JMX & Your Systems Health

A briefer history…(If its good enough for Hawking…)JSR 3Released in December of 2002JSR 160 Released in October of 2003Added remote API for MBean Servers

TermsManageable ResourceAny device, application, or entity that can be accessed or wrapped by Java.MBeanManaged Bean – A Java class that implements elements of the JMX spec.MBean ServerA Java class that manages a group of MBeans – the place you register your MBeans.JMX AgentA Java process that provides a set of services for managing MBeans – the container for the MBean server.

Terms cont.Protocol AdaptorsProvide a management view of the JMX agent through a given protocol, e.g. SNMP, HTTPConnectorsConvey management operations transparently point-to-point over a specific protocol, e.g. RMI. NotificationsJava objects published by MBeans and MBean servers to encapsulate events, alerts, or general information.InstrumentationThe exposing of a manageable resource via an MBean.

Architectural layersInstrumentationAllows for management of resources – your apps objects etc… via MBeansAgentHome of the MBean server, hosts all of your MBeans.ManagerProvides the environment through which your MBeans talk to the outside world.

Architectural layers

Who’s using JMX?Major App Server VendorsJBossWebLogicWebSphereESB VendorsSonicIBMJBI – Java Business IntegrationJSR 208

Why JMX – why them-us-me?A cheap way to manage Java applicationsBonus – it’s now part of JSE 5Will be supported by JEE 5If need be you can interrogate the JVMShort learning curve as compared to technologies like SNMPIf you know basic Java principles and patterns you are close to writing your own MBeansVery component oriented Even the MBean Server is a component – they’re all components!

Why JMX – why them-us-me? (cont.)Handy little features likeAlertsEventsStatisticsNotification ModelBroadcastersListeners

Why JMX – why them-us-me? (cont.)ServicesTimer MBeansMonitor MBeansCounterGaugeStringRelations

When to ponder?You can add JMX to a system anytime – but if you wait…It’ll require some refactoringTends to not be woven into the fabric of the designKinda like adding on that mother-in-law addition to the house…Best to do it earlyConsider support needs in requirements gatheringWhat will you want to know as the system is running in production?Design for itLook at macro and micro pictureFrom components, tiers, and system perspectivesCan be an aid for unit and integration testing

Plumbing for better healthInstrumentation of key system resourcesBusiness process controllersChannels (queues)Data AccessorsExternal interfacesNotifications ofThreshold violations and near missesAlmost a violation but not quite!VolumesThroughput

Where to look -Tier interfacesDelegatesFacadesSystem infrastructure –foundational classes e.g.Exception handling – levels, countsLogging – file sizesSecurity – violation countsSystem InterfacesGatewaysEndpoints

What to look withMBeans – helpful little buggersStandardDynamicOpenModelStandard MBeanQuickest to implementMost limitedModel MBeanSomewhat more complicated to work withOffer the most flexibility

So how does this relate to real systems?

Where to look - revisitedUsing the ‘real’ system on the previous slide, we’ll identify points of interest to instrumentEach of those cute little graphics represents a business component – a candidate for instrumentation…What aspects of these subsystems do we care about once the app is in production?Lets highlight and talk about some of them.

Where to look - revisited (cont.)E-commerce WebsiteNumber of hits an hourAverage length of stayShopping cartNumber of active shopping cart instances in an hourAverage length of time taken to process an orderCheck outAverage length of time to process credit purchasesNumber credit purchases in a hour Shipping How many confirmed in an hour – reflects B2B integration point

Why we’re lookingWe want to understand the systems performance so we gather stats on -Volumes of Units of Work (UOW) in subsystemsE.g. Hits on the websiteThe length of time that its takes to complete business processesE.g. The time to complete a credit transactionWe want to know when we’re experiencing level of service issues so -Send alerts when preset thresholds are Exceeded - reactiveReach a percentage of capacity - preventive

How to look -Gathering stats.package com.ecommerce.systemhealthpublic interface WebsiteMetricsMBean { public int getOrdersPerHour();}public class WebsiteMetrics implements WebsiteMetricsMBean { private int ordersPerHour; public void addToOrdersPerHour(int count){…} public int getOrdersPerHour() {…}}

How to look -Sending alerts.package com.ecommerce.systemhealthpublic interface WebsiteAlertsMBean { public int areOrdersPerHourNearThreshold(int orders);}public class WebsiteAlerts extends NotificationBroadcasterSupport implements WebsiteAlertsMBean { public void areOrdersPerHourNearThreshold(int orders) { // check the new value against the threshold if exceeded sendNotification(notification); }}

Ways to watch – management toolsPart of the gameSun’s JConsoleOpen sourceXMOJOMX4JGenerous LicensesMC4JEJTools JMX BrowserPaywareWil-Co Cockpit – provides graphical front components for JMX services in a designer view.

Who to tell and how?Staff inApplication supportServer supportIntegration support – B2B partnersDBAsLet them know viaEmail PagerMonitoring control dashboards, e.g. Tivoli

Some handy linkshttp://java.sun.com/j2se/1.5.0/docs/guide/jmx/http://java.sun.com/products/JavaManagement/index.jsphttp://java-source.net/open-source/jmxhttp://devresource.hp.com/drc/resources/jmxds/index.jsp

Some booksJMX in Action -- by Benjamin G. Sullins Java Management Extensions -- by J. Steven Perry I have both of the above, the first seems to be the most comprehensiveJava and JMX: Building Manageable Systems -- by Heather Kreger