Ubuntu 13.04 + XPS Dell + sound is not working

Recently I have upgraded my Ubuntu OS from 12.10 to 13.04 on my Dell XPS.

But suddenly I faced issue with my sound. I am not able to get sound form my machine.

After googling, I found solution for Dell Vostro, but after some time I found for dell xps too. I tried solution on my Dell box and my sound is back.

Here is the solution,

sudo gedit /etc/modprobe.d/alsa-base.conf

Add following line at the bottom of a file

options snd-hda-intel model=dell-bios

But don't forget to reboot your machine.
References :
http://askubuntu.com/questions/288503/vostro-3560-sound-is-not-working-after-upgrade-to-ubuntu-13-04
http://ubuntuforums.org/showthread.php?t=1457676

Rails 4 - Transaction isolation level

After long time I am writing small post, as now a days not able manage a time or you can say I am just working ;)

TL;DR - In Rails 4, Jon Leighton has added a support for specifying transaction isolation level. This transaction level we can pass when starting transaction(or you can say while calling transaction method)

Note : This blog post is copied from Jon Leighton commits, which he did in a rails repository

Before continuing reading this post, it will be good if you read about Transaction Isolation over here.

Isolation is a property that defines how/when the changes made by one operation become visible to other concurrent operations. Isolation is one of the ACID (Atomicity, Consistency, Isolation, Durability) properties.

Highlevel of Isolation does affect on Concurrency property of ACID, as it require to use locks or multiversion concurrency control.

Anyways here is a documentation which Jon Leighton has added in rails trank.

If your database supports setting the isolation level for a transaction, you can set it like so:

Post.transaction(isolation: :serializable) do
  # ...
end

Valid isolation levels are:
* `:read_uncommitted`
* `:read_committed`
* `:repeatable_read`
* `:serializable`

You should consult the documentation for your database to understand the semantics of these different levels:

* http://www.postgresql.org/docs/9.1/static/transaction-iso.html
* https://dev.mysql.com/doc/refman/5.0/en/set-transaction.html

An `ActiveRecord::TransactionIsolationError` will be raised if:
* The adapter does not support setting the isolation level
* You are joining an existing open transaction
* You are creating a nested (savepoint) transaction

The mysql, mysql2 and postgresql adapters support setting the transaction isolation level. However, support is disabled for mysql versions below 5, because they are affected by a bug (http://bugs.mysql.com/bug.php?id=39170) which means the isolation level gets persisted outside the transaction.

References :
http://en.wikipedia.org/wiki/Isolation_(database_systems)
http://www.postgresql.org/docs/9.1/static/transaction-iso.html
https://dev.mysql.com/doc/refman/5.0/en/set-transaction.html
https://github.com/rails/rails/commit/392eeecc11a291e406db927a18b75f41b2658253

bundle install + tar_input.rb:49:in `initialize': not in gzip format (Zlib::GzipFile::Error)

This is one of the pending post since 6 month, thought it might helpful to some people.

Today on production server our system team found very strange issue with REE and bundler which lead production server was down for 20 min. This issue did not occur on test (Since on test and production have different version of REE)

Issue is as follows,


Issue was new to me, so I started digging into it using the almighty google.

The solution which I found on net was not applicable since we couldn't afford a downtime.

Issue is actually with ruby-enterprise-1.8.7-2010.02. Which is fixed in ruby-enterprise-1.8.7-2011.01 as described in release note.

http://blog.phusion.nl/2011/02/12/ruby-enterprise-edition-1-8-7-2011-01-released/

But we don't have a time to upgrade REE at this point. So I digged into it and found temporary solution described here.

http://stackoverflow.com/questions/2494659/strange-bundler-error-tar-input-rb49in-initialize-not-in-gzip-format-zlib

Basically you have to clear you gem cache either you are use rvm or not. so I have simply deleted content from my gems folder
like,

sudo rm -rf /opt/ruby-enterprise-1.8.7-2010.02/lib/ruby/gems/1.8/cache/

And this worked !!!....

