Monitoring Framework SPI's is used internally by the ORB to instrument
-for JMX based Management and Monitoring. The
-
framework is very generic and easy to use and acts as facade to retrieve
-the information from the running CORBA system.
-
This framework helps in building a nice Hierarchical Structure of Monitored
-Objects that contains Monitored Attributes.
-
com.sun.corba.se.spi.orb.ORB has an API to get the RootMonitoredObject
-and then User can traverse through the tree to
-
either instrument or retrieve the information for Monitoring.
-
1. Connection State
-
2. Response time statistics to Appeserver Admin Console or CLI
-
-
/**
-
* Step 1: Define a Monitored Attribute Class by extending
-
*
-StringMonitoredAttributeBase
-
*/
-
/**
-
* ConnectionState gets the value on demand.
-
*/
-
#import com.sun.corba.se.spi.monitoring.LongMonitoredAttributeBase
-
#import com.sun.corba.se.spi.transport.CorbaConnection;
-
public class ConnectionStateMonitoredAttribute extends StringMonitoredAttributeBase
-
{
-
CorbaConnection connection;
-
public ConnectionInUseMonitoredAttribute( String
-name, String desc,
-
CorbaConnection con )
-
{
-
super( name, desc );
-
connection = con;
-
}
-
public Object getValue( ) {
-
// Delegate the getValue
-call to connection
-
// so, there is no state
-maintained in this attribute object itself
-
// and also the locking
-will be the responsibility of Connection
-
// Object. By doing this
-we will avoid global locking and possibly
-
// avoiding the bottleneck
-
return connection.getState(
-);
-
}
-
// IMPORTANT: In this case we don't have to implement
-clearState() method
-
// If there is a need to implement this method like
-for POACounter, the
-
// call again can be delegated to the Object which
-maintains the real
-
// state. clearState() is invoked whenever there
-is a call to CORBAMBean.startMonitoring()
-
}
-
-
/**
-
* Step 2: Create Connection Manager Monitored Object and
-add that to
-
* Root
-Monitored Object.
-
*/
-
import com.sun.corba.se.spi.monitoring.MonitoringFactories;
-
import com.sun.corba.se.spi.monitoring.MonitoredObject;
-
private static MonitoredObject connectionManagerMonitoredObject;
-
private static MonitoredObject connectionMonitoredObject;
-
-
private void instrumentConnectionManager( ) {
-
connectionManagerMonitoredObject
-=
-
-MonitoringFactories.getMonitoredObjectFactory().createMonitoredObject(
-
-"ConnectionManagerMonitoredObject",
-
-"Used to Monitor the stats on All IIOP Connections " );
-
orb.getRootMonitoredObject().addChild(connectionManagerMonitoredObject
-);
-
}
-
-
/**
-
* Step 3: Create Connection Monitored Object and
-add it to Connection Manager Monitored Object
-
*
-
* Step 4: Instantiate Concrete Attribute (ConnectionStateMonitoredAttribute)
-Class and add that to
-
*
-the Connection MonitoredObject
-
*
-
* Step 5: Add ConnectionMonitoredObject to ConnectionManagerMonitoredObject
-
*/
-
private void instrumentConnectionObject( CorbConnection connection
-) {
-
// Step 3
-
MonitoredObject connectionMonitoredObject =
-
MonitoringFactories.getMonitoredObjectFactory().createMonitoredObject(
-
-connection.getName(),
-
-"Used to Monitor the stats on one connection" );
-
// Step 4
-
ConnectionStateMonitoredAttribute connectionState
-=
-
new ConnectionStateMonitoredAttribute(
-"Connection_State",
-
-"Provides the state of the IIOP Connection ...", connection );
-
connectionMonitoredObject.addAttribute( connectionState
-);
-
// Step 5
-
connectionManagerMonitoredObject.addChild( connectionMonitoredObject
-);
-
}
-
-
-
Code Snippet to Instrument A Statistic Type Monitored -Attribute -
/**
-
* Assuming ConnectionMonitoredObject is already added
-to the MonitoredObject Hierarchy.
