Refactor interfaces to use a runner manager and an environment manager.

See https://gitlab.hpi.de/codeocean/codemoon/poseidon/-/issues/44.

Makefile

@@ -55,7 +55,6 @@ snaked_name=$(shell sed -e "s/\([A-Z]\)/_\L\1/g" -e "s/^_//" <<< "$(name)")
 mock: deps ## Create/Update a mock. Example: make mock name=apiQuerier pkg=./nomad
 	@mockery \
       --name=$(name) \
-      --output=$(pkg) \
       --structname=$(name)Mock \
       --filename=$(snaked_name)_mock.go \
       --inpackage \

README.md

@@ -105,8 +105,7 @@ $ make e2e-docker DOCKER_OPTS=""
 
 ### Mocks
 
-For mocks we use [mockery](https://github.com/vektra/mockery). To generate a mock, first navigate to the package the interface is defined in.
-You can then create a mock for the interface of your choice by running
+For mocks we use [mockery](https://github.com/vektra/mockery). You can create a mock for the interface of your choice by running
 
 ```bash
 make mock name=INTERFACE_NAME pkg=./PATH/TO/PKG
@@ -120,4 +119,26 @@ For example, for an interface called `ExecutorApi` in the package `nomad`, you m
 make mock name=ExecutorApi pkg=./nomad
 ```
 
-If the interface changes, you can rerun this command.
+If the interface changes, you can rerun this command (deleting the mock file first to avoid errors may be necessary).
+
+Mocks can also be generated by using mockery directly on a specific interface. To do this, first navigate to the package the interface is defined in. Then run
+
+```bash
+mockery \
+  --name=<<interface_name>> \
+  --structname=<<interface_name>>Mock \
+  --filename=<<interface_name>>Mock.go \
+  --inpackage
+```
+
+For example, for an interface called `ExecutorApi` in the package `nomad`, you might run
+
+```bash
+mockery \
+--name=ExecutorApi \
+--structname=ExecutorApiMock \
+--filename=ExecutorApiMock.go \
+--inpackage
+```
+
+Note that per default, the mocks are created in a `mocks` sub-folder. However, in some cases (if the mock implements private interface methods), it needs to be in the same package as the interface it is mocking. The `--inpackage` flag can be used to avoid creating it in a subdirectory.

api/api.go

@@ -5,7 +5,7 @@ import (
 	"gitlab.hpi.de/codeocean/codemoon/poseidon/api/auth"
 	"gitlab.hpi.de/codeocean/codemoon/poseidon/environment"
 	"gitlab.hpi.de/codeocean/codemoon/poseidon/logging"
-	"gitlab.hpi.de/codeocean/codemoon/poseidon/nomad"
+	"gitlab.hpi.de/codeocean/codemoon/poseidon/runner"
 	"net/http"
 )
 
@@ -17,32 +17,34 @@ const (
 	RouteRunners = "/runners"
 )
 
-// NewRouter returns an HTTP handler (http.Handler) which can be
+// NewRouter returns a *mux.Router which can be
 // used by the net/http package to serve the routes of our API. It
 // always returns a router for the newest version of our API. We
 // use gorilla/mux because it is more convenient than net/http, e.g.
 // when extracting path parameters.
-func NewRouter(apiClient nomad.ExecutorApi, runnerPool environment.RunnerPool) *mux.Router {
+func NewRouter(runnerManager runner.Manager, environmentManager environment.Manager) *mux.Router {
 	router := mux.NewRouter()
 	// this can later be restricted to a specific host with
 	// `router.Host(...)` and to HTTPS with `router.Schemes("https")`
-	router = newRouterV1(router, apiClient, runnerPool)
+	configureV1Router(router, runnerManager, environmentManager)
 	router.Use(logging.HTTPLoggingMiddleware)
 	return router
 }
 
-// newRouterV1 returns a sub-router containing the routes of version 1 of our API.
-func newRouterV1(router *mux.Router, apiClient nomad.ExecutorApi, runnerPool environment.RunnerPool) *mux.Router {
+// configureV1Router configures a given router with the routes of version 1 of our API.
+func configureV1Router(router *mux.Router, runnerManager runner.Manager, environmentManager environment.Manager) {
 	v1 := router.PathPrefix(RouteBase).Subrouter()
 	v1.HandleFunc(RouteHealth, Health).Methods(http.MethodGet)
 
+	runnerController := &RunnerController{manager: runnerManager}
+
 	if auth.InitializeAuthentication() {
 		// Create new authenticated subrouter.
 		// All routes added to v1 after this require authentication.
-		v1 = v1.PathPrefix("").Subrouter()
-		v1.Use(auth.HTTPAuthenticationMiddleware)
+		authenticatedV1Router := v1.PathPrefix("").Subrouter()
+		authenticatedV1Router.Use(auth.HTTPAuthenticationMiddleware)
+		runnerController.ConfigureRoutes(authenticatedV1Router)
+	} else {
+		runnerController.ConfigureRoutes(v1)
 	}
-	registerRunnerRoutes(v1.PathPrefix(RouteRunners).Subrouter(), apiClient, runnerPool)
-
-	return v1
 }

api/api_test.go

@@ -4,7 +4,6 @@ import (
 	"github.com/gorilla/mux"
 	"github.com/stretchr/testify/assert"
 	"gitlab.hpi.de/codeocean/codemoon/poseidon/config"
-	"gitlab.hpi.de/codeocean/codemoon/poseidon/environment"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -17,7 +16,7 @@ func mockHTTPHandler(writer http.ResponseWriter, _ *http.Request) {
 func TestNewRouterV1WithAuthenticationDisabled(t *testing.T) {
 	config.Config.Server.Token = ""
 	router := mux.NewRouter()
-	v1 := newRouterV1(router, nil, environment.NewLocalRunnerPool())
+	configureV1Router(router, nil, nil)
 
 	t.Run("health route is accessible", func(t *testing.T) {
 		request, err := http.NewRequest(http.MethodGet, "/api/v1/health", nil)
@@ -30,7 +29,7 @@ func TestNewRouterV1WithAuthenticationDisabled(t *testing.T) {
 	})
 
 	t.Run("added route is accessible", func(t *testing.T) {
-		v1.HandleFunc("/test", mockHTTPHandler)
+		router.HandleFunc("/api/v1/test", mockHTTPHandler)
 		request, err := http.NewRequest(http.MethodGet, "/api/v1/test", nil)
 		if err != nil {
 			t.Fatal(err)
@@ -44,7 +43,7 @@ func TestNewRouterV1WithAuthenticationDisabled(t *testing.T) {
 func TestNewRouterV1WithAuthenticationEnabled(t *testing.T) {
 	config.Config.Server.Token = "TestToken"
 	router := mux.NewRouter()
-	v1 := newRouterV1(router, nil, environment.NewLocalRunnerPool())
+	configureV1Router(router, nil, nil)
 
 	t.Run("health route is accessible", func(t *testing.T) {
 		request, err := http.NewRequest(http.MethodGet, "/api/v1/health", nil)
@@ -56,9 +55,8 @@ func TestNewRouterV1WithAuthenticationEnabled(t *testing.T) {
 		assert.Equal(t, http.StatusNoContent, recorder.Code)
 	})
 
-	t.Run("added route is not accessible", func(t *testing.T) {
-		v1.HandleFunc("/test", mockHTTPHandler)
-		request, err := http.NewRequest(http.MethodGet, "/api/v1/test", nil)
+	t.Run("protected route is not accessible", func(t *testing.T) {
+		request, err := http.NewRequest(http.MethodPost, "/api/v1/runners", nil)
 		if err != nil {
 			t.Fatal(err)
 		}

api/dto/dto.go

@@ -18,6 +18,9 @@ type RunnerResponse struct {
 	Id string `json:"runnerId"`
 }
 
+// FileCreation is the expected json structure of the request body for the copy files route.
+type FileCreation struct{}
+
 // WebsocketResponse is the expected response when creating an execution for a runner.
 type WebsocketResponse struct {
 	WebsocketUrl string `json:"websocketUrl"`

api/environments.go

@@ -0,0 +1,20 @@
+package api
+
+import (
+	"gitlab.hpi.de/codeocean/codemoon/poseidon/environment"
+	"net/http"
+)
+
+type EnvironmentController struct {
+	manager environment.Manager // nolint:unused,structcheck
+}
+
+// create creates a new execution environment on the executor.
+func (e *EnvironmentController) create(writer http.ResponseWriter, request *http.Request) { // nolint:unused
+
+}
+
+// delete removes an execution environment from the executor
+func (e *EnvironmentController) delete(writer http.ResponseWriter, request *http.Request) { // nolint:unused
+
+}

api/health.go

@@ -4,7 +4,8 @@ import (
 	"net/http"
 )
 
-// Health tries to respond that the server is alive.
+// Health handles the health route.
+// It tries to respond that the server is alive.
 // If it is not, the response won't reach the client.
 func Health(writer http.ResponseWriter, _ *http.Request) {
 	writer.WriteHeader(http.StatusNoContent)

api/runners.go

@@ -1,13 +1,10 @@
 package api
 
 import (
-	"errors"
 	"fmt"
 	"github.com/gorilla/mux"
 	"gitlab.hpi.de/codeocean/codemoon/poseidon/api/dto"
 	"gitlab.hpi.de/codeocean/codemoon/poseidon/config"
-	"gitlab.hpi.de/codeocean/codemoon/poseidon/environment"
-	"gitlab.hpi.de/codeocean/codemoon/poseidon/nomad"
 	"gitlab.hpi.de/codeocean/codemoon/poseidon/runner"
 	"net/http"
 	"net/url"
@@ -21,30 +18,50 @@ const (
 	ExecutionIdKey = "executionId"
 )
 
