In this second (and last) part of the using a thermometer with RHQ and JBossON, I am guiding you through the plugin code.

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When starting this post I set the title to "Home automation with RHQ".

But this would have been a little exaggerated at first and perhaps RHQ is - if you don't have other stuff to monitor and manage - like to break a butterfly on a wheel. But anyway a system like RHQ is (or will be) well suited to be the central brain of a home automation system. Of course, if I say RHQ, this applies to JBossON 2 as well....

RHQ and JBossON allow you to monitor Apache servers through its apache plugin. We have official support via precompiled plugins for Linux and Windows and instructions in the JBossON wiki on how to compile this for other Unixoids. While Mac OS X is a Unixoid (under the covers , the compile of the snmp module will not directly succeed.

I want to show here how to do that anyway

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While RHQ is focusing on providing specific resource types with specific operations and metrics on them, it is possible to just connect to any JMX server (actually that code is in SVN Head as of today).

This example will show you how you could use this to e.g. monitor your Eclipse instance.

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We have started to bring High-Availability to the RHQ Server.

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While developing on RHQ I encountered several situations where things were slow. One starts to look at the code, add a few print statements here and there and tries to guess what it happening.
Running the whole show through a debugger usually also doesn't help as digging deep into method calls will let you run into transaction timeouts from which point on, results are just useless.

Luckily there is a different sort of debugging help: Profilers

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Sometimes when you start the RHQ agent (on commandline), it will not proceed to the sending> prompt, but sit there and wait for something. This post will talk about some of the possibilities.

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In the realm of extremely early prototype I've started an RHQ plugin that is meant to provide monitoring for some useful aspects of hardware. It only does anything useful on linux with IBM hardware or if you have smartmontools installed. The idea will be to collect some standard hardware info in a common model that isn't specific to a certain hardware.

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When writing a plugin for RHQ, one has to write the plugin descriptor. While this is not complicated, it still leaves some room for errors. The good thing (but you will hate it, when you run into it) is that when deploying the plugin, its descriptor will be validated against the defining XML Schema - and errors will reported.

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I've gone ahead and committed a new plugin for RHQ that provides monitoring of a Hudson continuous integration server. It's not a particularly complex plugin, but it gives a decent example of using JSON within a plugin.

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Since I have created the SNMPtrapd plugin for RHQ, I have updated it with a lot of little features and corrections.

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The JavaDoc for plugin-development related classes is online now.

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... I mentioned in my last post that I had started working on integration with Augeas. Initially, it was just kinda slopped together to be shown off at Red Hat Summit. It got some good feedback, so in my downtime I've been working on cleaning up what we have. ...

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I have just committed an experimental SNMP trapd plugin for RHQ. Currently it is only able to listen for V1 traps at a fixed address, but I am sure this will change Incoming traps will be forwarded as Events into the events subsystem, so you can view them in the GUI and even define alarms on them (that trigger SNMP traps

This posting also shows how to handle events within RHQ plugins.

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In trying to find better ways to view large amounts of data I stumbled across a project called TreeViz that has some nice ways to render hierarchical data. I hooked a few of these up to RHQ to help show the availability of thousands of resources in a single snapshot. One I really like is the sunburst display.

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Yesterday I was at 11th Java Forum Stuttgart (JFS), a regional Java conference with 1100 attendees. The JFS featured 42 sessions in 6 parallel tracks in one day.
I had a talk and a BOF session - both of course showing RHQ in one way or other

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We just released RHQ Version 1.0.1 and JBossOn 2.0.1 in the wild.

Both are bugfix releases and ...

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Yesterday we held a SIG-JBoss meeting in Stuttgart about RHQ. Attendance was not that great - mostly due to the second semi-final of the European Soccer Championship.

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RHQ has a powerful grouping feature: you can generate groups of resources (of compatible and mixed type).
How can you easily find out which groups are containing a certain resource?

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When creating a database and database user for RHQ, Postgres knows two commands to create a user:

create user

and

create role

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The agents managing resources can (and will) live on a different system than the server. So sometimes the question arises when a resource is marked as unavailable if the resource itself is down - or the connection between agent and server.

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Do you know more or less than you think you do? RHQ and related acronyms.

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When writing a plugin, you have to do a few things (even if it is very easy in then as you can read in my developing a plugin series).

Jay wrote a plugin skeleton generator that makes the task of writing plugins even easier.

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...RHQ has had from the very first design session a rich, hierarchical model for resources. This hierarchy, specifically the parent-child relationships, rather precludes a complex authorization model. Instead, RHQ complements a flexible inventory with a more simplistic authorization scheme...

