Mgmt Plug-in / OSLine refuses to work / Perl returns non suitable values?

Question

Hi,
I am currently developing a simple management plugin to integrate basic metrics about our J2EE service in EM. So far I have defined two metrics (Response using OS and Availability using OSLine). In a first step both metrics should collect data from simple Perl scripts (just print commands). The Repsonse metric works perfectly fine, but I am getting an Error in EM when I want to display the Availability metric (Unable to obtain data for metric Container Availability).
The Availability metric is a table with 4 columns (or lines) and uses the OSLine fetchlet. When the Perl script returns a single Value (i.e. print "Value1") it works fine, but as soon as the script returns more than 1 line (i.e. print "Value1\nValue2\nValue3\nValue4", like the example in the Extensibility Guide, Chapter 9 - Fetchlets, to fill the whole table) I get an error when clicking on the metric in EM. So I suspect that the Perl script is returning something in the wrong format (hidden control character or something...).
I already took the following steps to solve the problem:
1. Read Extensibility Guide and study examples
2. Check that the fetchlets are available in fetchlet.reg
3. Compare code to oracle_listener.xml
4. Validate XMLs against the DTDs
5. Used OSLineToken without a delimiter (so it should act like OSLine), same problem
6. Used a shell script with echo (same problem)
7. Searched the forum :)
Here is the source code for my plugin (including the perl scripts):
J2EE_Target.xml:
<?xml version="1.0"?>
<!DOCTYPE TargetMetadata SYSTEM "../dtds/TargetMetadata.dtd">
<TargetMetadata META_VER="1.0" TYPE="J2EE_TARGET">
     <Display>
          <Label NLSID="J2EE_TARGET">J2EE Target</Label>
     </Display>
     <Metric NAME="Response" TYPE="TABLE" USAGE_TYPE="VIEW_COLLECT">
          <Display>
               <Label NLSID="Response">Response</Label>
          </Display>
          <TableDescriptor>
               <ColumnDescriptor NAME="Status" TYPE="NUMBER">
                    <Display>
                         <Label NLSID="Status">Status</Label>
                    </Display>
               </ColumnDescriptor>
          </TableDescriptor>
          <QueryDescriptor FETCHLET_ID="OS" NEED_CHARSET_CONVERT="FALSE">
               <Property NAME="command" SCOPE="GLOBAL">perl /usr/oracle/custom_target/j2ee_status.pl</Property>
          </QueryDescriptor>
     </Metric>
     <Metric NAME="Container Availability" TYPE="TABLE" USAGE_TYPE="VIEW_COLLECT">
          <Display>
               <Label NLSID="Container Availability">Container Availability</Label>
          </Display>
          <TableDescriptor>
               <ColumnDescriptor NAME="Availability" TYPE="STRING">
                    <Display>
                         <Label NLSID="Availability">Availability</Label>
                    </Display>
               </ColumnDescriptor>
               <ColumnDescriptor NAME="NumberofContainers" TYPE="STRING">
                    <Display>
                         <Label NLSID="NumberofContainers">NumberofContainers</Label>
                    </Display>
               </ColumnDescriptor>
               <ColumnDescriptor NAME="NumberofApplications" TYPE="STRING">
                    <Display>
                         <Label NLSID="NumberofApplications">NumberofApplications</Label>
                    </Display>
               </ColumnDescriptor>
               <ColumnDescriptor NAME="NumberofOwners" TYPE="STRING">
                    <Display>
                         <Label NLSID="NumberofOwners">NumberofOwners</Label>
                    </Display>
               </ColumnDescriptor>
          </TableDescriptor>
          <QueryDescriptor FETCHLET_ID="OSLine" NEED_CHARSET_CONVERT="FALSE">
               <Property NAME="command" SCOPE="GLOBAL">perl /usr/oracle/custom_target/avail_status.pl</Property>
          </QueryDescriptor>
     </Metric>
</TargetMetadata>
J2EE_Collection.xml:
<!-- $Header: oracle_listener.xml 25-apr-2005.05:33:05 jpegu Exp $ -->
<!DOCTYPE TargetCollection SYSTEM "../dtds/TargetCollection.dtd">
<TargetCollection TYPE="J2EE_TARGET" >
<CollectionItem NAME="Response">
<Schedule>
<IntervalSchedule INTERVAL="1" TIME_UNIT="Min"/>
</Schedule>
<Condition COLUMN_NAME="Status" CRITICAL="0" OPERATOR="EQ"
MESSAGE="The target is down."
MESSAGE_NLSID="Response_Status_alertmessage"
               CLEAR_MESSAGE="The J2EE Service is up."
               CLEAR_MESSAGE_NLSID="Response_Status_clearmessage"/>
</CollectionItem>
</TargetCollection>
Perl:
j2ee_status.pl:
print "100";
avail_status.pl (V1:causes error in EM):
print "Value1\nValue2\nValue3\nValue4";
avail_status.pl (V2: works fine, but only first line of metric table is filled as expected):
print "Value1";
Perhaps you can spot the error.
Thanks in advance!
Andre

Answer 1

And is there a reason why you're not using the OS Line Token fetchlet? You could just as easily:
print "Value1|Value2|Value3|Value4";
and have it work...
You may also consider changing your column types to NUMBER, as it looks like that's what they'll be. It won't make a difference to the agent, which will parse everything as a string anyway, but it will make a difference in the repository and through the UI. Making those columns NUMBER will put the values in charts in the UI, whereas if you leave them as STRING all you will ever see is a text display.