-// provideRunner tries to respond with the id of a runner
+type RunnerController struct {
+	manager      runner.Manager
+	runnerRouter *mux.Router
+}
+
+// ConfigureRoutes configures a given router with the runner routes of our API.
+func (r *RunnerController) ConfigureRoutes(router *mux.Router) {
+	runnersRouter := router.PathPrefix(RouteRunners).Subrouter()
+	runnersRouter.HandleFunc("", r.provide).Methods(http.MethodPost)
+	r.runnerRouter = runnersRouter.PathPrefix(fmt.Sprintf("/{%s}", RunnerIdKey)).Subrouter()
+	r.runnerRouter.Use(r.findRunnerMiddleware)
+	r.runnerRouter.HandleFunc(ExecutePath, r.execute).Methods(http.MethodPost).Name(ExecutePath)
+	r.runnerRouter.HandleFunc(WebsocketPath, connectToRunner).Methods(http.MethodGet).Name(WebsocketPath)
+	r.runnerRouter.HandleFunc("", r.delete).Methods(http.MethodDelete).Name(DeleteRoute)
+}
+
+// provide handles the provide runners API route.
+// It tries to respond with the id of a unused runner.
 // This runner is then reserved for future use
-func provideRunner(writer http.ResponseWriter, request *http.Request) {
+func (r *RunnerController) provide(writer http.ResponseWriter, request *http.Request) {
 	runnerRequest := new(dto.RunnerRequest)
 	if err := parseJSONRequestBody(writer, request, runnerRequest); err != nil {
 		return
 	}
-	executionEnvironment, err := environment.GetExecutionEnvironment(runnerRequest.ExecutionEnvironmentId)
+	environmentId := runner.EnvironmentId(runnerRequest.ExecutionEnvironmentId)
+	nextRunner, err := r.manager.Use(environmentId)
 	if err != nil {
+		if err == runner.ErrUnknownExecutionEnvironment {
 			writeNotFound(writer, err)
-		return
-	}
-	nextRunner, err := executionEnvironment.NextRunner()
-	if err != nil {
+		} else if err == runner.ErrNoRunnersAvailable {
 			writeInternalServerError(writer, err, dto.ErrorNomadOverload)
+		} else {
+			writeInternalServerError(writer, err, dto.ErrorUnknown)
+		}
 		return
 	}
+
 	sendJson(writer, &dto.RunnerResponse{Id: nextRunner.Id()}, http.StatusOK)
 }
 
-// executeCommand takes an ExecutionRequest and stores it for a runner.
+// execute handles the execute API route.
+// It takes an ExecutionRequest and stores it for a runner.
 // It returns a url to connect to for a websocket connection to this execution in the corresponding runner.
-func executeCommand(router *mux.Router) func(w http.ResponseWriter, r *http.Request) {
-	return func(writer http.ResponseWriter, request *http.Request) {
+func (r *RunnerController) execute(writer http.ResponseWriter, request *http.Request) {
 	executionRequest := new(dto.ExecutionRequest)
 	if err := parseJSONRequestBody(writer, request, executionRequest); err != nil {
 		return
@@ -56,15 +73,15 @@ func executeCommand(router *mux.Router) func(w http.ResponseWriter, r *http.Requ
 	} else {
 		scheme = "ws"
 	}
-		r, _ := runner.FromContext(request.Context())
+	targetRunner, _ := runner.FromContext(request.Context())
 
-		path, err := router.Get(WebsocketPath).URL(RunnerIdKey, r.Id())
+	path, err := r.runnerRouter.Get(WebsocketPath).URL(RunnerIdKey, targetRunner.Id())
 	if err != nil {
 		log.WithError(err).Error("Could not create runner websocket URL.")
 		writeInternalServerError(writer, err, dto.ErrorUnknown)
 		return
 	}
-		id, err := r.AddExecution(*executionRequest)
+	id, err := targetRunner.AddExecution(*executionRequest)
 	if err != nil {
 		log.WithError(err).Error("Could not store execution.")
 		writeInternalServerError(writer, err, dto.ErrorUnknown)
@@ -78,49 +95,39 @@ func executeCommand(router *mux.Router) func(w http.ResponseWriter, r *http.Requ
 	}
 
 	sendJson(writer, &dto.WebsocketResponse{WebsocketUrl: websocketUrl.String()}, http.StatusOK)
-	}
 }
 
 // The findRunnerMiddleware looks up the runnerId for routes containing it
 // and adds the runner to the context of the request.
-func findRunnerMiddleware(runnerPool environment.RunnerPool) func(handler http.Handler) http.Handler {
-	return func(next http.Handler) http.Handler {
+func (r *RunnerController) findRunnerMiddleware(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
 		// Find runner
 		runnerId := mux.Vars(request)[RunnerIdKey]
-			r, ok := runnerPool.Get(runnerId)
-			if !ok {
-				writeNotFound(writer, errors.New("no runner with this id"))
+		r, err := r.manager.Get(runnerId)
+		if err != nil {
+			writeNotFound(writer, err)
 			return
 		}
 		ctx := runner.NewContext(request.Context(), r.(runner.Runner))
 		requestWithRunner := request.WithContext(ctx)
 		next.ServeHTTP(writer, requestWithRunner)
 	})
-	}
 }
 
-func deleteRunner(apiClient nomad.ExecutorApi, runnerPool environment.RunnerPool) func(writer http.ResponseWriter, request *http.Request) {
-	return func(writer http.ResponseWriter, request *http.Request) {
+// delete handles the delete runner API route.
+// It destroys the given runner on the executor and removes it from the used runners list.
+func (r *RunnerController) delete(writer http.ResponseWriter, request *http.Request) {
 	targetRunner, _ := runner.FromContext(request.Context())
 
-		err := apiClient.DeleteRunner(targetRunner.Id())
+	err := r.manager.Return(targetRunner)
 	if err != nil {
+		if err == runner.ErrUnknownExecutionEnvironment {
+			writeNotFound(writer, err)
+		}
+
 		writeInternalServerError(writer, err, dto.ErrorNomadInternalServerError)
 		return
 	}
 
-		runnerPool.Delete(targetRunner.Id())
-
 	writer.WriteHeader(http.StatusNoContent)
-	}
-}
-
-func registerRunnerRoutes(router *mux.Router, apiClient nomad.ExecutorApi, runnerPool environment.RunnerPool) {
-	router.HandleFunc("", provideRunner).Methods(http.MethodPost)
-	runnerRouter := router.PathPrefix(fmt.Sprintf("/{%s}", RunnerIdKey)).Subrouter()
-	runnerRouter.Use(findRunnerMiddleware(runnerPool))
-	runnerRouter.HandleFunc(ExecutePath, executeCommand(runnerRouter)).Methods(http.MethodPost).Name(ExecutePath)
-	runnerRouter.HandleFunc(WebsocketPath, connectToRunner).Methods(http.MethodGet).Name(WebsocketPath)
-	runnerRouter.HandleFunc("", deleteRunner(apiClient, runnerPool)).Methods(http.MethodDelete).Name(DeleteRoute)
 }

api/runners_test.go

@@ -3,15 +3,12 @@ package api
 import (
 	"bytes"
 	"encoding/json"
-	"errors"
 	"fmt"
 	"github.com/gorilla/mux"
 	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/mock"
 	"github.com/stretchr/testify/suite"
 	"gitlab.hpi.de/codeocean/codemoon/poseidon/api/dto"
 	"gitlab.hpi.de/codeocean/codemoon/poseidon/environment"
-	"gitlab.hpi.de/codeocean/codemoon/poseidon/nomad"
 	"gitlab.hpi.de/codeocean/codemoon/poseidon/runner"
 	"net/http"
 	"net/http/httptest"
@@ -20,11 +17,27 @@ import (
 	"testing"
 )
 
-func TestFindRunnerMiddleware(t *testing.T) {
-	runnerPool := environment.NewLocalRunnerPool()
+type MiddlewareTestSuite struct {
+	suite.Suite
+	manager          *runner.ManagerMock
+	router           *mux.Router
+	runnerController *RunnerController
+	testRunner       runner.Runner
+}
+
+func (suite *MiddlewareTestSuite) SetupTest() {
+	suite.manager = &runner.ManagerMock{}
+	suite.router = mux.NewRouter()
+	suite.runnerController = &RunnerController{suite.manager, suite.router}
+	suite.testRunner = runner.NewRunner("runner")
+}
+
+func TestMiddlewareTestSuite(t *testing.T) {
+	suite.Run(t, new(MiddlewareTestSuite))
+}
+
+func (suite *MiddlewareTestSuite) TestFindRunnerMiddleware() {
 	var capturedRunner runner.Runner
-	testRunner := runner.NewExerciseRunner("testRunner")
-	runnerPool.Add(testRunner)
 
 	testRunnerIdRoute := func(writer http.ResponseWriter, request *http.Request) {
 		var ok bool
@@ -35,12 +48,8 @@ func TestFindRunnerMiddleware(t *testing.T) {
 			writer.WriteHeader(http.StatusInternalServerError)
 		}
 	}
-	router := mux.NewRouter()
-	router.Use(findRunnerMiddleware(runnerPool))
-	router.HandleFunc(fmt.Sprintf("/test/{%s}", RunnerIdKey), testRunnerIdRoute).Name("test-runner-id")
-
 	testRunnerRequest := func(t *testing.T, runnerId string) *http.Request {
-		path, err := router.Get("test-runner-id").URL(RunnerIdKey, runnerId)
+		path, err := suite.router.Get("test-runner-id").URL(RunnerIdKey, runnerId)
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -51,36 +60,57 @@ func TestFindRunnerMiddleware(t *testing.T) {
 		return request
 	}
 
