Michael Semb Wever created CASSANDRA-21697:
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Summary: A table that fails to unload leaves the rest of the
keyspace loaded and its metrics registered
Key: CASSANDRA-21697
URL: https://issues.apache.org/jira/browse/CASSANDRA-21697
Project: Apache Cassandra
Issue Type: Bug
Components: Local/Other
Reporter: Michael Semb Wever
{{Keyspace.unload}} unloads the tables and then releases the keyspace metrics:
{code:java}
public void unload(boolean dropData)
{
for (ColumnFamilyStore cfs : getColumnFamilyStores())
unloadCf(cfs, dropData);
metric.release();
}
{code}
Neither step is guarded. {{unloadCf}} calls {{cfs.unloadCf()}}, which does a
blocking flush, and {{cfs.invalidate(true, dropData)}}, which shuts the
compaction strategy down, drops the sstables and invalidates the indexes. Any
of those can throw: a write error on the flush, an undeletable file in
{{LifecycleTransaction.waitForDeletions()}}, or a custom index whose invalidate
task fails.
One such failure aborts the loop. The tables after it keep their MBeans
registered and their compaction strategy running, and {{metric.release()}}
never runs. The keyspace gauges stay in the metrics registry holding a
reference to the dead {{Keyspace}} object.
{{CassandraMetricsRegistry.register}} returns the existing metric on a name
clash rather than replacing it, so a keyspace later created under the same name
reports the values of the dropped one, and the dropped {{Keyspace}} is never
collected.
The only caller is {{Schema.dropKeyspace}}, so an operator meets this on a
{{DROP KEYSPACE}} that hits a disk error, or on a keyspace that holds an index
whose invalidation fails.
The patch accumulates the failures with {{Throwables.perform}}, releases the
metrics, and rethrows the first failure, so every table is unloaded and the
caller still learns of the error.
Patch:
[mck/upstream/keyspace-unload-partial-failure/5.0|https://github.com/thelastpickle/cassandra/tree/mck/upstream/keyspace-unload-partial-failure/5.0]
Provenance:
[f9d34a98a6|https://github.com/datastax/cassandra/commit/f9d34a98a611a35cded1a77c04937d73c26713dd]
by [~mfleming]. That commit guards {{unloadCf}} itself and logs the failure
instead of rethrowing it, which suits a service that must never let a schema
change fail. This patch keeps the failure visible to the caller, because
dropping it silently would change what {{DROP KEYSPACE}} reports. That commit
carries no test; this patch adds one.
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