Github user kevinxu021 commented on a diff in the pull request:
https://github.com/apache/incubator-trafodion/pull/1209#discussion_r136739857
--- Diff:
dcs/src/main/java/org/trafodion/dcs/master/listener/ListenerWorker.java ---
@@ -86,39 +86,43 @@ public void run() {
DataEvent dataEvent;
while(true) {
- // Wait for data to become available
- synchronized(queue) {
- while(queue.isEmpty()) {
- try {
- queue.wait();
- } catch (InterruptedException e) {
+ try {
+ // Wait for data to become available
+ synchronized(queue) {
+ while(queue.isEmpty()) {
+ try {
+ queue.wait();
+ } catch (InterruptedException e) {
+ }
}
+ dataEvent = queue.remove(0);
}
- dataEvent = queue.remove(0);
- }
- SelectionKey key = dataEvent.key;
- SocketChannel client = (SocketChannel) key.channel();
- Socket s = client.socket();
- ClientData clientData = (ClientData) key.attachment();
- ListenerService server = dataEvent.server;
- dataEvent.key = null;
- dataEvent.server = null;
-
- switch (clientData.hdr.getOperationId()){
- case ListenerConstants.DCS_MASTER_GETSRVRAVAILABLE:
- clientData =
requestGetObjectRef.processRequest(clientData, s);
- break;
- case ListenerConstants.DCS_MASTER_CANCELQUERY:
- clientData =
requestCancelQuery.processRequest(clientData, s);
- break;
- default:
- clientData = requestUnknown.processRequest(clientData,
s);
- break;
+ SelectionKey key = dataEvent.key;
+ SocketChannel client = (SocketChannel) key.channel();
+ Socket s = client.socket();
+ ClientData clientData = (ClientData) key.attachment();
+ ListenerService server = dataEvent.server;
+ dataEvent.key = null;
+ dataEvent.server = null;
+
+ switch (clientData.hdr.getOperationId()){
+ case ListenerConstants.DCS_MASTER_GETSRVRAVAILABLE:
+ clientData =
requestGetObjectRef.processRequest(clientData, s);
+ break;
+ case ListenerConstants.DCS_MASTER_CANCELQUERY:
+ clientData =
requestCancelQuery.processRequest(clientData, s);
+ break;
+ default:
+ clientData =
requestUnknown.processRequest(clientData, s);
+ break;
+ }
+ // Return to sender
+ int requestReply = clientData.requestReply;
+ key.attach(clientData);
+ server.send(new PendingRequest(key, requestReply));
+ } catch (Exception e){
+ LOG.error("Unexpected Exception", e);
--- End diff --
I would suggest to print 100 times instead of exiting. Because 100
NullPointExceptions belongs to 100 requests, that will not hang the rest of the
requests. it'll not impact each other. By the way, as you see, there are some
changes in a internal request catching Exception and return back to the client,
then the outer catch is for the exception out of the request. It doesn't have
so much code which rarely has chance for the exception out of control. if you
still worry about it, we can add a limitation for the number of the exceptions
in a reasonable time range.
OutOfMemoryError will lead to process exiting and client will get socket
timeout exception in 60s, at this time, DCSMaster will not hang.
Again, in the past, the request from client lead to the issue, as you see,
in the loop, there should be a different request for each round of loop. Unless
the client send the same request again and again, it should be a big problem.
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