package handler import ( "bytes" "context" "encoding/json" "fmt" "log" "net/http" "sync" "github.com/99designs/gqlgen/graphql" "github.com/gorilla/websocket" "github.com/vektah/gqlparser" "github.com/vektah/gqlparser/ast" "github.com/vektah/gqlparser/gqlerror" "github.com/vektah/gqlparser/validator" ) const ( connectionInitMsg = "connection_init" // Client -> Server connectionTerminateMsg = "connection_terminate" // Client -> Server startMsg = "start" // Client -> Server stopMsg = "stop" // Client -> Server connectionAckMsg = "connection_ack" // Server -> Client connectionErrorMsg = "connection_error" // Server -> Client dataMsg = "data" // Server -> Client errorMsg = "error" // Server -> Client completeMsg = "complete" // Server -> Client //connectionKeepAliveMsg = "ka" // Server -> Client TODO: keepalives ) type operationMessage struct { Payload json.RawMessage `json:"payload,omitempty"` ID string `json:"id,omitempty"` Type string `json:"type"` } type wsConnection struct { ctx context.Context conn *websocket.Conn exec graphql.ExecutableSchema active map[string]context.CancelFunc mu sync.Mutex cfg *Config } func connectWs(exec graphql.ExecutableSchema, w http.ResponseWriter, r *http.Request, cfg *Config) { ws, err := cfg.upgrader.Upgrade(w, r, http.Header{ "Sec-Websocket-Protocol": []string{"graphql-ws"}, }) if err != nil { log.Printf("unable to upgrade %T to websocket %s: ", w, err.Error()) sendErrorf(w, http.StatusBadRequest, "unable to upgrade") return } conn := wsConnection{ active: map[string]context.CancelFunc{}, exec: exec, conn: ws, ctx: r.Context(), cfg: cfg, } if !conn.init() { return } conn.run() } func (c *wsConnection) init() bool { message := c.readOp() if message == nil { c.close(websocket.CloseProtocolError, "decoding error") return false } switch message.Type { case connectionInitMsg: c.write(&operationMessage{Type: connectionAckMsg}) case connectionTerminateMsg: c.close(websocket.CloseNormalClosure, "terminated") return false default: c.sendConnectionError("unexpected message %s", message.Type) c.close(websocket.CloseProtocolError, "unexpected message") return false } return true } func (c *wsConnection) write(msg *operationMessage) { c.mu.Lock() c.conn.WriteJSON(msg) c.mu.Unlock() } func (c *wsConnection) run() { for { message := c.readOp() if message == nil { return } switch message.Type { case startMsg: if !c.subscribe(message) { return } case stopMsg: c.mu.Lock() closer := c.active[message.ID] c.mu.Unlock() if closer == nil { c.sendError(message.ID, gqlerror.Errorf("%s is not running, cannot stop", message.ID)) continue } closer() case connectionTerminateMsg: c.close(websocket.CloseNormalClosure, "terminated") return default: c.sendConnectionError("unexpected message %s", message.Type) c.close(websocket.CloseProtocolError, "unexpected message") return } } } func (c *wsConnection) subscribe(message *operationMessage) bool { var reqParams params if err := jsonDecode(bytes.NewReader(message.Payload), &reqParams); err != nil { c.sendConnectionError("invalid json") return false } doc, qErr := gqlparser.LoadQuery(c.exec.Schema(), reqParams.Query) if qErr != nil { c.sendError(message.ID, qErr...) return true } op := doc.Operations.ForName(reqParams.OperationName) if op == nil { c.sendError(message.ID, gqlerror.Errorf("operation %s not found", reqParams.OperationName)) return true } vars, err := validator.VariableValues(c.exec.Schema(), op, reqParams.Variables) if err != nil { c.sendError(message.ID, err) return true } reqCtx := c.cfg.newRequestContext(doc, reqParams.Query, vars) ctx := graphql.WithRequestContext(c.ctx, reqCtx) if op.Operation != ast.Subscription { var result *graphql.Response if op.Operation == ast.Query { result = c.exec.Query(ctx, op) } else { result = c.exec.Mutation(ctx, op) } c.sendData(message.ID, result) c.write(&operationMessage{ID: message.ID, Type: completeMsg}) return true } ctx, cancel := context.WithCancel(ctx) c.mu.Lock() c.active[message.ID] = cancel c.mu.Unlock() go func() { defer func() { if r := recover(); r != nil { userErr := reqCtx.Recover(ctx, r) c.sendError(message.ID, &gqlerror.Error{Message: userErr.Error()}) } }() next := c.exec.Subscription(ctx, op) for result := next(); result != nil; result = next() { c.sendData(message.ID, result) } c.write(&operationMessage{ID: message.ID, Type: completeMsg}) c.mu.Lock() delete(c.active, message.ID) c.mu.Unlock() cancel() }() return true } func (c *wsConnection) sendData(id string, response *graphql.Response) { b, err := json.Marshal(response) if err != nil { c.sendError(id, gqlerror.Errorf("unable to encode json response: %s", err.Error())) return } c.write(&operationMessage{Type: dataMsg, ID: id, Payload: b}) } func (c *wsConnection) sendError(id string, errors ...*gqlerror.Error) { var errs []error for _, err := range errors { errs = append(errs, err) } b, err := json.Marshal(errs) if err != nil { panic(err) } c.write(&operationMessage{Type: errorMsg, ID: id, Payload: b}) } func (c *wsConnection) sendConnectionError(format string, args ...interface{}) { b, err := json.Marshal(&gqlerror.Error{Message: fmt.Sprintf(format, args...)}) if err != nil { panic(err) } c.write(&operationMessage{Type: connectionErrorMsg, Payload: b}) } func (c *wsConnection) readOp() *operationMessage { _, r, err := c.conn.NextReader() if err != nil { c.sendConnectionError("invalid json") return nil } message := operationMessage{} if err := jsonDecode(r, &message); err != nil { c.sendConnectionError("invalid json") return nil } return &message } func (c *wsConnection) close(closeCode int, message string) { c.mu.Lock() _ = c.conn.WriteMessage(websocket.CloseMessage, websocket.FormatCloseMessage(closeCode, message)) c.mu.Unlock() _ = c.conn.Close() }