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Bernhard Schmidt

2013-Feb-01 14:16 UTC

[Puppet Users] Debugging a facter problem

Hello,

for the last couple of hours I''ve been trying to wrap my head around a
problem writing a custom facter plugin and I''m not getting it.

I''m trying to export LLDP neighbors as facter variables. I''ve
already
found https://gist.github.com/1424959 and I''m quite happy with it, so
the issue is not pressing. But I''d like to understand it.

If the neighbor provides an ifAlias (like Cisco) I want to use this,
but if it doesn''t I want to use description.

Sidenote: This is my first time with Ruby and it looks quite ugly

First try:
---
require ''facter/util/ip''

Facter::Util::IP.get_interfaces.each do |interface|

  # Make a fact for each detail of each interface.  Yay.
  Facter.add("lldp_neighbor_" + Facter::Util::IP.alphafy(interface))
do
    setcode do
      device = Facter::Util::Resolution.exec("/usr/sbin/lldpctl -f keyvalue
" + interface + " | grep chassis.name | cut -d ''=''
-f 2")
      ifdescr = Facter::Util::Resolution.exec("/usr/sbin/lldpctl -f
keyvalue " + interface + " | grep port.descr | cut -d
''='' -f 2")
      ifalias = Facter::Util::Resolution.exec("/usr/sbin/lldpctl -f
keyvalue " + interface + " | grep port.ifalias | cut -d
''='' -f 2")
      if device
        if ifalias
          device + " " + ifalias
        else
          device + " "  + ifdescr
        end
      end
    end
  end
end
---

This is highly inefficient, but works

lldp_neighbor_eth0 => swg1-kic B23
lldp_neighbor_eth4 => csr1-kic Gi4/3


Next I wanted to try to parse the whole output to get rid of all the 
spawning

---
require ''facter''
require ''facter/util/ip''

if not FileTest.exists?("/usr/sbin/lldpctl")
  nil
end

config = Hash[]
output = Facter::Util::Resolution.exec("/usr/sbin/lldpctl -f
keyvalue")

if output == ""
  nil
end

for line in output.split("\n") do
  # Drop Multiline
  if line =~ /^lldp/
    key, value = line.split(''='')
    prefix, int, key2 = key.split(''.'', 3)
    if not config.has_key?(int)
      config[int] = Hash[]
    end
    config[int][key2] = value
  end
end

for interface in config.keys do
  Facter.add("lldp_neighbor_" + Facter::Util::IP.alphafy(interface))
do
    setcode do
      device = config[interface].fetch(''chassis.name'',
"")
      ifdescr = config[interface].fetch(''port.descr'',
"")
      ifalias = config[interface].fetch(''port.ifalias'',
"")
      if device != ""
        if ifalias != ""
          device + " " + ifalias
        else
          device + " "  + ifdescr
        end
      end
    end
  end
end
---

This errorneously reports the same neighbor for both interfaces

lldp_neighbor_eth0 => csr1-kic Gi4/3
lldp_neighbor_eth4 => csr1-kic Gi4/3

I somehow cannot execute the whole facter plugin using irb, but when I
replace the second part of the script with

---
for interface in config.keys do
  device = config[interface].fetch(''chassis.name'',
"")
  ifdescr = config[interface].fetch(''port.descr'',
"")
  ifalias = config[interface].fetch(''port.ifalias'',
"")
  if device != ""
    if ifalias != ""
      puts interface + " " + device + " " + ifalias
    else
      puts interface + " " + device + " "  + ifdescr
    end
  end
end
---

it does display the right information

eth0 swg1-kic B23
eth4 csr1-kic Gi4/3

Also, if I just open irb and run the first part of the script (the data
collection) the resulting hash looks fine

irb(main):030:0> pp config
{"eth0"=>
  {"via"=>"LLDP",
   "rid"=>"1",
   "age"=>"0 day, 00:51:37",
   "chassis.mac"=>"00:01:e7:df:df:00",
   "chassis.name"=>"swg1-kic",
   "chassis.descr"=>
    "HP J4865A ProCurve Switch 4108GL, revision G.07.109, ROM G.05.02
(/sw/code/build/gamo(m03))",
   "chassis.mgmt-ip"=>"xxxx",
   "chassis.Bridge.enabled"=>"on",
   "chassis.Router.enabled"=>"off",
   "port.local"=>"47",
   "port.descr"=>"B23"},
 "eth4"=>
  {"via"=>"LLDP",
   "rid"=>"2",
   "age"=>"0 day, 00:47:03",
   "chassis.mac"=>"68:ef:bd:7e:ee:86",
   "chassis.name"=>"csr1-kic",
   "chassis.descr"=>
    "Cisco IOS Software, s72033_rp Software
(s72033_rp-ADVIPSERVICESK9_WAN-M), Version 12.2(33)SXI2a, RELEASE SOFTWARE
(fc2)",
   "chassis.mgmt-ip"=>"xxx.xxx.xxx.xxx",
   "chassis.Bridge.enabled"=>"off",
   "chassis.Router.enabled"=>"on",
   "port.ifalias"=>"Gi4/3",
   "port.descr"=>"Mirror-Port, moni-kic",
   "port.auto-negotiation.supported"=>"no",
   "port.auto-negotiation.enabled"=>"yes",
   "port.auto-negotiation.1000Base-T.hd"=>"no",
   "port.auto-negotiation.1000Base-T.fd"=>"yes",
   "port.auto-negotiation.current"=>"unknown"}}

So something is obviously wrong in my facter part, but I cannot find it. 

I''ve tried several attempts (like explicitly resetting the variables
in the setcode block), but ...

Help! :-)

Bernhard

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jcbollinger

2013-Feb-04 18:40 UTC

head link

[Puppet Users] Re: Debugging a facter problem

On Friday, February 1, 2013 8:16:12 AM UTC-6, Bernhard Schmidt
wrote:>
> --- 
> require ''facter'' 
> require ''facter/util/ip'' 
>
> if not FileTest.exists?("/usr/sbin/lldpctl") 
>   nil 
> end 
>

That last bit probably doesn''t do what you want.  That is to say, it 
evaluates to nil in every case (implicitly when the condition is not 
satisfied), and has no effect on anything else in the fact implementation.  
Perhaps you meant to put the rest of the body in an ''else''
clause?  Or,
reverse the sense of the test and put everything else inside the condition?

>
> config = Hash[] 
> output = Facter::Util::Resolution.exec("/usr/sbin/lldpctl -f
keyvalue")
>
> if output == "" 
>   nil 
> end

Again, a not-what-you-intended conditional statement.  In this case,
it''s
probably altogether unnecessary.

>
> for line in output.split("\n") do 
>   # Drop Multiline 
>   if line =~ /^lldp/ 
>     key, value = line.split(''='') 
>     prefix, int, key2 = key.split(''.'', 3) 
>     if not config.has_key?(int) 
>       config[int] = Hash[] 
>     end 
>     config[int][key2] = value 
>   end 
> end 
>

More idiomatic Ruby might be:

# This hash automatically creates appropriate new
# entries as needed:
config = Hash.new { |h, k| h[k] = Hash.new }

output.lines.grep(/^lldp/).each do |line|
    # note the ''chomp'':
    key, value = line.chomp.split(''='') 
    prefix, int, key2 = key.split(''.'', 3) 
    config[int][key2] = value 
end

Other than the "chomp", however, I don''t think that will
change the results.

> for interface in config.keys do 
>   Facter.add("lldp_neighbor_" +
Facter::Util::IP.alphafy(interface)) do
>     setcode do 
>       device = config[interface].fetch(''chassis.name'',
"")
>       ifdescr = config[interface].fetch(''port.descr'',
"")
>       ifalias = config[interface].fetch(''port.ifalias'',
"")

      if device != "" >         if ifalias != "" 
>           device + " " + ifalias 
>         else 
>           device + " "  + ifdescr 
>         end 
>       end 
>     end 
>   end 
> end 
>

More idiomatic:

config.each_pair do | interface, props | 
  Facter.add("lldp_neighbor_" + Facter::Util::IP.alphafy(interface))
do
    setcode do 
      device = props.fetch(''chassis.name'', "") 
      if device != ""
        # note: although clean and concise, this is not 100%
        # equivalent to the original if ''port.ifalias'' can be
present but
        # empty:
        device + '' '' +
props.fetch(''port.ifalias'',
props[''port.descr''])
      else
        # default value when device is empty
        ''no config''
      end 
    end 
  end 
end

I think that might solve your problem, too.  Here''s what I think is 
happening to you: your ''for'' loop runs, setting variable
''interface'' in
turn to each key of the ''config'' hash.  At each iteration, it
creates a
block of code that Facter will execute (later) to determine the value of 
one fact.  Ruby blocks are closures, so where yours later reference the 
value of ''interface'' they are getting the then-current value
in the context
where the block was created.  By that time, that''s the value after the 
iteration is done (apparently the last key iterated).

I think the rewritten version will solve that problem because at each 
iteration, the values of the key and (inner) hash are captured as distinct 
local variables (''interface'' and ''props''),
very much as if the block passed
to ''each_pair'' were an independent function.  This is a Ruby
subtlety, so
you have chosen a good example to attempt to expand your understanding of 
Ruby.

John

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Puppet users - Feb 2013 - Debugging a facter problem

[Puppet Users] Debugging a facter problem

[Puppet Users] Re: Debugging a facter problem