Make the REST API handlers independent from the core.Engine

After this commit, the only place the Engine is used in the api/ package tests, and only in a few places that will be easy to refactor after we remove it completely.

api/server.go

@@ -1,28 +1,44 @@
 package api
 
 import (
+	"context"
 	"fmt"
 	"net/http"
 	"time"
 
 	"github.com/sirupsen/logrus"
 
-	"go.k6.io/k6/api/common"
 	v1 "go.k6.io/k6/api/v1"
-	"go.k6.io/k6/core"
+	"go.k6.io/k6/execution"
+	"go.k6.io/k6/lib"
+	"go.k6.io/k6/metrics"
+	"go.k6.io/k6/metrics/engine"
 )
 
-func newHandler(logger logrus.FieldLogger) http.Handler {
+func newHandler(cs *v1.ControlSurface) http.Handler {
 	mux := http.NewServeMux()
-	mux.Handle("/v1/", v1.NewHandler())
-	mux.Handle("/ping", handlePing(logger))
-	mux.Handle("/", handlePing(logger))
+	mux.Handle("/v1/", v1.NewHandler(cs))
+	mux.Handle("/ping", handlePing(cs.RunState.Logger))
+	mux.Handle("/", handlePing(cs.RunState.Logger))
 	return mux
 }
 
 // GetServer returns a http.Server instance that can serve k6's REST API.
-func GetServer(addr string, engine *core.Engine, logger logrus.FieldLogger) *http.Server {
-	mux := withEngine(engine, newLogger(logger, newHandler(logger)))
+func GetServer(
+	runCtx context.Context, addr string, runState *lib.TestRunState,
+	samples chan metrics.SampleContainer, me *engine.MetricsEngine, es *execution.Scheduler,
+) *http.Server {
+	// TODO: reduce the control surface as much as possible? For example, if
+	// we refactor the Runner API, we won't need to send the Samples channel.
+	cs := &v1.ControlSurface{
+		RunCtx:        runCtx,
+		Samples:       samples,
+		MetricsEngine: me,
+		Scheduler:     es,
+		RunState:      runState,
+	}
+
+	mux := withLoggingHandler(runState.Logger, newHandler(cs))
 	return &http.Server{Addr: addr, Handler: mux, ReadHeaderTimeout: 10 * time.Second}
 }
 
@@ -36,8 +52,8 @@ func (w wrappedResponseWriter) WriteHeader(status int) {
 	w.ResponseWriter.WriteHeader(status)
 }
 
-// newLogger returns the middleware which logs response status for request.
-func newLogger(l logrus.FieldLogger, next http.Handler) http.HandlerFunc {
+// withLoggingHandler returns the middleware which logs response status for request.
+func withLoggingHandler(l logrus.FieldLogger, next http.Handler) http.HandlerFunc {
 	return func(rw http.ResponseWriter, r *http.Request) {
 		wrapped := wrappedResponseWriter{ResponseWriter: rw, status: 200} // The default status code is 200 if it's not set
 		next.ServeHTTP(wrapped, r)
@@ -46,13 +62,6 @@ func newLogger(l logrus.FieldLogger, next http.Handler) http.HandlerFunc {
 	}
 }
 
-func withEngine(engine *core.Engine, next http.Handler) http.HandlerFunc {
-	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
-		r = r.WithContext(common.WithEngine(r.Context(), engine))
-		next.ServeHTTP(rw, r)
-	})
-}
-
 func handlePing(logger logrus.FieldLogger) http.Handler {
 	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
 		rw.Header().Add("Content-Type", "text/plain; charset=utf-8")

api/server_test.go

@@ -9,15 +9,8 @@ import (
 	"github.com/sirupsen/logrus"
 	logtest "github.com/sirupsen/logrus/hooks/test"
 	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
 
-	"go.k6.io/k6/api/common"
-	"go.k6.io/k6/core"
-	"go.k6.io/k6/execution"
-	"go.k6.io/k6/lib"
 	"go.k6.io/k6/lib/testutils"
-	"go.k6.io/k6/lib/testutils/minirunner"
-	"go.k6.io/k6/metrics"
 )
 
 func testHTTPHandler(rw http.ResponseWriter, r *http.Request) {
@@ -37,7 +30,7 @@ func TestLogger(t *testing.T) {
 
 					l, hook := logtest.NewNullLogger()
 					l.Level = logrus.DebugLevel
-					newLogger(l, http.HandlerFunc(testHTTPHandler))(rw, r)
+					withLoggingHandler(l, http.HandlerFunc(testHTTPHandler))(rw, r)
 
 					res := rw.Result()
 					assert.Equal(t, http.StatusOK, res.StatusCode)
@@ -57,36 +50,10 @@ func TestLogger(t *testing.T) {
 	}
 }
 
