keith-turner commented on code in PR #4524:
URL: https://github.com/apache/accumulo/pull/4524#discussion_r1672888980
##########
core/src/main/java/org/apache/accumulo/core/fate/user/UserFateStore.java:
##########
@@ -151,6 +157,95 @@ protected void create(FateId fateId, FateKey fateKey) {
+ " and fateKey " + fateKey + " after " + maxAttempts + " attempts");
}
+ @Override
+ public Optional<FateTxStore<T>> tryReserve(FateId fateId) {
+ // Create a unique FateReservation for this reservation attempt
+ FateReservation reservation = FateReservation.from(lockID,
UUID.randomUUID());
+
+ FateMutator.Status status =
newMutator(fateId).putReservedTx(reservation).tryMutate();
+ if (status.equals(FateMutator.Status.ACCEPTED)) {
+ return Optional.of(new FateTxStoreImpl(fateId, reservation));
+ } else if (status.equals(FateMutator.Status.UNKNOWN)) {
+ // If the status is UNKNOWN, this means an error occurred after the
mutation was
+ // sent to the TabletServer, and it is unknown if the mutation was
written. We
+ // need to check if the mutation was written and if it was written by
this
+ // attempt at reservation. If it was written by this reservation attempt,
+ // we can return the FateTxStore since it was successfully reserved in
this
+ // attempt, otherwise we return empty (was written by another reservation
+ // attempt or was not written at all).
+ try (Scanner scanner = context.createScanner(tableName,
Authorizations.EMPTY)) {
+ scanner.setRange(getRow(fateId));
+
scanner.fetchColumn(TxColumnFamily.RESERVATION_COLUMN.getColumnFamily(),
+ TxColumnFamily.RESERVATION_COLUMN.getColumnQualifier());
+ FateReservation persistedRes = scanner.stream()
+ .filter(entry ->
FateReservation.isFateReservation(entry.getValue().toString()))
+ .map(entry ->
FateReservation.from(entry.getValue().toString())).findFirst()
Review Comment:
If the reservation parsing code is not really strict and the code writing
reservations has a bug, then could end with the case were reservation is
silently ignored because it did not have the correct format. Would be better
to fail rather than ignore things that are not recognized. Some of the code
seems to have the following pattern
```java
f(value look like <lock id>:<uuid) {
// process reserved
} else {
// assume not reserved, but could have been an incorrectly written
reservation
}
```
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