sneakybits

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2009-09-17T11:21:00.001-04:00

Ruby-Processing and java.lang.ExceptionInInitializerError

2009-05-22T10:51:00.003-04:00

rp5 run samples/jwishy.rb 
RubyGlobal.java:135:in `createGlobals': java.lang.ExceptionInInitializerError
    from Ruby.java:939:in `init'
    from Ruby.java:172:in `newInstance'
    from Main.java:199:in `run'
    from Main.java:110:in `run'
    from Main.java:94:in `main'

... the culprit was the alternative version of the JRE I was using (OpenJDK). After swtiching to the standard Sun JDK everything worked fine.

Golem Statemachine

2009-04-18T00:06:00.012-04:00

Following a frustrating week with the acts_as_state_machine/AASM plugin, I ended up writing my own finite state machine library for Ruby.

It's called Golem, and it's now on Github, here: http://github.com/zuk/golem_statemachine/tree/master

The code is cleaner than AASM's (or at least I think so), which should make debugging less frustrating. There's also a nice DSL for defining the state machine.

For example, to implement this statemachine:

You would define it like so:

define_statemachine do
  initial_state :HUNGRY

  state :HUNGRY do
    on :eat do
      transition :to => :SATIATED, :if => :likes?
      transition do
        action do |monster| 
          puts "#{monster} says BLAH!!"
        end
      end
    end
  end

  state :SATIATED do
    enter do |monster|
      puts "#{monster} says BURP!!!"
    end
  end
end

The state machine definition goes inside your Ruby class (or ActiveRecord model), endowing the class with finite state machine behavior:

require 'golem'

class Monster
  include Golem

  attr_accessor :state

  def initialize(name)
    @name = name
  end

  def to_s
    @name
  end

  def likes?(food)
    food.kind_of?(String)
  end

  define_statemachine do
    # ...
  end
end

m = Monster.new("Stringosaurus")
puts m.current_state # ==> :HUNGRY
m.eat(12345)         # ==> "Stringosaurus says BLAH!!"
puts m.current_state # ==> :HUNGRY
m.eat("abcde")       # ==> "Stringosaurus says BURP!!"
puts m.current_state # ==> :SATIATED

python-xml woes

2009-02-09T17:50:00.005-05:00

Python ImportErrors like the following (stemming from the recent deprecation of the python-xml library in Ubuntu):

Failed to load application: No module named ext

... can be easily addressed by:

sudo apt-get install python-xml
export PYTHONPATH=$PYTHONPATH:/usr/lib/python2.5/site-packages/oldxml

This caused me a good few hours' grief earlier today.

A PHP Client for JasperServer (via SOAP)

2008-11-12T13:32:00.011-05:00

I needed a PHP version of my Ruby SOAP client for JaserpServer.

Here it is: http://gist.github.com/26205

Usage (this runs the report unit '/my_report' and returns the result in PDF format):

 
  $jasper_url = "http://jasper.example.com/jasperserver/services/repository";
  $jasper_username = "jasperadmin";
  $jasper_password = "topsecret";


  $client = new JasperClient($jasper_url, $jasper_username, $jasper_password);

  $report_unit = "/my_report";
  $report_format = "PDF";
  $report_params = array('foo' => 'bar', 'fruit' => 'apple');
 
  $result = $client->requestReport($report_unit, $report_format,$report_params);

  header('Content-type: application/pdf');
  echo $result;

gittidy

2008-10-23T10:03:00.007-04:00

I had my first run in with git today. After trying to sync an out-of-whack git-svn local repo with github things turned ugly:

git push
error: remote 'refs/heads/master' is not a strict subset of local ref 'refs/heads/master'. maybe you are not up-to-date and need to pull first?
error: failed to push to 'git@github.com:gunark/rubycas-server.git'

Turns out that remotely deleting the master branch on github (as described here) and then recreating it fixed the problem:

git push origin :heads/master
deleting 'refs/heads/master'
Everything up-to-date
git push origin master
updating 'refs/heads/master'
  from 0000000000000000000000000000000000000000
  to   6dd64b1b025c324d0b287805d6c18183b9f20b9e
Generating pack...
Done counting 1395 objects.
Deltifying 1395 objects...
 100% (1395/1395) done
Writing 1395 objects...
 100% (1395/1395) done
Total 1395 (delta 960), reused 0 (delta 0)

Yay

There was some weirdness in the github project page after this, but performing another commit and push seems to have taken things back to normal.

