de-co-de

Ejabberd restore

2010-11-24T15:02:00.001-08:00

You may get the following error when you use ejabberdctl to restore an ejabberd database.

Problem 'error {case_clause,{aborted,eacces}}' occurred executing the command.
Stacktrace: [{ejabberd_admin,restore_mnesia,1},
             {ejabberd_ctl,call_command,3},
             {ejabberd_ctl,try_call_command,3},
             {ejabberd_ctl,process2,3},
             {ejabberd_ctl,process,1},
             {rpc,'-handle_call/3-fun-0-',5}]

The fix is to make the backup file and all the directories to it readable to everybody.

I hope this helps :)

AWS Load Balancer glitches

2010-06-24T17:17:00.000-07:00

There is one situation in which an Amazon Web Services Elastic Load Balancer can generate errors in the browser. In my experience this happens when you add instances in different availability zones AND you use SSL in addition to regular http. The ELB keeps track of the instances being added to the queue as it should. In addition to the instances the ELB also keeps track of their availability zones.

Start with an ELB with one instance and add a second instance in a second availability zone. In the AWS Console you will see two instances and two availability zones.

Let's remove now one of the instances from the ELB. In this case in the AWS Console you will see that there is just one instance available but there are two availability zones. If you have a tool to monitor your site you will start getting access errors on the SSL URL.

The fix is simply to remove the bad availability zone from the ELB.

I hope this helps,

Marius

RightHere

2010-04-15T22:27:00.000-07:00

Here is my first iPad experiment: one small PhoneGap application that allows one to write and execute html+javascript code right on the iPad. A long way to self hosted development :)

The github project is here: http://github.com/decodeideas/RightHere

An example is here. The top left textarea contains the code, it is executed when you hit Run.

The code in this example:
<input type="button" id="hello" value="Hello World">

<script>x$("hello").click(function(){

alert("hello world")})</script>

EC2 key not found, yet another possible reason

2010-03-25T10:02:00.000-07:00

You may get the following error on EC2 when trying to start a new instance.
Client.InvalidKeyPair.NotFound: The key pair 'some-name' does not exist

This may be due to multiple reasons such as you did not generate the key (I use the AWS console nowadays for this) or you have a typo somewhere. One other possible failure is that you picked the wrong availability zone. There is no key sharing between the 3 Amazon zones US West, US East and EU West.

Hope this helps,

Marius

RubyMine cannot find rubygems

2010-03-22T20:15:00.000-07:00

Sometimes RubyMine seems to be totally lost and cannot find critical gems including rubygems. Using tools like rvm generally complicate things.

The issue is that the command line environment is different from the application one, specially on OS X. One of the easy fix is to run RubyMine from the command line, for example



/Applications/RubyMine/Contents/MacOS/rubymine

This tip is from the jetbrain support team on their discussion group.

Grails can't convert ID

2010-03-21T18:33:00.000-07:00

If you are getting the following error it may be because you are sending a value that cannot be converted to a long.



Provided id of the wrong type for class com.aaa.Bbbb. Expected: class java.lang.Long, got class java.lang.String

For example this may be caused by the user selecting an option from a html <select> with a missing value attribute.

Enable slow log on amazon rds

2010-01-08T21:14:00.000-08:00



rds-create-db-parameter-group primary --description primary --engine MySql5.1

rds-modify-db-parameter-group primary --parameters "name=slow_query_log, value=true, method=immediate"

rds-modify-db-instance YOUR_INSTANCE --db-parameter-group-name primary

Deploying rails assets to the Amazon CDN

2009-11-21T14:53:00.000-08:00

Rails uses a ?timestamp in the URL for cache busting. Together with an expired header in the far future this allows you to get the maximum benefits out of browser caching.

Unfortunately this scheme does not seem to work on the Amazon CDN. I just contributed some changes to the Asset Packager that allow you to better use assets on the CDN

http://github.com/decodeideas/asset_packager

ec2_upload_bundle and ruby 1.9: can't convert Fixnum into String

2009-11-07T09:34:00.000-08:00

The following applies to the following scenari

- ubuntu karmic, ec2 ami
- ruby 1.9.2 installed as /usr/bin/ruby
- the latest ec2 tools

When you use ec2_upload_bundle to re-bundle an AMI that you modified you will get the error



ERROR: can't convert Fixnum into String

The trick to debug this is to pass --debug to the ec2 commands. The fix is on
line 19 of /usr/lib/ec2-ami-tools/lib/ec2/amitools/util.rb
you need to change ?A to ?A.ord to get this line:



(0..19).inject("") {|ident, n| ident+(?A.ord + Kernel.rand(26)).chr}

Before doing the change you can reproduce the problem with



ruby1.9 -r /usr/lib/ec2-ami-tools/lib/ec2/amitools/util -e 'puts

gen_ident'

After applying the patch you should get a short sequence of random
letters.

