f20eba426a
Here we add special handling for sending an error response when the write timeout of the HTTP server is just about to expire. This is surprisingly difficult to get right, since is must be ensured that all output is fully flushed in time, which needs support from multiple levels of the RPC handler stack: The timeout response can't use chunked transfer-encoding because there is no way to write the final terminating chunk. net/http writes it when the topmost handler returns, but the timeout will already be over by the time that happens. We decided to disable chunked encoding by setting content-length explicitly. Gzip compression must also be disabled for timeout responses because we don't know the true content-length before compressing all output, i.e. compression would reintroduce chunked transfer-encoding.
130 lines
4.0 KiB
Go
130 lines
4.0 KiB
Go
// Copyright 2019 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package graphql
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import (
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"context"
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"encoding/json"
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"net/http"
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"strconv"
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"sync"
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"time"
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"github.com/ethereum/go-ethereum/eth/filters"
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"github.com/ethereum/go-ethereum/internal/ethapi"
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"github.com/ethereum/go-ethereum/node"
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"github.com/ethereum/go-ethereum/rpc"
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"github.com/graph-gophers/graphql-go"
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gqlErrors "github.com/graph-gophers/graphql-go/errors"
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)
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type handler struct {
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Schema *graphql.Schema
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}
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func (h handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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var params struct {
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Query string `json:"query"`
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OperationName string `json:"operationName"`
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Variables map[string]interface{} `json:"variables"`
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}
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if err := json.NewDecoder(r.Body).Decode(¶ms); err != nil {
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http.Error(w, err.Error(), http.StatusBadRequest)
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return
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}
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var (
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ctx = r.Context()
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responded sync.Once
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timer *time.Timer
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cancel context.CancelFunc
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)
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ctx, cancel = context.WithCancel(ctx)
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defer cancel()
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if timeout, ok := rpc.ContextRequestTimeout(ctx); ok {
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timer = time.AfterFunc(timeout, func() {
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responded.Do(func() {
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// Cancel request handling.
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cancel()
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// Create the timeout response.
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response := &graphql.Response{
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Errors: []*gqlErrors.QueryError{{Message: "request timed out"}},
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}
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responseJSON, err := json.Marshal(response)
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if err != nil {
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http.Error(w, err.Error(), http.StatusInternalServerError)
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return
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}
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// Setting this disables gzip compression in package node.
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w.Header().Set("transfer-encoding", "identity")
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// Flush the response. Since we are writing close to the response timeout,
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// chunked transfer encoding must be disabled by setting content-length.
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w.Header().Set("content-type", "application/json")
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w.Header().Set("content-length", strconv.Itoa(len(responseJSON)))
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w.Write(responseJSON)
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if flush, ok := w.(http.Flusher); ok {
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flush.Flush()
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}
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})
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})
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}
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response := h.Schema.Exec(ctx, params.Query, params.OperationName, params.Variables)
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timer.Stop()
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responded.Do(func() {
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responseJSON, err := json.Marshal(response)
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if err != nil {
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http.Error(w, err.Error(), http.StatusInternalServerError)
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return
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}
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if len(response.Errors) > 0 {
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w.WriteHeader(http.StatusBadRequest)
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}
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w.Header().Set("Content-Type", "application/json")
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w.Write(responseJSON)
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})
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}
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// New constructs a new GraphQL service instance.
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func New(stack *node.Node, backend ethapi.Backend, filterSystem *filters.FilterSystem, cors, vhosts []string) error {
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_, err := newHandler(stack, backend, filterSystem, cors, vhosts)
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return err
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}
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// newHandler returns a new `http.Handler` that will answer GraphQL queries.
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// It additionally exports an interactive query browser on the / endpoint.
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func newHandler(stack *node.Node, backend ethapi.Backend, filterSystem *filters.FilterSystem, cors, vhosts []string) (*handler, error) {
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q := Resolver{backend, filterSystem}
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s, err := graphql.ParseSchema(schema, &q)
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if err != nil {
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return nil, err
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}
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h := handler{Schema: s}
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handler := node.NewHTTPHandlerStack(h, cors, vhosts, nil)
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stack.RegisterHandler("GraphQL UI", "/graphql/ui", GraphiQL{})
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stack.RegisterHandler("GraphQL", "/graphql", handler)
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stack.RegisterHandler("GraphQL", "/graphql/", handler)
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return &h, nil
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}
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