From d235e2c6a5788ec4a6cff15a16f56b38a3876a0d Mon Sep 17 00:00:00 2001 From: Determinant Date: Sun, 28 Jun 2020 14:47:41 -0400 Subject: ... --- rpc/client.go | 625 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 625 insertions(+) create mode 100644 rpc/client.go (limited to 'rpc/client.go') diff --git a/rpc/client.go b/rpc/client.go new file mode 100644 index 0000000..1c7058b --- /dev/null +++ b/rpc/client.go @@ -0,0 +1,625 @@ +// Copyright 2016 The go-ethereum Authors +// This file is part of the go-ethereum library. +// +// The go-ethereum library is free software: you can redistribute it and/or modify +// it under the terms of the GNU Lesser General Public License as published by +// the Free Software Foundation, either version 3 of the License, or +// (at your option) any later version. +// +// The go-ethereum library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU Lesser General Public License for more details. +// +// You should have received a copy of the GNU Lesser General Public License +// along with the go-ethereum library. If not, see . + +package rpc + +import ( + "bytes" + "context" + "encoding/json" + "errors" + "fmt" + "net/url" + "reflect" + "strconv" + "sync/atomic" + "time" + + "github.com/ava-labs/go-ethereum/log" +) + +var ( + ErrClientQuit = errors.New("client is closed") + ErrNoResult = errors.New("no result in JSON-RPC response") + ErrSubscriptionQueueOverflow = errors.New("subscription queue overflow") + errClientReconnected = errors.New("client reconnected") + errDead = errors.New("connection lost") +) + +const ( + // Timeouts + defaultDialTimeout = 10 * time.Second // used if context has no deadline + subscribeTimeout = 5 * time.Second // overall timeout eth_subscribe, rpc_modules calls +) + +const ( + // Subscriptions are removed when the subscriber cannot keep up. + // + // This can be worked around by supplying a channel with sufficiently sized buffer, + // but this can be inconvenient and hard to explain in the docs. Another issue with + // buffered channels is that the buffer is static even though it might not be needed + // most of the time. + // + // The approach taken here is to maintain a per-subscription linked list buffer + // shrinks on demand. If the buffer reaches the size below, the subscription is + // dropped. + maxClientSubscriptionBuffer = 20000 +) + +// BatchElem is an element in a batch request. +type BatchElem struct { + Method string + Args []interface{} + // The result is unmarshaled into this field. Result must be set to a + // non-nil pointer value of the desired type, otherwise the response will be + // discarded. + Result interface{} + // Error is set if the server returns an error for this request, or if + // unmarshaling into Result fails. It is not set for I/O errors. + Error error +} + +// Client represents a connection to an RPC server. +type Client struct { + idgen func() ID // for subscriptions + isHTTP bool + services *serviceRegistry + + idCounter uint32 + + // This function, if non-nil, is called when the connection is lost. + reconnectFunc reconnectFunc + + // writeConn is used for writing to the connection on the caller's goroutine. It should + // only be accessed outside of dispatch, with the write lock held. The write lock is + // taken by sending on requestOp and released by sending on sendDone. + writeConn jsonWriter + + // for dispatch + close chan struct{} + closing chan struct{} // closed when client is quitting + didClose chan struct{} // closed when client quits + reconnected chan ServerCodec // where write/reconnect sends the new connection + readOp chan readOp // read messages + readErr chan error // errors from read + reqInit chan *requestOp // register response IDs, takes write lock + reqSent chan error // signals write completion, releases write lock + reqTimeout chan *requestOp // removes response IDs when call timeout expires +} + +type reconnectFunc func(ctx context.Context) (ServerCodec, error) + +type clientContextKey struct{} + +type clientConn struct { + codec ServerCodec + handler *handler +} + +func (c *Client) newClientConn(conn ServerCodec) *clientConn { + ctx := context.WithValue(context.Background(), clientContextKey{}, c) + handler := newHandler(ctx, conn, c.idgen, c.services) + return &clientConn{conn, handler} +} + +func (cc *clientConn) close(err error, inflightReq *requestOp) { + cc.handler.close(err, inflightReq) + cc.codec.Close() +} + +type readOp struct { + msgs []*jsonrpcMessage + batch bool +} + +type requestOp struct { + ids []json.RawMessage + err error + resp chan *jsonrpcMessage // receives up to len(ids) responses + sub *ClientSubscription // only set for EthSubscribe requests +} + +func (op *requestOp) wait(ctx context.Context, c *Client) (*jsonrpcMessage, error) { + select { + case <-ctx.Done(): + // Send the timeout to dispatch so it can remove the request IDs. + if !c.isHTTP { + select { + case c.reqTimeout <- op: + case <-c.closing: + } + } + return nil, ctx.Err() + case resp := <-op.resp: + return resp, op.err + } +} + +// Dial creates a new client for the given URL. +// +// The currently supported URL schemes are "http", "https", "ws" and "wss". If rawurl is a +// file name with no URL scheme, a local socket connection is established using UNIX +// domain sockets on supported platforms and named pipes on Windows. If you want to +// configure transport options, use DialHTTP, DialWebsocket or DialIPC instead. +// +// For websocket connections, the origin is set to the local host name. +// +// The client reconnects automatically if the connection is lost. +func Dial(rawurl string) (*Client, error) { + return DialContext(context.Background(), rawurl) +} + +// DialContext creates a new RPC client, just like Dial. +// +// The context is used to cancel or time out the initial connection establishment. It does +// not affect subsequent interactions with the client. +func DialContext(ctx context.Context, rawurl string) (*Client, error) { + u, err := url.Parse(rawurl) + if err != nil { + return nil, err + } + switch u.Scheme { + case "http", "https": + return DialHTTP(rawurl) + case "ws", "wss": + return DialWebsocket(ctx, rawurl, "") + //case "stdio": + // return DialStdIO(ctx) + //case "": + // return DialIPC(ctx, rawurl) + default: + return nil, fmt.Errorf("no known transport for URL scheme %q", u.Scheme) + } +} + +// Client retrieves the client from the context, if any. This can be used to perform +// 'reverse calls' in a handler method. +func ClientFromContext(ctx context.Context) (*Client, bool) { + client, ok := ctx.Value(clientContextKey{}).(*Client) + return client, ok +} + +func newClient(initctx context.Context, connect reconnectFunc) (*Client, error) { + conn, err := connect(initctx) + if err != nil { + return nil, err + } + c := initClient(conn, randomIDGenerator(), new(serviceRegistry)) + c.reconnectFunc = connect + return c, nil +} + +func initClient(conn ServerCodec, idgen func() ID, services *serviceRegistry) *Client { + _, isHTTP := conn.(*httpConn) + c := &Client{ + idgen: idgen, + isHTTP: isHTTP, + services: services, + writeConn: conn, + close: make(chan struct{}), + closing: make(chan struct{}), + didClose: make(chan struct{}), + reconnected: make(chan ServerCodec), + readOp: make(chan readOp), + readErr: make(chan error), + reqInit: make(chan *requestOp), + reqSent: make(chan error, 1), + reqTimeout: make(chan *requestOp), + } + if !isHTTP { + go c.dispatch(conn) + } + return c +} + +// RegisterName creates a service for the given receiver type under the given name. When no +// methods on the given receiver match the criteria to be either a RPC method or a +// subscription an error is returned. Otherwise a new service is created and added to the +// service collection this client provides to the server. +func (c *Client) RegisterName(name string, receiver interface{}) error { + return c.services.registerName(name, receiver) +} + +func (c *Client) nextID() json.RawMessage { + id := atomic.AddUint32(&c.idCounter, 1) + return strconv.AppendUint(nil, uint64(id), 10) +} + +// SupportedModules calls the rpc_modules method, retrieving the list of +// APIs that are available on the server. +func (c *Client) SupportedModules() (map[string]string, error) { + var result map[string]string + ctx, cancel := context.WithTimeout(context.Background(), subscribeTimeout) + defer cancel() + err := c.CallContext(ctx, &result, "rpc_modules") + return result, err +} + +// Close closes the client, aborting any in-flight requests. +func (c *Client) Close() { + if c.isHTTP { + return + } + select { + case c.close <- struct{}{}: + <-c.didClose + case <-c.didClose: + } +} + +// Call performs a JSON-RPC call with the given arguments and unmarshals into +// result if no error occurred. +// +// The result must be a pointer so that package json can unmarshal into it. You +// can also pass nil, in which case the result is ignored. +func (c *Client) Call(result interface{}, method string, args ...interface{}) error { + ctx := context.Background() + return c.CallContext(ctx, result, method, args...) +} + +// CallContext performs a JSON-RPC call with the given arguments. If the context is +// canceled before the call has successfully returned, CallContext returns immediately. +// +// The result must be a pointer so that package json can unmarshal into it. You +// can also pass nil, in which case the result is ignored. +func (c *Client) CallContext(ctx context.Context, result interface{}, method string, args ...interface{}) error { + msg, err := c.newMessage(method, args...) + if err != nil { + return err + } + op := &requestOp{ids: []json.RawMessage{msg.ID}, resp: make(chan *jsonrpcMessage, 1)} + + if c.isHTTP { + err = c.sendHTTP(ctx, op, msg) + } else { + err = c.send(ctx, op, msg) + } + if err != nil { + return err + } + + // dispatch has accepted the request and will close the channel when it quits. + switch resp, err := op.wait(ctx, c); { + case err != nil: + return err + case resp.Error != nil: + return resp.Error + case len(resp.Result) == 0: + return ErrNoResult + default: + return json.Unmarshal(resp.Result, &result) + } +} + +// BatchCall sends all given requests as a single batch and waits for the server +// to return a response for all of them. +// +// In contrast to Call, BatchCall only returns I/O errors. Any error specific to +// a request is reported through the Error field of the corresponding BatchElem. +// +// Note that batch calls may not be executed atomically on the server side. +func (c *Client) BatchCall(b []BatchElem) error { + ctx := context.Background() + return c.BatchCallContext(ctx, b) +} + +// BatchCall sends all given requests as a single batch and waits for the server +// to return a response for all of them. The wait duration is bounded by the +// context's deadline. +// +// In contrast to CallContext, BatchCallContext only returns errors that have occurred +// while sending the request. Any error specific to a request is reported through the +// Error field of the corresponding BatchElem. +// +// Note that batch calls may not be executed atomically on the server side. +func (c *Client) BatchCallContext(ctx context.Context, b []BatchElem) error { + msgs := make([]*jsonrpcMessage, len(b)) + op := &requestOp{ + ids: make([]json.RawMessage, len(b)), + resp: make(chan *jsonrpcMessage, len(b)), + } + for i, elem := range b { + msg, err := c.newMessage(elem.Method, elem.Args...) + if err != nil { + return err + } + msgs[i] = msg + op.ids[i] = msg.ID + } + + var err error + if c.isHTTP { + err = c.sendBatchHTTP(ctx, op, msgs) + } else { + err = c.send(ctx, op, msgs) + } + + // Wait for all responses to come back. + for n := 0; n < len(b) && err == nil; n++ { + var resp *jsonrpcMessage + resp, err = op.wait(ctx, c) + if err != nil { + break + } + // Find the element corresponding to this response. + // The element is guaranteed to be present because dispatch + // only sends valid IDs to our channel. + var elem *BatchElem + for i := range msgs { + if bytes.Equal(msgs[i].ID, resp.ID) { + elem = &b[i] + break + } + } + if resp.Error != nil { + elem.Error = resp.Error + continue + } + if len(resp.Result) == 0 { + elem.Error = ErrNoResult + continue + } + elem.Error = json.Unmarshal(resp.Result, elem.Result) + } + return err +} + +// Notify sends a notification, i.e. a method call that doesn't expect a response. +func (c *Client) Notify(ctx context.Context, method string, args ...interface{}) error { + op := new(requestOp) + msg, err := c.newMessage(method, args...) + if err != nil { + return err + } + msg.ID = nil + + if c.isHTTP { + return c.sendHTTP(ctx, op, msg) + } else { + return c.send(ctx, op, msg) + } +} + +// EthSubscribe registers a subscripion under the "eth" namespace. +func (c *Client) EthSubscribe(ctx context.Context, channel interface{}, args ...interface{}) (*ClientSubscription, error) { + return c.Subscribe(ctx, "eth", channel, args...) +} + +// ShhSubscribe registers a subscripion under the "shh" namespace. +func (c *Client) ShhSubscribe(ctx context.Context, channel interface{}, args ...interface{}) (*ClientSubscription, error) { + return c.Subscribe(ctx, "shh", channel, args...) +} + +// Subscribe calls the "_subscribe" method with the given arguments, +// registering a subscription. Server notifications for the subscription are +// sent to the given channel. The element type of the channel must match the +// expected type of content returned by the subscription. +// +// The context argument cancels the RPC request that sets up the subscription but has no +// effect on the subscription after Subscribe has returned. +// +// Slow subscribers will be dropped eventually. Client buffers up to 20000 notifications +// before considering the subscriber dead. The subscription Err channel will receive +// ErrSubscriptionQueueOverflow. Use a sufficiently large buffer on the channel or ensure +// that the channel usually has at least one reader to prevent this issue. +func (c *Client) Subscribe(ctx context.Context, namespace string, channel interface{}, args ...interface{}) (*ClientSubscription, error) { + // Check type of channel first. + chanVal := reflect.ValueOf(channel) + if chanVal.Kind() != reflect.Chan || chanVal.Type().ChanDir()&reflect.SendDir == 0 { + panic("first argument to Subscribe must be a writable channel") + } + if chanVal.IsNil() { + panic("channel given to Subscribe must not be nil") + } + if c.isHTTP { + return nil, ErrNotificationsUnsupported + } + + msg, err := c.newMessage(namespace+subscribeMethodSuffix, args...) + if err != nil { + return nil, err + } + op := &requestOp{ + ids: []json.RawMessage{msg.ID}, + resp: make(chan *jsonrpcMessage), + sub: newClientSubscription(c, namespace, chanVal), + } + + // Send the subscription request. + // The arrival and validity of the response is signaled on sub.quit. + if err := c.send(ctx, op, msg); err != nil { + return nil, err + } + if _, err := op.wait(ctx, c); err != nil { + return nil, err + } + return op.sub, nil +} + +func (c *Client) newMessage(method string, paramsIn ...interface{}) (*jsonrpcMessage, error) { + msg := &jsonrpcMessage{Version: vsn, ID: c.nextID(), Method: method} + if paramsIn != nil { // prevent sending "params":null + var err error + if msg.Params, err = json.Marshal(paramsIn); err != nil { + return nil, err + } + } + return msg, nil +} + +// send registers op with the dispatch loop, then sends msg on the connection. +// if sending fails, op is deregistered. +func (c *Client) send(ctx context.Context, op *requestOp, msg interface{}) error { + select { + case c.reqInit <- op: + err := c.write(ctx, msg) + c.reqSent <- err + return err + case <-ctx.Done(): + // This can happen if the client is overloaded or unable to keep up with + // subscription notifications. + return ctx.Err() + case <-c.closing: + return ErrClientQuit + } +} + +func (c *Client) write(ctx context.Context, msg interface{}) error { + // The previous write failed. Try to establish a new connection. + if c.writeConn == nil { + if err := c.reconnect(ctx); err != nil { + return err + } + } + err := c.writeConn.Write(ctx, msg) + if err != nil { + c.writeConn = nil + } + return err +} + +func (c *Client) reconnect(ctx context.Context) error { + if c.reconnectFunc == nil { + return errDead + } + + if _, ok := ctx.Deadline(); !ok { + var cancel func() + ctx, cancel = context.WithTimeout(ctx, defaultDialTimeout) + defer cancel() + } + newconn, err := c.reconnectFunc(ctx) + if err != nil { + log.Trace("RPC client reconnect failed", "err", err) + return err + } + select { + case c.reconnected <- newconn: + c.writeConn = newconn + return nil + case <-c.didClose: + newconn.Close() + return ErrClientQuit + } +} + +// dispatch is the main loop of the client. +// It sends read messages to waiting calls to Call and BatchCall +// and subscription notifications to registered subscriptions. +func (c *Client) dispatch(codec ServerCodec) { + var ( + lastOp *requestOp // tracks last send operation + reqInitLock = c.reqInit // nil while the send lock is held + conn = c.newClientConn(codec) + reading = true + ) + defer func() { + close(c.closing) + if reading { + conn.close(ErrClientQuit, nil) + c.drainRead() + } + close(c.didClose) + }() + + // Spawn the initial read loop. + go c.read(codec) + + for { + select { + case <-c.close: + return + + // Read path: + case op := <-c.readOp: + if op.batch { + conn.handler.handleBatch(op.msgs) + } else { + conn.handler.handleMsg(op.msgs[0]) + } + + case err := <-c.readErr: + conn.handler.log.Debug("RPC connection read error", "err", err) + conn.close(err, lastOp) + reading = false + + // Reconnect: + case newcodec := <-c.reconnected: + log.Debug("RPC client reconnected", "reading", reading, "conn", newcodec.RemoteAddr()) + if reading { + // Wait for the previous read loop to exit. This is a rare case which + // happens if this loop isn't notified in time after the connection breaks. + // In those cases the caller will notice first and reconnect. Closing the + // handler terminates all waiting requests (closing op.resp) except for + // lastOp, which will be transferred to the new handler. + conn.close(errClientReconnected, lastOp) + c.drainRead() + } + go c.read(newcodec) + reading = true + conn = c.newClientConn(newcodec) + // Re-register the in-flight request on the new handler + // because that's where it will be sent. + conn.handler.addRequestOp(lastOp) + + // Send path: + case op := <-reqInitLock: + // Stop listening for further requests until the current one has been sent. + reqInitLock = nil + lastOp = op + conn.handler.addRequestOp(op) + + case err := <-c.reqSent: + if err != nil { + // Remove response handlers for the last send. When the read loop + // goes down, it will signal all other current operations. + conn.handler.removeRequestOp(lastOp) + } + // Let the next request in. + reqInitLock = c.reqInit + lastOp = nil + + case op := <-c.reqTimeout: + conn.handler.removeRequestOp(op) + } + } +} + +// drainRead drops read messages until an error occurs. +func (c *Client) drainRead() { + for { + select { + case <-c.readOp: + case <-c.readErr: + return + } + } +} + +// read decodes RPC messages from a codec, feeding them into dispatch. +func (c *Client) read(codec ServerCodec) { + for { + msgs, batch, err := codec.Read() + if _, ok := err.(*json.SyntaxError); ok { + codec.Write(context.Background(), errorMessage(&parseError{err.Error()})) + } + if err != nil { + c.readErr <- err + return + } + c.readOp <- readOp{msgs, batch} + } +} -- cgit v1.2.3