keith-turner commented on a change in pull request #2293:
URL: https://github.com/apache/accumulo/pull/2293#discussion_r733213530
##########
File path:
server/gc/src/main/java/org/apache/accumulo/gc/GarbageCollectionAlgorithm.java
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@@ -217,11 +221,43 @@ private void confirmDeletes(GarbageCollectionEnvironment
gce,
throw new RuntimeException(
"Scanner over metadata table returned unexpected column : " +
entry.getKey());
}
+ Set<String> tableIdsAfter = gce.getTableIDs();
+ ensureAllTablesChecked(Collections.unmodifiableSet(tableIdsBefore),
+ Collections.unmodifiableSet(tableIdsSeen),
Collections.unmodifiableSet(tableIdsAfter));
confirmDeletesFromReplication(gce.getReplicationNeededIterator(),
candidateMap.entrySet().iterator());
}
+ @VisibleForTesting
+ /**
+ *
+ */
+ protected void ensureAllTablesChecked(Set<String> tableIdsBefore,
Set<String> tableIdsSeen,
+ Set<String> tableIdsAfter) {
+
+ // if a table was added or deleted during this run, it is acceptable to not
+ // have seen those tables ids when scanning the metadata table. So get the
intersection
+ Set<String> tableIdsMustHaveSeen = new HashSet<>(tableIdsBefore);
+ tableIdsMustHaveSeen.retainAll(tableIdsAfter);
+
+ if (tableIdsMustHaveSeen.isEmpty() && !tableIdsSeen.isEmpty()) {
+ // we saw no table ids in ZK but did in the metadata table. This is
unexpected.
Review comment:
> if all tables are deleted since the scan, then could this not be a
valid situation?
That could happen. This is a situation that could be caused by :
1. Tables being deleted and added concurrently w/ this code (going to or
from zero tables).
2. Something going wrong w/ ZK where it temporarily returns no tables ids,
even though there are tables ids.
This check is an attempt to defends against case 2 w/ the thinking that its
ok to ignore case 1 temporarily and let subsequent GC runs take care of things.
However I suppose the error message for the case 1 race condition could be
lead to false concerns.
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