Yu Li created HBASE-19260:
-----------------------------
Summary: Add lock back to avoid parallel accessing meta to locate
region
Key: HBASE-19260
URL: https://issues.apache.org/jira/browse/HBASE-19260
Project: HBase
Issue Type: Bug
Affects Versions: 1.1.12, 2.0.0-alpha-3, 1.2.6, 1.3.1
Reporter: Yu Li
In branch-0.98 we have below codes to avoid accessing meta in parallel in
{{HConnectionManager}}:
{code}
Result regionInfoRow;
// This block guards against two threads trying to load the meta
// region at the same time. The first will load the meta region and
// the second will use the value that the first one found.
if (useCache) {
if (TableName.META_TABLE_NAME.equals(parentTable) && usePrefetch &&
getRegionCachePrefetch(tableName)) {
synchronized (regionLockObject) {
// Check the cache again for a hit in case some other thread
made the
// same query while we were waiting on the lock.
...
}
}
...
{code}
while in HBASE-10018 we removed such logic along with
region-location-prefetching.
We regard this as an unexpected behavior change and observed below phenomenon
in our product env:
1. Unnecessary connection setup to meta when multiple threads locating region
in a client process
2. Priority handler of the RS holding meta region exhausted, application keep
retrying and cause a vicious circle
To resolve this problem, we propose to add the {{userRegionLock}} back and keep
the behavior in accordance with 0.98
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