Use buffered channels for close notify signaling (awslabs#78)

jslang · web-flow · commit f66f79a32a0f · 2020-09-29T13:06:14.000-07:00
Using unbuffered channels results in potential blocks during `notifyClosed` if calling code fails or is otherwise unable to receive on the returned channel. In particular this fixes an issue where calling code was awaiting either notify close or context done. When context done happened first this caused the notifyClose call to hang, causing an api gateway timeout.
diff --git a/core/response.go b/core/response.go
@@ -37,7 +37,7 @@ func NewProxyResponseWriter() *ProxyResponseWriter {
 }
 
 func (r *ProxyResponseWriter) CloseNotify() <-chan bool {
-	ch := make(chan bool)
+	ch := make(chan bool, 1)
 
 	r.observers = append(r.observers, ch)
 

Original file line number	Diff line number	Diff line change
`@@ -37,7 +37,7 @@ func NewProxyResponseWriter() *ProxyResponseWriter {`
`37`	`37`	`}`
`38`	`38`
`39`	`39`	`func (r *ProxyResponseWriter) CloseNotify() <-chan bool {`
`40`		`- ch := make(chan bool)`
	`40`	`+ ch := make(chan bool, 1)`
`41`	`41`
`42`	`42`	`r.observers = append(r.observers, ch)`
`43`	`43`