WS-Management + Openwsman + openSUSE + Ruby

2008-10-15T12:13:00.026-04:00

Yet another failed attempt at using SNMP for monitoring application-level services led me to WS-Management, an HTTP/SOAP-based protocol meant to replace SNMP. DS-Management might not be the first protocol to attempt usurping SNMP, but this one looks promising. Widespread support and implementation is claimed by Microsoft, and a reasonably mature open-source implementation -- Openwsman -- is sponsored by SuSE.

Documentation for Openwsman unfortunately seems rather lacking. It took some poking around, but I was able to get a basic client-server session going under openSUSE 10.3. Here's how:

First, add the development channel for openwsman and install the openwsman packages:

sudo smart channel --add http://download.opensuse.org/repositories/home:/kwk:/Management/openSUSE_10.3/home:kwk:Management.repo
sudo smart update home_kwk_Management
sudo smart install openwsman openwsman-client openwsman-server wsmancli openwsman-yast

If you run into PGP key problems, try disabling PGP key checking first:
smart config --set rpm-check-signatures=false

The openwsman-server package installs openwsmand -- a stand-alone server providing WS-Management services. We'll need to configure the authentication system before running the server. I was unable to get things going with the default Basic authentication, but Digest worked for me:

htdigest2 -c /etc/openwsman/digest_auth.passwd OPENWSMAN admin
Adding password for admin in realm OPENWSMAN.
New password: test
Re-type new password: test

Now edit the Openwsman config file to use Digest authentication. The config file is under /etc/openwsman/openwsman.conf and should be altered to look something like this (note that we've uncommented the 'digest_password_file' option):

[server]
port = 8889
#ssl_port = 8888
ssl_cert_file = /etc/openwsman/servercert.pem
ssl_key_file = /etc/openwsman/serverkey.pem
digest_password_file = /etc/openwsman/digest_auth.passwd
#basic_password_file = /etc/openwsman/simple_auth.passwd

min_threads = 4
max_threads = 10

#use_digest is OBSOLETED, see below.

#
# Authentication backend for BASIC authentication. Default is to read a configuration file defined with 'basic_password_file'
#

basic_authenticator = libwsman_pam_auth.so
basic_authenticator_arg = openwsman


[client]
port = 8889
agent = openwsman 0.6.0

#
# settings for the CIM plugin
#

[cim]
default_cim_namespace = root/cimv2

# The following are in part fake namespaces for some publicly available CIM implementations.
vendor_namespaces = OpenWBEM=http://schema.openwbem.org/wbem/wscim/1/cim-schema/2,Linux=http://sblim.sf.net/wbem/wscim/1/cim-schema/2,OMC=http://schema.omc-project.org/wbem/wscim/1/cim-schema/2

# CIMOM host, default is localhost
# host = localhost

# CIMOM port, default is 5988
# port = 5988

Okay, now we can run the server:

sudo /usr/sbin/openwsmand -d

We can now connect to the server using a few simple Ruby commands. Open an interactive ruby session (using irb) and enter the following:

require 'rwsman'
client = WsMan::Client.new('http', 'localhost', 8889, '/wsman', 'admin', 'test')
client_opt = WsMan::ClientOption.new
identify = client.identify(client_opt)
puts identify.rawxml

If everything worked, you should get a response that looks something like this:



 
 
   
     http://schemas.dmtf.org/wbem/wsman/1/wsman.xsd
     Openwsman Project
     1.5.9

The identify object returned by the client also exposes product_version, protocol_version, and product_vendor methods that return their respective values from the parsed XML data.

With the YAST plugin installed, Openwsman can access diagnostic information about your SuSE system. For example try this:

client_opt.property_add('ycp', '{ import "SuSERelease"; return SuSERelease::ReleaseInformation("/"); }' )
result = client.invoke('http://schema.opensuse.org/YaST/wsman-schema/10-3/YCP', 'eval', client_opt)
puts "SUSE Version: #{result.body}"