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Fix connection leak caused by references from peer (#644)

The peer object maintains a slice of connections, and when a connection
is removed, we reslice, but this does not clear references to the
connection.

Fixes #643.
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prashantv committed Aug 8, 2017
1 parent 998073d commit 63a486b96821eaa6fb2299663dda5c529cc04666
Showing with 105 additions and 2 deletions.
  1. +98 −0 conn_leak_test.go
  2. +2 −2 peer.go
  3. +5 −0 utils_for_test.go
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@@ -0,0 +1,98 @@
// 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 tchannel_test
import (
"io/ioutil"
"runtime"
"testing"
"time"
. "github.com/uber/tchannel-go"
"github.com/uber/tchannel-go/testutils"
"github.com/stretchr/testify/require"
)
// This is a regression test for https://github.com/uber/tchannel-go/issues/643
// We want to ensure that once a connection is closed, there are no references
// to the closed connection, and the GC frees the connection.
// We use `runtime.SetFinalizer` to detect whether the GC has freed the object.
// However, finalizers cannot be set on objects with circular references,
// so we cannot set a finalizer on the connection, but instead set a finalizer
// on a field of the connection which has the same lifetime. The connection
// logger is unique per connection and does not have circular references
// so we can use the logger, but need a pointer for `runtime.SetFinalizer`.
// loggerPtr is a Logger implementation that uses a pointer unlike other
// TChannel loggers.
type loggerPtr struct {
Logger
}
func (l *loggerPtr) WithFields(fields ...LogField) Logger {
return &loggerPtr{l.Logger.WithFields(fields...)}
}
func TestPeerConnectionLeaks(t *testing.T) {
// Disable log verification since we want to set our own logger.
opts := testutils.NewOpts().NoRelay().DisableLogVerification()
opts.Logger = &loggerPtr{NullLogger}
connFinalized := make(chan struct{})
setFinalizer := func(p *Peer, hostPort string) {
ctx, cancel := NewContext(time.Second)
defer cancel()
conn, err := p.GetConnection(ctx)
require.NoError(t, err, "Failed to get connection")
runtime.SetFinalizer(conn.Logger(), func(interface{}) {
close(connFinalized)
})
}
testutils.WithTestServer(t, opts, func(ts *testutils.TestServer) {
s2Opts := testutils.NewOpts().SetServiceName("s2")
s2Opts.Logger = NewLogger(ioutil.Discard)
s2 := ts.NewServer(s2Opts)
// Set a finalizer to detect when the connection from s1 -> s2 is freed.
peer := ts.Server().Peers().GetOrAdd(s2.PeerInfo().HostPort)
setFinalizer(peer, s2.PeerInfo().HostPort)
// Close s2, so that the connection in s1 to s2 is released.
s2.Close()
closed := testutils.WaitFor(time.Second, s2.Closed)
require.True(t, closed, "s2 didn't close")
// Trigger the GC which will call the finalizer, and ensure
// that the connection logger was finalized.
finalized := testutils.WaitFor(time.Second, func() bool {
runtime.GC()
select {
case <-connFinalized:
return true
default:
return false
}
})
require.True(t, finalized, "Connection was not freed")
})
}
View
@@ -497,9 +497,9 @@ func (p *Peer) removeConnection(connsPtr *[]*Connection, changed *Connection) bo
conns := *connsPtr
for i, c := range conns {
if c == changed {
// Remove the connection by moving to the end and slicing the list.
// Remove the connection by moving the last item forward, and slicing the list.
last := len(conns) - 1
conns[i], conns[last] = conns[last], conns[i]
conns[i], conns[last] = conns[last], nil
*connsPtr = conns[:last]
return true
}
View
@@ -61,6 +61,11 @@ func (c *Connection) Ping(ctx context.Context) error {
return c.ping(ctx)
}
// Logger returns the logger for the specific connection.
func (c *Connection) Logger() Logger {
return c.log
}
// OutboundConnection returns the underlying connection for an outbound call.
func OutboundConnection(call *OutboundCall) (*Connection, net.Conn) {
conn := call.conn

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