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java.lang.Objectorg.apache.hadoop.hbase.client.HConnectionManager
public class HConnectionManager
A non-instantiable class that manages HConnection
s.
This class has a static Map of HConnection
instances keyed by
Configuration
; all invocations of getConnection(Configuration)
that pass the same Configuration
instance will be returned the same
HConnection
instance (Adding properties to a Configuration
instance does not change its object identity). Sharing HConnection
instances is usually what you want; all clients of the HConnection
instances share the HConnections' cache of Region locations rather than each
having to discover for itself the location of meta, root, etc. It makes
sense for the likes of the pool of HTables class HTablePool
, for
instance (If concerned that a single HConnection
is insufficient
for sharing amongst clients in say an heavily-multithreaded environment,
in practise its not proven to be an issue. Besides, HConnection
is
implemented atop Hadoop RPC and as of this writing, Hadoop RPC does a
connection per cluster-member, exclusively).
But sharing connections
makes clean up of HConnection
instances a little awkward. Currently,
clients cleanup by calling
deleteConnection(Configuration, boolean)
. This will shutdown the
zookeeper connection the HConnection was using and clean up all
HConnection resources as well as stopping proxies to servers out on the
cluster. Not running the cleanup will not end the world; it'll
just stall the closeup some and spew some zookeeper connection failed
messages into the log. Running the cleanup on a HConnection
that is
subsequently used by another will cause breakage so be careful running
cleanup.
To create a HConnection
that is not shared by others, you can
create a new Configuration
instance, pass this new instance to
getConnection(Configuration)
, and then when done, close it up by
doing something like the following:
Configuration newConfig = new Configuration(originalConf);
HConnection connection = HConnectionManager.getConnection(newConfig);
// Use the connection to your hearts' delight and then when done...
HConnectionManager.deleteConnection(newConfig, true);
Cleanup used to be done inside in a shutdown hook. On startup we'd
register a shutdown hook that called deleteAllConnections(boolean)
on its way out but the order in which shutdown hooks run is not defined so
were problematic for clients of HConnection that wanted to register their
own shutdown hooks so we removed ours though this shifts the onus for
cleanup to the client.
Constructor Summary | |
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protected |
HConnectionManager()
|
Method Summary | |
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static void |
deleteAllConnections(boolean stopProxy)
Delete information for all connections. |
static void |
deleteConnection(org.apache.hadoop.conf.Configuration conf,
boolean stopProxy)
Delete connection information for the instance specified by configuration. |
static HConnection |
getConnection(org.apache.hadoop.conf.Configuration conf)
Get the connection that goes with the passed conf
configuration instance. |
Methods inherited from class java.lang.Object |
---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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protected HConnectionManager()
Method Detail |
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public static HConnection getConnection(org.apache.hadoop.conf.Configuration conf) throws ZooKeeperConnectionException
conf
configuration instance.
If no current connection exists, method creates a new connection for the
passed conf
instance.
conf
- configuration
conf
ZooKeeperConnectionException
public static void deleteConnection(org.apache.hadoop.conf.Configuration conf, boolean stopProxy)
conf
- configuration whose identity is used to find HConnection
instance.stopProxy
- Shuts down all the proxy's put up to cluster members
including to cluster HMaster. Calls HBaseRPC.stopProxy(org.apache.hadoop.ipc.VersionedProtocol)
.public static void deleteAllConnections(boolean stopProxy)
stopProxy
- stop the proxy as well
IOException
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