Include data alongside errors for a service's partial success

cmd/gateway/go.mod

@@ -4,6 +4,6 @@ go 1.16
 
 require (
 	github.com/nautilus/gateway v0.3.17
-	github.com/nautilus/graphql v0.0.25
+	github.com/nautilus/graphql v0.0.26
 	github.com/spf13/cobra v0.0.5
 )

cmd/gateway/go.sum

@@ -78,6 +78,8 @@ github.com/nautilus/graphql v0.0.23 h1:uiQV2SxOfl63xNr4E5Qk9IxecD2llM/gVqKbM2lEH
 github.com/nautilus/graphql v0.0.23/go.mod h1:eoqPxo/+IdRSfLQKZ2V0al2vYeoMJKO72XpTsUYOmFI=
 github.com/nautilus/graphql v0.0.25 h1:N+wwpxnlob3nQK/+HTUPeGfSR0ayehhNqeJq1cdcqSU=
 github.com/nautilus/graphql v0.0.25/go.mod h1:ex8FB+RiAJoWGlL9iUcCWvetFOICVpvYP2jWi0cxp9E=
+github.com/nautilus/graphql v0.0.26 h1:Mfv0Eazj+xKWlSSIcXgJN1zFWhbSQkPsz4IWSk0G5EQ=
+github.com/nautilus/graphql v0.0.26/go.mod h1:ex8FB+RiAJoWGlL9iUcCWvetFOICVpvYP2jWi0cxp9E=
 github.com/opentracing/opentracing-go v1.0.2/go.mod h1:UkNAQd3GIcIGf0SeVgPpRdFStlNbqXla1AfSYxPUl2o=
 github.com/opentracing/opentracing-go v1.2.0 h1:uEJPy/1a5RIPAJ0Ov+OIO8OxWu77jEv+1B0VhjKrZUs=
 github.com/opentracing/opentracing-go v1.2.0/go.mod h1:GxEUsuufX4nBwe+T+Wl9TAgYrxe9dPLANfrWvHYVTgc=

execute.go

@@ -32,7 +32,7 @@ type ParallelExecutor struct{}
 type queryExecutionResult struct {
 	InsertionPoint []string
 	Result         map[string]interface{}
-	StripNode      bool
+	Err            error
 }
 
 // execution is broken up into two phases:
@@ -83,7 +83,7 @@ func (executor *ParallelExecutor) Execute(ctx *ExecutionContext) (map[string]int
 	// the root step could have multiple steps that have to happen
 	for _, step := range ctx.Plan.RootStep.Then {
 		stepWg.Add(1)
-		go executeStep(ctx, ctx.Plan, step, []string{}, resultLock, ctx.Variables, resultCh, errCh, stepWg)
+		go executeStep(ctx, ctx.Plan, step, []string{}, resultLock, ctx.Variables, resultCh, stepWg)
 	}
 
 	// the list of errors we have encountered while executing the plan
@@ -95,24 +95,23 @@ func (executor *ParallelExecutor) Execute(ctx *ExecutionContext) (map[string]int
 			select {
 			// we have a new result
 			case payload := <-resultCh:
-				if payload == nil {
-					continue
-				}
 				ctx.logger.Debug("Inserting result into ", payload.InsertionPoint)
 				ctx.logger.Debug("Result: ", payload.Result)
 
