Working with Moncli part2: Creating a simple request

In our previous post we have covered how to create an example plugin which allows you to generate the size of directories as a metric. A plugin on itself doesn't do that much at all. When a plugin is executed it returns the values of that very moment. Executing a plugin is done by Moncli itself and we want to have control over that as much as possible.

moncli_request

A request is a JSON document which is submitted to the message broker on which the Moncli clients are listening for incoming requests. Creating and submitting a request could be doneby hand, but that's not practical at all. Moncli_request is a simple request generator tool which generates and submits a valid JSON document to Moncli to work with. Let's generate a request for our dir_size plugin we created in the previous article. Moncli_request takes a base JSON document and completes it with the parameters you feed to it. So let run through the required steps:

Install moncli_request from git:

$ git clone https://smetj@github.com/smetj/moncli_request.git /opt/moncli_request

Copy the skeleton base document over to a new default check called DirSize:

$ cp /opt/moncli_request/repository/skeleton /opt/moncli_request/repository/.default/DirSize

Complete our newly created DirSize base document with the plugin name and hash:
```
{
 "plugin":{
 "name":"dir_size",
 "hash":"a1161fc0d2dfcd6b4e9f52651e88a1d0",
 "timeout":60
 },
 "report":{
 "message":""
 },
 "request":{
 "cycle":60
 },
 "evaluators":{
 },
 "tags":[]
}
```
The name is the name of the plugin we created in the previous post and stored in Moncli's local repository. This actually corresponds to the directory name containing the plugin. The hash is the md5sum of the plugin. Parameters is a list of parameters we want to feed to the script.

Now execute moncli_request without the --broker parameter. This will print the request which you can submit to Moncli through the message broker on STDOUT:

$ /opt/moncli_request/moncli_request --host indigo --subject 'DirSize' --parameters [\"\'/tmp/test/*\'\"]
{"request":{"source":"indigo","month":3,"week_of_year":10,"time":"2012-03-11T19:58:54+01:00","day_of_year":71,"uuid":"DDB2AFC8-6BA3-11E1-B62D-8DA2DAFBAEBF","day":11,"day_of_week":7,"cycle":60,"year":2012},"plugin":{"parameters":["'/tmp/test/*'"],"hash":"a1161fc0d2dfcd6b4e9f52651e88a1d0","timeout":60,"name":"dir_size"},"report":{"message":""},"destination":{"subject":"DirSize","name":"indigo"},"evaluators":{},"tags":[]}

After verifying the content we can 'inject' the request into the message broker on which Moncli is listening:

$ /opt/moncli_request/moncli_request --broker sandbox --host sandbox --subject 'DirSize' --parameters [\"\'/tmp/test/*\'\"]
A new Report Request (7373E8A2-6B6C-11E1-A438-D193DAFBAEBF) has been submitted.

Keep in mind that the --broker parameter is the address/hostname of your broker and the --host is the hostname of the host on which Moncli is started. Each started Moncli instance creates a queue in the broker with its hostname as the queue name.

Report

When we consume the result from the broker (see this post) we get following result:

{
   "evaluators":{

   },
   "tags":[

   ],
   "destination":{
      "name":"indigo",
      "subject":"DirSize"
   },
   "request":{
      "uuid":"3FF36DE4-6BA4-11E1-8B44-B4A2DAFBAEBF",
      "year":2012,
      "day_of_year":71,
      "day_of_week":7,
      "month":3,
      "source":"indigo",
      "week_of_year":10,
      "time":"2012-03-11T20:01:38+01:00",
      "day":11,
      "cycle":60
   },
   "report":{
      "month":3,
      "year":2012,
      "timezone":"+0100",
      "message":"",
      "day":11,
      "uuid":"35672bb1-2cb8-46ea-8e23-bf5b98cbeaf4",
      "day_of_year":71,
      "day_of_week":0,
      "source":"indigo",
      "week_of_year":10,
      "time":"2012-03-11T19:02:06+0100"
   },
   "plugin":{
      "metrics":{
         "pre_epoch":1331488926.0,
         "/tmp/test/2":"24576",
         "/tmp/test/1":"24576",
         "pre_/tmp/test/1":"24576",
         "pre_/tmp/test/3":"24576",
         "pre_/tmp/test/2":"24576",
         "/tmp/test/3":"24576",
         "epoch":1331488926.0
      },
      "raw":[
         "/tmp/test/1:24576\n",
         "/tmp/test/2:24576\n",
         "/tmp/test/3:24576\n"
      ],
      "name":"dir_size",
      "verbose":[

      ]
   }
}

Conclusion:

We have seen how to create a plugin and how to generate a request for it. We let Moncli execute the plugin by generating and submitting a request with moncli_request and we have verified the incoming results. In this request we haven't done any evaluations which is something we will cover in the next article in this series.