-	t.Run("sets runner in context if runner exists", func(t *testing.T) {
+	suite.router.Use(suite.runnerController.findRunnerMiddleware)
+	suite.router.HandleFunc(fmt.Sprintf("/test/{%s}", RunnerIdKey), testRunnerIdRoute).Name("test-runner-id")
+
+	suite.manager.On("Get", suite.testRunner.Id()).Return(suite.testRunner, nil)
+	suite.T().Run("sets runner in context if runner exists", func(t *testing.T) {
 		capturedRunner = nil
 
 		recorder := httptest.NewRecorder()
-		router.ServeHTTP(recorder, testRunnerRequest(t, testRunner.Id()))
+		suite.router.ServeHTTP(recorder, testRunnerRequest(t, suite.testRunner.Id()))
 
 		assert.Equal(t, http.StatusOK, recorder.Code)
-		assert.Equal(t, testRunner, capturedRunner)
+		assert.Equal(t, suite.testRunner, capturedRunner)
 	})
 
-	t.Run("returns 404 if runner does not exist", func(t *testing.T) {
+	invalidID := "some-invalid-runner-id"
+	suite.manager.On("Get", invalidID).Return(nil, runner.ErrRunnerNotFound)
+	suite.T().Run("returns 404 if runner does not exist", func(t *testing.T) {
 		recorder := httptest.NewRecorder()
-		router.ServeHTTP(recorder, testRunnerRequest(t, "some-invalid-runner-id"))
+		suite.router.ServeHTTP(recorder, testRunnerRequest(t, invalidID))
 
 		assert.Equal(t, http.StatusNotFound, recorder.Code)
 	})
 }
 
-func TestExecuteRoute(t *testing.T) {
-	runnerPool := environment.NewLocalRunnerPool()
-	router := NewRouter(nil, runnerPool)
-	testRunner := runner.NewExerciseRunner("testRunner")
-	runnerPool.Add(testRunner)
+func TestRunnerRouteTestSuite(t *testing.T) {
+	suite.Run(t, new(RunnerRouteTestSuite))
+}
 
-	path, err := router.Get(ExecutePath).URL(RunnerIdKey, testRunner.Id())
+type RunnerRouteTestSuite struct {
+	suite.Suite
+	runnerManager      *runner.ManagerMock
+	environmentManager *environment.ManagerMock
+	router             *mux.Router
+	runner             runner.Runner
+}
+
+func (suite *RunnerRouteTestSuite) SetupTest() {
+	suite.runnerManager = &runner.ManagerMock{}
+	suite.environmentManager = &environment.ManagerMock{}
+	suite.router = NewRouter(suite.runnerManager, suite.environmentManager)
+	suite.runner = runner.NewRunner("test_runner")
+	suite.runnerManager.On("Get", suite.runner.Id()).Return(suite.runner, nil)
+}
+
+func (suite *RunnerRouteTestSuite) TestExecuteRoute() {
+	path, err := suite.router.Get(ExecutePath).URL(RunnerIdKey, suite.runner.Id())
 	if err != nil {
-		t.Fatal(err)
+		suite.T().Fatal()
 	}
 
-	t.Run("valid request", func(t *testing.T) {
+	suite.Run("valid request", func() {
 		recorder := httptest.NewRecorder()
 		executionRequest := dto.ExecutionRequest{
 			Command:     "command",
@@ -89,83 +119,60 @@ func TestExecuteRoute(t *testing.T) {
 		}
 		body, err := json.Marshal(executionRequest)
 		if err != nil {
-			t.Fatal(err)
+			suite.T().Fatal(err)
 		}
 		request, err := http.NewRequest(http.MethodPost, path.String(), bytes.NewReader(body))
 		if err != nil {
-			t.Fatal(err)
+			suite.T().Fatal(err)
 		}
 
-		router.ServeHTTP(recorder, request)
+		suite.router.ServeHTTP(recorder, request)
 
 		var websocketResponse dto.WebsocketResponse
 		err = json.NewDecoder(recorder.Result().Body).Decode(&websocketResponse)
 		if err != nil {
-			t.Fatal(err)
+			suite.T().Fatal(err)
 		}
 
-		assert.Equal(t, http.StatusOK, recorder.Code)
+		suite.Equal(http.StatusOK, recorder.Code)
 
-		t.Run("creates an execution request for the runner", func(t *testing.T) {
+		suite.Run("creates an execution request for the runner", func() {
 			url, err := url.Parse(websocketResponse.WebsocketUrl)
 			if err != nil {
-				t.Fatal(err)
+				suite.T().Fatal(err)
 			}
 			executionId := url.Query().Get(ExecutionIdKey)
-			storedExecutionRequest, ok := testRunner.Execution(runner.ExecutionId(executionId))
+			storedExecutionRequest, ok := suite.runner.Execution(runner.ExecutionId(executionId))
 
-			assert.True(t, ok, "No execution request with this id: ", executionId)
-			assert.Equal(t, executionRequest, storedExecutionRequest)
+			suite.True(ok, "No execution request with this id: ", executionId)
+			suite.Equal(executionRequest, storedExecutionRequest)
 		})
 	})
 
-	t.Run("invalid request", func(t *testing.T) {
+	suite.Run("invalid request", func() {
 		recorder := httptest.NewRecorder()
 		body := ""
 		request, err := http.NewRequest(http.MethodPost, path.String(), strings.NewReader(body))
 		if err != nil {
-			t.Fatal(err)
+			suite.T().Fatal(err)
 		}
-		router.ServeHTTP(recorder, request)
+		suite.router.ServeHTTP(recorder, request)
 
-		assert.Equal(t, http.StatusBadRequest, recorder.Code)
+		suite.Equal(http.StatusBadRequest, recorder.Code)
 	})
 }
 
-func TestDeleteRunnerRouteTestSuite(t *testing.T) {
-	suite.Run(t, new(DeleteRunnerRouteTestSuite))
-}
-
-type DeleteRunnerRouteTestSuite struct {
-	suite.Suite
-	runnerPool environment.RunnerPool
-	apiClient  *nomad.ExecutorApiMock
-	router     *mux.Router
-	testRunner runner.Runner
-	path       string
-}
-
-func (suite *DeleteRunnerRouteTestSuite) SetupTest() {
-	suite.runnerPool = environment.NewLocalRunnerPool()
-	suite.apiClient = &nomad.ExecutorApiMock{}
-	suite.router = NewRouter(suite.apiClient, suite.runnerPool)
-
-	suite.testRunner = runner.NewExerciseRunner("testRunner")
-	suite.runnerPool.Add(suite.testRunner)
-
-	var err error
-	runnerUrl, err := suite.router.Get(DeleteRoute).URL(RunnerIdKey, suite.testRunner.Id())
+func (suite *RunnerRouteTestSuite) TestDeleteRoute() {
+	deleteURL, err := suite.router.Get(DeleteRoute).URL(RunnerIdKey, suite.runner.Id())
 	if err != nil {
 		suite.T().Fatal(err)
 	}
-	suite.path = runnerUrl.String()
-}
-
-func (suite *DeleteRunnerRouteTestSuite) TestValidRequestReturnsNoContent() {
-	suite.apiClient.On("DeleteRunner", mock.AnythingOfType("string")).Return(nil)
+	deletePath := deleteURL.String()
+	suite.runnerManager.On("Return", suite.runner).Return(nil)
 
+	suite.Run("valid request", func() {
 		recorder := httptest.NewRecorder()
-	request, err := http.NewRequest(http.MethodDelete, suite.path, nil)
+		request, err := http.NewRequest(http.MethodDelete, deletePath, nil)
 		if err != nil {
 			suite.T().Fatal(err)
 		}
@@ -174,46 +181,8 @@ func (suite *DeleteRunnerRouteTestSuite) TestValidRequestReturnsNoContent() {
 
 		suite.Equal(http.StatusNoContent, recorder.Code)
 
-	suite.Run("runner is deleted on nomad", func() {
-		suite.apiClient.AssertCalled(suite.T(), "DeleteRunner", suite.testRunner.Id())
+		suite.Run("runner was returned to runner manager", func() {
+			suite.runnerManager.AssertCalled(suite.T(), "Return", suite.runner)
 		})
-
-	suite.Run("runner is deleted from runnerPool", func() {
-		returnedRunner, ok := suite.runnerPool.Get(suite.testRunner.Id())
-		suite.Nil(returnedRunner)
-		suite.False(ok)
 	})
 }
-
-func (suite *DeleteRunnerRouteTestSuite) TestReturnInternalServerErrorWhenApiCallToNomadFailed() {
-	suite.apiClient.On("DeleteRunner", mock.AnythingOfType("string")).Return(errors.New("API call failed"))
-
-	recorder := httptest.NewRecorder()
-	request, err := http.NewRequest(http.MethodDelete, suite.path, nil)
-	if err != nil {
-		suite.T().Fatal(err)
-	}
-
-	suite.router.ServeHTTP(recorder, request)
-
-	suite.Equal(http.StatusInternalServerError, recorder.Code)
-}
-
-func (suite *DeleteRunnerRouteTestSuite) TestDeleteInvalidRunnerIdReturnsNotFound() {
-	var err error
-	runnersUrl, err := suite.router.Get(DeleteRoute).URL(RunnerIdKey, "1nv4l1dID")
-	if err != nil {
-		suite.T().Fatal(err)
-	}
-	suite.path = runnersUrl.String()
-
-	recorder := httptest.NewRecorder()
-	request, err := http.NewRequest(http.MethodDelete, suite.path, nil)
-	if err != nil {
-		suite.T().Fatal(err)
-	}
-
-	suite.router.ServeHTTP(recorder, request)
-
-	suite.Equal(http.StatusNotFound, recorder.Code)
-}

api/websocket_test.go

@@ -2,7 +2,6 @@ package api
 
 import (
 	"fmt"
-	"github.com/gorilla/mux"
 	"github.com/gorilla/websocket"
 	"github.com/stretchr/testify/suite"
 	"gitlab.hpi.de/codeocean/codemoon/poseidon/api/dto"
@@ -15,10 +14,8 @@ import (
 )
 
 type WebsocketTestSuite struct {
-	suite.Suite
-	runner      runner.Runner
+	RunnerRouteTestSuite
 	server      *httptest.Server
-	router      *mux.Router
 	executionId runner.ExecutionId
 }
 
