KAFKA-2779; Close SSL socket channel on remote connection close

Close socket channel in finally block to avoid file descriptor leak when remote end closes the connection

Author: Rajini Sivaram <[email protected]>

Reviewers: Ismael Juma <[email protected]>, Jun Rao <[email protected]>

Closes apache#460 from rajinisivaram/KAFKA-2779

clients/src/main/java/org/apache/kafka/common/network/SslTransportLayer.java

@@ -137,11 +137,9 @@ public boolean isConnected() {
 
     /**
     * Sends a SSL close message and closes socketChannel.
-    * @throws IOException if an I/O error occurs
-    * @throws IOException if there is data on the outgoing network buffer and we are unable to flush it
     */
     @Override
-    public void close() throws IOException {
+    public void close() {
         if (closing) return;
         closing = true;
         sslEngine.closeOutbound();
@@ -159,10 +157,15 @@ public void close() throws IOException {
             }
             netWriteBuffer.flip();
             flush(netWriteBuffer);
-            socketChannel.socket().close();
-            socketChannel.close();
         } catch (IOException ie) {
             log.warn("Failed to send SSL Close message ", ie);
+        } finally {
+            try {
+                socketChannel.socket().close();
+                socketChannel.close();
+            } catch (IOException e) {
+                log.warn("Failed to close SSL socket channel: " + e);
+            }
         }
         key.attach(null);
         key.cancel();