Tag Archive java

A more technical article today.

In adding some more Exchange Monitoring we ran into some issues, and solutions, that may help others.  Some things in recent Exchange versions can only be monitored by Powershell. (Perfmon, WMI, Powershell, all needed for different versions of Exchange…. I wish they’d make up their mind…)

So the first issue was that Powershell scripts, when called from a LogicMonitor agent, never returned. This wasn’t too hard – simply pass the parameter -inputformat with the (undocumented) option “none”, and the agent can successfully run Powershell commands:

powershell -inputformat none dbstatus.ps1

(Why? The Microsoft.PowerShell.ConsoleHost class constructs a M.PS.WrappedDeserializer passing the STDIN TextReader as one of the parameters. By default, the WrappedDeserializer will call ReadLine() on this STDIN TextReader and wait indefinitely, effectively hanging PowerShell and the calling process. That’s why.)

So past that hurdle, but the next one:
>> powershell -inputformat none dbstatus.ps1
Add-PSSnapin : No snap-ins have been registered for Windows PowerShell version 2.

Yet running the exact same command from the command shell on the host running the agent resulted in the output we were expecting. And we could see the Exchange snap in, called by the Powershell script, was correctly registered, and in fact worked fine.

But.. our agent was running on a 32 bit JVM and Exchange 2010 (in our lab, at least) is installed on 64 bit Windows. The Powershell snap in was only visible when powershell was started from a 64 bit app. When I started powershell from the cmd.exe in SysWOW64, I got the same error about missing snap-ins as our agent reported.

The solution – it doesn’t matter that our agent was installed as a 32 bit app, in Program files (x86). What mattered was that the Java virtual machine launched by the agent, that ultimately launched Powershell, be a 64 bit JVM, not the default 32 bit JVM installed from Java.com. (At least, a 32 bit JVM is the default when you browse to Java.com with a 32 bit browser.)

So, running the LogicMonitor agent with a 64 bit JVM, and Powershell started with “-inputformat none” gives us full access to Powershell output and all its snap ins, so expect some datasources released very shortly to take advantage of that.


The many faces of JMX monitoring

Posted by & filed under Uncategorized .

We like monitoring. We like Java. Not to slight other languages – we like Ruby, perl, php, .NET and other platforms, too, and like to monitor them, also.

However, unlike most other languages, Java provides an explicit technology for monitoring applications and system objects.   JMX is supported on any platform running the JVM, but like most other monitoring protocols, there are lots of interesting nuances and ways to use it. Which means lots of nuances in how to detect it and monitor it.

We have quiet a few customers that use LogicMonitor for JMX monitoring, of both standard and custom applications, so we’ve run into quite a few little issues, and solved them.

One example is that the naming convention for JMX objects is loosely defined.  Initially, the JMX collector for LogicMonitor assumed that every object would have a “type” key property, as specified in best practices. Of course, this is a rule “more honored in the breach than in the observance”, as widespread applications such as WowzaMediaServer and even Tomcat do not adhere to it.

Another example is that JMX supports complex datatypes.  We have customers who do not register different Mbeans for all their classes of data, but instead expose Mbeans that return maps of maps. Our collectors and ActiveDiscovery did not initially deal with these datatypes, as we hadn’t anticipated their use.  But, there are good reasons to use them in a variety of cases, so LogicMonitor should support the wishes of the user – that’s one of our tenets, that LogicMonitor enables user’s to work the way they want, instead of constraining them to a preconceived idea.  So we extended our ActiveDiscovery to iterate through maps, and maps of maps, and composite datatypes.

This enables our customers to instrument their applications in the way they think is most appropriate, while automating the configuration of management and alerting.  While we think we’ve got all the permutations of JMX covered, I’m not taking any bets that a new customer won’t come along with a new variant that adds a perfectly logical use case that we do not support.  Of course, if that’s the case, we’ll support it within a month or so – and all our customers – current and future – will be able to immediately reap the benefits. That’s just one of the niceties of the hosted SaaS model.


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