-
* This example code shows how to instrument ConnectionMonitoredObject
-with a new
-
* StatisticMonitoredAttribute.
-
*
-
* IMPORTANT: StatisticsMonitoredAttribute
-is mostly write mostly and read sparingly, i.e.,
-
* the frequency of writes(Collecting samples)
-is high. It is the responsibility of user to synchronize
-
* the sample() method and the StatisticMonitoredAttribute
-will synchronize clearState() and
-
* getValue() using the mutex object sent.
-
*/
-
private void instrumentStatsToConnectionObject( MonitoredObject connectionMonitoredObject
-) {
-
// Step 4
-
StatisticsAccumulator connectRequestStatsAccumulator
-=
-
// Microseconds is the unit
-used for statistics measure
-
new StatisticsAccumulator(
-"Micro Seconds" );
-
// Pass Name, Description, Statistic Accumulator
-Instance, Mutex (The
-
// Object on which we need to synchronize for stats
-sample collection)
-
StatisticMonitoredAttribute sm = new StatisticMonitoredAttribute(
-
connection.getName() + "Stats",
-
"Connection Request Stats",
-connectRequestStatsAccumulator, this );
-
connectionMonitoredObject.addAttribute( sm );
-
-
// Now, The user can accumulate the samples by calling
-into
-
// connectRequestStatsAccumulator.sample( <value>
-);
-
// Finally When ASAdmin request for the value of
-this Stats Monitored Attribute
-
// by using standard getValue() call. It will return
-a formatted Stats Value like
-
// For Example
-
//
-
// Minimum Value = 200 Microseconds
-
// Maximum Value = 928 Microseconds
-
// Average Value = 523 Microseconds
-
// Standard Deviation = 53.72 Microseconds
-
// Sample Collected = 435
-
} -
Caution On Global Locking (Synchronization): -
It's important to make sure that collecting Stats and other state information
-for monitoring doesn't impact performance. Please look at the following
-don'ts
-
to understand better.
-
Do not add a special mutex for synchronizing MonitoredObject:
-
Let's take an example of exposing a counter that counts Requests on
-this connection and 2 possible ways of doing this
-
1. Define Counter by extending LongMonitoredAttributeBase
-
public class Counter extends LongMonitoredAttributeBase
-{
-
private long counter;
-
-
Counter( String name, String
-desc ) {
-
-super( name, desc );
-
}
-
-
public synchronized
-void increment( ) {
-
-counter++;
-
}
-
public synchronized
-Object getValue( ) {
-
-return new Long( counter );
-
}
-
}
-
-
2. Or Define a RequestCounter by extending LongMonitoredAttributeBase
-again, but no special
-
synchronization is done
-
public class RequestCounter extends LongMonitoredAttributeBase
-{
-
private CorbaConnection
-connection;
-
RequestCounter( String name,
-String desc, CorbaConnection con ) {
-
-super( name, desc );
-
-connection = con;
-
}
-
public Object getValue( )
-{
-
-return connection.getRequestCount( );
-
}
-
}
-
The problem with Alternative (1) is that there may
-be unneccesary extra synchronization happening for every method and it
-may become a bottle neck
-
particularly if this object is accessed quite
-often. In Alternative (2), the synchronization happens only in the Connection
-object and no special sync
-
is required in the RequestCounter object.
-
-
Important Thing To Know On StatisticMonitoredAttribute
-type:
-
The clearState() and getValue() call will be synchronized using the
-mutex passed by the external object, but sample() method in StatisticsAccumulator
-
is not synchronized. It is the responsibility of user to synchronize
-to make sure that the samples collected (The mutex passed into the StatisticsAccumulator must be the one used to synchronize calls to sample() ).
-
-
@since JDK1.5 @serial exclude - -