 				// we have to grab the value in the result and write it to the appropriate spot in the
 				// acumulator.
-				err := executorInsertObject(ctx, result, resultLock, payload.InsertionPoint, payload.Result)
-				if err != nil {
-					errCh <- err
-					continue
+				insertErr := executorInsertObject(ctx, result, resultLock, payload.InsertionPoint, payload.Result)
+
+				switch {
+				case payload.Err != nil: // response errors are the highest priority to return
+					errCh <- payload.Err
+				case insertErr != nil:
+					errCh <- insertErr
+				default:
+					ctx.logger.Debug("Done. ", result)
+					// one of the queries is done
+					stepWg.Done()
 				}
-
-				ctx.logger.Debug("Done. ", result)
-				// one of the queries is done
-				stepWg.Done()
-
 			case err := <-errCh:
 				if err != nil {
 					errMutex.Lock()
@@ -158,9 +157,41 @@ func executeStep(
 	resultLock *sync.Mutex,
 	queryVariables map[string]interface{},
 	resultCh chan *queryExecutionResult,
-	errCh chan error,
 	stepWg *sync.WaitGroup,
 ) {
+	queryResult, dependentSteps, queryErr := executeOneStep(ctx, plan, step, insertionPoint, resultLock, queryVariables)
+	// before publishing the current result, tell the wait-group about the dependent steps to wait for
+	stepWg.Add(len(dependentSteps))
+	ctx.logger.Debug("Pushing Result. Insertion point: ", insertionPoint, ". Value: ", queryResult)
+	// send the result to be stitched in with our accumulator
+	resultCh <- &queryExecutionResult{
+		InsertionPoint: insertionPoint,
+		Result:         queryResult,
+		Err:            queryErr,
+	}
+	// We need to collect all the dependent steps and execute them after emitting the parent result in this function.
+	// This avoids a race condition, where the result of a dependent request is published to the
+	// result channel even before the result created in this iteration.
+	// Execute dependent steps after the main step has been published.
+	for _, sr := range dependentSteps {
+		ctx.logger.Info("Spawn ", sr.insertionPoint)
+		go executeStep(ctx, plan, sr.step, sr.insertionPoint, resultLock, queryVariables, resultCh, stepWg)
+	}
+}
+
+type dependentStepArgs struct {
+	step           *QueryPlanStep
+	insertionPoint []string
+}
+
+func executeOneStep(
+	ctx *ExecutionContext,
+	plan *QueryPlan,
+	step *QueryPlanStep,
+	insertionPoint []string,
+	resultLock *sync.Mutex,
+	queryVariables map[string]interface{},
+) (map[string]interface{}, []dependentStepArgs, error) {
 	ctx.logger.Debug("Executing step to be inserted in ", step.ParentType, ". Insertion point: ", insertionPoint)
 
 	ctx.logger.Debug(step.SelectionSet)
@@ -186,14 +217,12 @@ func executeStep(
 		// get the data of the point
 		pointData, err := executorGetPointData(head)
 		if err != nil {
-			errCh <- err
-			return
+			return nil, nil, err
 		}
 
 		// if we dont have an id
 		if pointData.ID == "" {
-			errCh <- fmt.Errorf("Could not find id in path")
-			return
+			return nil, nil, fmt.Errorf("Could not find id in path")
 		}
 
 		// save the id as a variable to the query
@@ -202,8 +231,7 @@ func executeStep(
 
 	// if there is no queryer
 	if step.Queryer == nil {
-		errCh <- errors.New(" could not find queryer for step")
-		return
+		return nil, nil, errors.New(" could not find queryer for step")
 	}
 
 	// the query we will use
@@ -233,8 +261,7 @@ func executeStep(
 	}, &queryResult)
 	if err != nil {
 		ctx.logger.Warn("Network Error: ", err)
-		errCh <- err
-		return
+		return queryResult, nil, err
 	}
 
 	// NOTE: this insertion point could point to a list of values. If it did, we have to have
@@ -249,36 +276,19 @@ func executeStep(
 		// get the result from the response that we have to stitch there
 		extractedResult, err := executorExtractValue(ctx, queryResult, resultLock, []string{"node"})
 		if err != nil {
-			errCh <- err
-			return
+			return nil, nil, err
 		}
 
 		resultObj, ok := extractedResult.(map[string]interface{})
 		if !ok {
-			errCh <- fmt.Errorf("Query result of node query was not an object: %v", queryResult)
-			return
+			return nil, nil, fmt.Errorf("Query result of node query was not an object: %v", queryResult)
 		}
 
