/**
* Iterate through shards attempting to extract itemsToPeek items. Will return once itemToPeek
* items have been read or all shards have been checked.
*
* <p>Note that this call does not take into account the message trigger time and will likely
* return messages that aren't due to be executed yet.
*
* @return List of items
*/
@Override
public List<Message> peekMessages(int itemsToPeek) throws MessageQueueException {
List<Message> messages = Lists.newArrayList();
for (MessageQueueShard shard : shardReaderPolicy.listShards()) {
messages.addAll(peekMessages(shard.getName(), itemsToPeek - messages.size()));
if (messages.size() == itemsToPeek) return messages;
}
return messages;
}
@Override
public void clearMessages() throws MessageQueueException {
LOG.info("Clearing messages from '" + getName() + "'");
MutationBatch mb = keyspace.prepareMutationBatch().setConsistencyLevel(consistencyLevel);
for (MessageQueueShard partition : shardReaderPolicy.listShards()) {
mb.withRow(queueColumnFamily, partition.getName()).delete();
}
try {
mb.execute();
} catch (ConnectionException e) {
throw new MessageQueueException("Failed to clear messages from queue " + getName(), e);
}
}
private List<MessageContext> readAndReturnShard(MessageQueueShard shard, int itemsToPop)
throws MessageQueueException, BusyLockException, InterruptedException {
List<MessageContext> messages = null;
try {
messages = readMessagesFromShard(shard.getName(), itemsToPop);
} finally {
if (messages == null || messages.isEmpty()) {
queue.stats.incEmptyPartitionCount();
}
}
return messages;
}
