org.apache.hadoop.hbase.client
Class HConnectionManager

java.lang.Object
  org.apache.hadoop.hbase.client.HConnectionManager

@InterfaceAudience.Public
@InterfaceStability.Evolving
public class HConnectionManager
extends Object

A non-instantiable class that manages creation of HConnections.

The simplest way to use this class is by using createConnection(Configuration). This creates a new HConnection that is managed by the caller. From this HConnection HTableInterface implementations are retrieved with HConnection.getTable(byte[]). Example:

 HConnection connection = HConnectionManager.createConnection(config);
 HTableInterface table = connection.getTable("table1");
 // use the table as needed, for a single operation and a single thread
 table.close();
 connection.close();
 
 

The following logic and API will be removed in the future:

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; for more on how this is done see HConnectionKey). 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, 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). 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() 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.

Field Summary

static int	MAX_CACHED_CONNECTION_INSTANCES
static String	RETRIES_BY_SERVER_KEY

Method Summary

static HConnection	createConnection(org.apache.hadoop.conf.Configuration conf) Create a new HConnection instance using the passed conf instance.
static HConnection	createConnection(org.apache.hadoop.conf.Configuration conf, ExecutorService pool) Create a new HConnection instance using the passed conf instance.
static void	deleteAllConnections() Deprecated. kept for backward compatibility, but the behavior is broken. HBASE-8983
static void	deleteAllConnections(boolean staleConnection) Deprecated.
static void	deleteConnection(org.apache.hadoop.conf.Configuration conf) Deprecated.
static void	deleteStaleConnection(HConnection connection) Deprecated.
static <T> T	execute(HConnectable<T> connectable) This convenience method invokes the given HConnectable.connect(org.apache.hadoop.hbase.client.HConnection) implementation using a HConnection instance that lasts just for the duration of the invocation.
static HConnection	getConnection(org.apache.hadoop.conf.Configuration conf) Deprecated.
static void	setServerSideHConnectionRetries(org.apache.hadoop.conf.Configuration c, String sn, org.apache.commons.logging.Log log) Set the number of retries to use serverside when trying to communicate with another server over HConnection.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

RETRIES_BY_SERVER_KEY

public static final String RETRIES_BY_SERVER_KEY

See Also:

Constant Field Values

MAX_CACHED_CONNECTION_INSTANCES

public static final int MAX_CACHED_CONNECTION_INSTANCES

Method Detail

getConnection

@Deprecated
public static HConnection getConnection(org.apache.hadoop.conf.Configuration conf)
                                 throws IOException

Deprecated.

Get the connection that goes with the passed conf configuration instance. If no current connection exists, method creates a new connection and keys it using connection-specific properties from the passed Configuration; see HConnectionKey.

Parameters:

conf - configuration

Returns:

HConnection object for conf

Throws:

ZooKeeperConnectionException

IOException

createConnection

public static HConnection createConnection(org.apache.hadoop.conf.Configuration conf)
                                    throws IOException

Create a new HConnection instance using the passed conf instance.

Note: This bypasses the usual HConnection life cycle management done by getConnection(Configuration). The caller is responsible for calling Closeable.close() on the returned connection instance. This is the recommended way to create HConnections. HConnection connection = HConnectionManager.createConnection(conf); HTableInterface table = connection.getTable("mytable"); table.get(...); ... table.close(); connection.close();

Parameters:

conf - configuration

Returns:

HConnection object for conf

Throws:

ZooKeeperConnectionException

IOException

createConnection

public static HConnection createConnection(org.apache.hadoop.conf.Configuration conf,
                                           ExecutorService pool)
                                    throws IOException

Create a new HConnection instance using the passed conf instance.

Note: This bypasses the usual HConnection life cycle management done by getConnection(Configuration). The caller is responsible for calling Closeable.close() on the returned connection instance. This is the recommended way to create HConnections. ExecutorService pool = ...; HConnection connection = HConnectionManager.createConnection(conf, pool); HTableInterface table = connection.getTable("mytable"); table.get(...); ... table.close(); connection.close();

Parameters:

conf - configuration

pool - the thread pool to use for batch operation in HTables used via this HConnection

Returns:

HConnection object for conf

Throws:

ZooKeeperConnectionException

IOException

deleteConnection

public static void deleteConnection(org.apache.hadoop.conf.Configuration conf)

Deprecated.

Delete connection information for the instance specified by passed configuration. If there are no more references to the designated connection connection, this method will then close connection to the zookeeper ensemble and let go of all associated resources.

Parameters:

conf - configuration whose identity is used to find HConnection instance.

deleteStaleConnection

public static void deleteStaleConnection(HConnection connection)

Deprecated.

Cleanup a known stale connection. This will then close connection to the zookeeper ensemble and let go of all resources.

Parameters:

connection -

deleteAllConnections

public static void deleteAllConnections(boolean staleConnection)

Deprecated.

Delete information for all connections. Close or not the connection, depending on the staleConnection boolean and the ref count. By default, you should use it with staleConnection to true.

deleteAllConnections

@Deprecated
public static void deleteAllConnections()

Deprecated. kept for backward compatibility, but the behavior is broken. HBASE-8983

Delete information for all connections..

execute

public static <T> T execute(HConnectable<T> connectable)
                 throws IOException

This convenience method invokes the given HConnectable.connect(org.apache.hadoop.hbase.client.HConnection) implementation using a HConnection instance that lasts just for the duration of the invocation.

Type Parameters:

T - the return type of the connect method

Parameters:

connectable - the HConnectable instance

Returns:

the value returned by the connect method

Throws:

IOException

setServerSideHConnectionRetries

public static void setServerSideHConnectionRetries(org.apache.hadoop.conf.Configuration c,
                                                   String sn,
                                                   org.apache.commons.logging.Log log)

Set the number of retries to use serverside when trying to communicate with another server over HConnection. Used updating catalog tables, etc. Call this method before we create any Connections.

Parameters:

c - The Configuration instance to set the retries into.

log - Used to log what we set in here.