Query Caching Example

example/caching/cache/hint.go

@@ -0,0 +1,98 @@
+// Package cache implements caching of GraphQL requests by allowing resolvers to provide hints about their cacheability,
+// which can be used by the transport handlers (e.g. HTTP) to provide caching indicators in the response.
+package cache
+
+import (
+	"context"
+	"fmt"
+	"time"
+)
+
+type ctxKey string
+
+const (
+	hintsKey ctxKey = "hints"
+)
+
+type scope int
+
+// Cache control scopes.
+const (
+	ScopePublic scope = iota
+	ScopePrivate
+)
+
+const (
+	hintsBuffer = 20
+)
+
+// Hint defines a hint as to how long something should be cached for.
+type Hint struct {
+	MaxAge *time.Duration
+	Scope  scope
+}
+
+// String resolves the HTTP Cache-Control value of the Hint.
+func (h Hint) String() string {
+	var s string
+	switch h.Scope {
+	case ScopePublic:
+		s = "public"
+	case ScopePrivate:
+		s = "private"
+	}
+	return fmt.Sprintf("%s, max-age=%d", s, int(h.MaxAge.Seconds()))
+}
+
+// TTL defines the cache duration.
+func TTL(d time.Duration) *time.Duration {
+	return &d
+}
+
+// AddHint applies a caching hint to the request context.
+func AddHint(ctx context.Context, hint Hint) {
+	c := hints(ctx)
+	if c == nil {
+		return
+	}
+	c <- hint
+}
+
+// Hintable extends the context with the ability to add cache hints.
+func Hintable(ctx context.Context) (hintCtx context.Context, hint <-chan Hint, done func()) {
+	hints := make(chan Hint, hintsBuffer)
+	h := make(chan Hint)
+	go func() {
+		h <- resolve(hints)
+	}()
+	done = func() {
+		close(hints)
+	}
+	return context.WithValue(ctx, hintsKey, hints), h, done
+}
+
+func hints(ctx context.Context) chan Hint {
+	h, ok := ctx.Value(hintsKey).(chan Hint)
+	if !ok {
+		return nil
+	}
+	return h
+}
+
+func resolve(hints <-chan Hint) Hint {
+	var minAge *time.Duration
+	s := ScopePublic
+	for h := range hints {
+		if h.Scope == ScopePrivate {
+			s = h.Scope
+		}
+		if h.MaxAge != nil && (minAge == nil || *h.MaxAge < *minAge) {
+			minAge = h.MaxAge
+		}
+	}
+	if minAge == nil {
+		var noCache time.Duration
+		minAge = &noCache
+	}
+	return Hint{MaxAge: minAge, Scope: s}
+}

example/caching/caching.go

@@ -0,0 +1,43 @@
+package caching
+
+import (
+	"context"
+	"time"
+
+	"github.com/graph-gophers/graphql-go/example/caching/cache"
+)
+
+const Schema = `
+	schema {
+		query: Query
+	}
+
+	type Query {
+		hello(name: String!): String!
+		me: UserProfile!
+	}
+
+	type UserProfile {
+		name: String!
+	}
+`
+
+type Resolver struct{}
+
+func (r Resolver) Hello(ctx context.Context, args struct{ Name string }) string {
+	cache.AddHint(ctx, cache.Hint{MaxAge: cache.TTL(1 * time.Hour), Scope: cache.ScopePublic})
+	return "Hello " + args.Name + "!"
+}
+
+func (r Resolver) Me(ctx context.Context) *UserProfile {
+	cache.AddHint(ctx, cache.Hint{MaxAge: cache.TTL(1 * time.Minute), Scope: cache.ScopePrivate})
+	return &UserProfile{name: "World"}
+}
+
+type UserProfile struct {
+	name string
+}
+
+func (p *UserProfile) Name() string {
+	return p.name
+}

