d1f17fa7e0
Move all (almost all) Go files in middleware into their own packages. This makes for better naming and discoverability. Lot of changes elsewhere to make this change. The middleware.State was renamed to request.Request which is better, but still does not cover all use-cases. It was also moved out middleware because it is used by `dnsserver` as well. A pkg/dnsutil packages was added for shared, handy, dns util functions. All normalize functions are now put in normalize.go
64 lines
1.6 KiB
Go
64 lines
1.6 KiB
Go
/*
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Copyright 2012 Google Inc.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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// Package singleflight provides a duplicate function call suppression
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// mechanism.
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package singleflight
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import "sync"
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// call is an in-flight or completed Do call
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type call struct {
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wg sync.WaitGroup
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val interface{}
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err error
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}
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// Group represents a class of work and forms a namespace in which
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// units of work can be executed with duplicate suppression.
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type Group struct {
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mu sync.Mutex // protects m
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m map[string]*call // lazily initialized
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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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func (g *Group) Do(key string, fn func() (interface{}, error)) (interface{}, error) {
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g.mu.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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g.mu.Unlock()
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c.wg.Wait()
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return c.val, c.err
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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.mu.Unlock()
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c.val, c.err = fn()
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c.wg.Done()
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g.mu.Lock()
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delete(g.m, key)
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g.mu.Unlock()
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return c.val, c.err
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}
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