org.apache.hadoop.hbase.client
Interface HConnection

All Superinterfaces:
Abortable

public interface HConnection
extends Abortable

Cluster connection. Hosts a connection to the ZooKeeper ensemble and thereafter into the HBase cluster. Knows how to locate regions out on the cluster, keeps a cache of locations and then knows how to recalibrate after they move. HConnectionManager manages instances of this class.

HConnections are used by HTable mostly but also by HBaseAdmin, CatalogTracker, and ZooKeeperWatcher. HConnection instances can be shared. Sharing is usually what you want because rather than each HConnection instance having to do its own discovery of regions out on the cluster, instead, all clients get to share the one cache of locations. Sharing makes cleanup of HConnections awkward. See HConnectionManager for cleanup discussion.

See Also:
HConnectionManager

Method Summary
 void clearRegionCache()
          Allows flushing the region cache.
 void clearRegionCache(byte[] tableName)
          Allows flushing the region cache of all locations that pertain to tableName
 org.apache.hadoop.conf.Configuration getConfiguration()
           
 HRegionInterface getHRegionConnection(HServerAddress regionServer)
          Establishes a connection to the region server at the specified address.
 HRegionInterface getHRegionConnection(HServerAddress regionServer, boolean getMaster)
          Establishes a connection to the region server at the specified address.
 HTableDescriptor getHTableDescriptor(byte[] tableName)
           
 HMasterInterface getMaster()
           
 boolean getRegionCachePrefetch(byte[] tableName)
          Check whether region cache prefetch is enabled or not.
 HRegionLocation getRegionLocation(byte[] tableName, byte[] row, boolean reload)
          Find region location hosting passed row
<T> T
getRegionServerWithoutRetries(ServerCallable<T> callable)
          Pass in a ServerCallable with your particular bit of logic defined and this method will pass it to the defined region server.
<T> T
getRegionServerWithRetries(ServerCallable<T> callable)
          Pass in a ServerCallable with your particular bit of logic defined and this method will manage the process of doing retries with timed waits and refinds of missing regions.
 ZooKeeperWatcher getZooKeeperWatcher()
          Retrieve ZooKeeperWatcher used by this connection.
 boolean isMasterRunning()
           
 boolean isTableAvailable(byte[] tableName)
           
 boolean isTableDisabled(byte[] tableName)
           
 boolean isTableEnabled(byte[] tableName)
          A table that isTableEnabled == false and isTableDisabled == false is possible.
 HTableDescriptor[] listTables()
          List all the userspace tables.
 HRegionLocation locateRegion(byte[] regionName)
          Gets the location of the region of regionName.
 HRegionLocation locateRegion(byte[] tableName, byte[] row)
          Find the location of the region of tableName that row lives in.
 List<HRegionLocation> locateRegions(byte[] tableName)
          Gets the locations of all regions in the specified table, tableName.
 void prewarmRegionCache(byte[] tableName, Map<HRegionInfo,HServerAddress> regions)
          Load the region map and warm up the global region cache for the table.
 void processBatch(List<Row> actions, byte[] tableName, ExecutorService pool, Object[] results)
          Process a mixed batch of Get, Put and Delete actions.
 void processBatchOfPuts(List<Put> list, byte[] tableName, ExecutorService pool)
          Deprecated. Use HConnectionManager::processBatch instead.
 HRegionLocation relocateRegion(byte[] tableName, byte[] row)
          Find the location of the region of tableName that row lives in, ignoring any value that might be in the cache.
 void setRegionCachePrefetch(byte[] tableName, boolean enable)
          Enable or disable region cache prefetch for the table.
 
Methods inherited from interface org.apache.hadoop.hbase.Abortable
abort
 

Method Detail

getConfiguration

org.apache.hadoop.conf.Configuration getConfiguration()
Returns:
Configuration instance being used by this HConnection instance.

getZooKeeperWatcher

ZooKeeperWatcher getZooKeeperWatcher()
                                     throws IOException
Retrieve ZooKeeperWatcher used by this connection.

Returns:
ZooKeeperWatcher handle being used by the connection.
Throws:
IOException - if a remote or network exception occurs

getMaster

HMasterInterface getMaster()
                           throws MasterNotRunningException,
                                  ZooKeeperConnectionException
Returns:
proxy connection to master server for this instance
Throws:
MasterNotRunningException - if the master is not running
ZooKeeperConnectionException - if unable to connect to zookeeper

isMasterRunning

boolean isMasterRunning()
                        throws MasterNotRunningException,
                               ZooKeeperConnectionException
Returns:
- true if the master server is running
Throws:
MasterNotRunningException
ZooKeeperConnectionException

isTableEnabled

boolean isTableEnabled(byte[] tableName)
                       throws IOException
A table that isTableEnabled == false and isTableDisabled == false is possible. This happens when a table has a lot of regions that must be processed.

Parameters:
tableName - table name
Returns:
true if the table is enabled, false otherwise
Throws:
IOException - if a remote or network exception occurs

isTableDisabled

boolean isTableDisabled(byte[] tableName)
                        throws IOException
Parameters:
tableName - table name
Returns:
true if the table is disabled, false otherwise
Throws:
IOException - if a remote or network exception occurs

isTableAvailable

boolean isTableAvailable(byte[] tableName)
                         throws IOException
Parameters:
tableName - table name
Returns:
true if all regions of the table are available, false otherwise
Throws:
IOException - if a remote or network exception occurs

listTables

HTableDescriptor[] listTables()
                              throws IOException
List all the userspace tables. In other words, scan the META table. If we wanted this to be really fast, we could implement a special catalog table that just contains table names and their descriptors. Right now, it only exists as part of the META table's region info.