@@ -26,10 +23,12 @@ func TestWebsocketTestSuite(t *testing.T) {
 	suite.Run(t, new(WebsocketTestSuite))
 }
 
-func (suite *WebsocketTestSuite) SetupSuite() {
-	runnerPool := environment.NewLocalRunnerPool()
-	suite.runner = runner.NewExerciseRunner("testRunner")
-	runnerPool.Add(suite.runner)
+func (suite *WebsocketTestSuite) SetupTest() {
+	suite.runnerManager = &runner.ManagerMock{}
+	suite.environmentManager = &environment.ManagerMock{}
+	suite.router = NewRouter(suite.runnerManager, suite.environmentManager)
+	suite.runner = runner.NewRunner("test_runner")
+	suite.runnerManager.On("Get", suite.runner.Id()).Return(suite.runner, nil)
 	var err error
 	suite.executionId, err = suite.runner.AddExecution(dto.ExecutionRequest{
 		Command:     "command",
@@ -38,11 +37,12 @@ func (suite *WebsocketTestSuite) SetupSuite() {
 	})
 	suite.Require().NoError(err)
 
-	router := mux.NewRouter()
-	router.Use(findRunnerMiddleware(runnerPool))
-	router.HandleFunc(fmt.Sprintf("%s/{%s}%s", RouteRunners, RunnerIdKey, WebsocketPath), connectToRunner).Methods(http.MethodGet).Name(WebsocketPath)
-	suite.server = httptest.NewServer(router)
-	suite.router = router
+	// router.HandleFunc(fmt.Sprintf("%s/{%s}%s", RouteRunners, RunnerIdKey, WebsocketPath), connectToRunner).Methods(http.MethodGet).Name(WebsocketPath)
+	suite.server = httptest.NewServer(suite.router)
+}
+
+func (suite *WebsocketTestSuite) TearDownSuite() {
+	suite.server.Close()
 }
 
 func (suite *WebsocketTestSuite) websocketUrl(scheme, runnerId string, executionId runner.ExecutionId) (*url.URL, error) {
@@ -56,10 +56,6 @@ func (suite *WebsocketTestSuite) websocketUrl(scheme, runnerId string, execution
 	return websocketUrl, nil
 }
 
-func (suite *WebsocketTestSuite) TearDownSuite() {
-	suite.server.Close()
-}
-
 func (suite *WebsocketTestSuite) TestWebsocketConnectionCanBeEstablished() {
 	path, err := suite.websocketUrl("ws", suite.runner.Id(), suite.executionId)
 	suite.Require().NoError(err)

environment/execution_environment.go

@@ -1,106 +0,0 @@
-package environment
-
-import (
-	"errors"
-	"gitlab.hpi.de/codeocean/codemoon/poseidon/logging"
-	"gitlab.hpi.de/codeocean/codemoon/poseidon/nomad"
-	"gitlab.hpi.de/codeocean/codemoon/poseidon/runner"
-	"time"
-)
-
-var log = logging.GetLogger("execution_environment")
-
-// ExecutionEnvironment is a partial image of an execution environment in CodeOcean.
-type ExecutionEnvironment interface {
-	// NextRunner gets the next available runner and marks it as running.
-	// If no runner is available it throws a error after a small timeout
-	NextRunner() (runner.Runner, error)
-	// Refresh fetches the runners for this execution environment and sends them to the pool.
-	// This function does not terminate. Instead it fetches new runners periodically.
-	Refresh()
-}
-
-// NomadExecutionEnvironment is an implementation that returns a nomad specific execution environment.
-// Here it is mapped on a Job in Nomad.
-// The jobId has to match the only Nomad task group name!
-type NomadExecutionEnvironment struct {
-	id               int
-	jobId            string
-	availableRunners chan runner.Runner
-	allRunners       RunnerPool
-	nomadApiClient   nomad.ExecutorApi
-}
-
-var executionEnvironment ExecutionEnvironment
-
-// DebugInit initializes one execution environment so that its runners can be provided.
-// ToDo: This should be replaced by a create Execution Environment route
-func DebugInit(runnersPool RunnerPool, nomadApi nomad.ExecutorApi) {
-	executionEnvironment = &NomadExecutionEnvironment{
-		id:               0,
-		jobId:            "python",
-		availableRunners: make(chan runner.Runner, 5),
-		nomadApiClient:   nomadApi,
-		allRunners:       runnersPool,
-	}
-	go executionEnvironment.Refresh()
-}
-
-// GetExecutionEnvironment returns a previously added ExecutionEnvironment.
-// This way you can access all Runners for that environment,
-func GetExecutionEnvironment(id int) (ExecutionEnvironment, error) {
-	// TODO: Remove hardcoded execution environment
-	return executionEnvironment, nil
-}
-
-func (environment *NomadExecutionEnvironment) NextRunner() (r runner.Runner, err error) {
-	select {
-	case r = <-environment.availableRunners:
-		r.SetStatus(runner.StatusRunning)
-		return r, nil
-	case <-time.After(50 * time.Millisecond):
-		return nil, errors.New("no runners available")
-	}
-}
-
-// Refresh Big ToDo: Improve this function!! State out that it also rescales the job; Provide context to be terminable...
-func (environment *NomadExecutionEnvironment) Refresh() {
-	for {
-		runners, err := environment.nomadApiClient.LoadRunners(environment.jobId)
-		if err != nil {
-			log.WithError(err).Warn("Failed fetching runners")
-			break
-		}
-		for _, r := range environment.unusedRunners(runners) {
-			// ToDo: Listen on Nomad event stream
-			log.WithField("allocation", r).Debug("Adding allocation")
-			environment.allRunners.Add(r)
-			environment.availableRunners <- r
-		}
-		jobScale, err := environment.nomadApiClient.JobScale(environment.jobId)
-		if err != nil {
-			log.WithError(err).Warn("Failed get allocation count")
-			break
-		}
-		neededRunners := cap(environment.availableRunners) - len(environment.availableRunners) + 1
-		runnerCount := jobScale + neededRunners
-		time.Sleep(50 * time.Millisecond)
-		log.WithField("count", runnerCount).Debug("Set job scaling")
-		err = environment.nomadApiClient.SetJobScale(environment.jobId, runnerCount, "Runner Requested")
-		if err != nil {
-			log.WithError(err).Warn("Failed to set allocation scaling")
-			continue
-		}
-	}
-}
-
-func (environment *NomadExecutionEnvironment) unusedRunners(fetchedRunnerIds []string) (newRunners []runner.Runner) {
-	newRunners = make([]runner.Runner, 0)
-	for _, runnerId := range fetchedRunnerIds {
-		_, ok := environment.allRunners.Get(runnerId)
-		if !ok {
-			newRunners = append(newRunners, runner.NewExerciseRunner(runnerId))
-		}
-	}
-	return
-}