example/caching/server/server.go

@@ -0,0 +1,139 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+
+	"github.com/graph-gophers/graphql-go"
+	"github.com/graph-gophers/graphql-go/example/caching"
+	"github.com/graph-gophers/graphql-go/example/caching/cache"
+)
+
+var schema *graphql.Schema
+
+func init() {
+	schema = graphql.MustParseSchema(caching.Schema, &caching.Resolver{})
+}
+
+func main() {
+	http.Handle("/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Write(page)
+	}))
+
+	http.Handle("/query", &Handler{Schema: schema})
+
+	log.Fatal(http.ListenAndServe(":8080", nil))
+}
+
+type Handler struct {
+	Schema *graphql.Schema
+}
+
+func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	p, ok := h.parseRequest(w, r)
+	if !ok {
+		return
+	}
+	var response *graphql.Response
+	var hint *cache.Hint
+	if cacheable(r) {
+		ctx, hints, done := cache.Hintable(r.Context())
+		response = h.Schema.Exec(ctx, p.Query, p.OperationName, p.Variables)
+		done()
+		v := <-hints
+		hint = &v
+	} else {
+		response = h.Schema.Exec(r.Context(), p.Query, p.OperationName, p.Variables)
+	}
+	responseJSON, err := json.Marshal(response)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	if hint != nil {
+		w.Header().Set("Cache-Control", hint.String())
+	}
+	w.Header().Set("Content-Type", "application/json")
+	w.Write(responseJSON)
+}
+
+func (h *Handler) parseRequest(w http.ResponseWriter, r *http.Request) (params, bool) {
+	var p params
+	switch r.Method {
+	case http.MethodGet:
+		q := r.URL.Query()
+		if p.Query = q.Get("query"); p.Query == "" {
+			http.Error(w, "A non-empty 'query' parameter is required", http.StatusBadRequest)
+			return params{}, false
+		}
+		p.OperationName = q.Get("operationName")
+		if vars := q.Get("variables"); vars != "" {
+			if err := json.Unmarshal([]byte(vars), &p.Variables); err != nil {
+				http.Error(w, err.Error(), http.StatusBadRequest)
+				return params{}, false
+			}
+		}
+		return p, true
+	case http.MethodPost:
+		if err := json.NewDecoder(r.Body).Decode(&p); err != nil {
+			http.Error(w, err.Error(), http.StatusBadRequest)
+			return params{}, false
+		}
+		return p, true
+	default:
+		http.Error(w, fmt.Sprintf("unsupported HTTP method: %s", r.Method), http.StatusMethodNotAllowed)
+		return params{}, false
+	}
+}
+
+func cacheable(r *http.Request) bool {
+	return r.Method == http.MethodGet
+}
+
+type params struct {
+	Query         string                 `json:"query"`
+	OperationName string                 `json:"operationName"`
+	Variables     map[string]interface{} `json:"variables"`
+}
+
+var page = []byte(`
+<!DOCTYPE html>
+<html>
+	<head>
+		<link href="https://cdnjs.cloudflare.com/ajax/libs/graphiql/0.11.11/graphiql.min.css" rel="stylesheet" />
+		<script src="https://cdnjs.cloudflare.com/ajax/libs/es6-promise/4.1.1/es6-promise.auto.min.js"></script>
+		<script src="https://cdnjs.cloudflare.com/ajax/libs/fetch/2.0.3/fetch.min.js"></script>
+		<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.2.0/umd/react.production.min.js"></script>
+		<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.2.0/umd/react-dom.production.min.js"></script>
+		<script src="https://cdnjs.cloudflare.com/ajax/libs/graphiql/0.11.11/graphiql.min.js"></script>
+	</head>
+	<body style="width: 100%; height: 100%; margin: 0; overflow: hidden;">
+		<div id="graphiql" style="height: 100vh;">Loading...</div>
+		<script>
+			function graphQLFetcher(graphQLParams) {
+				const uri = "/query?query=" + encodeURIComponent(graphQLParams.query || "") + "&operationName=" + encodeURIComponent(graphQLParams.operationName || "") + "&variables=" + encodeURIComponent(graphQLParams.variables || "");
+				return fetch(uri, {
+					method: "get",
+					credentials: "include",
+				}).then(function (response) {
+					return response.text();
+				}).then(function (responseBody) {
+					try {
+						return JSON.parse(responseBody);
+					} catch (error) {
+						return responseBody;
+					}
+				});
+			}
+
+			ReactDOM.render(
+				React.createElement(GraphiQL, {fetcher: graphQLFetcher}),
+				document.getElementById("graphiql")
+			);
+		</script>
+	</body>
+</html>
+`)