node: refactor package node (#21105)

This PR significantly changes the APIs for instantiating Ethereum nodes in
a Go program. The new APIs are not backwards-compatible, but we feel that
this is made up for by the much simpler way of registering services on
node.Node. You can find more information and rationale in the design
document: https://gist.github.com/renaynay/5bec2de19fde66f4d04c535fd24f0775.

There is also a new feature in Node's Go API: it is now possible to
register arbitrary handlers on the user-facing HTTP server. In geth, this
facility is used to enable GraphQL.

There is a single minor change relevant for geth users in this PR: The
GraphQL API is no longer available separately from the JSON-RPC HTTP
server. If you want GraphQL, you need to enable it using the
./geth --http --graphql flag combination.

The --graphql.port and --graphql.addr flags are no longer available.

graphql/service.go

@@ -17,99 +17,36 @@
 package graphql
 
 import (
-	"fmt"
-	"net"
-	"net/http"
-
 	"github.com/ethereum/go-ethereum/internal/ethapi"
-	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/node"
-	"github.com/ethereum/go-ethereum/p2p"
-	"github.com/ethereum/go-ethereum/rpc"
 	"github.com/graph-gophers/graphql-go"
 	"github.com/graph-gophers/graphql-go/relay"
 )
 
-// Service encapsulates a GraphQL service.
-type Service struct {
-	endpoint string           // The host:port endpoint for this service.
-	cors     []string         // Allowed CORS domains
-	vhosts   []string         // Recognised vhosts
-	timeouts rpc.HTTPTimeouts // Timeout settings for HTTP requests.
-	backend  ethapi.Backend   // The backend that queries will operate on.
-	handler  http.Handler     // The `http.Handler` used to answer queries.
-	listener net.Listener     // The listening socket.
-}
-
 // New constructs a new GraphQL service instance.
-func New(backend ethapi.Backend, endpoint string, cors, vhosts []string, timeouts rpc.HTTPTimeouts) (*Service, error) {
-	return &Service{
-		endpoint: endpoint,
-		cors:     cors,
-		vhosts:   vhosts,
-		timeouts: timeouts,
-		backend:  backend,
-	}, nil
-}
-
-// Protocols returns the list of protocols exported by this service.
-func (s *Service) Protocols() []p2p.Protocol { return nil }
-
-// APIs returns the list of APIs exported by this service.
-func (s *Service) APIs() []rpc.API { return nil }
-
-// Start is called after all services have been constructed and the networking
-// layer was also initialized to spawn any goroutines required by the service.
-func (s *Service) Start(server *p2p.Server) error {
-	var err error
-	s.handler, err = newHandler(s.backend)
-	if err != nil {
-		return err
+func New(stack *node.Node, backend ethapi.Backend, cors, vhosts []string) error {
+	if backend == nil {
+		panic("missing backend")
 	}
-	if s.listener, err = net.Listen("tcp", s.endpoint); err != nil {
-		return err
-	}
-	// create handler stack and wrap the graphql handler
-	handler := node.NewHTTPHandlerStack(s.handler, s.cors, s.vhosts)
-	// make sure timeout values are meaningful
-	node.CheckTimeouts(&s.timeouts)
-	// create http server
-	httpSrv := &http.Server{
-		Handler:      handler,
-		ReadTimeout:  s.timeouts.ReadTimeout,
-		WriteTimeout: s.timeouts.WriteTimeout,
-		IdleTimeout:  s.timeouts.IdleTimeout,
-	}
-	go httpSrv.Serve(s.listener)
-	log.Info("GraphQL endpoint opened", "url", fmt.Sprintf("http://%s", s.endpoint))
-	return nil
+	// check if http server with given endpoint exists and enable graphQL on it
+	return newHandler(stack, backend, cors, vhosts)
 }
 
 // newHandler returns a new `http.Handler` that will answer GraphQL queries.
 // It additionally exports an interactive query browser on the / endpoint.
-func newHandler(backend ethapi.Backend) (http.Handler, error) {
+func newHandler(stack *node.Node, backend ethapi.Backend, cors, vhosts []string) error {
 	q := Resolver{backend}
 
 	s, err := graphql.ParseSchema(schema, &q)
 	if err != nil {
-		return nil, err
+		return err
 	}
 	h := &relay.Handler{Schema: s}
+	handler := node.NewHTTPHandlerStack(h, cors, vhosts)
 
-	mux := http.NewServeMux()
-	mux.Handle("/", GraphiQL{})
-	mux.Handle("/graphql", h)
-	mux.Handle("/graphql/", h)
-	return mux, nil
-}
+	stack.RegisterHandler("GraphQL UI", "/graphql/ui", GraphiQL{})
+	stack.RegisterHandler("GraphQL", "/graphql", handler)
+	stack.RegisterHandler("GraphQL", "/graphql/", handler)
 
-// Stop terminates all goroutines belonging to the service, blocking until they
-// are all terminated.
-func (s *Service) Stop() error {
-	if s.listener != nil {
-		s.listener.Close()
-		s.listener = nil
-		log.Info("GraphQL endpoint closed", "url", fmt.Sprintf("http://%s", s.endpoint))
-	}
 	return nil
 }