environment/execution_environment_test.go

@@ -1,109 +0,0 @@
-package environment
-
-import (
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/mock"
-	"github.com/stretchr/testify/suite"
-	"gitlab.hpi.de/codeocean/codemoon/poseidon/nomad"
-	"gitlab.hpi.de/codeocean/codemoon/poseidon/runner"
-	"testing"
-	"time"
-)
-
-const anotherRunnerId = "4n0th3r-1d"
-const jobId = "4n0th3r-1d"
-
-func TestGetNextRunnerTestSuite(t *testing.T) {
-	suite.Run(t, new(GetNextRunnerTestSuite))
-}
-
-type GetNextRunnerTestSuite struct {
-	suite.Suite
-	nomadExecutionEnvironment *NomadExecutionEnvironment
-	exerciseRunner            runner.Runner
-}
-
-func (suite *GetNextRunnerTestSuite) SetupTest() {
-	suite.nomadExecutionEnvironment = &NomadExecutionEnvironment{
-		availableRunners: make(chan runner.Runner, 50),
-		allRunners:       NewLocalRunnerPool(),
-	}
-	suite.exerciseRunner = CreateTestRunner()
-}
-
-func (suite *GetNextRunnerTestSuite) TestGetNextRunnerReturnsRunnerIfAvailable() {
-	suite.nomadExecutionEnvironment.availableRunners <- suite.exerciseRunner
-
-	receivedRunner, err := suite.nomadExecutionEnvironment.NextRunner()
-	suite.NoError(err)
-	suite.Equal(suite.exerciseRunner, receivedRunner)
-}
-
-func (suite *GetNextRunnerTestSuite) TestGetNextRunnerChangesStatusOfRunner() {
-	suite.nomadExecutionEnvironment.availableRunners <- suite.exerciseRunner
-
-	receivedRunner, _ := suite.nomadExecutionEnvironment.NextRunner()
-	suite.Equal(runner.StatusRunning, receivedRunner.Status())
-}
-
-func (suite *GetNextRunnerTestSuite) TestGetNextRunnerDoesNotReturnTheSameRunnerTwice() {
-	suite.nomadExecutionEnvironment.availableRunners <- suite.exerciseRunner
-	suite.nomadExecutionEnvironment.availableRunners <- runner.NewExerciseRunner(anotherRunnerId)
-
-	firstReceivedRunner, _ := suite.nomadExecutionEnvironment.NextRunner()
-	secondReceivedRunner, _ := suite.nomadExecutionEnvironment.NextRunner()
-	suite.NotEqual(firstReceivedRunner, secondReceivedRunner)
-}
-
-func (suite *GetNextRunnerTestSuite) TestGetNextRunnerThrowsAnErrorIfNoRunnersAvailable() {
-	receivedRunner, err := suite.nomadExecutionEnvironment.NextRunner()
-	suite.Nil(receivedRunner)
-	suite.Error(err)
-}
-
-func TestRefreshFetchRunners(t *testing.T) {
-	apiMock, environment := newRefreshMock([]string{RunnerId}, NewLocalRunnerPool())
-	// ToDo: Terminate Refresh when test finished (also in other tests)
-	go environment.Refresh()
-	_, _ = environment.NextRunner()
-	apiMock.AssertCalled(t, "LoadRunners", jobId)
-}
-
-func TestRefreshFetchesRunnersIntoChannel(t *testing.T) {
-	_, environment := newRefreshMock([]string{RunnerId}, NewLocalRunnerPool())
-	go environment.Refresh()
-	availableRunner, _ := environment.NextRunner()
-	assert.Equal(t, availableRunner.Id(), RunnerId)
-}
-
-func TestRefreshScalesJob(t *testing.T) {
-	apiMock, environment := newRefreshMock([]string{RunnerId}, NewLocalRunnerPool())
-	go environment.Refresh()
-	_, _ = environment.NextRunner()
-	time.Sleep(100 * time.Millisecond) // ToDo: Be safe this test is not flaky
-	apiMock.AssertCalled(t, "SetJobScale", jobId, 52, "Runner Requested")
-}
-
-func TestRefreshAddsRunnerToPool(t *testing.T) {
-	runnersInUse := NewLocalRunnerPool()
-	_, environment := newRefreshMock([]string{RunnerId}, runnersInUse)
-	go environment.Refresh()
-	availableRunner, _ := environment.NextRunner()
-	poolRunner, ok := runnersInUse.Get(availableRunner.Id())
-	assert.True(t, ok)
-	assert.Equal(t, availableRunner, poolRunner)
-}
-
-func newRefreshMock(returnedRunnerIds []string, allRunners RunnerPool) (apiClient *nomad.ExecutorApiMock, environment *NomadExecutionEnvironment) {
-	apiClient = &nomad.ExecutorApiMock{}
-	apiClient.On("LoadRunners", jobId).Return(returnedRunnerIds, nil)
-	apiClient.On("JobScale", jobId).Return(len(returnedRunnerIds), nil)
-	apiClient.On("SetJobScale", jobId, mock.AnythingOfType("int"), "Runner Requested").Return(nil)
-	environment = &NomadExecutionEnvironment{
-		jobId:            jobId,
-		availableRunners: make(chan runner.Runner, 50),
-		allRunners:       allRunners,
-		nomadApiClient:   apiClient,
-	}
-	return
-}

environment/manager.go

@@ -0,0 +1,59 @@
+package environment
+
+import (
+	"gitlab.hpi.de/codeocean/codemoon/poseidon/nomad"
+	"gitlab.hpi.de/codeocean/codemoon/poseidon/runner"
+)
+
+// Manager encapsulates API calls to the executor API for creation and deletion of execution environments.
+type Manager interface {
+	// Load fetches all already created execution environments from the executor and registers them at the runner manager.
+	// It should be called during the startup process (e.g. on creation of the Manager).
+	Load()
+
+	// Create creates a new execution environment on the executor.
+	Create(
+		id string,
+		prewarmingPoolSize uint,
+		cpuLimit uint,
+		memoryLimit uint,
+		image string,
+		networkAccess bool,
+		exposedPorts []uint16,
+	)
+
+	// Delete remove the execution environment with the given id from the executor.
+	Delete(id string)
+}
+
+func NewNomadEnvironmentManager(runnerManager runner.Manager, apiClient nomad.ExecutorApi) *NomadEnvironmentManager {
+	environmentManager := &NomadEnvironmentManager{runnerManager, apiClient}
+	environmentManager.Load()
+	return environmentManager
+}
+
+type NomadEnvironmentManager struct {
+	runnerManager runner.Manager
+	api           nomad.ExecutorApi
+}
+
+func (m *NomadEnvironmentManager) Create(
+	id string,
+	prewarmingPoolSize uint,
+	cpuLimit uint,
+	memoryLimit uint,
+	image string,
+	networkAccess bool,
+	exposedPorts []uint16,
+) {
+
+}
+
+func (m *NomadEnvironmentManager) Delete(id string) {
+
+}
+
+func (m *NomadEnvironmentManager) Load() {
+	// ToDo: remove create default execution environment for debugging purposes
+	m.runnerManager.RegisterEnvironment(runner.EnvironmentId(0), "python", 5)
+}

environment/manager_mock.go

@@ -0,0 +1,25 @@
+// Code generated by mockery v0.0.0-dev. DO NOT EDIT.
+
+package environment
+
+import mock "github.com/stretchr/testify/mock"
+
+// ManagerMock is an autogenerated mock type for the Manager type
+type ManagerMock struct {
+	mock.Mock
+}
+
+// Create provides a mock function with given fields: id, prewarmingPoolSize, cpuLimit, memoryLimit, image, networkAccess, exposedPorts
+func (_m *ManagerMock) Create(id string, prewarmingPoolSize uint, cpuLimit uint, memoryLimit uint, image string, networkAccess bool, exposedPorts []uint16) {
+	_m.Called(id, prewarmingPoolSize, cpuLimit, memoryLimit, image, networkAccess, exposedPorts)
+}
+
+// Delete provides a mock function with given fields: id
+func (_m *ManagerMock) Delete(id string) {
+	_m.Called(id)
+}
+
+// Load provides a mock function with given fields:
+func (_m *ManagerMock) Load() {
+	_m.Called()
+}

environment/test_constants.go

@@ -1,9 +0,0 @@
-package environment
-
-import "gitlab.hpi.de/codeocean/codemoon/poseidon/runner"
-
-const RunnerId = "s0m3-r4nd0m-1d"
-
-func CreateTestRunner() runner.Runner {
-	return runner.NewExerciseRunner(RunnerId)
-}

go.mod

@@ -5,7 +5,7 @@ go 1.16
 require (
 	github.com/google/uuid v1.2.0
 	github.com/gorilla/mux v1.8.0
-	github.com/gorilla/websocket v1.4.2 // indirect
+	github.com/gorilla/websocket v1.4.2
 	github.com/hashicorp/go-cleanhttp v0.5.2 // indirect
 	github.com/hashicorp/nomad v1.0.4
 	github.com/hashicorp/nomad/api v0.0.0-20210505182403-7d5a9ecde95c

main.go

@@ -7,6 +7,7 @@ import (
 	"gitlab.hpi.de/codeocean/codemoon/poseidon/environment"
 	"gitlab.hpi.de/codeocean/codemoon/poseidon/logging"
 	"gitlab.hpi.de/codeocean/codemoon/poseidon/nomad"
+	"gitlab.hpi.de/codeocean/codemoon/poseidon/runner"
 	"net/http"
 	"os"
 	"os/signal"
@@ -38,13 +39,22 @@ func runServer(server *http.Server) {
 	}
 }
 
-func initServer(apiClient nomad.ExecutorApi, runnerPool environment.RunnerPool) *http.Server {
+func initServer() *http.Server {
+	// API initialization
+	nomadAPIClient, err := nomad.NewExecutorApi(config.Config.NomadAPIURL(), config.Config.Nomad.Namespace)
+	if err != nil {
+		log.WithError(err).WithField("nomad url", config.Config.NomadAPIURL()).Fatal("Error parsing the nomad url")
+	}
+
+	runnerManager := runner.NewNomadRunnerManager(nomadAPIClient)
+	environmentManager := environment.NewNomadEnvironmentManager(runnerManager, nomadAPIClient)
+
 	return &http.Server{
 		Addr:         config.Config.PoseidonAPIURL().Host,
 		WriteTimeout: time.Second * 15,
 		ReadTimeout:  time.Second * 15,
 		IdleTimeout:  time.Second * 60,
-		Handler:      api.NewRouter(apiClient, runnerPool),
+		Handler:      api.NewRouter(runnerManager, environmentManager),
 	}
 }
 
@@ -68,17 +78,7 @@ func main() {
 	}
 	logging.InitializeLogging(config.Config.Logger.Level)
 