Plugin not found with ruby 1.9, rails 2.3.4

2009-11-06T12:33:00.000-08:00

When using rails 2.3.4 with ruby 1.9.1 you cannot install plugins from git. You will get an error like the following:



script/plugin install git://github.com/giraffesoft/resource_controller.git

Plugin not found: ["git://github.com/giraffesoft/resource_controller.git"]

The simplest workaround is to use ruby 1.8 to run the above. On Snow Leopard you have it very likely as /usr/bin/ruby, so you can do



/usr/bin/ruby script/plugin install git://github.com/giraffesoft/resource_controller.git

On Ubuntu you probably have it as ruby1.8.

Using mov files in Powerpoint

2009-10-19T10:00:00.000-07:00

I found out that .mov files play unreliably when imported into Powerpoint. I tried transforming into avi and wmv files using a plethora of tools. The most reliable workflow I found so far is:

1. in Final Cut (Express) generate the mov files in H.264, one bit rate that worked acceptably for me is 1500kbps
2. move to the vista system
3. open Windows Movie Maker
4. import the mov file, add to the history line
5. select Publish to the local system
6. select Custom format
7. select Windows Media Video, DVD 3000kbps
8. write the file, for some annoying reason you cannot use the same name as the mov file even though the file will have the extension wmv

Import the wmv file in power point

Ruby gems on Snow Leopard

2009-09-03T14:59:00.000-07:00

After upgrading to Snow Leopard I am getting all kind of weird errors in my ruby gems, for example:


dlopen(/Library/Ruby/Gems/1.8/gems/nokogiri-1.3.3/lib/nokogiri/nokogiri.bundle, 9): no suitable image found.  Did find:
 /Library/Ruby/Gems/1.8/gems/nokogiri-1.3.3/lib/nokogiri/nokogiri.bundle: mach-o, but wrong architecture - /Library/Ruby/Gems/1.8/gems/nokogiri-1.3.3/lib/nokogiri/nokogiri.bundle

I just deleted all the files under /Library/Ruby/Gems/1.8/gems and I am reinstalling the gems.

SQS connection between Ruby and Python

2009-08-31T21:05:00.000-07:00

If you try to use Amazon SQS to connect Right_aws with Boto you have to keep in mind that Boto expects the body of the message to be encoded in base64. To make life even more interesting the Boto frameawork will crash in the XML parser for some content of the body.

Right scale gem on ruby 1.9

2009-08-04T13:31:00.000-07:00

If you try to use the right_aws gem on ruby 1.9 you will encounter a couple of errors including



no such file to load -- md5

and



right_aws-1.10.0/lib/s3/right_s3_interface.rb:1133: syntax error, unexpected ':', expecting keyword_then or ',' or ';' or '\n'

when 'LastModified' : @result[:last_modified] = @text

^

right_aws-1.10.0/lib/s3/right_s3_interface.rb:1134: syntax error, unexpected keyword_when, expecting keyword_end

when 'ETag'         : @result[:e_tag]         = @text

^

right_aws-1.10.0/lib/s3/right_s3_interface.rb:1134: syntax error, unexpected ':', expecting keyword_end

when 'ETag'         : @result[:e_tag]         = @text

^

right_aws-1.10.0/lib/s3/right_s3_interface.rb:1175: syntax error, unexpected keyword_end, expecting $end

In this case you can use the following patch to port the gem to ruby 1.9. The patch may stop working as Right Scale updates their code, the changes are relatively small and you should be able to re-port the patch to the new code.



diff -crB right_aws-1.10.0-orig/lib/awsbase/right_awsbase.rb right_aws-1.10.0/lib/awsbase/right_awsbase.rb

