEnvironmentIDAsInteger,