org.apache.hadoop.hbase.client

Interface Connection

All Superinterfaces:

org.apache.hadoop.hbase.Abortable, AutoCloseable, Closeable

@InterfaceAudience.Public
public interface Connection
extends org.apache.hadoop.hbase.Abortable, Closeable

A cluster connection encapsulating lower level individual connections to actual servers and a connection to zookeeper. Connections are instantiated through the ConnectionFactory class. The lifecycle of the connection is managed by the caller, who has to close() the connection to release the resources.

The connection object contains logic to find the master, locate regions out on the cluster, keeps a cache of locations and then knows how to re-calibrate after they move. The individual connections to servers, meta cache, zookeeper connection, etc are all shared by the Table and Admin instances obtained from this connection.

Connection creation is a heavy-weight operation. Connection implementations are thread-safe, so that the client can create a connection once, and share it with different threads. Table and Admin instances, on the other hand, are light-weight and are not thread-safe. Typically, a single connection per client application is instantiated and every thread will obtain its own Table instance. Caching or pooling of Table and Admin is not recommended.

Since:

0.99.0

See Also:

ConnectionFactory

Method Summary

Modifier and Type	Method and Description
void	clearRegionLocationCache() Clear all the entries in the region location cache, for all the tables.
void	close()
Admin	getAdmin() Retrieve an Admin implementation to administer an HBase cluster.
BufferedMutator	getBufferedMutator(BufferedMutatorParams params) Retrieve a BufferedMutator for performing client-side buffering of writes.
BufferedMutator	getBufferedMutator(TableName tableName) Retrieve a BufferedMutator for performing client-side buffering of writes.
org.apache.hadoop.conf.Configuration	getConfiguration()
RegionLocator	getRegionLocator(TableName tableName) Retrieve a RegionLocator implementation to inspect region information on a table.
default Table	getTable(TableName tableName) Retrieve a Table implementation for accessing a table.
default Table	getTable(TableName tableName, ExecutorService pool) Retrieve a Table implementation for accessing a table.
TableBuilder	getTableBuilder(TableName tableName, ExecutorService pool) Returns an TableBuilder for creating Table.
boolean	isClosed() Returns whether the connection is closed or not.

Methods inherited from interface org.apache.hadoop.hbase.Abortable

abort, isAborted

Method Detail

getConfiguration

org.apache.hadoop.conf.Configuration getConfiguration()

Returns:

Configuration instance being used by this Connection instance.

getTable

default Table getTable(TableName tableName)
                throws IOException

Retrieve a Table implementation for accessing a table. The returned Table is not thread safe, a new instance should be created for each using thread. This is a lightweight operation, pooling or caching of the returned Table is neither required nor desired.

The caller is responsible for calling Table.close() on the returned table instance.

Since 0.98.1 this method no longer checks table existence. An exception will be thrown if the table does not exist only when the first operation is attempted.

Parameters:

tableName - the name of the table

Returns:

a Table to use for interactions with this table

Throws:

IOException

getTable

default Table getTable(TableName tableName,
                       ExecutorService pool)
                throws IOException

Retrieve a Table implementation for accessing a table. The returned Table is not thread safe, a new instance should be created for each using thread. This is a lightweight operation, pooling or caching of the returned Table is neither required nor desired.

The caller is responsible for calling Table.close() on the returned table instance.

Since 0.98.1 this method no longer checks table existence. An exception will be thrown if the table does not exist only when the first operation is attempted.

Parameters:

tableName - the name of the table

pool - The thread pool to use for batch operations, null to use a default pool.

Returns:

a Table to use for interactions with this table

Throws:

IOException

getBufferedMutator

BufferedMutator getBufferedMutator(TableName tableName)
                            throws IOException

Retrieve a BufferedMutator for performing client-side buffering of writes. The BufferedMutator returned by this method is thread-safe. This BufferedMutator will use the Connection's ExecutorService. This object can be used for long lived operations.

The caller is responsible for calling BufferedMutator.close() on the returned BufferedMutator instance.

This accessor will use the connection's ExecutorService and will throw an exception in the main thread when an asynchronous exception occurs.

Parameters:

tableName - the name of the table

Returns:

a BufferedMutator for the supplied tableName.

Throws:

IOException

getBufferedMutator

BufferedMutator getBufferedMutator(BufferedMutatorParams params)
                            throws IOException

Retrieve a BufferedMutator for performing client-side buffering of writes. The BufferedMutator returned by this method is thread-safe. This object can be used for long lived table operations. The caller is responsible for calling BufferedMutator.close() on the returned BufferedMutator instance.

Parameters:

params - details on how to instantiate the BufferedMutator.

Returns:

a BufferedMutator for the supplied tableName.

Throws:

IOException

getRegionLocator

RegionLocator getRegionLocator(TableName tableName)
                        throws IOException

Retrieve a RegionLocator implementation to inspect region information on a table. The returned RegionLocator is not thread-safe, so a new instance should be created for each using thread. This is a lightweight operation. Pooling or caching of the returned RegionLocator is neither required nor desired.
The caller is responsible for calling Closeable.close() on the returned RegionLocator instance. RegionLocator needs to be unmanaged

Parameters:

tableName - Name of the table who's region is to be examined

Returns:

A RegionLocator instance

Throws:

IOException

clearRegionLocationCache

void clearRegionLocationCache()

Clear all the entries in the region location cache, for all the tables.

If you only want to clear the cache for a specific table, use RegionLocator.clearRegionLocationCache().

This may cause performance issue so use it with caution.

getAdmin

Admin getAdmin()
        throws IOException

Retrieve an Admin implementation to administer an HBase cluster. The returned Admin is not guaranteed to be thread-safe. A new instance should be created for each using thread. This is a lightweight operation. Pooling or caching of the returned Admin is not recommended.
The caller is responsible for calling Admin.close() on the returned Admin instance.

Returns:

an Admin instance for cluster administration

Throws:

IOException

close

void close()
    throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException

isClosed

boolean isClosed()

Returns whether the connection is closed or not.

Returns:

true if this connection is closed

getTableBuilder

TableBuilder getTableBuilder(TableName tableName,
                             ExecutorService pool)

Returns an TableBuilder for creating Table.

Parameters:

tableName - the name of the table

pool - the thread pool to use for requests like batch and scan