*** right_aws-1.10.0-orig/lib/awsbase/right_awsbase.rb 2009-08-04 13:40:56.000000000 -0700

--- right_aws-1.10.0/lib/awsbase/right_awsbase.rb 2009-08-04 13:23:53.000000000 -0700

***************

*** 23,29 ****



# Test

module RightAws

!   require 'md5'

require 'pp'



class AwsUtils #:nodoc:

--- 23,29 ----



# Test

module RightAws

!   require 'digest/md5'

require 'pp'



class AwsUtils #:nodoc:

diff -crB right_aws-1.10.0-orig/lib/s3/right_s3.rb right_aws-1.10.0/lib/s3/right_s3.rb

*** right_aws-1.10.0-orig/lib/s3/right_s3.rb 2009-08-04 13:40:56.000000000 -0700

--- right_aws-1.10.0/lib/s3/right_s3.rb 2009-08-04 13:26:37.000000000 -0700

***************

*** 761,769 ****

@name  = name

@perms = perms.to_a

case action

!           when :apply:             apply

!           when :refresh:           refresh

!           when :apply_and_refresh: apply; refresh

end

end



--- 761,769 ----

@name  = name

@perms = perms.to_a

case action

!           when :apply then             apply

!           when :refresh then           refresh

!           when :apply_and_refresh then apply; refresh

end

end



diff -crB right_aws-1.10.0-orig/lib/s3/right_s3_interface.rb right_aws-1.10.0/lib/s3/right_s3_interface.rb

*** right_aws-1.10.0-orig/lib/s3/right_s3_interface.rb 2009-08-04 13:40:56.000000000 -0700

--- right_aws-1.10.0/lib/s3/right_s3_interface.rb 2009-08-04 13:25:39.000000000 -0700

***************

*** 1130,1137 ****

end

def tagend(name)

case name

!         when 'LastModified' : @result[:last_modified] = @text

!         when 'ETag'         : @result[:e_tag]         = @text

end

end

end

--- 1130,1137 ----

end

def tagend(name)

case name

!         when 'LastModified' then @result[:last_modified] = @text

!         when 'ETag'         then @result[:e_tag]         = @text

end

end

end

Postgres after mac migration

2009-07-01T20:39:00.000-07:00

After you migrate your files to a new mac all the postgres data will be present but the postgres user won't exist. The postgres server won't start in this case. To create the user you need to figure out the postgres userid. You can run ls -l /usr/local/psql (substitute your postgres installation directory). The data subfolder needs to belong to the postgres user and you will see just a numeric userid. You will also see the postgres groupid. The example below assumes that both IDs are 103, make sure to substitute the IDs for your setup.

To create the user and group do the following as root:


dscl . -create /Users/postgres UserID 103
dscl . -create /Groups/postgres PrimaryGroupID 103
dscl / -append /Groups/postgres GroupMembership postgres

The packet8 scam

2009-06-12T15:38:00.001-07:00

I was seldom using my packet8 account and I had a low usage account paying $14/month. They sent an email that they will automatically upgrade my account to double that price since they do not offer low usage anymore. This doesn't make sense for me since I really never use my account. I started canceling my account which you cannot do over their automated system. You have to call them and they transfer you to a voicemail. They call you back after 1 day and if you are unlucky to miss the call you have to call back, identify yourself, get transferred, identify yourself again and then listen to somebody doing their best effort to keep your account.

This is all pretty standard albeit a bit shadu. What is not standard is that in the time it took to do all this the new month started. My account got canceled on the 2nd of the month but I was charged $30 on the 3rd of the month. I called somebody there and I was informed that I am liable for that month even though it is not my fault their lengthy process let me to this situation.

Are you a happy packet8 customer or an unhappy former packet 8 customer? Leave a comment.

Marius

Ruby on Rails.tmbundle for ruby1.9

2009-06-02T17:07:00.000-07:00

I forked Dr. Nic's TextMate bundle for Ruby On Rails and I started fixing issues related to ruby1.9

http://github.com/decodeideas/ruby-on-rails-tmbundle/tree/master

Let me know of any issue.

Benefits of local .gitignore

2009-06-01T07:50:00.000-07:00

When you avoid tracking files in a git repository you can out the file names (or a regex matching them) in .gitignore files. Some weeks ago I realized you can sprinkle .gitignore file through out your directory structure. Generally it makes sense to keep information modularized so I started using .gitignore files in my subfolders.

