github.com/dgraph-io/dgraph@v1.2.8/graphql/api/context.go (about)

     1  /*
     2   * Copyright 2019 Dgraph Labs, Inc. and Contributors
     3   *
     4   * Licensed under the Apache License, Version 2.0 (the "License");
     5   * you may not use this file except in compliance with the License.
     6   * You may obtain a copy of the License at
     7   *
     8   *     http://www.apache.org/licenses/LICENSE-2.0
     9   *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16  
    17  package api
    18  
    19  import (
    20  	"context"
    21  	"net/http"
    22  
    23  	"github.com/google/uuid"
    24  )
    25  
    26  // Various functions for getting and setting context, etc. used
    27  // throughout the GraphQL API.
    28  
    29  type apiKey string
    30  
    31  const (
    32  	requestID    = apiKey("requestID")
    33  	nilRequestID = "a1111111-b222-c333-d444-e55555555555"
    34  
    35  	gqlQuery    = apiKey("gqlQuery")
    36  	nilGQLQuery = "aGraphQLQuery {}"
    37  )
    38  
    39  // WithRequestID adds a HTTP middleware handler that sets a UUID as request ID
    40  // into the handler chain.
    41  func WithRequestID(h http.Handler) http.Handler {
    42  	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    43  		reqID := uuid.New().String()
    44  		h.ServeHTTP(w, r.WithContext(
    45  			context.WithValue(r.Context(), requestID, reqID)))
    46  	})
    47  }
    48  
    49  // WithQueryString returns a new context where QueryString() returns query.
    50  func WithQueryString(ctx context.Context, query string) context.Context {
    51  	return context.WithValue(ctx, gqlQuery, query)
    52  }
    53  
    54  // RequestID gets the request ID from a context.  If no request ID is set,
    55  // it returns "a1111111-b222-c333-d444-e55555555555".
    56  func RequestID(ctx context.Context) string {
    57  	return stringFromContext(ctx, requestID, nilRequestID)
    58  }
    59  
    60  // QueryString gets the GraphQL query from a context.  If no query is set,
    61  // it returns "aGraphQLQuery {}"
    62  func QueryString(ctx context.Context) string {
    63  	return stringFromContext(ctx, gqlQuery, nilGQLQuery)
    64  }
    65  
    66  func stringFromContext(ctx context.Context, key apiKey, def string) string {
    67  	if val := ctx.Value(key); val != nil {
    68  		if str, ok := val.(string); ok {
    69  			return str
    70  		}
    71  	}
    72  	return def
    73  }