-	// API initialization
-	nomadAPIClient, err := nomad.NewExecutorApi(config.Config.NomadAPIURL(), config.Config.Nomad.Namespace)
-	if err != nil {
-		log.WithError(err).WithField("nomad url", config.Config.NomadAPIURL()).Fatal("Error parsing the nomad url")
-	}
-
-	// ToDo: Move to create execution environment
-	runnerPool := environment.NewLocalRunnerPool()
-	environment.DebugInit(runnerPool, nomadAPIClient)
-
-	server := initServer(nomadAPIClient, runnerPool)
+	server := initServer()
 	go runServer(server)
 	shutdownOnOSSignal(server)
 }

nomad/api_querier_mock.go

@@ -72,8 +72,8 @@ func (_m *apiQuerierMock) LoadJobList() ([]*api.JobListStub, error) {
 	return r0, r1
 }
 
-// SetJobScaling provides a mock function with given fields: jobId, count, reason
-func (_m *apiQuerierMock) SetJobScaling(jobId string, count int, reason string) error {
+// SetJobScale provides a mock function with given fields: jobId, count, reason
+func (_m *apiQuerierMock) SetJobScale(jobId string, count int, reason string) error {
 	ret := _m.Called(jobId, count, reason)
 
 	var r0 error
@@ -122,17 +122,3 @@ func (_m *apiQuerierMock) loadRunners(jobId string) ([]*api.AllocationListStub,
 
 	return r0, r1
 }
-
-// SetJobScale provides a mock function with given fields: jobId, count, reason
-func (_m *apiQuerierMock) SetJobScale(jobId string, count int, reason string) error {
-	ret := _m.Called(jobId, count, reason)
-
-	var r0 error
-	if rf, ok := ret.Get(0).(func(string, int, string) error); ok {
-		r0 = rf(jobId, count, reason)
-	} else {
-		r0 = ret.Error(0)
-	}
-
-	return r0
-}

runner/manager.go

@@ -0,0 +1,145 @@
+package runner
+
+import (
+	"errors"
+	"gitlab.hpi.de/codeocean/codemoon/poseidon/logging"
+	"gitlab.hpi.de/codeocean/codemoon/poseidon/nomad"
+	"time"
+)
+
+var (
+	log                            = logging.GetLogger("runner")
+	ErrUnknownExecutionEnvironment = errors.New("execution environment not found")
+	ErrNoRunnersAvailable          = errors.New("no runners available for this execution environment")
+	ErrRunnerNotFound              = errors.New("no runner found with this id")
+)
+
+// Manager keeps track of the used and unused runners of all execution environments in order to provide unused runners to new clients and ensure no runner is used twice.
+type Manager interface {
+	// RegisterEnvironment adds a new environment for being managed.
+	RegisterEnvironment(environmentId EnvironmentId, nomadJobId NomadJobId, desiredIdleRunnersCount int)
+
+	// Use returns a new runner.
+	// It makes sure that runner is not in use yet and returns an error if no runner could be provided.
+	Use(id EnvironmentId) (Runner, error)
+
+	// Get returns the used runner with the given runnerId.
+	// If no runner with the given runnerId is currently used, it returns an error.
+	Get(runnerId string) (Runner, error)
+
+	// Return hands back the runner.
+	// The runner is deleted or cleaned up for reuse depending on the used executor.
+	Return(r Runner) error
+}
+
+func NewNomadRunnerManager(apiClient nomad.ExecutorApi) *NomadRunnerManager {
+	return &NomadRunnerManager{
+		apiClient,
+		make(map[EnvironmentId]*NomadJob),
+		NewLocalRunnerPool(),
+	}
+}
+
+type EnvironmentId int
+type NomadJobId string
+
+type NomadJob struct {
+	jobId                   NomadJobId
+	idleRunners             Pool
+	desiredIdleRunnersCount int
+}
+
+type NomadRunnerManager struct {
+	apiClient   nomad.ExecutorApi
+	jobs        map[EnvironmentId]*NomadJob
+	usedRunners Pool
+}
+
+func (m *NomadRunnerManager) RegisterEnvironment(environmentId EnvironmentId, nomadJobId NomadJobId, desiredIdleRunnersCount int) {
+	m.jobs[environmentId] = &NomadJob{
+		nomadJobId,
+		NewLocalRunnerPool(),
+		desiredIdleRunnersCount,
+	}
+	go m.refreshEnvironment(environmentId)
+}
+
+func (m *NomadRunnerManager) Use(environmentId EnvironmentId) (Runner, error) {
+	job, ok := m.jobs[environmentId]
+	if !ok {
+		return nil, ErrUnknownExecutionEnvironment
+	}
+	runner, ok := job.idleRunners.Sample()
+	if !ok {
+		return nil, ErrNoRunnersAvailable
+	}
+	m.usedRunners.Add(runner)
+	return runner, nil
+}
+
+func (m *NomadRunnerManager) Get(runnerId string) (r Runner, err error) {
+	runner, ok := m.usedRunners.Get(runnerId)
+	if !ok {
+		return nil, ErrRunnerNotFound
+	}
+	return runner.(Runner), nil
+}
+
+func (m *NomadRunnerManager) Return(r Runner) (err error) {
+	err = m.apiClient.DeleteRunner(r.Id())
+	if err != nil {
+		return err
+	}
+	m.usedRunners.Delete(r.Id())
+	return
+}
+
+// Refresh Big ToDo: Improve this function!! State out that it also rescales the job; Provide context to be terminable...
+func (m *NomadRunnerManager) refreshEnvironment(id EnvironmentId) {
+	job := m.jobs[id]
+	lastJobScaling := -1
+	for {
+		runners, err := m.apiClient.LoadRunners(string(job.jobId))
+		if err != nil {
+			log.WithError(err).Printf("Failed fetching runners")
+			break
+		}
+		for _, r := range m.unusedRunners(id, runners) {
+			// ToDo: Listen on Nomad event stream
+			log.Printf("Adding allocation %+v", r)
+
+			job.idleRunners.Add(r)
+		}
+		jobScale, err := m.apiClient.JobScale(string(job.jobId))
+		if err != nil {
+			log.WithError(err).Printf("Failed get allocation count")
+			break
+		}
+		neededRunners := job.desiredIdleRunnersCount - job.idleRunners.Len() + 1
+		runnerCount := jobScale + neededRunners
+		time.Sleep(50 * time.Millisecond)
+		if runnerCount != lastJobScaling {
+			log.Printf("Set job scaling %d", runnerCount)
+			err = m.apiClient.SetJobScale(string(job.jobId), runnerCount, "Runner Requested")
+			if err != nil {
+				log.WithError(err).Printf("Failed set allocation scaling")
+				continue
+			}
+			lastJobScaling = runnerCount
+		}
+	}
+}
+
+func (m *NomadRunnerManager) unusedRunners(environmentId EnvironmentId, fetchedRunnerIds []string) (newRunners []Runner) {
+	newRunners = make([]Runner, 0)
+	for _, runnerId := range fetchedRunnerIds {
+		_, ok := m.usedRunners.Get(runnerId)
+		if !ok {
+			_, ok = m.jobs[environmentId].idleRunners.Get(runnerId)
+			if !ok {
+				newRunners = append(newRunners, NewRunner(runnerId))
+			}
+		}
+	}
+	return
+}

runner/manager_mock.go

@@ -0,0 +1,75 @@
+// Code generated by mockery v0.0.0-dev. DO NOT EDIT.
+
+package runner
+
+import mock "github.com/stretchr/testify/mock"
+
+// ManagerMock is an autogenerated mock type for the Manager type
+type ManagerMock struct {
+	mock.Mock
+}
+
+// Get provides a mock function with given fields: runnerId
+func (_m *ManagerMock) Get(runnerId string) (Runner, error) {
+	ret := _m.Called(runnerId)
+
+	var r0 Runner
+	if rf, ok := ret.Get(0).(func(string) Runner); ok {
+		r0 = rf(runnerId)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(Runner)
+		}
+	}
+
+	var r1 error
+	if rf, ok := ret.Get(1).(func(string) error); ok {
+		r1 = rf(runnerId)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
+// RegisterEnvironment provides a mock function with given fields: environmentId, nomadJobId, desiredIdleRunnersCount
+func (_m *ManagerMock) RegisterEnvironment(environmentId EnvironmentId, nomadJobId NomadJobId, desiredIdleRunnersCount int) {
+	_m.Called(environmentId, nomadJobId, desiredIdleRunnersCount)
+}
+
+// Return provides a mock function with given fields: r
+func (_m *ManagerMock) Return(r Runner) error {
+	ret := _m.Called(r)
+
+	var r0 error
+	if rf, ok := ret.Get(0).(func(Runner) error); ok {
+		r0 = rf(r)
+	} else {
+		r0 = ret.Error(0)
+	}
+
+	return r0
+}
+
+// Use provides a mock function with given fields: id
+func (_m *ManagerMock) Use(id EnvironmentId) (Runner, error) {
+	ret := _m.Called(id)
+
+	var r0 Runner
+	if rf, ok := ret.Get(0).(func(EnvironmentId) Runner); ok {
+		r0 = rf(id)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(Runner)
+		}
+	}
+
+	var r1 error
+	if rf, ok := ret.Get(1).(func(EnvironmentId) error); ok {
+		r1 = rf(id)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}