Configure Repository In Redmine

As Rubyist, most of us we use Redmine for Project Management and git for source code management. Written using the Ruby on Rails framework, it is cross-platform and cross-database. Redmine is open source and released under the terms of the GNU General Public License v2 (GPL).

Git is a free & open source, distributed version control system designed to handle everything from small to very large projects with speed and efficiency.

Redmine provides many features out of that is SCM integration (SVN, CVS, Git, Mercurial, Bazaar and Darcs), which I going to explaing you in this blog post.

I am explaning this because, many time we do a code review for team members. Also some time we need to review a perticuler fix done for any bug. At that time it is very difficult to go through a git log.

So it will be great to use to redmine for this, were we can attach a code to feature or bug and even from git log to issue.

Redmine has this great feature, http://www.redmine.org/projects/redmine/wiki/RedmineRepositories#Repository-user-mapping

Now if we have already git server then, then their are two solution available,

1. Make git server to support http protocol
2. Replicate git server on Redmine server it self

both above option are very easy but issue in second option. Issue if you have git server which is runnning separately. Which happens in my case.

Our git server is only accessisble via git protocol like

git clone user_name@repository_server:path_to_project.git

Our git server is used by more than 30 developers were more than 13 repositories get accessed. So I don't want to distrub the development process. So I have decided to replicate git server on redmine.

A. Replicate git server to be used by Redmine

1. Login to your Redmine server from console
2. Clone the repository with following command

  # change to your respective user 
 $ su - name_of_user   
  
  # Create a folder to hold your repository
 $ mkdir /any/path/to/create/repo
 
  # change directory
 $ cd /any/path/to/create/repo
 
 # Make a bare clone of the repo
 $ git clone --bare ssh://git@reposerver/usr/local/git_root/foo-project.git
 
  # Switch to repository
 $ cd foo-project.git
 
  # add orignal repository in newly created repository for fetching changes done in orignal repository 
 $ git remote add origin ssh://git@reposerver/usr/local/git_root/foo-project.git
 
  # Above command will feches commit from origanl repo
 $ git fetch origin
 $ git reset --soft refs/remotes/origin/master

  #Make sure bypass the password prompt using ssh config for following command to work from crontab.
 
  # Add the following to your crontab
 */10 * * * * cd /var/local/git_copies/foo-project.git && git fetch origin && git reset --soft refs/remotes/origin/master > /dev/null

Using above command we have setuped a replica of git server on redmine server.

B. Add project repository in Redmine

Go to the redmine, select your project and add repository local path. Goto => setting => repository

C. Fetch commits into redmine

When you first browse the repository, Redmine retrieves the description of all of the existing commits and stores them in the database.
This is done only once per repository but can take a very long time (or even time out) if your repository has hundreds of commits.

To avoid this, you can do it offline.
Run the following rake command on redmine server:

$ ruby script/runner "Repository.fetch_changesets" -e production

All commits will be retrieved in to the Redmine database.

Since Redmdine 0.9.x, you can use following link of your redmine to execute fetch_changesets for a specific project, or all.
http://redmine.example.com/sys/fetch_changesets (=> fetches changesets for all active projects)
http://redmine.example.com/sys/fetch_changesets?id=foo (=> fetches changesets for project foo only)

Now we have sucessfully configured git reposiroty in Redmine.

Now you can use following link for linking revision and commits to issue and vice-varsa.
http://www.redmine.org/projects/redmine/wiki/RedmineTextFormatting

Passenger tuning for rails application

Guys, it has been a long over due post. I have finished tuning passenger long back but caught up with Diwali celebration.

Anyways generally I prefer simple and easily understandable configuration. So following configuration is as per my best knowledge and google findings. ;)

I have verified my configuration using ab - Apache HTTP server benchmarking tool. Also tried other tools such as Jmeter, httperf. I have also used passenger-memory-stats for finding rails instance size and passenger-status for finding number of request which are pending in global queue.

I have started passenger tuning using passenger nginx user guide. You will also find passenger-apache guide.

As I am using nginx, following configuration is with respect to nginx but same will applies for apache except some extra directives and syntax.

After digging into passenger tuning, I realized that passenger well configured for production. But still Based on nginx-passenger user guide I have collected following list of directive, which we can configure according to our needs.