Today I found out the benefits of local .gitignore files. I started a new project with a git repository encompassing multiple modules: rails app, backend processing, deployment scripts. Later on I could not figure out how to use Capistrano to deploy a rails out from a folder and I split the big repository in smaller repositories, one per project.

Since the subfolders have their own .gitignore files they were automatically picked up by each git subproject. Nice :)

Upgrading libxml on OS X from sources: DON'T!

2009-05-31T15:06:00.001-07:00

I upgraded the libxml/libxslt libraries on my MBP. After ./configure && make && sudo make install the new libraries ended up in /usr/local which is fine. I renamed the existing libraries from /usr/lib and that was the end of it. I had to reboot from an external firewire backup to restore the files and get my system back.

The series of unfortunate events that leads to a broken OS are:

the libxml build process generates only i386 files
it is not obvious how to generate universal binary, or at least x86_64 with the libtool used in the libxml source
the sudo exe depends on a library that in turn depends on the x86_64 libxml
without libxml from the distribution there is no more sudo so you cannot rename the shared libraries back

Rake1.9 gotcha

2009-05-30T21:29:00.000-07:00

Note that if you installed ruby 1.9 in parallel with ruby 1.8 then you got a rake1.9 that you should use with the upgraded projects. Unfortunately rake1.9 does not call gem1.9, it falls back to gem when you run commands like rake1.9 gems:install RAILS_ENV=test. If you want to install gems for the 1.9 environment you need to use gem1.9 explicitly, for example


sudo gem1.9 install thoughtbot-factory_girl

Mysql ruby1.9 extensions on OS X / Ubuntu 9.0.4

2009-05-30T19:33:00.000-07:00

If you get the errors below when installing the mysql gem for ruby 1.9 then just go to the link below and follow the instructions to compile the ruby extension manually. Remember to use ruby1.9 if you installed it in parallel with 1.8.6

http://www.tmtm.org/en/mysql/ruby/

The instructions worked for me both on OS X 10.5.6 and Ubuntu 9.0.4. Here are the errors I was getting with gem install mysql.


mysql.c:6:21: error: version.h: No such file or directory
mysql.c: In function ‘make_field_obj’:
mysql.c:185: warning: unused variable ‘hash’
mysql.c: In function ‘escape_string’:

Git on ubuntu 9.04 server

2009-05-30T08:27:00.000-07:00

If you try to install git on ubuntu 9.04 server, without Tcl/TK, you will get an error similar to the following:


GITGUI_VERSION = 0.12.0.23.ga91be
    * new locations or Tcl/Tk interpreter
    GEN git-gui
    INDEX lib/
    * tclsh failed; using unoptimized loading
    MSGFMT    po/de.msg make[1]: *** [po/de.msg] Error 127

One fix is to not build the GITGUI extensions. A complete list of commands follows, replace 1.6.3.1 with the current stable version of git.


http://kernel.org/pub/software/scm/git/git-1.6.3.1.tar.bz2
tar xjf git-1.6.3.1.tar.bz2
cd git-1.6.3.1
./configure --without-tcltk
make 
sudo make install

Python new not called

2009-05-20T10:10:00.000-07:00

I was trying to build a quick and dirty singleton in python 2.5. I defined a __new__ method for my class and returned the one and only instance in there of the desired subject. To my surprise __new__ was not called, at all. After some more digging it turns out that your class needs to inherit from object. See the example below.

class NoNew:
    def __new__(cls):
        print "New Called for NoNew"

class YesNew(object):
    def __new__(cls):
        print "New Called for YesNew"


NoNew()
YesNew()

Executing the above generates


$ python test.py
New Called for YesNew

As you can see there is no line with NoNew and you need to inherit from object to be able to override __new__.

Another interesting fact is that printing an object will output something that looks like a physical address and that can be used to ensure that your objects are a singleton. Writing unit test cases for this is harder and I decide it is not worth the time.

CocoaHeads Sacramento/Roseville/Davis

2009-05-11T06:43:00.000-07:00

I am trying to start a CocoaHeads group in the CA Central Valley around Sacramento. Inaugural meeting this Thursday May 14th at 6:30pm. We are meeting at Common Grounds in Davis, CA. See you there if interested :)

Shipped my iPhone app

2009-05-05T09:18:00.000-07:00

Checkout my iPhone app, see the links under http://windsesh.com. Some of the code is open sourced at github.