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JBoss is providing a free trial version of JBoss ON 2, built on top of RHQ.

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The SIG-JBoss in the Stuttgart Java User Group will have a meeting on Thu 26th about RHQ.

I will talk about RHQ and JBossON 2 in general and we will perhaps have a look at writing plugins. Bring your laptops with you.

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Autodiscovery of resources is running at regular intervals in RHQ. But sometimes you want to directly add a new managed resource like a freshly installed JBossAS server ...

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... But I also found the time to work on some black projects as well. Augeas is a Red Hat project, providing APIs for configuring various Linux based services, such as GRUB, /etc/hosts, and yum and apt repositories. Once the base Augeas connection was in place, I was able to pretty quickly add a number of these services to RHQ. ...

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Here's an interesting use case for DynaGroups.

One customer might have a few dozen/hundred JBoss AS instances, but only a handful of them have a web app deployed called, say, "someapp.war". They want to know what set of expressions they could use to maintain a group of all appservers that have that webapp deployed.

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In RHQ and JBossON 2, that is built on top of RHQ, you have the possibility to graph metrics for (more or less) arbitrary time ranges.

But sometimes the display is not moving and not showing any data that you'd expect to see.

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Metric data that is gathered on the agents will be sent to the server and stored in the database. Now if you want to e.g. compare metrics from two different sources (e.g. the load of two JBossAS servers in a cluster), you can only make sense out of it when the metrics have been taken at the same time ....

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I've checked in two more new RHQ plugins to publish. These are also in the experimental stage right now. There's an Oracle plugin with some basic monitoring and an OpenSSH plugin that also experiments with augeas for configuration management.

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I finally got a chance to checkin a couple more plugins that I had been working on. The virt plugin uses libvirt to do a bit of xen monitoring and management.

...

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The Stuttgart SIG-JBoss will hold a meeting on June 26th in the premises of Red Hat Germany.

Topic for this meeting is a presentation of RHQ – and if we have time about how to write plugins.

You can view the full announcement at the Stuttgart Java User Group page

Please register as indicated in the announcement page – registration is free!

I have a written a three part series on how to write a simple RHQ plugin.

As an example scenario the plugin will try to reach a http server, see if the base URL is available and return the status code + the time it took to reach it.

Part one talks about the structure of RHQ itself
Part two introduces the involved components
and
[Part three|http://javablogs.com/Jump.action?...

... So what do we have to show for it? To be honest, a lot. When I have to look back and work with our 1.4 release I feel cramped with its relative lack of features. Features aside, the entire 2.0 package feels considerably smoother, faster, and just plain cooler. ...

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As your enterprise grows, it becomes increasingly difficult to individually manage the resources in your inventory.

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A recent chat with a colleague reminded me today how important it is to clearly distinguish between what's in your enterprise and what's in your inventory.

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Sometimes one of the most difficult things to do as a plugin developer is to bring some semblance, some order to the wide variety of features and functions that exist in software today. What may seem like a perfectly logical way to capture that information to you may seem utterly backwards to someone else. And the reason should come as no surprise - we all think about things differently.

So what's the trick to developing a single solution that is going to make everyone happy? Well,...

The RHQ plugin system is called AMPS or Advanced Management Plugin System. Don't blame me over the name... Mazz came up with it. Anyway, why is it advanced? On the outside it seems pretty plain vanilla. You've got an XML file to define the metadata and you write some code to do the work. Pretty typical. And it may not seem all that sexy, but I do think it demonstrates some new enhancements to a field that's had some pretty tough extension models to date....

How to test framework systems that have varying usage is something we've hit with the RHQ project. Plugins to the platform could expose many types of data at varying frequencies and scales and so we've developed a flexible framework for performance testing. The nice thing about this system is its relative simplicity. We were able to create a standard RHQ plugin that can simulate large complex inventories of resources with just a few settings. How many server resources?...

...
The current approach is to treat it as a package on the EAR resource. I'll reiterate that to be clear: there is an EAR file discovered as a package on the inventoried EAR resource. Once you get past the terminology disparity, it's not too difficult to comprehend.
...

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I stumbled across this timeline visualization project from MIT recently and thought it would make for a pretty neat way to combine the many types of events collected by RHQ. Managed resources can have configuration change events, operations that are executed, events that are collected and alerts against those and collected monitoring data.

...

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From a blog I wrote to announce the RHQ project on Red Hat Blogs.
http://www.press.redhat.com/2008/02/28/introducing-rhq-management-middleware/

Management software has typically fallen into one of two categories: big, integrated, and expensive or small, disjoint, and unconnected. Neither of these models are sufficient to meet the needs of all communities. On top of that,...