Directive	Default Value	Nginx Block	Use
passenger_max_pool_size <integer>	6	http	Maximum instances on server
passenger_pool_idle_time <integer>	300 sec	http	instance idle time
passenger_max_instances_per_app <integer>	0	http	Maximum instances allowed to single app
passenger_min_instances <integer>	1	http, server, location, if	minimum number of application instances which are always active
passenger_pre_start <url>	-	http	Pre start application
passenger_use_global_queue <on|off>	on	http, server, location, if	Turns the use of global queuing on or off
passenger_ignore_client_abort <on|off>	off	http, server, location, if	Ignore client aborts
rails_framework_spawner_idle_time <integer>	1800 sec	http, server, location, if	FrameworkSpawner server idle time
rails_app_spawner_idle_time <integer>	600 sec	http, server, location, if	ApplicationSpawner server idle time
passenger_log_level <integer>	0 (Can be 0, 1, 2, 3)	http	for how much information Passenger should write into error.log
passenger_debug_log_file <filename>	error.log	http	allow to specify the file that debugging and error messages should be written
passenger_pass_header <header name>		http, server, location, if	Used to pass headers

Almost all of these directive has default value which is good enough for an applications. But there are some directive which very important to configure depending on our application environment.

1. passenger_max_pool_size :
            The maximum number of Ruby on Rails or Rack application instances that may be simultaneously active. A larger number results in higher memory usage, but improved ability to handle concurrent HTTP clients.
            The value should be at least equal to the number of CPUs (or CPU cores) that you have. If your system has 2 GB of RAM, then we recommend a value of 30. If your system is a Virtual Private Server (VPS) and has about 256 MB RAM, and is also running other services such as MySQL, then we recommend a value of 2.
            I recomond you to find your application instance size using passenger-memory-stats and configure value of passenger_max_pool_size.
            e.g.  If your application instance size is 300 MB and RAM size 2 GB then value of passenger_max_pool_size should be 4 because 1200 MB(4*300) will be used by application instance and remaning for other process.

2. passenger_max_instances_per_app :
            The maximum number of application instances that may be simultaneously active for a single application. This helps to make sure that a single application will not occupy all available slots in the application pool.
            This value must be less than passenger_max_pool_size. A value of 0 means that there is no limit placed on the number of instances a single application may use, i.e. only the global limit of passenger_max_pool_size will be enforced.

3. passenger_pre_start :
            By default, Phusion Passenger does not start any application instances until said web application is first accessed. The result is that the first visitor of said web application might experience a small delay as Phusion Passenger is starting the web application on demand. If that is undesirable, then this directive can be used to pre-started application instances during Nginx startup.
            This directive accepts the URL of the web application you want to pre-start. It may be specified any number of times.

passenger_pre_start http://foo.com/; 
passenger_pre_start http://bar.com:3500/; 
passenger_pre_start http://myblog.com/store;

Let's get into live scenarios

1. A server with multiple rails applications (Development and test server)
            I have a server with 16 GB of RAM and 8 core cpu, on which redmine(bug tracking system), test rails app and other developers app instances are running. Means you can say mutiple apps are running.
            According to passenger-memory-stats redmine is taking 300 MB and other rails app 500 MB. So I have kept following configuration

passenger_max_pool_size 16;
# arround 8 GB for rails application and remaning for other process
passenger_pool_idle_time 150;
# reduced idle time as multiple app are running
passenger_max_instances_per_app 8; 
# since single app should not use whole pool size, but simuteniouly should handle mutiple requests

2. A server with single rails application (Production server)
            On my production enviroment we have 8 GB of RAM and 4 core cpu, on which only single rails application is running.
            As my rails application instance size is 500 MB, I have kept following configuration on production

passenger_max_pool_size 10;
# arround 5 GB for rails application and remaning for other process
passenger_pool_idle_time 600;
# Increased as it is production
passenger_min_instances 2;
# atlease two instances should in memory at any time
passenger_pre_start http://myprodapp.com/;
# pre start my instance at the time of nginx start instade on first request

For testing whether required instances are forked or not use ab (Apache benchmark) as described above.

