Caché Monitoring Guide - InterSystems Documentation

Using the Caché Monitor
3.2.2.1 Generating Metrics
The %Monitor.SampleAgent class is the class that does the actual sampling. It is this class that invokes the Initialize() and
GetSample() methods of the metrics classes.
The %Monitor.SampleAgent.%New(n) constructor takes one argument, the name of the metrics class it is to run. It creates
an instance of that class, and invokes the Startup() method on that class. Then, each time the
%Monitor.SampleAgent.Collect() method is invoked, the Sample Agent invokes the Initialize() method for the class,
then repeatedly invokes the GetSample() method for the class. On each call to GetSample(), %Monitor.SampleAgent creates
a sample class for the metrics class; the pseudocode for these operations is:
Set sampler = ##class(%Monitor.SampleAgent).%New("MyMetrics.Freespace")
/* at this point, the sampler has created an instance of MyMetrics.Freespace,
and invoked its Startup method */
for I=1:1:10 d sampler.Collect() h 10
/* at each iteration, sampler calls MyMetrics.Freespace.Initialize(), then loops
on GetSample(). Whenever GetSample() returns $$$OK, sampler creates a new
MyMetrics.Sample.Freespace instance, with the sample data. When GetSample()
returns an error value, no sample is created, and sampler.Collect() returns. */
3.2.2.2 Viewing Metrics Data
All metrics classes are CSP-enabled; the CSP code is generated automatically when the sample class is generated. Therefore,
the simplest way to view metrics is using a web browser; for example, based on the example in Generating Metrics, the
CSP URL is: http://localhost:57772/csp/user/MyMetrics.Sample.Freespace.cls, which displays output similar to:
Monitor - Freespace c:\cache51\
Name of dataset: c:\cache51\
Current amount of Freespace: 8.2MB
Monitor - Freespace c:\cache51\mgr\
Name of dataset: c:\cache51\mgr\
Current amount of Freespace: 6.4MB
Alternatively, you can use the Display() method of the %Monitor.View class; for example:
%SYS>s mclass="Monitor.Test.Freespace"
%SYS>s col=##class(%Monitor.SampleAgent).%New(mclass)
%SYS>w col.Collect()
1
%SYS>w ##class(%Monitor.View).Display(mclass)
Monitor - Freespace c:\cache51\
Name of dataset: c:\cache51\
Current amount of Freespace: 8.2MB
Monitor - Freespace c:\cache51\mgr\
Name of dataset: c:\cache51\mgr\
Current amount of Freespace: 6.4MB
3.2.3 Writing User-defined Monitor Classes
In addition to predefined classes for monitoring system metrics, you can write your own monitor classes to monitor user
application data and counters.
A monitor class is any class that inherits from the abstract Monitor class, %Monitor.Adaptor; the %Monitor.System classes
are examples of Monitor classes. To create your own user-defined monitor classes:
1. Write a class that inherits from %Monitor.Adaptor. The inheritance provides persistence, parameters, properties, code
generation, and a projection that generates the monitor metadata from your class definition. See the %Monitor.Adaptor
class documentation in the Caché Class Reference for full details on this class, as well as the code you must write.
2. Compile your class. Compiling classes that inherit from %Monitor.Adaptor generates new classes in a subpackage of
the users class called Sample. So, for example, if you compile A.B.MyMetric, a new class is generated in
A.B.Sample.MyMetric. You do not need to do anything with the generated class.
30 Caché Monitoring Guide