THRIFT-5240: Disable go server side connectivity check by default

Client: go

This is a follow up to 4db7a0a.

Due to the go runtime bug [1], the 1ms ticker used by this feature could
cause excessive cpu usage. So until the bug is fixed in go it's better
to leave this behavior disabled by default. The instructions in the
README file has been updated to how to enable this feature if needed.

[1] golang/go#27707

CHANGES.md

@@ -28,7 +28,7 @@
 - [THRIFT-5164](https://issues.apache.org/jira/browse/THRIFT-5164) - Add ClientMiddleware function type and WrapClient function to support wrapping a TClient with middleware functions.
 - [THRIFT-5164](https://issues.apache.org/jira/browse/THRIFT-5164) - Add ProcessorMiddleware function type and WrapProcessor function to support wrapping a TProcessor with middleware functions.
 - [THRIFT-5233](https://issues.apache.org/jira/browse/THRIFT-5233) - Add context deadline check to ReadMessageBegin in TBinaryProtocol, TCompactProtocol, and THeaderProtocol.
-- [THRIFT-5240](https://issues.apache.org/jira/browse/THRIFT-5240) - The context passed into server handler implementations will be canceled when we detected that the client closed the connection.
+- [THRIFT-5240](https://issues.apache.org/jira/browse/THRIFT-5240) - The context passed into server handler implementations will be canceled when we detected that the client closed the connection (This feature is disabled by default due to a go runtime bug. Check [go library README](lib/go/README.md) on more details and how to enable it.)
 
 ## 0.13.0
 

lib/go/README.md

@@ -85,12 +85,21 @@ which will generate:
 A note about server handler implementations
 ===========================================
 
-The context object passed into the server handler function will be canceled when
-the client closes the connection (this is a best effort check, not a guarantee
--- there's no guarantee that the context object is always canceled when client
-closes the connection, but when it's canceled you can always assume the client
-closed the connection). When implementing Go Thrift server, you can take
-advantage of that to abandon requests that's no longer needed:
+The thrift compiler compiled go code has the ability to check connectivity with
+a ticker and cancel the context object passed into the server handler function
+when it detects the client side closed the connection (this is a best effort
+check, not a guarantee -- there's no guarantee that the context object is always
+canceled when client closes the connection, but when it's canceled you can
+always assume the client closed the connection). By default this feature is
+disabled due to a Go runtime [bug](https://github.com/golang/go/issues/27707)
+that could cause excessive CPU usage. If you want to enable this feature, set
+the ticker interval to a positive value early in your main function:
+
+    // Enable server side connectivity check with 1ms ticker interval
+    thrift.ServerConnectivityCheckInterval = time.Millisecond
+
+After enabled it, when implementing Go Thrift server, you can take advantage of
+that to abandon requests that's no longer needed:
 
     func MyEndpoint(ctx context.Context, req *thriftRequestType) (*thriftResponseType, error) {
         ...
@@ -100,11 +109,4 @@ advantage of that to abandon requests that's no longer needed:
         ...
     }
 
-This feature would add roughly 1 millisecond of latency overhead to the server
-handlers (along with roughly 2 goroutines per request).
-If that is unacceptable, it can be disabled by having this line early in your
-main function:
-
-    thrift.ServerConnectivityCheckInterval = 0
-
-This feature is also only enabled on non-oneway endpoints.
+This feature is also only available on non-oneway endpoints.

lib/go/thrift/simple_server.go

@@ -45,8 +45,16 @@ var ErrAbandonRequest = errors.New("request abandoned")
 // It's defined as a variable instead of constant, so that thrift server
 // implementations can change its value to control the behavior.
 //
-// If it's changed to <=0, the feature will be disabled.
-var ServerConnectivityCheckInterval = time.Millisecond
+// The feature is disabled when it's <=0. Set it to a positive value early in
+// your main function to enable this feature, e.g.:
+//
+//     func main() {
+//       // Enable server connectivity check with 1ms interval ticker.
+//       thrift.ServerConnectivityCheckInterval = time.Millisecond
+//
+//       // ... other main function code
+//     }
+var ServerConnectivityCheckInterval time.Duration = 0
 
 /*
  * This is not a typical TSimpleServer as it is not blocked after accept a socket.