Returns:
- returns an array of HTableDescriptors
Throws:
IOException - if a remote or network exception occurs

getHTableDescriptor

HTableDescriptor getHTableDescriptor(byte[] tableName)
                                     throws IOException
Parameters:
tableName - table name
Returns:
table metadata
Throws:
IOException - if a remote or network exception occurs

locateRegion

HRegionLocation locateRegion(byte[] tableName,
                             byte[] row)
                             throws IOException
Find the location of the region of tableName that row lives in.

Parameters:
tableName - name of the table row is in
row - row key you're trying to find the region of
Returns:
HRegionLocation that describes where to find the region in question
Throws:
IOException - if a remote or network exception occurs

clearRegionCache

void clearRegionCache()
Allows flushing the region cache.


clearRegionCache

void clearRegionCache(byte[] tableName)
Allows flushing the region cache of all locations that pertain to tableName

Parameters:
tableName - Name of the table whose regions we are to remove from cache.

relocateRegion

HRegionLocation relocateRegion(byte[] tableName,
                               byte[] row)
                               throws IOException
Find the location of the region of tableName that row lives in, ignoring any value that might be in the cache.

Parameters:
tableName - name of the table row is in
row - row key you're trying to find the region of
Returns:
HRegionLocation that describes where to find the region in question
Throws:
IOException - if a remote or network exception occurs

locateRegion

HRegionLocation locateRegion(byte[] regionName)
                             throws IOException
Gets the location of the region of regionName.

Parameters:
regionName - name of the region to locate
Returns:
HRegionLocation that describes where to find the region in question
Throws:
IOException - if a remote or network exception occurs

locateRegions

List<HRegionLocation> locateRegions(byte[] tableName)
                                    throws IOException
Gets the locations of all regions in the specified table, tableName.

Parameters:
tableName - table to get regions of
Returns:
list of region locations for all regions of table
Throws:
IOException

getHRegionConnection

HRegionInterface getHRegionConnection(HServerAddress regionServer)
                                      throws IOException
Establishes a connection to the region server at the specified address.

Parameters:
regionServer - - the server to connect to
Returns:
proxy for HRegionServer
Throws:
IOException - if a remote or network exception occurs

getHRegionConnection

HRegionInterface getHRegionConnection(HServerAddress regionServer,
                                      boolean getMaster)
                                      throws IOException
Establishes a connection to the region server at the specified address.

Parameters:
regionServer - - the server to connect to
getMaster - - do we check if master is alive
Returns:
proxy for HRegionServer
Throws:
IOException - if a remote or network exception occurs

getRegionLocation

HRegionLocation getRegionLocation(byte[] tableName,
                                  byte[] row,
                                  boolean reload)
                                  throws IOException
Find region location hosting passed row

Parameters:
tableName - table name
row - Row to find.
reload - If true do not use cache, otherwise bypass.
Returns:
Location of row.
Throws:
IOException - if a remote or network exception occurs

getRegionServerWithRetries

<T> T getRegionServerWithRetries(ServerCallable<T> callable)
                             throws IOException,
                                    RuntimeException
Pass in a ServerCallable with your particular bit of logic defined and this method will manage the process of doing retries with timed waits and refinds of missing regions.

Type Parameters:
T - the type of the return value
Parameters:
callable - callable to run
Returns:
an object of type T
Throws:
IOException - if a remote or network exception occurs
RuntimeException - other unspecified error

getRegionServerWithoutRetries

<T> T getRegionServerWithoutRetries(ServerCallable<T> callable)
                                throws IOException,
                                       RuntimeException
Pass in a ServerCallable with your particular bit of logic defined and this method will pass it to the defined region server.

Type Parameters:
T - the type of the return value
Parameters:
callable - callable to run
Returns:
an object of type T
Throws:
IOException - if a remote or network exception occurs
RuntimeException - other unspecified error

processBatch

void processBatch(List<Row> actions,
                  byte[] tableName,
                  ExecutorService pool,
                  Object[] results)
                  throws IOException,
                         InterruptedException
Process a mixed batch of Get, Put and Delete actions. All actions for a RegionServer are forwarded in one RPC call.

Parameters:
actions - The collection of actions.
tableName - Name of the hbase table
pool - thread pool for parallel execution
results - An empty array, same size as list. If an exception is thrown, you can test here for partial results, and to determine which actions processed successfully.
Throws:
IOException - if there are problems talking to META. Per-item exceptions are stored in the results array.
InterruptedException

processBatchOfPuts

void processBatchOfPuts(List<Put> list,
                        byte[] tableName,
                        ExecutorService pool)
                        throws IOException
Deprecated. Use HConnectionManager::processBatch instead.

Process a batch of Puts.

Parameters:
list - The collection of actions. The list is mutated: all successful Puts are removed from the list.
tableName - Name of the hbase table
pool - Thread pool for parallel execution
Throws:
IOException

setRegionCachePrefetch

void setRegionCachePrefetch(byte[] tableName,
                            boolean enable)
Enable or disable region cache prefetch for the table. It will be applied for the given table's all HTable instances within this connection. By default, the cache prefetch is enabled.

Parameters:
tableName - name of table to configure.
enable - Set to true to enable region cache prefetch.

getRegionCachePrefetch

boolean getRegionCachePrefetch(byte[] tableName)
Check whether region cache prefetch is enabled or not.

Parameters:
tableName - name of table to check
Returns:
true if table's region cache prefetch is enabled. Otherwise it is disabled.

prewarmRegionCache

void prewarmRegionCache(byte[] tableName,
                        Map<HRegionInfo,HServerAddress> regions)
Load the region map and warm up the global region cache for the table.

Parameters:
tableName - name of the table to perform region cache prewarm.
regions - a region map.


Copyright © 2011 The Apache Software Foundation. All Rights Reserved.