Vihang Karajgaonkar created IMPALA-9139:
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Summary: Invalidate metadata adds all the tables to background
loading pool unnecessarily
Key: IMPALA-9139
URL: https://issues.apache.org/jira/browse/IMPALA-9139
Project: IMPALA
Issue Type: Bug
Reporter: Vihang Karajgaonkar
I see the following code in the reset() method of CatalogServiceCatalog
{code:java}
// Build a new DB cache, populate it, and replace the existing cache in
one
// step.
Map<String, Db> newDbCache = new ConcurrentHashMap<String, Db>();
List<TTableName> tblsToBackgroundLoad = new ArrayList<>();
try (MetaStoreClient msClient = getMetaStoreClient()) {
List<String> allDbs = msClient.getHiveClient().getAllDatabases();
int numComplete = 0;
for (String dbName: allDbs) {
if (isBlacklistedDb(dbName)) {
LOG.info("skip blacklisted db: " + dbName);
continue;
}
String annotation = String.format("invalidating metadata - %s/%s dbs
complete",
numComplete++, allDbs.size());
try (ThreadNameAnnotator tna = new ThreadNameAnnotator(annotation)) {
dbName = dbName.toLowerCase();
Db oldDb = oldDbCache.get(dbName);
Pair<Db, List<TTableName>> invalidatedDb = invalidateDb(msClient,
dbName, oldDb);
if (invalidatedDb == null) continue;
newDbCache.put(dbName, invalidatedDb.first);
tblsToBackgroundLoad.addAll(invalidatedDb.second);
}
}
}
dbCache_.set(newDbCache);
// Identify any deleted databases and add them to the delta log.
Set<String> oldDbNames = oldDbCache.keySet();
Set<String> newDbNames = newDbCache.keySet();
oldDbNames.removeAll(newDbNames);
for (String dbName: oldDbNames) {
Db removedDb = oldDbCache.get(dbName);
updateDeleteLog(removedDb);
}
// Submit tables for background loading.
for (TTableName tblName: tblsToBackgroundLoad) {
tableLoadingMgr_.backgroundLoad(tblName);
}
{code}
If you notice above, the tables are being added to the backgroundLoad with
checking the flag {{loadInBackground_}}. This means that even if the flag is
unset, after we issue a invalidate metadata command, all the tables in the
system are being loaded in the background. Note that this code is only loading
the tables, not adding the loaded tables to the catalog which is good otherwise
the memory footprint of catalog would be increased after every invalidate
metadata command.
This bug has 2 implications:
1. We are obviously wasting a lot of cpu cycles without getting anything out of
it.
2. The more subtle side-effect is that this would fill up the
{{tableLoadingDeque_}}. This means any other background load task will take a
longer duration to complete.
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