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server.go
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server.go
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// Copyright (c) 2017 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 server implements a network server.
package server
import (
"net"
"sync"
"sync/atomic"
"time"
xnet "github.com/m3db/m3/src/x/net"
"github.com/m3db/m3/src/x/retry"
"github.com/uber-go/tally"
"go.uber.org/zap"
)
// Server is a server capable of listening to incoming traffic and closing itself
// when it's shut down.
type Server interface {
// ListenAndServe forever listens to new incoming connections and
// handles data from those connections.
ListenAndServe() error
// Serve accepts and handles incoming connections on the listener l forever.
Serve(l net.Listener) error
// Close closes the server.
Close()
}
// Handler can handle the data received on connection.
// It's used in Server once a connection was established.
type Handler interface {
// Handle handles the data received on the connection, this function
// should be blocking until the connection is closed or received error.
Handle(conn net.Conn)
// Close closes the handler.
Close()
}
type serverMetrics struct {
openConnections tally.Gauge
}
func newServerMetrics(scope tally.Scope) serverMetrics {
return serverMetrics{
openConnections: scope.Gauge("open-connections"),
}
}
type addConnectionFn func(conn net.Conn) bool
type removeConnectionFn func(conn net.Conn)
type server struct {
sync.Mutex
address string
listener net.Listener
log *zap.Logger
retryOpts retry.Options
reportInterval time.Duration
tcpConnectionKeepAlive bool
tcpConnectionKeepAlivePeriod time.Duration
closed bool
closedChan chan struct{}
numConns int32
conns []net.Conn
wgConns sync.WaitGroup
metrics serverMetrics
handler Handler
listenerOpts xnet.ListenerOptions
addConnectionFn addConnectionFn
removeConnectionFn removeConnectionFn
}
// NewServer creates a new server.
func NewServer(address string, handler Handler, opts Options) Server {
instrumentOpts := opts.InstrumentOptions()
scope := instrumentOpts.MetricsScope()
s := &server{
address: address,
log: instrumentOpts.Logger(),
retryOpts: opts.RetryOptions(),
reportInterval: instrumentOpts.ReportInterval(),
tcpConnectionKeepAlive: opts.TCPConnectionKeepAlive(),
tcpConnectionKeepAlivePeriod: opts.TCPConnectionKeepAlivePeriod(),
closedChan: make(chan struct{}),
metrics: newServerMetrics(scope),
handler: handler,
listenerOpts: opts.ListenerOptions(),
}
// Set up the connection functions.
s.addConnectionFn = s.addConnection
s.removeConnectionFn = s.removeConnection
// Start reporting metrics.
go s.reportMetrics()
return s
}
func (s *server) ListenAndServe() error {
listener, err := s.listenerOpts.Listen("tcp", s.address)
if err != nil {
return err
}
return s.Serve(listener)
}
func (s *server) Serve(l net.Listener) error {
s.address = l.Addr().String()
s.listener = l
go s.serve()
return nil
}
func (s *server) serve() {
connCh, errCh := xnet.StartForeverAcceptLoop(s.listener, s.retryOpts)
for conn := range connCh {
conn := conn
if tcpConn, ok := conn.(*net.TCPConn); ok {
tcpConn.SetKeepAlive(s.tcpConnectionKeepAlive)
if s.tcpConnectionKeepAlivePeriod != 0 {
tcpConn.SetKeepAlivePeriod(s.tcpConnectionKeepAlivePeriod)
}
}
if !s.addConnectionFn(conn) {
conn.Close()
} else {
s.wgConns.Add(1)
go func() {
s.handler.Handle(conn)
conn.Close()
s.removeConnectionFn(conn)
s.wgConns.Done()
}()
}
}
err := <-errCh
s.log.Error("server unexpectedly closed", zap.Error(err))
}
func (s *server) Close() {
s.Lock()
if s.closed {
s.Unlock()
return
}
s.closed = true
close(s.closedChan)
openConns := make([]net.Conn, len(s.conns))
copy(openConns, s.conns)
s.Unlock()
// Close all open connections.
for _, conn := range openConns {
conn.Close()
}
// Close the listener.
if s.listener != nil {
s.listener.Close()
}
// Wait for all connection handlers to finish.
s.wgConns.Wait()
// Close the handler.
s.handler.Close()
}
func (s *server) addConnection(conn net.Conn) bool {
s.Lock()
defer s.Unlock()
if s.closed {
return false
}
s.conns = append(s.conns, conn)
atomic.AddInt32(&s.numConns, 1)
return true
}
func (s *server) removeConnection(conn net.Conn) {
s.Lock()
defer s.Unlock()
numConns := len(s.conns)
for i := 0; i < numConns; i++ {
if s.conns[i] == conn {
// Move the last connection to i and reduce the number of connections by 1.
s.conns[i] = s.conns[numConns-1]
s.conns = s.conns[:numConns-1]
atomic.AddInt32(&s.numConns, -1)
return
}
}
}
func (s *server) reportMetrics() {
t := time.NewTicker(s.reportInterval)
for {
select {
case <-t.C:
s.metrics.openConnections.Update(float64(atomic.LoadInt32(&s.numConns)))
case <-s.closedChan:
t.Stop()
return
}
}
}