keith-turner commented on code in PR #4524:
URL: https://github.com/apache/accumulo/pull/4524#discussion_r1672878600
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core/src/main/java/org/apache/accumulo/core/fate/user/UserFateStore.java:
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@@ -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 going with the NOT_RESERVED value approach it would be good to make the
validation of the column value more strict, will make a comment about that
elsewhere.
Nevermind the code does not work exactly the way I thought it did. I was
thinking when reading reservations could do something like the following
```java
if(value look like <lock id>:<uuid) {
// process reserved
} else if (value is NOT_RESERVED) {
//process not reserved
} else {
throw new IllegalArgumentException("invalid reseved column value");
}
```
However the is not a place in the code that reads reservations in this way.
Was thinking the code should fail if the reserved column value was something
like '`1234` because it does not look like a reservation and it also does not
look like NOT_RESERVED
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