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package rpcclient
import (
"context"
"encoding/json"
"fmt"
"math/rand"
"net"
"net/http"
"sync"
"time"
"github.com/gorilla/websocket"
"github.com/pkg/errors"
metrics "github.com/rcrowley/go-metrics"
types "github.com/tendermint/tendermint/rpc/lib/types"
cmn "github.com/tendermint/tmlibs/common"
)
const (
defaultMaxReconnectAttempts = 25
defaultWriteWait = 0
defaultReadWait = 0
defaultPingPeriod = 0
)
// WSClient is a WebSocket client. The methods of WSClient are safe for use by
// multiple goroutines.
type WSClient struct {
cmn.BaseService
conn *websocket.Conn
Address string // IP:PORT or /path/to/socket
Endpoint string // /websocket/url/endpoint
Dialer func(string, string) (net.Conn, error)
// Time between sending a ping and receiving a pong. See
// https://godoc.org/github.com/rcrowley/go-metrics#Timer.
PingPongLatencyTimer metrics.Timer
// Single user facing channel to read RPCResponses from, closed only when the client is being stopped.
ResponsesCh chan types.RPCResponse
// Callback, which will be called each time after successful reconnect.
onReconnect func()
// internal channels
send chan types.RPCRequest // user requests
backlog chan types.RPCRequest // stores a single user request received during a conn failure
reconnectAfter chan error // reconnect requests
readRoutineQuit chan struct{} // a way for readRoutine to close writeRoutine
wg sync.WaitGroup
mtx sync.RWMutex
sentLastPingAt time.Time
reconnecting bool
// Maximum reconnect attempts (0 or greater; default: 25).
maxReconnectAttempts int
// Time allowed to write a message to the server. 0 means block until operation succeeds.
writeWait time.Duration
// Time allowed to read the next message from the server. 0 means block until operation succeeds.
readWait time.Duration
// Send pings to server with this period. Must be less than readWait. If 0, no pings will be sent.
pingPeriod time.Duration
}
// NewWSClient returns a new client. See the commentary on the func(*WSClient)
// functions for a detailed description of how to configure ping period and
// pong wait time. The endpoint argument must begin with a `/`.
func NewWSClient(remoteAddr, endpoint string, options ...func(*WSClient)) *WSClient {
addr, dialer := makeHTTPDialer(remoteAddr)
c := &WSClient{
Address: addr,
Dialer: dialer,
Endpoint: endpoint,
PingPongLatencyTimer: metrics.NewTimer(),
maxReconnectAttempts: defaultMaxReconnectAttempts,
readWait: defaultReadWait,
writeWait: defaultWriteWait,
pingPeriod: defaultPingPeriod,
}
c.BaseService = *cmn.NewBaseService(nil, "WSClient", c)
for _, option := range options {
option(c)
}
return c
}
// MaxReconnectAttempts sets the maximum number of reconnect attempts before returning an error.
// It should only be used in the constructor and is not Goroutine-safe.
func MaxReconnectAttempts(max int) func(*WSClient) {
return func(c *WSClient) {
c.maxReconnectAttempts = max
}
}
// ReadWait sets the amount of time to wait before a websocket read times out.
// It should only be used in the constructor and is not Goroutine-safe.
func ReadWait(readWait time.Duration) func(*WSClient) {
return func(c *WSClient) {
c.readWait = readWait
}
}
// WriteWait sets the amount of time to wait before a websocket write times out.
// It should only be used in the constructor and is not Goroutine-safe.
func WriteWait(writeWait time.Duration) func(*WSClient) {
return func(c *WSClient) {
c.writeWait = writeWait
}
}
// PingPeriod sets the duration for sending websocket pings.
// It should only be used in the constructor - not Goroutine-safe.
func PingPeriod(pingPeriod time.Duration) func(*WSClient) {
return func(c *WSClient) {
c.pingPeriod = pingPeriod
}
}
// OnReconnect sets the callback, which will be called every time after
// successful reconnect.
func OnReconnect(cb func()) func(*WSClient) {
return func(c *WSClient) {
c.onReconnect = cb
}
}
// String returns WS client full address.
func (c *WSClient) String() string {
return fmt.Sprintf("%s (%s)", c.Address, c.Endpoint)
}
// OnStart implements cmn.Service by dialing a server and creating read and
// write routines.
func (c *WSClient) OnStart() error {
err := c.dial()
if err != nil {
return err
}
c.ResponsesCh = make(chan types.RPCResponse)
c.send = make(chan types.RPCRequest)
// 1 additional error may come from the read/write
// goroutine depending on which failed first.
