streams.esper

Class EsperEngine

java.lang.Object

streams.esper.EsperEngine

All Implemented Interfaces:

stream.Configurable, stream.service.Service

public class EsperEngine
extends Object
implements stream.service.Service, stream.Configurable

Abstract class that provides basic Esper support for the Streams platform.

Esper is a Complex Event Processing (CEP) platform for the Java and .Net languages. Esper must be started from custom code. It provides parallel execution but no distribution. The Streams stream processing platform allows to distribute Esper over different processes.

This package on the other hand allows integrating Complex Event Processing with a high level query language, i.e., the Event Processing Language (EPL). The EPL is a SQL-like language. For further information please refer to the Esper documentation.

The configuration of an Esper engine as a Streams Service follows the Xml configuration of the Streams platform. The configuration may include an Esper config. EPL statements are added as Streams Processor in the form of Streams-Esper Query objects.

Example Configuration:

        <Service class="streams.esper.EsperEngineService" id="esperEngine01">
                <config>
                        <esper-configuration xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                                xmlns="http://www.espertech.com/schema/esper"
                                xsi:schemaLocation="http://www.espertech.com/schema/esper http://www.espertech.com/schema/esper/esper-configuration-2.0.xsd">
 
                                <engine-settings>
                                        <defaults>
                                                <threading>
                                                        <internal-timer msec-resolution="1" enabled="false" />
                                                </threading>
                                        </defaults>
                                </engine-settings>
 
                                <event-type name="LeftEvent">
                                        <java-util-map start-timestamp-property-name="timestamp">
                                                <map-property name="timestamp" class="long" />
                                                <map-property name="id" class="string" />
                                        </java-util-map>
                                </event-type>
                                <event-type name="RightEvent">
                                        <java-util-map start-timestamp-property-name="timestamp">
                                                <map-property name="timestamp" class="long" />
                                                <map-property name="id" class="string" />
                                        </java-util-map>
                                </event-type>
 
                        </esper-configuration>
                </config>
        </Service>
 

Since:

0.3.0

Version:

0.3.0

Author:

Thomas Scharrenbach

See Also:

Query

Field Summary

Fields

Modifier and Type	Field and Description
protected com.espertech.esper.client.EPRuntime	_epRuntime
protected com.espertech.esper.client.EPServiceProvider	_epService
static String	DEFAULT_ID
static long	DEFAULT_TIME_TOLERANCE The default amount of difference in time up to which events are still considered for processing.
static String	ESPER_CONFIG_LOCAL_NAME
static String	ESPER_NS
static String	ESPER_STATEMENT_LOCAL_NAME
static String	EVENT_TYPE_KEY

Constructor Summary

Constructors

Constructor and Description
EsperEngine() Initializes the following components: an empty Esper Configuration, the maps for types with a start and an end timsestamp, the list of Esper statements ( Query ), and the default values for the time tolerance.

Method Summary

Methods

Modifier and Type	Method and Description
void	addEsperQuery(EsperStatementBean epStatement) Add a statement to the Esper engine.
void	addEsperQuery(EsperStatementBean epStatement, boolean increaseShutdownCount)
protected static Class<?>	classForName(String name)
void	configure(Element document) Parses the <configuration> ...
com.espertech.esper.client.Configuration	getConfiguration() Getter for the Esper configuration.
static EsperEngine	getEsperEngine(String id) If the engine with the specified id has not yet been registered but the id is equal to the default id, then a new engine with the default id will be created and registered and finally returned.
String	getId() Getter for the id of this service.
long	getInitialTime() Getter for the initial timestamp of the Esper engine.
String	getProviderUri() Getter for the URI of the Esper engine.
long	getTimeTolerance() Getter for the maximal difference a timestamp may reach into the past.
String[]	getTypes() Getter for the map of Esper types to Java classes via a streams attribute.
void	init() Initializes the Esper service.
void	notifyShutdown()
void	reset() Calls EPServiceProvider.destroy().
void	setId(String id)
void	setInitialTime(long initialTime)
void	setProviderUri(String providerUri)
void	setTimeTolerance(long timeTolerance)
void	setTypes(String[] types)
boolean	write(stream.Data input) Decodes a Data input item and sends it to the Esper engine.

