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9eaf824398
* add jaeger support, link hot container & req span * adds jaeger support now with FN_JAEGER_URL, there's a simple tutorial in the operating/metrics.md file now and it's pretty easy to get up and running. * links a hot request span to a hot container span. when we change this to sample at a lower ratio we'll need to finagle the hot container span to always sample or something, otherwise we'll hide that info. at least, since we're sampling at 100% for now if this is flipped on, can see freeze/unfreeze etc. if they hit. this is useful for debugging. note that zipkin's exporter does not follow the link at all, hence jaeger... and they're backed by the Cloud Empire now (CNCF) so we'll probably use it anyway. * vendor: add thrift for jaeger
112 lines
2.8 KiB
Go
112 lines
2.8 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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// Package singleflight provides a duplicate function call suppression
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// mechanism.
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package singleflight // import "golang.org/x/sync/singleflight"
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import "sync"
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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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// These fields are written once before the WaitGroup is done
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// and are only read after the WaitGroup is done.
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val interface{}
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err error
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// These fields are read and written with the singleflight
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// mutex held before the WaitGroup is done, and are read but
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// not written after the WaitGroup is done.
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dups int
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chans []chan<- Result
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}
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// Group 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 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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// Result holds the results of Do, so they can be passed
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// on a channel.
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type Result struct {
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Val interface{}
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Err error
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Shared bool
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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 *Group) Do(key string, fn func() (interface{}, error)) (v interface{}, err error, shared bool) {
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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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c.dups++
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g.mu.Unlock()
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c.wg.Wait()
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return c.val, 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.mu.Unlock()
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g.doCall(c, key, fn)
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return c.val, c.err, c.dups > 0
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}
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// DoChan is like Do but returns a channel that will receive the
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// results when they are ready.
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func (g *Group) DoChan(key string, fn func() (interface{}, error)) <-chan Result {
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ch := make(chan Result, 1)
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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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c.dups++
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c.chans = append(c.chans, ch)
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g.mu.Unlock()
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return ch
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}
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c := &call{chans: []chan<- Result{ch}}
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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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go g.doCall(c, key, fn)
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return ch
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}
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// doCall handles the single call for a key.
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func (g *Group) doCall(c *call, key string, fn func() (interface{}, error)) {
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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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for _, ch := range c.chans {
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ch <- Result{c.val, c.err, c.dups > 0}
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}
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g.mu.Unlock()
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}
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// Forget tells the singleflight to forget about a key. Future calls
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// to Do for this key will call the function rather than waiting for
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// an earlier call to complete.
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func (g *Group) Forget(key string) {
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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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}
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