Reference : http://www.alfajango.com/blog/performance-tuning-for-phusion-passenger-an-introduction/

Simple nginx tuning for rails application on production server

Recently I was working on tuning my production environment for better performance. In production server mainly three things makes a difference to the web application,

1. REE-GC Tuning
2. Nginx Tuning
3. Passenger Tuning

As I have already done REE-GC tuning in previous articles, so lets discuss on Nginx tuning. Passenger tuning will be get covered in subsequent articles.

In Nginx there are many ways to boost your application performance, but I would like to share few important tweaks.

To validate performance improvement, you can use page-speed or Yslow

Before doing these tweaks on my rails application, yslow and page-speed score was around 25-35/100. After doing these tweaks it increased to 90-96/100

To get 100/100 we have to write a good code-design not best code-design ;). In our application the performance dip is due to not using CSS sprite.

A. Enable Gzip :

Gzip helps to compress and decompress the data on-the-fly between browser and server. Nginx has HttpGzipModule for same.

Add following lines into to http block nginx.conf

gzip  on;
gzip_types text/plain text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript application/javascript;
gzip_vary on;
gzip_disable     "MSIE [1-6]\.";
#gzip_proxied any;
#gzip_buffers 128 128k;
#gzip_min_length  1100;

Depending on your need you can set the above commented directives.

B. Enable caching :

Setting an expiry date or a maximum age in the HTTP headers for static resources instructs the browser to load previously downloaded resources from local disk rather than over the network.

Add following lines into to server block nginx.conf

   location ~* \.(ico|css|js|gif|jpe?g|png|swf)(\?[0-9]+)?$ {
         expires max;
         break;
   }

C. Minify JavaScript :

Compacting JavaScript code can save many bytes of data and speed up downloading, parsing, and execution time.

For this you can use any third party tools or gems like Jammit,asset_packager to minify your JavaScript files. Rails 3 has built in support.

Sample nginx.conf :

Apart from this you can use multiple assets server for static resources, which will be covered in subsequent articles.

Install Redis server on Ubuntu maunally as service

This post is all about installing redis server manually on Ubuntu system and then setup it as a service.

For this post I have originally referred a blog post of denofubiquity.

By default Ubuntu provides redis server installation by

sudo apt-get install redis-server

And you done with the installation of redis server.

But if you want to install latest version of redis server, then you can go through the rest of post.

wget http://redis.googlecode.com/files/redis-2.2.12.tar.gz
# You can specify a link of redis-server which you want to install
tar -zxf redis-2.2.12.tar.gz
cd redis-2.2.12
make
sudo make install

Now setup a redis.conf. I have copied a redis.conf from default installation of redis-server which I have used. If you want to install redis-server for your production machine you may refer a redis.conf from denofubiquity's post

wget https://raw.github.com/gist/1164482/77e4ecf14ffac42b0e987e7ffe16cb757d734ff9/redis.conf
sudo mkdir /etc/redis
sudo mv redis.conf /etc/redis/redis.conf

Copy redis-server startup scripts.

wget https://raw.github.com/gist/1164503/d1bc2cc6782b943d9b28aa93fc7038f4ae5a905f/redis-server
sudo mv redis-server /etc/init.d/redis-server
sudo chmod +x /etc/init.d/redis-server

sudo useradd redis
sudo mkdir -p /var/lib/redis
sudo mkdir -p /var/log/redis
sudo chown redis.redis /var/lib/redis
sudo chown redis.redis /var/log/redis

Mark redis server as startup services.

sudo update-rc.d redis-server defaults

Start your redis server.

sudo /etc/init.d/redis-server start

Note :

You can customise your redis configuration as per your requirements.
Like from Redis 2.2, it supports unix socket, so you can use it if required.
- Specify socket in redis.conf using this line
unixsocket /tmp/redis.sock
- Tell Redis.new() to read it as required. like
Redis.new(:path => "/tmp/redis.sock")

Also you can customise memory configuration in your redis.conf.

Reference :

http://www.denofubiquity.com/nosql/412