johnyangk commented on a change in pull request #112: [NEMO-179] Delayed Task
Cloning
URL: https://github.com/apache/incubator-nemo/pull/112#discussion_r211816796
##########
File path:
runtime/master/src/main/java/edu/snu/nemo/runtime/master/BlockManagerMaster.java
##########
@@ -302,21 +297,36 @@ private BlockMetadata getBlockMetaData(final String
blockId) {
}
/**
- * Deals with a request for the location of a block.
- *
* @param message the request message.
* @param messageContext the message context which will be used for response.
*/
- void onRequestBlockLocation(final ControlMessage.Message message,
- final MessageContext messageContext) {
+ private void registerLocationRequest(final ControlMessage.Message message,
final MessageContext messageContext) {
assert (message.getType() ==
ControlMessage.MessageType.RequestBlockLocation);
final String blockIdWildcard =
message.getRequestBlockLocationMsg().getBlockIdWildcard();
final long requestId = message.getId();
final Lock readLock = lock.readLock();
readLock.lock();
try {
- final BlockRequestHandler locationFuture =
getBlockLocationHandler(blockIdWildcard);
- locationFuture.registerRequest(requestId, messageContext);
+ // (CASE 1) Check AVAILABLE blocks.
+ final List<BlockRequestHandler> availableBlocks =
getBlockHandlers(blockIdWildcard, BlockState.State.AVAILABLE);
+ if (!availableBlocks.isEmpty()) {
+ // random pick
+
availableBlocks.get(random.nextInt(availableBlocks.size())).registerRequest(requestId,
messageContext);
+ return;
+ }
+
+ // (CASE 2) Check IN_PROGRESS blocks.
+ final List<BlockRequestHandler> progressBlocks =
getBlockHandlers(blockIdWildcard, BlockState.State.IN_PROGRESS);
+ if (!progressBlocks.isEmpty()) {
+ // random pick
Review comment:
I prefer a random pick, as it is unknown which one of the IN_PROGRESS block
attempts will complete first. It may be that the first attempt is a straggler,
and the second attempt finishes faster.
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