Add concurrency limit template.

templates/concurrencylimit

@@ -0,0 +1,46 @@
+{{ $decorator := (or .Vars.DecoratorName (printf "%sWithConcurrencyLimit" .Interface.Name)) }}
+
+import (
+ "time"
+)
+
+// {{$decorator}} implements {{.Interface.Type}}
+type {{$decorator}} struct {
+ _base {{.Interface.Type}}
+ _burst chan int
+}
+
+// New{{$decorator}} instruments an implementation of the {{.Interface.Type}} with concurrency limiting
+func New{{$decorator}}(base {{.Interface.Type}}, concurrentCalls int) *{{$decorator}} {
+ d := &{{$decorator}}{
+ _base: base,
+ _burst: make(chan int, concurrentCalls),
+ }
+
+ return d
+}
+
+{{range $method := .Interface.Methods}}
+ // {{$method.Name}} implements {{$.Interface.Type}}
+ func (_d *{{$decorator}}) {{$method.Declaration}} {
+
+ {{- if (and $method.AcceptsContext $method.ReturnsError)}}
+ select {
+ case <-ctx.Done():
+ err = ctx.Err()
+ return
+ case _d._burst<-1:
+ defer func() {
+ <-_d._burst
+ }()
+ }
+ {{else}}
+ _d._burst<-1
+ defer func() {
+ <-_d._burst
+ }()
+ {{end}}
+
+ {{ $method.Pass "_d._base." }}
+ }
+{{end}}