Package org.aksw.jenax.dataaccess.sparql.connection.reconnect

Class SparqlQueryConnectionWithReconnect

java.lang.Object

org.aksw.jenax.dataaccess.sparql.connection.reconnect.SparqlQueryConnectionWithReconnect

All Implemented Interfaces:

AutoCloseable, TransactionalWrapper, SparqlQueryConnectionTmp, org.apache.jena.rdfconnection.SparqlQueryConnection, org.apache.jena.sparql.core.Transactional

public class SparqlQueryConnectionWithReconnect
extends Object
implements SparqlQueryConnectionTmp

A connection wrapper that tries to recover from loss of the underlying connection. Neither replays transactions nor individual queries. If a query fails due to a connection loss then attempts are made to establish a new connection. If an attempt is successful then a ConnectionReestablishedException is raised which indicates that the query failed but the connection would be ready to accept workloads again. The main benefit of this class that it removes the need of passing a java.sql.DataSource-like object to client methods that operate on a single connection. It also takes care of the resource management such as closing the connections used for probing. The client methods can catch the ConnectionReestablishedException and ConnectionLostException and act accordingly such as by replaying some queries or moving on the the next workload. This class is thread safe: In case of a connection problem, the health check runner is started by one of the threads that requested a query execution. All other threads are blocked while the health check is running and fire the appropriate exception once it finishes.

Author:

raven

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
class	SparqlQueryConnectionWithReconnect.QueryExecutionWithReconnect

Nested classes/interfaces inherited from interface org.apache.jena.sparql.core.Transactional

org.apache.jena.sparql.core.Transactional.Promote

Field Summary

Fields

Modifier and Type	Field	Description
protected org.apache.jena.rdfconnection.SparqlQueryConnection	activeDelegate	The currently active connection
protected Exception	connectionLostCause	True indicates that a recovery process was started which eventually failed
protected Callable<org.apache.jena.rdfconnection.SparqlQueryConnection>	dataConnectionSupplier
protected Supplier<org.aksw.commons.util.healthcheck.HealthcheckRunner.Builder<?>>	healthCheckBuilder
protected org.apache.jena.query.Query	healthCheckQuery
protected Callable<org.apache.jena.rdfconnection.SparqlQueryConnection>	probeConnectionSupplier
protected int	reconnectAttemptCount	Number of times the healthcheck runner was invoked in an attempt to reconnect.

Constructor Summary

Constructors

Constructor	Description
SparqlQueryConnectionWithReconnect(Callable<org.apache.jena.rdfconnection.SparqlQueryConnection> dataConnectionSupplier, Callable<org.apache.jena.rdfconnection.SparqlQueryConnection> probeConnectionSupplier, Supplier<org.aksw.commons.util.healthcheck.HealthcheckRunner.Builder<?>> healthCheckBuilder, org.apache.jena.rdfconnection.SparqlQueryConnection activeDelegate)

Method Summary

Modifier and Type	Method	Description
protected void	checkForConnectionLoss()
void	close()
static SparqlQueryConnectionWithReconnect	create(Callable<org.apache.jena.rdfconnection.SparqlQueryConnection> connectionSupplier)	Immediately obtain a connection from the supplier
protected void	forceCloseActiveConn()
org.apache.jena.sparql.core.Transactional	getDelegate()	This method needs to be overridden for transaction support
int	getReconnectAttemptCount()
protected void	handleConnectionProblem(Exception e, int timestamp)
boolean	isConnectionLost()
protected boolean	isConnectionProblemException(Throwable t)
org.apache.jena.query.QueryExecutionBuilder	newQuery()
org.apache.jena.query.QueryExecution	query(org.apache.jena.query.Query query)	Setup a SPARQL query execution.
protected void	testForConnectionProblem(Exception e, int timestamp)
protected void	tryRecovery()	This method is run by the healthcheck runner until there is no more exception

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.aksw.jenax.dataaccess.sparql.connection.query.SparqlQueryConnectionTmp

parse, query, queryAsk, queryAsk, queryConstruct, queryConstruct, queryDescribe, queryDescribe, queryResultSet, queryResultSet, querySelect, querySelect

