kevinrr888 commented on code in PR #4524:
URL: https://github.com/apache/accumulo/pull/4524#discussion_r1700582782
##########
core/src/main/java/org/apache/accumulo/core/fate/MetaFateStore.java:
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@@ -104,19 +109,108 @@ public FateId create() {
}
@Override
- protected void create(FateId fateId, FateKey key) {
+ public Optional<FateTxStore<T>> createAndReserve(FateKey fateKey) {
+ final var reservation = FateReservation.from(lockID, UUID.randomUUID());
+ final var fateId = fateIdGenerator.fromTypeAndKey(type(), fateKey);
+
try {
- zk.putPersistentData(getTXPath(fateId), new NodeValue(TStatus.NEW,
key).serialize(),
- NodeExistsPolicy.FAIL);
- } catch (KeeperException | InterruptedException e) {
+ byte[] nodeVal = zk.mutateOrCreate(getTXPath(fateId),
+ new NodeValue(TStatus.NEW, reservation, fateKey).serialize(),
currSerNodeVal -> {
+ // We are only returning a non-null value for the following cases:
+ // 1) The existing NodeValue for fateId is exactly the same as the
value set for the
+ // node if it doesn't yet exist:
+ // TStatus = TStatus.NEW, FateReservation = reservation, FateKey =
fateKey
+ // This might occur if there was a ZK server fault and the same
write is running a 2nd
+ // time
+ // 2) The existing NodeValue for fateId has:
+ // TStatus = TStatus.NEW, no FateReservation present, FateKey =
fateKey
+ // The fateId is NEW/unseeded and not reserved, so we can allow it
to be reserved
+ NodeValue currNodeVal = new NodeValue(currSerNodeVal);
+ if (currNodeVal.status == TStatus.NEW &&
currNodeVal.isReservedBy(reservation)) {
+ verifyFateKey(fateId, currNodeVal.fateKey, fateKey);
+ return currSerNodeVal;
+ } else if (currNodeVal.status == TStatus.NEW &&
!currNodeVal.isReserved()) {
+ verifyFateKey(fateId, currNodeVal.fateKey, fateKey);
+ // NEW/unseeded transaction and not reserved, so we can allow it
to be reserved
+ return new NodeValue(TStatus.NEW, reservation,
fateKey).serialize();
+ } else {
+ log.trace(
+ "fate id {} tstatus {} fate key {} is reserved {} is either
currently reserved "
+ + "or has already been seeded with work (non-NEW
status), or both",
+ fateId, currNodeVal.status, currNodeVal.fateKey.orElse(null),
+ currNodeVal.isReserved());
+ // This will not change the value to null but will return null
+ return null;
+ }
+ });
+ if (nodeVal != null) {
+ return Optional.of(new FateTxStoreImpl(fateId, reservation));
+ } else {
+ return Optional.empty();
+ }
+ } catch (InterruptedException | KeeperException |
AcceptableThriftTableOperationException e) {
+ throw new IllegalStateException(e);
+ }
+ }
+
+ @Override
+ public Optional<FateTxStore<T>> tryReserve(FateId fateId) {
+ // uniquely identify this attempt to reserve the fate operation data
+ FateReservation reservation = FateReservation.from(lockID,
UUID.randomUUID());
+
+ try {
+ byte[] newSerNodeVal = zk.mutateExisting(getTXPath(fateId),
currSerNodeVal -> {
Review Comment:
Ah okay, I thought we would want to throw the exception in the case the node
doesn't exist. Changed and added check to
MultipleStoresIT.testReserveUnreserve(). I see now that the tryReserve() for
UFS and MFS were different for this case: UFS would return empty optional, MFS
would throw an error, so this change is good and keeps them consistent. I
remember noticing this difference a while ago when I was writing this, but must
have forgot to write down/ask which functionality is expected. Glad this was
spotted again.
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