runner/manager_test.go

@@ -0,0 +1,172 @@
+package runner
+
+import (
+	"errors"
+	"github.com/stretchr/testify/mock"
+	"github.com/stretchr/testify/suite"
+	"gitlab.hpi.de/codeocean/codemoon/poseidon/nomad"
+	"testing"
+	"time"
+)
+
+const anotherRunnerId = "4n0th3r-runn3r-1d"
+const defaultEnvironmentId = EnvironmentId(0)
+const otherEnvironmentId = EnvironmentId(42)
+const jobId = "4n0th3r-j0b-1d"
+const waitTime = 100 * time.Millisecond
+
+func TestGetNextRunnerTestSuite(t *testing.T) {
+	suite.Run(t, new(ManagerTestSuite))
+}
+
+type ManagerTestSuite struct {
+	suite.Suite
+	apiMock            *nomad.ExecutorApiMock
+	nomadRunnerManager *NomadRunnerManager
+	exerciseRunner     Runner
+}
+
+func (suite *ManagerTestSuite) setUp(returnedRunnerIds []string) {
+	suite.apiMock = &nomad.ExecutorApiMock{}
+	suite.nomadRunnerManager = NewNomadRunnerManager(suite.apiMock)
+	suite.exerciseRunner = CreateTestRunner()
+	suite.mockRunnerQueries(returnedRunnerIds)
+	suite.registerDefaultEnvironment()
+}
+
+func (suite *ManagerTestSuite) mockRunnerQueries(returnedRunnerIds []string) {
+	suite.apiMock.On("LoadRunners", jobId).Return(returnedRunnerIds, nil)
+	suite.apiMock.On("JobScale", jobId).Return(len(returnedRunnerIds), nil)
+	suite.apiMock.On("SetJobScale", jobId, mock.AnythingOfType("int"), "Runner Requested").Return(nil)
+}
+
+func (suite *ManagerTestSuite) registerDefaultEnvironment() {
+	suite.nomadRunnerManager.RegisterEnvironment(defaultEnvironmentId, jobId, 5)
+}
+
+func (suite *ManagerTestSuite) TestRegisterEnvironmentAddsANewJob() {
+	suite.NotNil(suite.nomadRunnerManager.jobs[defaultEnvironmentId])
+}
+
+func (suite *ManagerTestSuite) TestUseReturnsNotFoundErrorIfEnvironmentNotFound() {
+	runner, err := suite.nomadRunnerManager.Use(EnvironmentId(42))
+	suite.Nil(runner)
+	suite.Equal(ErrUnknownExecutionEnvironment, err)
+}
+
+func (suite *ManagerTestSuite) TestUseReturnsRunnerIfAvailable() {
+	suite.nomadRunnerManager.jobs[defaultEnvironmentId].idleRunners.Add(suite.exerciseRunner)
+	receivedRunner, err := suite.nomadRunnerManager.Use(defaultEnvironmentId)
+	suite.NoError(err)
+	suite.Equal(suite.exerciseRunner, receivedRunner)
+}
+
+func (suite *ManagerTestSuite) TestUseReturnsErrorIfNoRunnerAvailable() {
+	suite.setUp([]string{})
+	time.Sleep(waitTime)
+	runner, err := suite.nomadRunnerManager.Use(defaultEnvironmentId)
+	suite.Nil(runner)
+	suite.Equal(ErrNoRunnersAvailable, err)
+}
+
+func (suite *ManagerTestSuite) TestUseReturnsNoRunnerOfDifferentEnvironment() {
+	suite.setUp([]string{})
+	suite.nomadRunnerManager.jobs[defaultEnvironmentId].idleRunners.Add(suite.exerciseRunner)
+	receivedRunner, err := suite.nomadRunnerManager.Use(otherEnvironmentId)
+	suite.Nil(receivedRunner)
+	suite.Error(err)
+}
+
+func (suite *ManagerTestSuite) TestUseDoesNotReturnTheSameRunnerTwice() {
+	suite.nomadRunnerManager.jobs[defaultEnvironmentId].idleRunners.Add(suite.exerciseRunner)
+	suite.nomadRunnerManager.jobs[defaultEnvironmentId].idleRunners.Add(NewRunner(anotherRunnerId))
+
+	firstReceivedRunner, _ := suite.nomadRunnerManager.Use(defaultEnvironmentId)
+	secondReceivedRunner, _ := suite.nomadRunnerManager.Use(defaultEnvironmentId)
+	suite.NotEqual(firstReceivedRunner, secondReceivedRunner)
+}
+
+func (suite *ManagerTestSuite) TestUseThrowsAnErrorIfNoRunnersAvailable() {
+	receivedRunner, err := suite.nomadRunnerManager.Use(defaultEnvironmentId)
+	suite.Nil(receivedRunner)
+	suite.Error(err)
+}
+
+func (suite *ManagerTestSuite) TestUseAddsRunnerToUsedRunners() {
+	suite.setUp([]string{RunnerId})
+	time.Sleep(waitTime)
+	receivedRunner, _ := suite.nomadRunnerManager.Use(defaultEnvironmentId)
+	savedRunner, ok := suite.nomadRunnerManager.usedRunners.Get(receivedRunner.Id())
+	suite.True(ok)
+	suite.Equal(savedRunner, receivedRunner)
+}
+
+func (suite *ManagerTestSuite) TestGetReturnsRunnerIfRunnerIsUsed() {
+	suite.setUp([]string{})
+	suite.nomadRunnerManager.usedRunners.Add(suite.exerciseRunner)
+	savedRunner, err := suite.nomadRunnerManager.Get(suite.exerciseRunner.Id())
+	suite.NoError(err)
+	suite.Equal(savedRunner, suite.exerciseRunner)
+}
+
+func (suite *ManagerTestSuite) TestGetReturnsErrorIfRunnerNotFound() {
+	suite.setUp([]string{})
+	savedRunner, err := suite.nomadRunnerManager.Get(RunnerId)
+	suite.Nil(savedRunner)
+	suite.Error(err)
+}
+
+func (suite *ManagerTestSuite) TestReturnRemovesRunnerFromUsedRunners() {
+	suite.setUp([]string{})
+	suite.apiMock.On("DeleteRunner", mock.AnythingOfType("string")).Return(nil)
+	suite.nomadRunnerManager.usedRunners.Add(suite.exerciseRunner)
+	err := suite.nomadRunnerManager.Return(suite.exerciseRunner)
+	suite.Nil(err)
+	_, ok := suite.nomadRunnerManager.usedRunners.Get(suite.exerciseRunner.Id())
+	suite.False(ok)
+}
+
+func (suite *ManagerTestSuite) TestReturnCallsDeleteRunnerApiMethod() {
+	suite.setUp([]string{})
+	suite.apiMock.On("DeleteRunner", mock.AnythingOfType("string")).Return(nil)
+	err := suite.nomadRunnerManager.Return(suite.exerciseRunner)
+	suite.Nil(err)
+	suite.apiMock.AssertCalled(suite.T(), "DeleteRunner", suite.exerciseRunner.Id())
+}
+
+func (suite *ManagerTestSuite) TestReturnThrowsErrorWhenApiCallFailed() {
+	suite.setUp([]string{})
+	suite.apiMock.On("DeleteRunner", mock.AnythingOfType("string")).Return(errors.New("return failed"))
+	err := suite.nomadRunnerManager.Return(suite.exerciseRunner)
+	suite.Error(err)
+}
+
+func (suite *ManagerTestSuite) TestRefreshFetchesRunners() {
+	suite.setUp([]string{RunnerId})
+	time.Sleep(waitTime)
+	suite.apiMock.AssertCalled(suite.T(), "LoadRunners", jobId)
+}
+
+func (suite *ManagerTestSuite) TestNewRunnersFoundInRefreshAreAddedToUnusedRunners() {
+	suite.setUp([]string{RunnerId})
+	time.Sleep(waitTime)
+	availableRunner, _ := suite.nomadRunnerManager.Use(defaultEnvironmentId)
+	suite.Equal(availableRunner.Id(), RunnerId)
+}
+
+func (suite *ManagerTestSuite) TestRefreshScalesJob() {
+	suite.setUp([]string{RunnerId})
+	time.Sleep(waitTime)
+	// use one runner
+	_, _ = suite.nomadRunnerManager.Use(defaultEnvironmentId)
+	time.Sleep(waitTime)
+	suite.apiMock.AssertCalled(suite.T(), "SetJobScale", jobId, 6, "Runner Requested")
+}
+
+func (suite *ManagerTestSuite) TestRefreshAddsRunnerToPool() {
+	suite.setUp([]string{RunnerId})
+	time.Sleep(waitTime)
+	poolRunner, ok := suite.nomadRunnerManager.jobs[defaultEnvironmentId].idleRunners.Get(RunnerId)
+	suite.True(ok)
+	suite.Equal(RunnerId, poolRunner.Id())
+}

runner/pool.go

@@ -1,35 +1,38 @@
-package environment
+package runner
 
 import (
-	"gitlab.hpi.de/codeocean/codemoon/poseidon/runner"
 	"gitlab.hpi.de/codeocean/codemoon/poseidon/store"
 	"sync"
 )
 
-// RunnerPool is a type of entity store that should store runner entities.
-type RunnerPool interface {
+// Pool is a type of entity store that should store runner entities.
+type Pool interface {
 	store.EntityStore
+
+	// Sample returns and removes an arbitrary entity from the pool.
+	// ok is true iff a runner was returned.
+	Sample() (r Runner, ok bool)
 }
 
 // localRunnerPool stores runner objects in the local application memory.
 // ToDo: Create implementation that use some persistent storage like a database
 type localRunnerPool struct {
 	sync.RWMutex
-	runners map[string]runner.Runner
+	runners map[string]Runner
 }
 
