dlmarion commented on a change in pull request #2329:
URL: https://github.com/apache/accumulo/pull/2329#discussion_r753226264
##########
File path:
core/src/main/java/org/apache/accumulo/fate/zookeeper/DistributedReadWriteLock.java
##########
@@ -218,22 +229,63 @@ 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 (iterator.next().getKey().equals(entry)) {
+ return true;
+ }
+ if (preemptBlockingTransactions) {
+ log.info("Preempting transactions that are blocking this transaction");
+ // Loop through all of the prior transactions that are waiting to
+ // acquire this write lock. If the transaction has not succeeded or
failed,
+ // then fail it and return false from this method so that
Utils.reserveX()
+ // will call this method again and will re-check the prior
transactions.
+ iterator = entries.entrySet().iterator();
+ while (iterator.hasNext()) {
+ Entry<Long,byte[]> e = iterator.next();
+ Long priorEntry = e.getKey();
+ ParsedLock priorLock = new ParsedLock(e.getValue());
+ long priorTxid = Long.valueOf(new String(priorLock.getUserData(),
UTF_8), 16);
+ if (!priorEntry.equals(entry)) {
+ log.info("Attempting to preempt blocking tx: {}",
Long.toHexString(priorTxid));
+ // If the prior tx id is reserved, then it's running. We can't
reserve it and set its
+ // status, we have to interrupt the thread.
+ if (store.isReserved(priorTxid)) {
+ store.cancel(priorTxid);
+ } else {
+ try {
+ store.reserve(priorTxid);
+ store.setStatus(priorTxid, TStatus.FAILED_IN_PROGRESS);
+ } finally {
+ store.unreserve(priorTxid, 0);
+ }
+ }
Review comment:
Good feedback, I will implement these changes.
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