open-consul/vendor/github.com/miekg/dns/singleinflight.go
Wim e3e56ff3c2 dns: fix memoryleak by upgrading outdated miekg/dns (#6748)
* Add updated github.com/miekg/dns to go modules
* Add updated github.com/miekg/dns to vendor
* Fix github.com/miekg/dns api breakage
* Decrease size when trimming UDP packets
Need more room for the header(?), if we don't decrease the size we get an
"overflow unpacking uint32" from the dns library
* Fix dns truncate tests with api changes
* Make windows build working again. Upgrade x/sys and x/crypto and vendor
This upgrade is needed because of API breakage in x/sys introduced
by the minimal x/sys dependency of miekg/dns

This API breakage has been fixed in commit
855e68c859
2019-12-16 22:31:27 +01:00

62 lines
1.6 KiB
Go

// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Adapted for dns package usage by Miek Gieben.
package dns
import "sync"
import "time"
// call is an in-flight or completed singleflight.Do call
type call struct {
wg sync.WaitGroup
val *Msg
rtt time.Duration
err error
dups int
}
// singleflight represents a class of work and forms a namespace in
// which units of work can be executed with duplicate suppression.
type singleflight struct {
sync.Mutex // protects m
m map[string]*call // lazily initialized
dontDeleteForTesting bool // this is only to be used by TestConcurrentExchanges
}
// Do executes and returns the results of the given function, making
// sure that only one execution is in-flight for a given key at a
// time. If a duplicate comes in, the duplicate caller waits for the
// original to complete and receives the same results.
// The return value shared indicates whether v was given to multiple callers.
func (g *singleflight) Do(key string, fn func() (*Msg, time.Duration, error)) (v *Msg, rtt time.Duration, err error, shared bool) {
g.Lock()
if g.m == nil {
g.m = make(map[string]*call)
}
if c, ok := g.m[key]; ok {
c.dups++
g.Unlock()
c.wg.Wait()
return c.val, c.rtt, c.err, true
}
c := new(call)
c.wg.Add(1)
g.m[key] = c
g.Unlock()
c.val, c.rtt, c.err = fn()
c.wg.Done()
if !g.dontDeleteForTesting {
g.Lock()
delete(g.m, key)
g.Unlock()
}
return c.val, c.rtt, c.err, c.dups > 0
}