software.amazon.qldb

Class PooledQldbDriver

java.lang.Object

software.amazon.qldb.PooledQldbDriver

All Implemented Interfaces:

AutoCloseable

@ThreadSafe
public class PooledQldbDriver
extends Object

Represents a factory for accessing pooled sessions to a specific ledger within QLDB. This class or QldbDriver should be the main entry points to any interaction with QLDB. getSession() will create a PooledQldbSession to the specified ledger within QLDB as a communication channel. Any acquired sessions must be cleaned up with PooledQldbSession.close() when they are no longer needed in order to return the session to the pool. If this is not done, this driver may become unusable if the pool limit is exceeded. This factory pools sessions and attempts to return unused but available sessions when getting new sessions. The advantage to using this over the non-pooling driver is that the underlying connection that sessions use to communicate with QLDB can be recycled, minimizing resource usage by preventing unnecessary connections and reducing latency by not making unnecessary requests to start new connections and end reusable, existing, ones. The pool does not remove stale sessions until a new session is retrieved. The default pool size is the maximum amount of connections the session client allows. close() should be called when this factory is no longer needed in order to clean up resources, ending all sessions in the pool. This object is thread-safe.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	PooledQldbDriver.PooledQldbDriverBuilder Builder object for creating a PooledQldbSession, allowing for configuration of the parameters of construction.

Field Summary

Fields

Modifier and Type	Field and Description
protected com.amazonaws.services.qldbsession.AmazonQLDBSession	amazonQldbSession
protected ExecutorService	executorService
protected com.amazon.ion.IonSystem	ionSystem
protected AtomicBoolean	isClosed
protected String	ledgerName
protected int	readAhead
protected int	retryLimit

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	PooledQldbDriver(String ledgerName, com.amazonaws.services.qldbsession.AmazonQLDBSession client, int retryLimit, int readAhead, int poolLimit, long timeout, com.amazon.ion.IonSystem ionSystem, ExecutorService executorService)

Method Summary

Modifier and Type	Method and Description
static PooledQldbDriver.PooledQldbDriverBuilder	builder() Retrieve a builder object for creating a PooledQldbDriver.
void	close()
QldbSession	getSession() Get a QldbSession object.

Methods inherited from class java.lang.Object

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

Field Detail

readAhead

protected final int readAhead

ledgerName

protected final String ledgerName

retryLimit

protected final int retryLimit

amazonQldbSession

protected final com.amazonaws.services.qldbsession.AmazonQLDBSession amazonQldbSession

ionSystem

protected final com.amazon.ion.IonSystem ionSystem

executorService

protected final ExecutorService executorService

isClosed

protected final AtomicBoolean isClosed

Constructor Detail

PooledQldbDriver

protected PooledQldbDriver(String ledgerName,
                           com.amazonaws.services.qldbsession.AmazonQLDBSession client,
                           int retryLimit,
                           int readAhead,
                           int poolLimit,
                           long timeout,
                           com.amazon.ion.IonSystem ionSystem,
                           ExecutorService executorService)

Method Detail

builder

public static PooledQldbDriver.PooledQldbDriverBuilder builder()

Retrieve a builder object for creating a PooledQldbDriver.

Returns:

The builder object for creating a PooledQldbDriver.

close

public void close()

Specified by:

close in interface AutoCloseable

getSession

public QldbSession getSession()

Get a QldbSession object. This will attempt to retrieve an active existing session, or it will start a new session with QLDB unless the number of allocated sessions has exceeded the pool size limit. If so, then it will continue trying to retrieve an active existing session until the timeout is reached, throwing a QldbClientException;

Returns:

The QldbSession object.

Throws:

IllegalStateException - if this driver has been closed.

QldbClientException - if a timeout is reached while attempting to retrieve a session.

com.amazonaws.AmazonClientException - if there is an error communicating with QLDB.