-func TestWithEngine(t *testing.T) {
-	logger := logrus.New()
-	logger.SetOutput(testutils.NewTestOutput(t))
-	registry := metrics.NewRegistry()
-	testState := &lib.TestRunState{
-		TestPreInitState: &lib.TestPreInitState{
-			Logger:         logger,
-			Registry:       registry,
-			BuiltinMetrics: metrics.RegisterBuiltinMetrics(registry),
-		},
-		Options: lib.Options{},
-		Runner:  &minirunner.MiniRunner{},
-	}
-
-	execScheduler, err := execution.NewScheduler(testState)
-	require.NoError(t, err)
-	engine, err := core.NewEngine(testState, execScheduler, nil)
-	require.NoError(t, err)
-
-	rw := httptest.NewRecorder()
-	r := httptest.NewRequest("GET", "http://example.com/", nil)
-	withEngine(engine, http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
-		assert.Equal(t, engine, common.GetEngine(r.Context()))
-	}))(rw, r)
-}
-
 func TestPing(t *testing.T) {
 	logger := logrus.New()
 	logger.SetOutput(testutils.NewTestOutput(t))
-	mux := newHandler(logger)
+	mux := handlePing(logger)
 
 	rw := httptest.NewRecorder()
 	r := httptest.NewRequest("GET", "/ping", nil)

api/v1/control_surface.go

@@ -0,0 +1,20 @@
+package v1
+
+import (
+	"context"
+
+	"go.k6.io/k6/execution"
+	"go.k6.io/k6/lib"
+	"go.k6.io/k6/metrics"
+	"go.k6.io/k6/metrics/engine"
+)
+
+// ControlSurface includes the methods the REST API can use to control and
+// communicate with the rest of k6.
+type ControlSurface struct {
+	RunCtx        context.Context
+	Samples       chan metrics.SampleContainer
+	MetricsEngine *engine.MetricsEngine
+	Scheduler     *execution.Scheduler
+	RunState      *lib.TestRunState
+}

api/v1/group_routes.go

@@ -3,14 +3,10 @@ package v1
 import (
 	"encoding/json"
 	"net/http"
-
-	"go.k6.io/k6/api/common"
 )
 
-func handleGetGroups(rw http.ResponseWriter, r *http.Request) {
-	engine := common.GetEngine(r.Context())
-
-	root := NewGroup(engine.ExecutionScheduler.GetRunner().GetDefaultGroup(), nil)
+func handleGetGroups(cs *ControlSurface, rw http.ResponseWriter, _ *http.Request) {
+	root := NewGroup(cs.RunState.Runner.GetDefaultGroup(), nil)
 	groups := FlattenGroup(root)
 
 	data, err := json.Marshal(newGroupsJSONAPI(groups))
@@ -21,10 +17,8 @@ func handleGetGroups(rw http.ResponseWriter, r *http.Request) {
 	_, _ = rw.Write(data)
 }
 
-func handleGetGroup(rw http.ResponseWriter, r *http.Request, id string) {
-	engine := common.GetEngine(r.Context())
-
-	root := NewGroup(engine.ExecutionScheduler.GetRunner().GetDefaultGroup(), nil)
+func handleGetGroup(cs *ControlSurface, rw http.ResponseWriter, _ *http.Request, id string) {
+	root := NewGroup(cs.RunState.Runner.GetDefaultGroup(), nil)
 	groups := FlattenGroup(root)
 
 	var group *Group

api/v1/group_routes_test.go

@@ -1,6 +1,7 @@
 package v1
 
 import (
+	"context"
 	"encoding/json"
 	"net/http"
 	"net/http/httptest"
@@ -10,12 +11,12 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
-	"go.k6.io/k6/core"
 	"go.k6.io/k6/execution"
 	"go.k6.io/k6/lib"
 	"go.k6.io/k6/lib/testutils"
 	"go.k6.io/k6/lib/testutils/minirunner"
 	"go.k6.io/k6/metrics"
+	"go.k6.io/k6/metrics/engine"
 )
 
 func getTestPreInitState(tb testing.TB) *lib.TestPreInitState {
@@ -41,6 +42,26 @@ func getTestRunState(tb testing.TB, options lib.Options, runner lib.Runner) *lib
 	}
 }
 
+func getControlSurface(tb testing.TB, testState *lib.TestRunState) *ControlSurface {
+	execScheduler, err := execution.NewScheduler(testState)
+	require.NoError(tb, err)
+
+	me, err := engine.NewMetricsEngine(execScheduler.GetState())
+	require.NoError(tb, err)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	tb.Cleanup(cancel)
+	ctx, _ = execution.NewTestRunContext(ctx, testState.Logger)
+
+	return &ControlSurface{
+		RunCtx:        ctx,
+		Samples:       make(chan metrics.SampleContainer, 1000),
+		MetricsEngine: me,
+		Scheduler:     execScheduler,
+		RunState:      testState,
+	}
+}
+
 func TestGetGroups(t *testing.T) {
 	g0, err := lib.NewGroup("", nil)
 	assert.NoError(t, err)
@@ -49,15 +70,11 @@ func TestGetGroups(t *testing.T) {
 	g2, err := g1.Group("group 2")
 	assert.NoError(t, err)
 
