forked from iron-io/functions
/
singleflight.go
50 lines (41 loc) · 1.08 KB
/
singleflight.go
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package server
// Imported from https://github.com/golang/groupcache/blob/master/singleflight/singleflight.go
import (
"sync"
"github.com/iron-io/functions/api/models"
)
// call is an in-flight or completed do call
type call struct {
wg sync.WaitGroup
val interface{}
err error
}
type singleflight struct {
mu sync.Mutex // protects m
m map[models.RouteFilter]*call // lazily initialized
}
// 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.
func (g *singleflight) do(key models.RouteFilter, fn func() (interface{}, error)) (interface{}, error) {
g.mu.Lock()
if g.m == nil {
g.m = make(map[models.RouteFilter]*call)
}
if c, ok := g.m[key]; ok {
g.mu.Unlock()
c.wg.Wait()
return c.val, c.err
}
c := new(call)
c.wg.Add(1)
g.m[key] = c
g.mu.Unlock()
c.val, c.err = fn()
c.wg.Done()
g.mu.Lock()
delete(g.m, key)
g.mu.Unlock()
return c.val, c.err
}