Methods inherited from class java.lang.Object

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

Field Detail

ESPER_CONFIG_LOCAL_NAME

public static final String ESPER_CONFIG_LOCAL_NAME

Since:

0.3.0

See Also:

Constant Field Values

ESPER_NS

public static final String ESPER_NS

Since:

0.3.0

See Also:

Constant Field Values

EVENT_TYPE_KEY

public static final String EVENT_TYPE_KEY

Since:

0.3.0

See Also:

Constant Field Values

ESPER_STATEMENT_LOCAL_NAME

public static final String ESPER_STATEMENT_LOCAL_NAME

Since:

0.3.0

See Also:

Constant Field Values

DEFAULT_ID

public static final String DEFAULT_ID

Since:

0.3.0

See Also:

Constant Field Values

DEFAULT_TIME_TOLERANCE

public static final long DEFAULT_TIME_TOLERANCE

The default amount of difference in time up to which events are still considered for processing.

Since:

0.3.0

See Also:

Constant Field Values

_epService

protected transient com.espertech.esper.client.EPServiceProvider _epService

_epRuntime

protected transient com.espertech.esper.client.EPRuntime _epRuntime

Constructor Detail

EsperEngine

public EsperEngine()

Initializes the following components:

• an empty Esper Configuration,
• the maps for types with a start and an end timsestamp,
• the list of Esper statements ( Query ), and
• the default values for the time tolerance.

Since:

0.3.0

Method Detail

getEsperEngine

public static EsperEngine getEsperEngine(String id)

If the engine with the specified id has not yet been registered but the id is equal to the default id, then a new engine with the default id will be created and registered and finally returned.

Parameters:

id -

Returns:

Since:

0.3.0

classForName

protected static Class<?> classForName(String name)

Parameters:

name -

Returns:

Since:

0.3.0

init

public void init()
          throws Exception

Initializes the Esper service.

Throws:

Exception

Since:

0.3.0

notifyShutdown

public void notifyShutdown()
                    throws Exception

Throws:

Exception

Since:

0.3.2

write

public boolean write(stream.Data input)
              throws Exception

Decodes a Data input item and sends it to the Esper engine. The result of the processing in the Esper engine is output to Sink objects asynchonously.

The method determines the type of input by evaluating the field "@stream". It sends a copy of the input Data item to the Esper EPRuntime.It removes the values for "@stream" and "@stream:id" from the copied Data item before sending it.

The the input Data item defines a start time, then this start time is compared with the current data time. If the time stamp of the input Data item is larger than the current data time, then the current data time is set to the input Data item's start time. A time event with the Data item's start time is sent to the Esper EPRuntime.

Returns:

null, since this implementation works asynchronously.

Throws:

Exception

Since:

0.3.0

reset

public void reset()
           throws Exception

Calls EPServiceProvider.destroy().

Specified by:

reset in interface stream.service.Service

Throws:

delegates - any Exception that might be thrown during the calls of this method.

Exception

Since:

0.3.0

configure

public void configure(Element document)

Parses the <configuration> ... </configuration> tag if provided.

The configuration may contain the following elements:

• An Esper configuration element <esper-configuration> ... </esper-configuration> .
• An arbitrary number of Esper statements, i.e., each statement enclosed by <statement> ... </statement> .

Specified by:

configure in interface stream.Configurable

Since:

0.3.0

addEsperQuery

public void addEsperQuery(EsperStatementBean epStatement,
                 boolean increaseShutdownCount)

addEsperQuery

public void addEsperQuery(EsperStatementBean epStatement)

Add a statement to the Esper engine.

Note that subscribers are added only for those statements that declare an output sink.

Parameters:

epStatement -

Since:

0.3.0

getConfiguration

public com.espertech.esper.client.Configuration getConfiguration()

Getter for the Esper configuration.

Returns:

Since:

0.3.0

getProviderUri

@Parameter(defaultValue="",
           description="The URI of the Esper Runtime.",
           required=false)
public String getProviderUri()

Getter for the URI of the Esper engine.

Returns:

Since:

0.3.0

setProviderUri

public void setProviderUri(String providerUri)

getInitialTime

public long getInitialTime()

Getter for the initial timestamp of the Esper engine.

Returns:

Since:

0.3.0

setInitialTime

@Parameter(required=false)
public void setInitialTime(long initialTime)

getTimeTolerance

public long getTimeTolerance()

Getter for the maximal difference a timestamp may reach into the past.

Returns:

Since:

0.3.0

setTimeTolerance

@Parameter(name="timeTolerance",
           defaultValue="100000",
           description="The tolerance how many msecs a time event may reach into the past to be still processed.",
           required=false)
public void setTimeTolerance(long timeTolerance)

setId

public void setId(String id)

getId

public String getId()

Getter for the id of this service.

Returns:

Since:

0.3.0

getTypes

public String[] getTypes()

Getter for the map of Esper types to Java classes via a streams attribute.

Returns:

Since:

0.3.0

setTypes

@Parameter(required=false,
           description="Simple key:value mapping of properties")
public void setTypes(String[] types)

Parameters:

types -

Since:

0.3.0