Fixed a case where received messages may not be released properly (#11)

Fixed a case where received messages may not be released properly if a lot of requests are timing out before their responses are received.

Author: connelly38

driver/src/main/java/oracle/nosql/driver/httpclient/HttpClient.java

@@ -7,6 +7,8 @@
 
 package oracle.nosql.driver.httpclient;
 
+import static oracle.nosql.driver.util.LogUtil.isFineEnabled;
+import static oracle.nosql.driver.util.LogUtil.logFine;
 import static oracle.nosql.driver.util.LogUtil.logInfo;
 import static oracle.nosql.driver.util.LogUtil.logWarning;
 
@@ -309,6 +311,18 @@ public Channel getChannel(int timeoutMs)
              * Ensure that the channel is in good shape
              */
             if (fut.isSuccess() && retChan.isActive()) {
+                /*
+                 * Clear out any previous state. The channel should not
+                 * have any state associated with it, but this code is here
+                 * just in case it does.
+                 */
+                if (retChan.attr(STATE_KEY).get() != null) {
+                    if (isFineEnabled(logger)) {
+                        logFine(logger, "HttpClient acquired a channel with " +
+                                "a still-active state: clearing.");
+                    }
+                    retChan.attr(STATE_KEY).set(null);
+                }
                 return retChan;
             }
             logInfo(logger,
@@ -319,6 +333,9 @@ public Channel getChannel(int timeoutMs)
     }
 
     public void releaseChannel(Channel channel) {
+        /* Clear any response handler state from channel before releasing it */
+        channel.attr(STATE_KEY).set(null);
+
         /*
          * If channel is not healthy/active it will be closed and removed
          * from the pool. Don't wait for completion.

driver/src/main/java/oracle/nosql/driver/httpclient/HttpClientHandler.java

@@ -7,6 +7,9 @@
 
 package oracle.nosql.driver.httpclient;
 
+import static oracle.nosql.driver.util.HttpConstants.REQUEST_ID_HEADER;
+import static oracle.nosql.driver.util.LogUtil.isFineEnabled;
+import static oracle.nosql.driver.util.LogUtil.logFine;
 import static oracle.nosql.driver.util.LogUtil.logWarning;
 
 import java.io.IOException;
@@ -43,6 +46,26 @@ public void channelRead(ChannelHandlerContext ctx, Object msg) {
 
         if (msg instanceof FullHttpResponse) {
             FullHttpResponse fhr = (FullHttpResponse) msg;
+
+            if (state == null) {
+                /*
+                 * This message came in after the client was done processing
+                 * a request in a different thread.
+                 * The client may have timed out waiting for this message.
+                 * Discard the message by releasing it and not calling receive().
+                 */
+                if (isFineEnabled(logger)) {
+                    String requestId = fhr.headers().get(REQUEST_ID_HEADER);
+                    if (requestId == null) {
+                        requestId = "(none)";
+                    }
+                    logFine(logger, "Discarding message with no response " +
+                                    "handler. requestId=" + requestId);
+                }
+                fhr.release();
+                return;
+            }
+
             state.setResponse(fhr);
 
             /*

driver/src/main/java/oracle/nosql/driver/httpclient/ResponseHandler.java

@@ -180,14 +180,24 @@ void receive(RequestState requestState) {
             String resReqId = requestState.getHeaders().get(REQUEST_ID_HEADER);
             if (resReqId == null || !resReqId.equals(requestId)) {
                 logFine(logger,
-                        "Discards unpaired response: expect for request " +
+                        "Discarding unpaired response: expect for request " +
                         requestId + ", but for request " + resReqId);
                 if (requestState.getResponse() != null) {
                     ReferenceCountUtil.release(requestState.getResponse());
                 }
                 return;
             }
         }
+
+        /*
+         * We got a valid message: don't accept any more for this handler.
+         * This logic may change if we enable full async and allow multiple
+         * messages to be processed by the same channel for the same client.
+         * This clears the response handler from this channel so that any
+         * additional messages on this channel will be properly discarded.
+         */
+        channel.attr(HttpClient.STATE_KEY).set(null);
+
         state = requestState;
         try {
             responseReceived(state.getStatus(),