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conn.go
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conn.go
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// Copyright (c) 2018 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package client
import (
"errors"
"math/rand"
"net"
"sync"
"time"
"github.com/m3db/m3/src/x/clock"
xio "github.com/m3db/m3/src/x/io"
"github.com/m3db/m3/src/x/retry"
"github.com/uber-go/tally"
)
const (
tcpProtocol = "tcp"
)
var (
errNoActiveConnection = errors.New("no active connection")
errInvalidConnection = errors.New("connection is invalid")
uninitWriter uninitializedWriter
)
type sleepFn func(time.Duration)
type connectWithLockFn func() error
type writeWithLockFn func([]byte) error
// connection is a persistent connection that retries establishing
// connection with exponential backoff if the connection goes down.
type connection struct {
sync.Mutex
addr string
connTimeout time.Duration
writeTimeout time.Duration
keepAlive bool
initThreshold int
multiplier int
maxThreshold int
maxDuration time.Duration
writeRetryOpts retry.Options
rngFn retry.RngFn
conn *net.TCPConn
writer xio.ResettableWriter
numFailures int
threshold int
lastConnectAttemptNanos int64
metrics connectionMetrics
// These are for testing purposes.
nowFn clock.NowFn
sleepFn sleepFn
connectWithLockFn connectWithLockFn
writeWithLockFn writeWithLockFn
}
// newConnection creates a new connection.
func newConnection(addr string, opts ConnectionOptions) *connection {
c := &connection{
addr: addr,
connTimeout: opts.ConnectionTimeout(),
writeTimeout: opts.WriteTimeout(),
keepAlive: opts.ConnectionKeepAlive(),
initThreshold: opts.InitReconnectThreshold(),
multiplier: opts.ReconnectThresholdMultiplier(),
maxThreshold: opts.MaxReconnectThreshold(),
maxDuration: opts.MaxReconnectDuration(),
writeRetryOpts: opts.WriteRetryOptions(),
rngFn: rand.New(rand.NewSource(time.Now().UnixNano())).Int63n,
nowFn: opts.ClockOptions().NowFn(),
sleepFn: time.Sleep,
threshold: opts.InitReconnectThreshold(),
writer: opts.RWOptions().ResettableWriterFn()(
uninitWriter,
xio.ResettableWriterOptions{WriteBufferSize: 0},
),
metrics: newConnectionMetrics(opts.InstrumentOptions().MetricsScope()),
}
c.connectWithLockFn = c.connectWithLock
c.writeWithLockFn = c.writeWithLock
c.Lock()
if err := c.connectWithLockFn(); err != nil {
c.numFailures++
}
c.Unlock()
return c
}
// Write sends data onto the connection, and attempts to re-establish
// connection if the connection is down.
func (c *connection) Write(data []byte) error {
var err error
c.Lock()
if c.conn == nil {
if err = c.checkReconnectWithLock(); err != nil {
c.numFailures++
c.Unlock()
return err
}
}
if err = c.writeAttemptWithLock(data); err == nil {
c.Unlock()
return nil
}
for i := 1; i <= c.writeRetryOpts.MaxRetries(); i++ {
if backoffDur := time.Duration(retry.BackoffNanos(
i,
c.writeRetryOpts.Jitter(),
c.writeRetryOpts.BackoffFactor(),
c.writeRetryOpts.InitialBackoff(),
c.writeRetryOpts.MaxBackoff(),
c.rngFn,
)); backoffDur > 0 {
c.sleepFn(backoffDur)
}
c.metrics.writeRetries.Inc(1)
if err = c.writeAttemptWithLock(data); err == nil {
c.Unlock()
return nil
}
}
c.numFailures++
c.Unlock()
return err
}
func (c *connection) Close() {
c.Lock()
c.closeWithLock()
c.Unlock()
}
// writeAttemptWithLock attempts to establish a new connection and writes raw bytes
// to the connection while holding the write lock.
// If the write succeeds, c.conn is guaranteed to be a valid connection on return.
// If the write fails, c.conn is guaranteed to be nil on return.
func (c *connection) writeAttemptWithLock(data []byte) error {
if c.conn == nil {
if err := c.connectWithLockFn(); err != nil {
return err
}
}
if err := c.writeWithLockFn(data); err != nil {
c.closeWithLock()
return err
}
return nil
}
func (c *connection) connectWithLock() error {
c.lastConnectAttemptNanos = c.nowFn().UnixNano()
conn, err := net.DialTimeout(tcpProtocol, c.addr, c.connTimeout)
if err != nil {
c.metrics.connectError.Inc(1)
return err
}
tcpConn := conn.(*net.TCPConn)
if err := tcpConn.SetKeepAlive(c.keepAlive); err != nil {
c.metrics.setKeepAliveError.Inc(1)
}
if c.conn != nil {
c.conn.Close() // nolint: errcheck
}
c.conn = tcpConn
c.writer.Reset(tcpConn)
return nil
}
func (c *connection) checkReconnectWithLock() error {
// If we haven't accumulated enough failures to warrant another reconnect
// and we haven't past the maximum duration since the last time we attempted
// to connect then we simply return false without reconnecting.
tooManyFailures := c.numFailures >= c.threshold
sufficientTimePassed := c.nowFn().UnixNano()-c.lastConnectAttemptNanos >= c.maxDuration.Nanoseconds()
if !tooManyFailures && !sufficientTimePassed {
return errNoActiveConnection
}
err := c.connectWithLockFn()
if err == nil {
c.resetWithLock()
return nil
}
// Only raise the threshold when it is crossed, not when the max duration is reached.
if tooManyFailures && c.threshold < c.maxThreshold {
newThreshold := c.threshold * c.multiplier
if newThreshold > c.maxThreshold {
newThreshold = c.maxThreshold
}
c.threshold = newThreshold
}
return err
}
func (c *connection) writeWithLock(data []byte) error {
if err := c.conn.SetWriteDeadline(c.nowFn().Add(c.writeTimeout)); err != nil {
c.metrics.setWriteDeadlineError.Inc(1)
}
if _, err := c.writer.Write(data); err != nil {
c.metrics.writeError.Inc(1)
return err
}
if err := c.writer.Flush(); err != nil {
c.metrics.writeError.Inc(1)
return err
}
return nil
}
func (c *connection) resetWithLock() {
c.numFailures = 0
c.threshold = c.initThreshold
}
func (c *connection) closeWithLock() {
if c.conn != nil {
c.conn.Close() // nolint: errcheck
}
c.conn = nil
}
const (
errorMetric = "errors"
errorMetricType = "error-type"
)
type connectionMetrics struct {
connectError tally.Counter
writeError tally.Counter
writeRetries tally.Counter
setKeepAliveError tally.Counter
setWriteDeadlineError tally.Counter
}
func newConnectionMetrics(scope tally.Scope) connectionMetrics {
return connectionMetrics{
connectError: scope.Tagged(map[string]string{errorMetricType: "connect"}).
Counter(errorMetric),
writeError: scope.Tagged(map[string]string{errorMetricType: "write"}).
Counter(errorMetric),
writeRetries: scope.Tagged(map[string]string{"action": "write"}).Counter("retries"),
setKeepAliveError: scope.Tagged(map[string]string{errorMetricType: "tcp-keep-alive"}).
Counter(errorMetric),
setWriteDeadlineError: scope.Tagged(map[string]string{errorMetricType: "set-write-deadline"}).
Counter(errorMetric),
}
}
type uninitializedWriter struct{}
func (u uninitializedWriter) Write(p []byte) (int, error) { return 0, errInvalidConnection }
func (u uninitializedWriter) Close() error { return nil }