-// NewLocalRunnerPool responds with a RunnerPool implementation
+// NewLocalRunnerPool responds with a Pool implementation
 // This implementation stores the data thread-safe in the local application memory
 func NewLocalRunnerPool() *localRunnerPool {
 	return &localRunnerPool{
-		runners: make(map[string]runner.Runner),
+		runners: make(map[string]Runner),
 	}
 }
 
 func (pool *localRunnerPool) Add(r store.Entity) {
 	pool.Lock()
 	defer pool.Unlock()
-	runnerEntity, ok := r.(runner.Runner)
+	runnerEntity, ok := r.(Runner)
 	if !ok {
 		log.
 			WithField("pool", pool).
@@ -51,3 +54,17 @@ func (pool *localRunnerPool) Delete(id string) {
 	defer pool.Unlock()
 	delete(pool.runners, id)
 }
+
+func (pool *localRunnerPool) Sample() (Runner, bool) {
+	pool.Lock()
+	defer pool.Unlock()
+	for _, runner := range pool.runners {
+		delete(pool.runners, runner.Id())
+		return runner, true
+	}
+	return nil, false
+}
+
+func (pool *localRunnerPool) Len() int {
+	return len(pool.runners)
+}

runner/pool_test.go

@@ -1,10 +1,9 @@
-package environment
+package runner
 
 import (
 	"github.com/sirupsen/logrus"
 	"github.com/sirupsen/logrus/hooks/test"
 	"github.com/stretchr/testify/suite"
-	"gitlab.hpi.de/codeocean/codemoon/poseidon/runner"
 	"testing"
 )
 
@@ -21,7 +20,7 @@ func TestRunnerPoolTestSuite(t *testing.T) {
 type RunnerPoolTestSuite struct {
 	suite.Suite
 	runnerPool *localRunnerPool
-	runner     runner.Runner
+	runner     Runner
 }
 
 func (suite *RunnerPoolTestSuite) SetupTest() {
@@ -60,7 +59,7 @@ func (suite *RunnerPoolTestSuite) TestAddedRunnerCanBeRetrieved() {
 }
 
 func (suite *RunnerPoolTestSuite) TestRunnerWithSameIdOverwritesOldOne() {
-	otherRunnerWithSameId := runner.NewExerciseRunner(suite.runner.Id())
+	otherRunnerWithSameId := NewRunner(suite.runner.Id())
 	// assure runner is actually different
 	suite.NotEqual(suite.runner, otherRunnerWithSameId)
 

runner/runner.go

@@ -9,9 +9,6 @@ import (
 	"sync"
 )
 
-// Status is the type for the status of a Runner.
-type Status string
-
 // ContextKey is the type for keys in a request context.
 type ContextKey string
 
@@ -19,11 +16,6 @@ type ContextKey string
 type ExecutionId string
 
 const (
-	StatusReady    Status = "ready"
-	StatusRunning  Status = "running"
-	StatusTimeout  Status = "timeout"
-	StatusFinished Status = "finished"
-
 	// runnerContextKey is the key used to store runners in context.Context
 	runnerContextKey ContextKey = "runner"
 )
@@ -31,37 +23,33 @@ const (
 type Runner interface {
 	store.Entity
 
-	// SetStatus sets the status of the runner.
-	SetStatus(Status)
-
-	// Status gets the status of the runner.
-	Status() Status
-
-	// Execution looks up an ExecutionId for the runner and returns the associated RunnerRequest.
-	// If this request does not exit, ok is false, else true.
-	Execution(ExecutionId) (request dto.ExecutionRequest, ok bool)
-
 	// AddExecution saves the supplied ExecutionRequest for the runner and returns an ExecutionId to retrieve it again.
 	AddExecution(dto.ExecutionRequest) (ExecutionId, error)
 
+	Execution(ExecutionId) (executionRequest dto.ExecutionRequest, ok bool)
+
 	// DeleteExecution deletes the execution of the runner with the specified id.
 	DeleteExecution(ExecutionId)
+
+	// Execute executes the execution with the given ID.
+	Execute(ExecutionId)
+
+	// Copy copies the specified files into the runner.
+	Copy(dto.FileCreation)
 }
 
-// ExerciseRunner is an abstraction to communicate with Nomad allocations.
-type ExerciseRunner struct {
+// NomadAllocation is an abstraction to communicate with Nomad allocations.
+type NomadAllocation struct {
 	sync.RWMutex
 	id         string
-	status     Status
 	ch         chan bool
 	executions map[ExecutionId]dto.ExecutionRequest
 }
 
-// NewExerciseRunner creates a new exercise runner with the provided id.
-func NewExerciseRunner(id string) *ExerciseRunner {
-	return &ExerciseRunner{
+// NewRunner creates a new runner with the provided id.
+func NewRunner(id string) Runner {
+	return &NomadAllocation{
 		id:         id,
-		status:     StatusReady,
 		ch:         make(chan bool),
 		executions: make(map[ExecutionId]dto.ExecutionRequest),
 	}
@@ -69,40 +57,26 @@ func NewExerciseRunner(id string) *ExerciseRunner {
 
 // MarshalJSON implements json.Marshaler interface.
 // This exports private attributes like the id too.
-func (r *ExerciseRunner) MarshalJSON() ([]byte, error) {
+func (r *NomadAllocation) MarshalJSON() ([]byte, error) {
 	return json.Marshal(struct {
 		Id string `json:"runnerId"`
-		Status Status `json:"status"`
 	}{
 		Id: r.Id(),
-		Status: r.Status(),
 	})
 }
 
-func (r *ExerciseRunner) SetStatus(status Status) {
-	r.Lock()
-	defer r.Unlock()
-	r.status = status
-}
-
-func (r *ExerciseRunner) Status() Status {
-	r.RLock()
-	defer r.RUnlock()
-	return r.status
-}
-
-func (r *ExerciseRunner) Id() string {
+func (r *NomadAllocation) Id() string {
 	return r.id
 }
 
-func (r *ExerciseRunner) Execution(id ExecutionId) (executionRequest dto.ExecutionRequest, ok bool) {
+func (r *NomadAllocation) Execution(id ExecutionId) (executionRequest dto.ExecutionRequest, ok bool) {
 	r.RLock()
 	defer r.RUnlock()
 	executionRequest, ok = r.executions[id]
 	return
 }
 
-func (r *ExerciseRunner) AddExecution(request dto.ExecutionRequest) (ExecutionId, error) {
+func (r *NomadAllocation) AddExecution(request dto.ExecutionRequest) (ExecutionId, error) {
 	r.Lock()
 	defer r.Unlock()
 	idUuid, err := uuid.NewRandom()
@@ -114,7 +88,15 @@ func (r *ExerciseRunner) AddExecution(request dto.ExecutionRequest) (ExecutionId
 	return id, err
 }
 
-func (r *ExerciseRunner) DeleteExecution(id ExecutionId) {
+func (r *NomadAllocation) Execute(id ExecutionId) {
+
+}
+
+func (r *NomadAllocation) Copy(files dto.FileCreation) {
+
+}
+
+func (r *NomadAllocation) DeleteExecution(id ExecutionId) {
 	r.Lock()
 	defer r.Unlock()
 	delete(r.executions, id)

runner/runner_test.go

@@ -9,32 +9,19 @@ import (
 )
 
 func TestIdIsStored(t *testing.T) {
-	runner := NewExerciseRunner("42")
+	runner := NewRunner("42")
 	assert.Equal(t, "42", runner.Id())
 }
 
-func TestStatusIsStored(t *testing.T) {
-	runner := NewExerciseRunner("42")
-	for _, status := range []Status{StatusReady, StatusRunning, StatusTimeout, StatusFinished} {
-		runner.SetStatus(status)
-		assert.Equal(t, status, runner.Status(), "The status is returned as it is stored")
-	}
-}
-
-func TestDefaultStatus(t *testing.T) {
-	runner := NewExerciseRunner("42")
-	assert.Equal(t, StatusReady, runner.status)
-}
-
 func TestMarshalRunner(t *testing.T) {
-	runner := NewExerciseRunner("42")
+	runner := NewRunner("42")
 	marshal, err := json.Marshal(runner)
 	assert.NoError(t, err)
-	assert.Equal(t, "{\"runnerId\":\"42\",\"status\":\"ready\"}", string(marshal))
+	assert.Equal(t, "{\"runnerId\":\"42\"}", string(marshal))
 }
 
 func TestExecutionRequestIsStored(t *testing.T) {
-	runner := NewExerciseRunner("42")
+	runner := NewRunner("42")
 	executionRequest := dto.ExecutionRequest{
 		Command:     "command",
 		TimeLimit:   10,
@@ -49,7 +36,7 @@ func TestExecutionRequestIsStored(t *testing.T) {
 }
 
 func TestNewContextReturnsNewContextWithRunner(t *testing.T) {
-	runner := NewExerciseRunner("testRunner")
+	runner := NewRunner("testRunner")
 	ctx := context.Background()
 	newCtx := NewContext(ctx, runner)
 	storedRunner := newCtx.Value(runnerContextKey).(Runner)
@@ -59,7 +46,7 @@ func TestNewContextReturnsNewContextWithRunner(t *testing.T) {
 }
 
 func TestFromContextReturnsRunner(t *testing.T) {
-	runner := NewExerciseRunner("testRunner")
+	runner := NewRunner("testRunner")
 	ctx := NewContext(context.Background(), runner)
 	storedRunner, ok := FromContext(ctx)
 

runner/test_constants.go

@@ -0,0 +1,7 @@
+package runner
+
+const RunnerId = "s0m3-r4nd0m-1d"
+
+func CreateTestRunner() Runner {
+	return NewRunner(RunnerId)
+}

store/entity_store.go

@@ -13,6 +13,9 @@ type EntityStore interface {
 
 	// Delete deletes the entity with the passed id from the store.
 	Delete(id string)
+
+	// Len returns the number of currently stored entities in the store.
+	Len() int
 }
 
 type Entity interface {