c.reconnectAfter = make(chan error, 1)
// capacity for 1 request. a user won't be able to send more because the send
// channel is unbuffered.
c.backlog = make(chan types.RPCRequest, 1)
c.startReadWriteRoutines()
go c.reconnectRoutine()
return nil
}
// OnStop implements cmn.Service.
func (c *WSClient) OnStop() {}
// Stop overrides cmn.Service#Stop. There is no other way to wait until Quit
// channel is closed.
func (c *WSClient) Stop() error {
if err := c.BaseService.Stop(); err != nil {
return err
}
// only close user-facing channels when we can't write to them
c.wg.Wait()
close(c.ResponsesCh)
return nil
}
// IsReconnecting returns true if the client is reconnecting right now.
func (c *WSClient) IsReconnecting() bool {
c.mtx.RLock()
defer c.mtx.RUnlock()
return c.reconnecting
}
// IsActive returns true if the client is running and not reconnecting.
func (c *WSClient) IsActive() bool {
return c.IsRunning() && !c.IsReconnecting()
}
// Send the given RPC request to the server. Results will be available on
// ResponsesCh, errors, if any, on ErrorsCh. Will block until send succeeds or
// ctx.Done is closed.
func (c *WSClient) Send(ctx context.Context, request types.RPCRequest) error {
select {
case c.send <- request:
c.Logger.Info("sent a request", "req", request)
return nil
case <-ctx.Done():
return ctx.Err()
}
}
// Call the given method. See Send description.
func (c *WSClient) Call(ctx context.Context, method string, params map[string]interface{}) error {
request, err := types.MapToRequest("ws-client", method, params)
if err != nil {
return err
}
return c.Send(ctx, request)
}
// CallWithArrayParams the given method with params in a form of array. See
// Send description.
func (c *WSClient) CallWithArrayParams(ctx context.Context, method string, params []interface{}) error {
request, err := types.ArrayToRequest("ws-client", method, params)
if err != nil {
return err
}
return c.Send(ctx, request)
}
///////////////////////////////////////////////////////////////////////////////
// Private methods
func (c *WSClient) dial() error {
dialer := &websocket.Dialer{
NetDial: c.Dialer,
Proxy: http.ProxyFromEnvironment,
}
rHeader := http.Header{}
conn, _, err := dialer.Dial("ws://"+c.Address+c.Endpoint, rHeader)
if err != nil {
return err
}
c.conn = conn
return nil
}
// reconnect tries to redial up to maxReconnectAttempts with exponential
// backoff.
func (c *WSClient) reconnect() error {
attempt := 0
c.mtx.Lock()
c.reconnecting = true
c.mtx.Unlock()
defer func() {
c.mtx.Lock()
c.reconnecting = false
c.mtx.Unlock()
}()
// 1s == (1e9 ns) == (1 Billion ns)
billionNs := float64(time.Second.Nanoseconds())
for {
jitterSeconds := time.Duration(rand.Float64() * billionNs)
backoffDuration := jitterSeconds + ((1 << uint(attempt)) * time.Second)
c.Logger.Info("reconnecting", "attempt", attempt+1, "backoff_duration", backoffDuration)
time.Sleep(backoffDuration)
err := c.dial()
if err != nil {
c.Logger.Error("failed to redial", "err", err)
} else {
c.Logger.Info("reconnected")
if c.onReconnect != nil {
go c.onReconnect()
}
return nil
}
attempt++
if attempt > c.maxReconnectAttempts {
return errors.Wrap(err, "reached maximum reconnect attempts")
}
}
}
func (c *WSClient) startReadWriteRoutines() {
c.wg.Add(2)
c.readRoutineQuit = make(chan struct{})
go c.readRoutine()
go c.writeRoutine()
}
func (c *WSClient) processBacklog() error {
select {
case request := <-c.backlog:
if c.writeWait > 0 {
if err := c.conn.SetWriteDeadline(time.Now().Add(c.writeWait)); err != nil {
c.Logger.Error("failed to set write deadline", "err", err)
}
}
if err := c.conn.WriteJSON(request); err != nil {
c.Logger.Error("failed to resend request", "err", err)
c.reconnectAfter <- err
// requeue request
c.backlog <- request
return err
}
c.Logger.Info("resend a request", "req", request)
default:
}
return nil
}
func (c *WSClient) reconnectRoutine() {
for {
select {
case originalError := <-c.reconnectAfter:
// wait until writeRoutine and readRoutine finish
c.wg.Wait()
if err := c.reconnect(); err != nil {
c.Logger.Error("failed to reconnect", "err", err, "original_err", originalError)
c.Stop()
return
} else {
// drain reconnectAfter
LOOP:
for {
select {
case <-c.reconnectAfter:
default:
break LOOP
}
}
err = c.processBacklog()
if err == nil {
c.startReadWriteRoutines()
}
}
case <-c.Quit():
return
}
}
}
// The client ensures that there is at most one writer to a connection by
// executing all writes from this goroutine.