Methods inherited from interface org.apache.jena.sparql.core.Transactional

begin, calc, calculate, calculateRead, calculateWrite, exec, execute, executeRead, executeWrite, promote

Methods inherited from interface org.aksw.jenax.dataaccess.sparql.common.TransactionalWrapper

abort, begin, begin, commit, end, getTransactionalDelegate, isInTransaction, promote, transactionMode, transactionType

Field Details

dataConnectionSupplier

protected Callable<org.apache.jena.rdfconnection.SparqlQueryConnection> dataConnectionSupplier

probeConnectionSupplier

protected Callable<org.apache.jena.rdfconnection.SparqlQueryConnection> probeConnectionSupplier

healthCheckQuery

protected org.apache.jena.query.Query healthCheckQuery

healthCheckBuilder

protected Supplier<org.aksw.commons.util.healthcheck.HealthcheckRunner.Builder<?>> healthCheckBuilder

connectionLostCause

protected transient Exception connectionLostCause

True indicates that a recovery process was started which eventually failed

reconnectAttemptCount

protected transient int reconnectAttemptCount

Number of times the healthcheck runner was invoked in an attempt to reconnect. Not to be confused with the number of reconnect attempts made by a single healthcheck run. This value is used as 'timestamp' when multiple requests are waiting for the connection to become available again

activeDelegate

protected org.apache.jena.rdfconnection.SparqlQueryConnection activeDelegate

The currently active connection

Constructor Details

SparqlQueryConnectionWithReconnect

public SparqlQueryConnectionWithReconnect(Callable<org.apache.jena.rdfconnection.SparqlQueryConnection> dataConnectionSupplier,
 Callable<org.apache.jena.rdfconnection.SparqlQueryConnection> probeConnectionSupplier,
 Supplier<org.aksw.commons.util.healthcheck.HealthcheckRunner.Builder<?>> healthCheckBuilder,
 org.apache.jena.rdfconnection.SparqlQueryConnection activeDelegate)

Method Details

isConnectionLost

public boolean isConnectionLost()

getReconnectAttemptCount

public int getReconnectAttemptCount()

create

public static SparqlQueryConnectionWithReconnect create(Callable<org.apache.jena.rdfconnection.SparqlQueryConnection> connectionSupplier)
                                                 throws Exception

Immediately obtain a connection from the supplier

Throws:

Exception

getDelegate

public org.apache.jena.sparql.core.Transactional getDelegate()

Description copied from interface: TransactionalWrapper

This method needs to be overridden for transaction support

Specified by:

getDelegate in interface TransactionalWrapper

checkForConnectionLoss

protected void checkForConnectionLoss()

query

public org.apache.jena.query.QueryExecution query(org.apache.jena.query.Query query)

Description copied from interface: SparqlQueryConnectionTmp

Setup a SPARQL query execution. See also SparqlQueryConnectionTmp.querySelect(Query, Consumer), SparqlQueryConnectionTmp.queryConstruct(Query), SparqlQueryConnectionTmp.queryDescribe(Query), SparqlQueryConnectionTmp.queryAsk(Query) for ways to execute queries for of a specific form.

Specified by:

query in interface org.apache.jena.rdfconnection.SparqlQueryConnection

Specified by:

query in interface SparqlQueryConnectionTmp

Returns:

QueryExecution

isConnectionProblemException

protected boolean isConnectionProblemException(Throwable t)

forceCloseActiveConn

protected void forceCloseActiveConn()

tryRecovery

protected void tryRecovery()
                    throws Exception

This method is run by the healthcheck runner until there is no more exception

Throws:

Exception

close

public void close()

Specified by:

close in interface AutoCloseable

Specified by:

close in interface org.apache.jena.rdfconnection.SparqlQueryConnection

testForConnectionProblem

protected void testForConnectionProblem(Exception e,
 int timestamp)

handleConnectionProblem

protected void handleConnectionProblem(Exception e,
 int timestamp)

newQuery

public org.apache.jena.query.QueryExecutionBuilder newQuery()

Specified by:

newQuery in interface org.apache.jena.rdfconnection.SparqlQueryConnection

Specified by:

newQuery in interface SparqlQueryConnectionTmp