keith-turner commented on a change in pull request #2329:
URL: https://github.com/apache/accumulo/pull/2329#discussion_r740290834
##########
File path:
core/src/main/java/org/apache/accumulo/fate/zookeeper/DistributedReadWriteLock.java
##########
@@ -218,22 +237,54 @@ public boolean tryLock() {
}
SortedMap<Long,byte[]> entries = qlock.getEarlierEntries(entry);
Iterator<Entry<Long,byte[]>> iterator = entries.entrySet().iterator();
- if (!iterator.hasNext())
+ if (!iterator.hasNext()) {
throw new IllegalStateException("Did not find our own lock in the
queue: " + this.entry
+ " userData " + new String(this.userData, UTF_8) + " lockType " +
lockType());
- return iterator.next().getKey().equals(entry);
+ }
+ if (!failBlockers) {
+ return iterator.next().getKey().equals(entry);
+ } else {
+ ZooStore<DistributedReadWriteLock> zs;
+ try {
+ zs = new ZooStore<>(zooPath, zrw);
+ } catch (KeeperException | InterruptedException e1) {
+ log.error("Error creating zoo store", e1);
+ return false;
+ }
+ final AdminUtil<DistributedReadWriteLock> util = new AdminUtil<>();
+ boolean result = true;
+ while (iterator.hasNext()) {
+ Entry<Long,byte[]> e = iterator.next();
+ if (!e.getKey().equals(entry)) {
+ result &= util.prepFail(zs, zrw, zooManagerPath,
Long.toString(e.getKey(), 16));
Review comment:
A fourth issue to consider is deadlock around the reserve() calls, which
I think may not happen but I am not completely sure. Calls to tryLock are made
by FATE ops that have already reserved a txid. Assume FATE op txidA is
reserved and it runs and calls tryLock which attempts to reserve tixdB. If
txidB is reserved and it calls tryLock trying to reserved txidA that leads to
deadlock. I think this change to tryLock will only attempt to reserve
transactions that started earlier than itself which seems like it would avoid
deadlock. Because if A started before B, then B would attempt to reserve A but
A would never attempt to reserve B because it started after.
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