func (c *WSClient) writeRoutine() {
var ticker *time.Ticker
if c.pingPeriod > 0 {
// ticker with a predefined period
ticker = time.NewTicker(c.pingPeriod)
} else {
// ticker that never fires
ticker = &time.Ticker{C: make(<-chan time.Time)}
}
defer func() {
ticker.Stop()
if err := c.conn.Close(); err != nil {
// ignore error; it will trigger in tests
// likely because it's closing an already closed connection
}
c.wg.Done()
}()
for {
select {
case request := <-c.send:
if c.writeWait > 0 {
if err := c.conn.SetWriteDeadline(time.Now().Add(c.writeWait)); err != nil {
c.Logger.Error("failed to set write deadline", "err", err)
}
}
if err := c.conn.WriteJSON(request); err != nil {
c.Logger.Error("failed to send request", "err", err)
c.reconnectAfter <- err
// add request to the backlog, so we don't lose it
c.backlog <- request
return
}
case <-ticker.C:
if c.writeWait > 0 {
if err := c.conn.SetWriteDeadline(time.Now().Add(c.writeWait)); err != nil {
c.Logger.Error("failed to set write deadline", "err", err)
}
}
if err := c.conn.WriteMessage(websocket.PingMessage, []byte{}); err != nil {
c.Logger.Error("failed to write ping", "err", err)
c.reconnectAfter <- err
return
}
c.mtx.Lock()
c.sentLastPingAt = time.Now()
c.mtx.Unlock()
c.Logger.Debug("sent ping")
case <-c.readRoutineQuit:
return
case <-c.Quit():
if err := c.conn.WriteMessage(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseNormalClosure, "")); err != nil {
c.Logger.Error("failed to write message", "err", err)
}
return
}
}
}
// The client ensures that there is at most one reader to a connection by
// executing all reads from this goroutine.
func (c *WSClient) readRoutine() {
defer func() {
if err := c.conn.Close(); err != nil {
// ignore error; it will trigger in tests
// likely because it's closing an already closed connection
}
c.wg.Done()
}()
c.conn.SetPongHandler(func(string) error {
// gather latency stats
c.mtx.RLock()
t := c.sentLastPingAt
c.mtx.RUnlock()
c.PingPongLatencyTimer.UpdateSince(t)
c.Logger.Debug("got pong")
return nil
})
for {
// reset deadline for every message type (control or data)
if c.readWait > 0 {
if err := c.conn.SetReadDeadline(time.Now().Add(c.readWait)); err != nil {
c.Logger.Error("failed to set read deadline", "err", err)
}
}
_, data, err := c.conn.ReadMessage()
if err != nil {
if !websocket.IsUnexpectedCloseError(err, websocket.CloseNormalClosure) {
return
}
c.Logger.Error("failed to read response", "err", err)
close(c.readRoutineQuit)
c.reconnectAfter <- err
return
}
var response types.RPCResponse
err = json.Unmarshal(data, &response)
if err != nil {
c.Logger.Error("failed to parse response", "err", err, "data", string(data))
continue
}
c.Logger.Info("got response", "resp", response.Result)
// Combine a non-blocking read on BaseService.Quit with a non-blocking write on ResponsesCh to avoid blocking
// c.wg.Wait() in c.Stop(). Note we rely on Quit being closed so that it sends unlimited Quit signals to stop
// both readRoutine and writeRoutine
select {
case <-c.Quit():
case c.ResponsesCh <- response:
}
}
}
///////////////////////////////////////////////////////////////////////////////
// Predefined methods
// Subscribe to a query. Note the server must have a "subscribe" route
// defined.
func (c *WSClient) Subscribe(ctx context.Context, query string) error {
params := map[string]interface{}{"query": query}
return c.Call(ctx, "subscribe", params)
}
// Unsubscribe from a query. Note the server must have a "unsubscribe" route
// defined.
func (c *WSClient) Unsubscribe(ctx context.Context, query string) error {
params := map[string]interface{}{"query": query}
return c.Call(ctx, "unsubscribe", params)
}
// UnsubscribeAll from all. Note the server must have a "unsubscribe_all" route
// defined.
func (c *WSClient) UnsubscribeAll(ctx context.Context) error {
params := map[string]interface{}{}
return c.Call(ctx, "unsubscribe_all", params)
}