keith-turner commented on a change in pull request #2329:
URL: https://github.com/apache/accumulo/pull/2329#discussion_r750691497
##########
File path:
core/src/main/java/org/apache/accumulo/fate/zookeeper/DistributedReadWriteLock.java
##########
@@ -218,22 +228,52 @@ 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.debug("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));
+ store.cancel(priorTxid);
Review comment:
If its not currently reserved, could possibly reserved it and change the
state to FAILED_IN_PROGRESS.
```java
if(reserved)
interrupt()
else
changeToFailedInProgress()
```
##########
File path: core/src/main/java/org/apache/accumulo/fate/ZooStore.java
##########
@@ -529,4 +527,16 @@ public long timeCreated(long tid) {
return dops;
}
}
+
+ /**
+ * Attempt to cancel the reserved transaction by interrupting the Thread
that is running it
+ *
+ * @param tid
+ * transaction id
+ */
+ public void cancel(long tid) {
+ if (reserved.containsKey(tid)) {
Review comment:
synchronization is needed in this method.
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