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HBASE-10785 Metas own location should be cached 

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/hbase-10070@1586653 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Enis Soztutar 2014-04-11 13:46:59 +00:00
parent 579f305bd0
commit 48ffa4d5e6
1 changed files with 35 additions and 1 deletions
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36
hbase-client/src/main/java/org/apache/hadoop/hbase/client/ConnectionManager.java
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@ -560,6 +560,9 @@ class ConnectionManager {
// package protected for the tests
ClusterStatusListener clusterStatusListener;
private final Object metaRegionLock = new Object();
// We have a single lock for master & zk to prevent deadlocks. Having
// one lock for ZK and one lock for master is not possible:
// When creating a connection to master, we need a connection to ZK to get
@ -1085,13 +1088,44 @@ class ConnectionManager {
}
if (tableName.equals(TableName.META_TABLE_NAME)) {
return this.registry.getMetaRegionLocation();
return locateMeta(tableName, useCache, replicaId);
} else {
// Region not in the cache - have to go to the meta RS
return locateRegionInMeta(tableName, row, useCache, retry, replicaId);
}
}
private RegionLocations locateMeta(final TableName tableName,
boolean useCache, int replicaId) throws IOException {
// HBASE-10785: We cache the location of the META itself, so that we are not overloading
// zookeeper with one request for every region lookup. We cache the META with empty row
// key in MetaCache.
byte[] metaCacheKey = HConstants.EMPTY_START_ROW; // use byte[0] as the row for meta
RegionLocations locations = null;
if (useCache) {
locations = getCachedLocation(tableName, metaCacheKey);
if (locations != null) {
return locations;
}
}
// only one thread should do the lookup.
synchronized (metaRegionLock) {
// Check the cache again for a hit in case some other thread made the
// same query while we were waiting on the lock.
locations = getCachedLocation(tableName, metaCacheKey);
if (locations != null) {
return locations;
}
// Look up from zookeeper
locations = this.registry.getMetaRegionLocation();
if (locations != null) {
cacheLocation(tableName, locations);
}
}
return locations;
}
/*
* Search the hbase:meta table for the HRegionLocation
* info that contains the table and row we're seeking.