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utils.go
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/
utils.go
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package mysqlctl
import (
log "github.com/golang/glog"
)
type MapFunc func(index int) error
// ConcurrentMap applies fun in a concurrent manner on integers from 0
// to n-1 (they are assumed to be indexes of some slice containing
// items to be processed). The first error returned by a fun
// application will returned (subsequent errors will only be
// logged). It will use concurrency goroutines.
func ConcurrentMap(concurrency, n int, fun MapFunc) error {
errors := make(chan error)
work := make(chan int, n)
for i := 0; i < n; i++ {
work <- i
}
close(work)
for j := 0; j < concurrency; j++ {
go func() {
for i := range work {
errors <- fun(i)
}
}()
}
var err error
for i := 0; i < n; i++ {
if e := <-errors; e != nil {
if err != nil {
log.Errorf("multiple errors, this one happened but it won't be returned: %v", err)
}
err = e
}
}
return err
}