[Nodebrain-users] Nagios integration and counting objects

Hi fellow nodebrain users!

I'd like to submit a solution for my problem that you can probably improve...

Let's suppose to define a tree node to store the status of a resource (let's say apache) of some servers (the total number of servers is dynamic and unknown):

define servers node tree;
and then populate the tree (via some servant scripts):

servers. assert ("srv1","apache")=0; # or alert servers("srv1","apache")=0
servers. assert ("srv2","apache")=0;
servers. assert ("srv3","apache")=0;
servers. assert ("srv4","apache")=0;
we'll get:

show servers

  "srv1"
    "apache"=0
  "srv2"
    "apache"=0
  "srv3"
    "apache"=0
  "srv1"
    "apache"=0
The goal is to count the number of server with apache != 0 (ie. resource not available).

The first thing I tried was:

define broken node tree; # a tree that contains servers without running apache

define r1 on(!servers(x,"apache")=0): broken(x); # very much like the tutorial (paragraph 6.3)

which should trigger on assert x="srv1" and check the status and eventually define "srv1"=1, like this:

servers. assert ("srv1","apache")=1;
Rule local.r1 fired (@.local.broken(@.local.x)=1)

show broken
broken = ! == node tree
    "srv1"=1
To clear the state when apache is available again I can define another rule:

define r2 on(servers(x,"apache")=0) ?broken(x); # or broken(x)=0

servers. assert ("srv1","apache")=0;
Rule local.r2 fired (@.local.broken(@.local.x)=?)
show broken
broken = ! == node tree
This works as far as x has the value of a server (i.e. to trigger those rules I have to assert x=). To me this doesn't sound as an elegant solution (and probably I should have used IF/ALERT instead of ON/ASSERT).

Then there is the problem that I want to know how many server are broken and call an adapter.

How can I count the cardinality of a tree (or the number of element with a given property/value directly on the servers tree)?

With those questions in mind I started to thing that probably the method I'm following is not the best (also because it resembles too closely an standard programming logic): is there a better way?

TIA


—  Dr. Marco Musso