 		queryResult = resultObj
 	}
 
-	// we need to collect all the dependent steps and execute them at last in this function
-	// to avoid a race condition, where the result of a dependent request is published to the
-	// result channel even before the result created in this iteration
-	type stepArgs struct {
-		step           *QueryPlanStep
-		insertionPoint []string
-	}
-	var dependentSteps []stepArgs
-	// defer the execution of the dependent steps after the main step has been published
-	defer func() {
-		for _, sr := range dependentSteps {
-			ctx.logger.Info("Spawn ", sr.insertionPoint)
-			go executeStep(ctx, plan, sr.step, sr.insertionPoint, resultLock, queryVariables, resultCh, errCh, stepWg)
-		}
-	}()
-
 	// if there are next steps
+	var dependentSteps []dependentStepArgs
 	if len(step.Then) > 0 {
 		ctx.logger.Debug("Kicking off child queries")
 		// we need to find the ids of the objects we are inserting into and then kick of the worker with the right
@@ -288,30 +298,19 @@ func executeStep(
 			copy(copiedInsertionPoint, insertionPoint)
 			insertPoints, err := executorFindInsertionPoints(ctx, resultLock, dependent.InsertionPoint, step.SelectionSet, queryResult, [][]string{copiedInsertionPoint}, step.FragmentDefinitions)
 			if err != nil {
-				// reset dependent steps - result would be discarded anyways
-				dependentSteps = nil
-				errCh <- err
-				return
+				return nil, nil, err
 			}
 
 			// this dependent needs to fire for every object that the insertion point references
 			for _, insertionPoint := range insertPoints {
-				dependentSteps = append(dependentSteps, stepArgs{
+				dependentSteps = append(dependentSteps, dependentStepArgs{
 					step:           dependent,
 					insertionPoint: insertionPoint,
 				})
 			}
 		}
 	}
-
-	// before publishing the current result, tell the wait-group about the dependent steps to wait for
-	stepWg.Add(len(dependentSteps))
-	ctx.logger.Debug("Pushing Result. Insertion point: ", insertionPoint, ". Value: ", queryResult)
-	// send the result to be stitched in with our accumulator
-	resultCh <- &queryExecutionResult{
-		InsertionPoint: insertionPoint,
-		Result:         queryResult,
-	}
+	return queryResult, dependentSteps, nil
 }
 
 func max(a, b int) int {
@@ -386,7 +385,7 @@ func executorFindInsertionPoints(ctx *ExecutionContext, resultLock *sync.Mutex,
 		// make sure we are looking at the top of the selection set next time
 		selectionSetRoot = foundSelection.SelectionSet
 
-		var value = resultChunk
+		value := resultChunk
 
 		// the bit of result chunk with the appropriate key should be a list
 		rootValue, ok := value[point]

gateway_test.go

@@ -753,3 +753,51 @@ type User {
 		}
 	`, resp.Body.String())
 }
+
+func TestDataAndErrorsBothReturnFromOneServicePartialSuccess(t *testing.T) {
+	t.Parallel()
+	schema, err := graphql.LoadSchema(`
+type Query {
+	foo: String
+	bar: String
+}
+`)
+	require.NoError(t, err)
+	queryerFactory := QueryerFactory(func(ctx *PlanningContext, url string) graphql.Queryer {
+		return graphql.QueryerFunc(func(input *graphql.QueryInput) (interface{}, error) {
+			return map[string]interface{}{
+					"foo": "foo",
+					"bar": nil,
+				}, graphql.ErrorList{
+					&graphql.Error{
+						Message: "bar is broken",
+						Path:    []interface{}{"bar"},
+					},
+				}
+		})
+	})
+	gateway, err := New([]*graphql.RemoteSchema{
+		{Schema: schema, URL: "boo"},
+	}, WithQueryerFactory(&queryerFactory))
+	require.NoError(t, err)
+
+	req := httptest.NewRequest(http.MethodPost, "/", strings.NewReader(`{"query": "query { foo bar }"}`))
+	resp := httptest.NewRecorder()
+	gateway.GraphQLHandler(resp, req)
+	assert.Equal(t, http.StatusOK, resp.Code)
+	assert.JSONEq(t, `
+		{
+			"data": {
+				"foo": "foo",
+				"bar": null
+			},
+			"errors": [
+				{
+					"message": "bar is broken",
+					"path": ["bar"],
+					"extensions": null
+				}
+			]
+		}
+	`, resp.Body.String())
+}

go.mod

@@ -5,7 +5,7 @@ go 1.17
 require (
 	github.com/99designs/gqlgen v0.17.15
 	github.com/mitchellh/mapstructure v1.4.1
-	github.com/nautilus/graphql v0.0.25
+	github.com/nautilus/graphql v0.0.26
 	github.com/sirupsen/logrus v1.9.3
 	github.com/stretchr/testify v1.9.0
 	github.com/vektah/gqlparser/v2 v2.5.16