public class HConnectionManager extends Object
HConnection
s.
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). 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)
. 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.
Modifier and Type | Class and Description |
---|---|
static class |
HConnectionManager.HConnectable<T>
This class makes it convenient for one to execute a command in the context
of a
HConnection instance based on the given Configuration . |
static class |
HConnectionManager.HConnectionKey
Denotes a unique key to a
HConnection instance. |
Modifier and Type | Field and Description |
---|---|
static int |
MAX_CACHED_HBASE_INSTANCES |
Modifier | Constructor and Description |
---|---|
protected |
HConnectionManager() |
Modifier and Type | Method and Description |
---|---|
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) |
static void |
deleteAllConnections()
Deprecated.
|
static void |
deleteAllConnections(boolean stopProxy)
Deprecated.
use
deleteAllConnections() instead |
static void |
deleteConnection(org.apache.hadoop.conf.Configuration conf)
Deprecated.
|
static void |
deleteConnection(org.apache.hadoop.conf.Configuration conf,
boolean stopProxy)
Deprecated.
|
static void |
deleteStaleConnection(HConnection connection)
Delete stale connection information for the instance specified by configuration.
|
static <T> T |
execute(HConnectionManager.HConnectable<T> connectable)
This convenience method invokes the given
HConnectionManager.HConnectable.connect(org.apache.hadoop.hbase.client.HConnection)
implementation using a HConnection instance that lasts just for the
duration of that invocation. |
static HConnection |
getConnection(org.apache.hadoop.conf.Configuration conf)
Get the connection that goes with the passed
conf
configuration instance. |
static void |
setServerSideHConnectionRetries(org.apache.hadoop.conf.Configuration c,
org.apache.commons.logging.Log log)
Set the number of retries to use serverside when trying to communicate
with another server over
HConnection . |
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
- configurationconf
ZooKeeperConnectionException
public static HConnection createConnection(org.apache.hadoop.conf.Configuration conf) throws ZooKeeperConnectionException
conf
instance.
Note: This bypasses the usual HConnection life cycle management.
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();
conf
- configurationconf
ZooKeeperConnectionException
public static HConnection createConnection(org.apache.hadoop.conf.Configuration conf, ExecutorService pool) throws IOException
IOException
@Deprecated public static void deleteConnection(org.apache.hadoop.conf.Configuration conf, boolean stopProxy)
createConnection(org.apache.hadoop.conf.Configuration)
insteadconf
- configuration whose identity is used to find HConnection
instance.stopProxy
- No longer used. This parameter is ignored.@Deprecated public static void deleteConnection(org.apache.hadoop.conf.Configuration conf)
conf
- configuration whose identity is used to find HConnection
instance.public static void deleteStaleConnection(HConnection connection)
connection
- @Deprecated public static void deleteAllConnections(boolean stopProxy)
deleteAllConnections()
insteadstopProxy
- No longer used. This parameter is ignored.@Deprecated public static void deleteAllConnections()
IOException
public static <T> T execute(HConnectionManager.HConnectable<T> connectable) throws IOException
HConnectionManager.HConnectable.connect(org.apache.hadoop.hbase.client.HConnection)
implementation using a HConnection
instance that lasts just for the
duration of that invocation.T
- the return type of the connect methodconnectable
- the HConnectionManager.HConnectable
instanceIOException
public static void setServerSideHConnectionRetries(org.apache.hadoop.conf.Configuration c, org.apache.commons.logging.Log log)
HConnection
. Used updating catalog
tables, etc. Call this method before we create any Connections.c
- The Configuration instance to set the retries into.log
- Used to log what we set in here.Copyright © 2014 The Apache Software Foundation. All Rights Reserved.