Initial GraphQL with query and mutation

dgraph/cmd/graphql/http.go

@@ -0,0 +1,95 @@
+/*
+ * Copyright 2019 Dgraph Labs, Inc. and Contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package graphql
+
+import (
+	"encoding/json"
+	"mime"
+	"net/http"
+
+	"github.com/golang/glog"
+
+	"github.com/dgraph-io/dgo"
+	"github.com/dgraph-io/dgraph/dgraph/cmd/graphql/resolve"
+	"github.com/dgraph-io/dgraph/dgraph/cmd/graphql/schema"
+	"github.com/vektah/gqlparser/ast"
+	"github.com/vektah/gqlparser/gqlerror"
+)
+
+type graphqlHandler struct {
+	dgraphClient *dgo.Dgraph
+	schema       *ast.Schema
+}
+
+// ServeHTTP handles GraphQL queries and mutations that get resolved
+// via GraphQL->Dgraph->GraphQL.  It writes a valid GraphQL JSON response
+// to w.
+func (gh *graphqlHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusOK)
+
+	if !gh.isValid() {
+		panic("graphqlHandler not initialised")
+	}
+
+	rh := gh.resolverForRequest(r)
+	res := rh.Resolve(r.Context())
+	_, err := res.WriteTo(w)
+	if err != nil {
+		glog.Error(err)
+	}
+}
+
+func (gh *graphqlHandler) isValid() bool {
+	return !(gh == nil || gh.schema == nil || gh.dgraphClient == nil)
+}
+
+func (gh *graphqlHandler) resolverForRequest(r *http.Request) (rr *resolve.RequestResolver) {
+	rr = resolve.New(schema.AsSchema(gh.schema), gh.dgraphClient)
+
+	switch r.Method {
+	case http.MethodGet:
+		// TODO: fill gqlReq in from parameters
+	case http.MethodPost:
+		mediaType, _, err := mime.ParseMediaType(r.Header.Get("Content-Type"))
+		if err != nil {
+			rr.WithErrors(gqlerror.Errorf("Unable to parse media type: %s", err))
+			return
+		}
+
+		switch mediaType {
+		case "application/json":
+			if err = json.NewDecoder(r.Body).Decode(&rr.GqlReq); err != nil {
+				rr.WithErrors(
+					gqlerror.Errorf("Not a valid GraphQL request body: %s", err))
+				return
+			}
+		default:
+			// https://graphql.org/learn/serving-over-http/#post-request says:
+			// "A standard GraphQL POST request should use the application/json
+			// content type ..."
+			rr.WithErrors(gqlerror.Errorf(
+				"Unrecognised Content-Type.  Please use application/json for GraphQL requests"))
+			return
+		}
+	default:
+		rr.WithErrors(gqlerror.Errorf(
+			"Unrecognised request method.  Please use GET or POST for GraphQL requests"))
+		return
+	}
+	return
+}

dgraph/cmd/graphql/resolve/dgraph.go

@@ -0,0 +1,109 @@
+/*
+ * Copyright 2019 Dgraph Labs, Inc. and Contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package resolve
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"github.com/golang/glog"
+
+	"github.com/dgraph-io/dgo"
+	"github.com/dgraph-io/dgraph/gql"
+	"github.com/pkg/errors"
+)
+
+func executeQuery(ctx context.Context, query *gql.GraphQuery, dgraphClient *dgo.Dgraph) ([]byte, error) {
+
+	q := asString(query)
+	if glog.V(3) {
+		glog.Infof("Executing Dgraph query: \n%s\n", q)
+	}
+
+	resp, err := dgraphClient.NewTxn().Query(ctx, q)
+	if err != nil {
+		// should I be inspecting this to work out if it's a bug,
+		// or a transient error?
+		return nil, errors.Wrap(err, "while querying Dgraph")
+	}
+
+	return resp.Json, nil
+}
+
+// TODO: once there's more below, extract out into gql package??
+//
+// There's not much of GraphQuery supported so far,
+// so just simple writes of what is supported.
+func asString(query *gql.GraphQuery) string {
+	var b strings.Builder
+
+	b.WriteString("query {\n")
+	writeQuery(&b, query, "  ")
+	b.WriteString("}")
+
+	return b.String()
+}
+
+func writeQuery(b *strings.Builder, query *gql.GraphQuery, prefix string) {
+	b.WriteString(prefix)
+	if query.Alias != "" {
+		b.WriteString(query.Alias)
+		b.WriteString(" : ")
+	}
+	b.WriteString(query.Attr)
+
+	writeFunction(b, query.Func)
+	writeFilter(b, query.Filter)
+
+	if len(query.Children) > 0 {
+		b.WriteString(" { \n")
+		for _, c := range query.Children {
+			writeQuery(b, c, prefix+"  ")
+		}
+		b.WriteString(prefix)
+		b.WriteString("}")
+	}
+	b.WriteString("\n")
+}
+
+func writeFunction(b *strings.Builder, f *gql.Function) {
+	if f != nil {
+		b.WriteString(fmt.Sprintf("(func: %s(0x%x)) ", f.Name, f.UID[0]))
+		// there's only uid(...) functions so far
+	}
+}
+
+func writeFilterFunction(b *strings.Builder, f *gql.Function) {
+	if f != nil {
+		b.WriteString(fmt.Sprintf("%s(%s) ", f.Name, f.Args[0].Value))
+	}
+}
+
+func writeFilter(b *strings.Builder, f *gql.FilterTree) {
+	if f == nil {
+		return
+	}
+
+	if f.Func.Name == "type" {
+		b.WriteString(fmt.Sprintf("@filter(type(%s)) ", f.Func.Args[0].Value))
+	} else {
+		b.WriteString("@filter(")
+		writeFilterFunction(b, f.Func)
+		b.WriteString(")")
+	}
+}