Call finishConnect() before try to call read(...) / write(...) when u…

…sing NIO

Motivation:

The JDK implementation of SocketChannel has an internal state that is tracked for its operations. Because of this we need to ensure we call finishConnect() before try to call read(...) / write(...) as otherwise it may produce a NotYetConnectedException.

Modifications:

First process OP_CONNECT flag.

Result:

No more possibility of NotYetConnectedException because OP_CONNECT is handled not early enough when processing interestedOps for a Channel.

transport/src/main/java/io/netty/channel/nio/NioEventLoop.java

@@ -613,6 +613,18 @@ private void processSelectedKey(SelectionKey k, AbstractNioChannel ch) {
 
         try {
             int readyOps = k.readyOps();
+            // We first need to call finishConnect() before try to trigger a read(...) or write(...) as otherwise
+            // the NIO JDK channel implementation may throw a NotYetConnectedException.
+            if ((readyOps & SelectionKey.OP_CONNECT) != 0) {
+                // remove OP_CONNECT as otherwise Selector.select(..) will always return without blocking
+                // See https://github.com/netty/netty/issues/924
+                int ops = k.interestOps();
+                ops &= ~SelectionKey.OP_CONNECT;
+                k.interestOps(ops);
+
+                unsafe.finishConnect();
+            }
+
             // Also check for readOps of 0 to workaround possible JDK bug which may otherwise lead
             // to a spin loop
             if ((readyOps & (SelectionKey.OP_READ | SelectionKey.OP_ACCEPT)) != 0 || readyOps == 0) {
@@ -626,15 +638,6 @@ private void processSelectedKey(SelectionKey k, AbstractNioChannel ch) {
                 // Call forceFlush which will also take care of clear the OP_WRITE once there is nothing left to write
                 ch.unsafe().forceFlush();
             }
-            if ((readyOps & SelectionKey.OP_CONNECT) != 0) {
-                // remove OP_CONNECT as otherwise Selector.select(..) will always return without blocking
-                // See https://github.com/netty/netty/issues/924
-                int ops = k.interestOps();
-                ops &= ~SelectionKey.OP_CONNECT;
-                k.interestOps(ops);
-
-                unsafe.finishConnect();
-            }
         } catch (CancelledKeyException ignored) {
             unsafe.close(unsafe.voidPromise());
         }