-	testState := getTestRunState(t, lib.Options{}, &minirunner.MiniRunner{Group: g0})
-	execScheduler, err := execution.NewScheduler(testState)
-	require.NoError(t, err)
-	engine, err := core.NewEngine(testState, execScheduler, nil)
-	require.NoError(t, err)
+	cs := getControlSurface(t, getTestRunState(t, lib.Options{}, &minirunner.MiniRunner{Group: g0}))
 
 	t.Run("list", func(t *testing.T) {
 		rw := httptest.NewRecorder()
-		NewHandler().ServeHTTP(rw, newRequestWithEngine(engine, "GET", "/v1/groups", nil))
+		NewHandler(cs).ServeHTTP(rw, httptest.NewRequest(http.MethodGet, "/v1/groups", nil))
 		res := rw.Result()
 		body := rw.Body.Bytes()
 		assert.Equal(t, http.StatusOK, res.StatusCode)
@@ -105,7 +122,7 @@ func TestGetGroups(t *testing.T) {
 	for _, gp := range []*lib.Group{g0, g1, g2} {
 		t.Run(gp.Name, func(t *testing.T) {
 			rw := httptest.NewRecorder()
-			NewHandler().ServeHTTP(rw, newRequestWithEngine(engine, "GET", "/v1/groups/"+gp.ID, nil))
+			NewHandler(cs).ServeHTTP(rw, httptest.NewRequest(http.MethodGet, "/v1/groups/"+gp.ID, nil))
 			res := rw.Result()
 			assert.Equal(t, http.StatusOK, res.StatusCode)
 		})

api/v1/metric_routes.go

@@ -4,21 +4,17 @@ import (
 	"encoding/json"
 	"net/http"
 	"time"
-
-	"go.k6.io/k6/api/common"
 )
 
-func handleGetMetrics(rw http.ResponseWriter, r *http.Request) {
-	engine := common.GetEngine(r.Context())
-
+func handleGetMetrics(cs *ControlSurface, rw http.ResponseWriter, _ *http.Request) {
 	var t time.Duration
-	if engine.ExecutionScheduler != nil {
-		t = engine.ExecutionScheduler.GetState().GetCurrentTestRunDuration()
+	if cs.Scheduler != nil {
+		t = cs.Scheduler.GetState().GetCurrentTestRunDuration()
 	}
 
-	engine.MetricsEngine.MetricsLock.Lock()
-	metrics := newMetricsJSONAPI(engine.MetricsEngine.ObservedMetrics, t)
-	engine.MetricsEngine.MetricsLock.Unlock()
+	cs.MetricsEngine.MetricsLock.Lock()
+	metrics := newMetricsJSONAPI(cs.MetricsEngine.ObservedMetrics, t)
+	cs.MetricsEngine.MetricsLock.Unlock()
 
 	data, err := json.Marshal(metrics)
 	if err != nil {
@@ -28,23 +24,21 @@ func handleGetMetrics(rw http.ResponseWriter, r *http.Request) {
 	_, _ = rw.Write(data)
 }
 
-func handleGetMetric(rw http.ResponseWriter, r *http.Request, id string) {
-	engine := common.GetEngine(r.Context())
-
+func handleGetMetric(cs *ControlSurface, rw http.ResponseWriter, _ *http.Request, id string) {
 	var t time.Duration
-	if engine.ExecutionScheduler != nil {
-		t = engine.ExecutionScheduler.GetState().GetCurrentTestRunDuration()
+	if cs.Scheduler != nil {
+		t = cs.Scheduler.GetState().GetCurrentTestRunDuration()
 	}
 
-	engine.MetricsEngine.MetricsLock.Lock()
-	metric, ok := engine.MetricsEngine.ObservedMetrics[id]
+	cs.MetricsEngine.MetricsLock.Lock()
+	metric, ok := cs.MetricsEngine.ObservedMetrics[id]
 	if !ok {
-		engine.MetricsEngine.MetricsLock.Unlock()
+		cs.MetricsEngine.MetricsLock.Unlock()
 		apiError(rw, "Not Found", "No metric with that ID was found", http.StatusNotFound)
 		return
 	}
 	wrappedMetric := newMetricEnvelope(metric, t)
-	engine.MetricsEngine.MetricsLock.Unlock()
+	cs.MetricsEngine.MetricsLock.Unlock()
 
 	data, err := json.Marshal(wrappedMetric)
 	if err != nil {