435c0d9fc8
This PR switches the Nomad repository from using govendor to Go modules for managing dependencies. Aspects of the Nomad workflow remain pretty much the same. The usual Makefile targets should continue to work as they always did. The API submodule simply defers to the parent Nomad version on the repository, keeping the semantics of API versioning that currently exists.
62 lines
1.6 KiB
Go
62 lines
1.6 KiB
Go
// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Adapted for dns package usage by Miek Gieben.
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package dns
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import "sync"
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import "time"
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// call is an in-flight or completed singleflight.Do call
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type call struct {
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wg sync.WaitGroup
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val *Msg
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rtt time.Duration
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err error
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dups int
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}
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// singleflight represents a class of work and forms a namespace in
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// which units of work can be executed with duplicate suppression.
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type singleflight struct {
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sync.Mutex // protects m
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m map[string]*call // lazily initialized
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dontDeleteForTesting bool // this is only to be used by TestConcurrentExchanges
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}
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// Do executes and returns the results of the given function, making
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// sure that only one execution is in-flight for a given key at a
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// time. If a duplicate comes in, the duplicate caller waits for the
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// original to complete and receives the same results.
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// The return value shared indicates whether v was given to multiple callers.
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func (g *singleflight) Do(key string, fn func() (*Msg, time.Duration, error)) (v *Msg, rtt time.Duration, err error, shared bool) {
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g.Lock()
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if g.m == nil {
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g.m = make(map[string]*call)
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}
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if c, ok := g.m[key]; ok {
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c.dups++
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g.Unlock()
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c.wg.Wait()
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return c.val, c.rtt, c.err, true
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}
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c := new(call)
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c.wg.Add(1)
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g.m[key] = c
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g.Unlock()
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c.val, c.rtt, c.err = fn()
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c.wg.Done()
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if !g.dontDeleteForTesting {
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g.Lock()
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delete(g.m, key)
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g.Unlock()
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}
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return c.val, c.rtt, c.err, c.dups > 0
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}
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