Exporting query results from MySQL

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Problem

You would like to export some query results from MySQL into a format that can be imported in LibreOffice, OpenOffice or Excel.

Solution

Try first with the default export options, as by doing a google search, there are a lot of different options for specifying field delimeters, lines terminated, etc.
So by not specifying any additional options the export is a tab delimited, linefeed-terminated file which should work in most of the programs.
So in order to do that you would need a folder in the MySQL server that should have write access. Usually /tmp should do. Then you can build your query and at the end add the INTO OUTFILE ‘/path’, like:

SELECT one,max(two) max_two,min(three) min_three 
FROM table 
WHERE one=1 
GROUP BY one 
INTO OUTFILE '/tmp/my_query.csv';

You can use any file ending but usually by specifying .csv the program that you will try to open will understand it.

Disabling SQL logging in rails development

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Problem

You are working on a new feature that outputs a lot of SQL code in your log file so it’s difficult to see what else is happening, and you would like to disable the SQL logging in your development environment temporarily.

Solution

You can add the following to your config/application.rb file:

if Rails.env.development?
  ActiveRecord::Base.logger = Logger.new('/dev/null')
end

Thanks to the solution here

Interrupting a cucumber test

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Problem

When you interrupt a cucumber test, usualy by presssing Ctrl+C twice, the database tables are not truncated, so you consequently could have a problem with duplicates records.

Solution

To make sure that the database is clear before running the test again run the following tasks to clear the database and clone it again:

rake db:test:purge
rake db:test:clone

Getting rails console on an amazon aws server when using rvm

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Problem

You would like to get access to your rails application console on an Amazon ec2 instance, and you are also using rvm.

Solution

  • Login with ssh to your server as normal: 
    ssh name@myserver.com -i amazon_key
  • Go to your application’s current folder: 
    cd /my/project/directory/current/
  • Run the following replacing the environment with your specific environment (ie production,beta,staging etc): 
    bundle exec rails c environment

Deleting old releases from rails app server using puppet

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Problem

You would like to automatically delete old releases from your rails app server using a puppet crontab resource.

Solution

Add the following to your modules/crontab/manifests/init.pp file and modify some of the values to what you need:

 # use // to suppress warning: Warning: Unrecognised escape sequence '\;'
  cron { remove_old_releases:
    command   => "test $(find /var/www/your/path/to/ror/app/ -maxdepth 1 -type d | wc -l) -gt 10 && find /var/www/your/path/to/ror/app/ -maxdepth 1 -type d -mtime +14 -exec rm -rf '{}' \\;",
    user      => ubuntu,
    hour      => 0,
    minute    => 15
  }

You should need to change the following:

/var/www/your/path/to/ror/app/ to your application’s release path
-gt 10 this is the number of minimum old releases you want to keep
-mtime +14 releases older than 14 days are deleted

UPDATE

There is chance that when you do not calculate the frequency of the releases right the above script can potentially delete all of your releases, so you end up with no releases 🙁

A better solution to keep the -n number of releases (based on the solution from here:

find /var/www/your/path/to/ror/app/* -type d -printf '%T@ %p\n' | sort -nr | tail -n+6 | cut -f 2- -d " "  | xargs -i rm -rf {}

and the explanation of each step:

  • find /var/www/your/path/to/ror/app/* -maxdepth 0 -type d -printf ‘%T@ %p\n’ find all the directories (-maxdepth 0 -type d) in the search path (/var/www/your/path/to/ror/app/*) excluding the . and .. directories (/*) and add to them the time information (‘%T %p\n’)
  • sort -nr sort them in numeric and reverse order – newer first, oldest last
  • tail -n+6 keep only the first 5 directories, starting from line 6 (tail -n+6)
  • cut -f 2- -d ” “ Remove the first field (ie the date information) keeping the file from the second field using the space as the delimiter (-d ” “)
  • xargs -i rm -rf {} Pass the rm -rf command to delete the directory for each line produced in the previous steps

So the puppet script should be as follows (including the escape characters \ for the % and the additional \):

 # use // to suppress warning: Warning: Unrecognised escape sequence '\;'
  cron { remove_old_releases:
    command   => "find /var/www/your/path/to/ror/app/* -maxdepth 0 -type d -printf '\\%T@ \\%p\\n' | sort -nr | tail -n+6 | cut -f 2- -d ' ' | xargs -i rm -rf '{}' \\;",
    user      => ubuntu,
    hour      => 0,
    minute    => 15
  }

Element is not currently visible and so may not be interacted with (Selenium::WebDriver::Error::ElementNotVisibleError)

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Problem

Trying to run your cucumber tests and interact with links,buttons in a page you have the following error page:

Element is not currently visible and so may not be interacted with (Selenium::WebDriver::Error::ElementNotVisibleError)

Solution

Try to use the :visible => true in your matchers, finders like:

find('#id_name',:visible => true).click

Firefox 19 and unable to obtain stable firefox connection in 60 seconds

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Problem
You have just upgraded your Firefox to the latest release (currently 19) and when running your javascript cucumber tests you get the following error:

 unable to obtain stable firefox connection in 60 seconds

Solution
Add the latest selenium-webdriver to your Gemfile and run bundle update:

gem "selenium-webdriver", "~> 2.30.0", :group => :test

bash: warning: setlocale: LC_ALL: cannot change locale (en_GB.UTF-8)

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Problem

When trying to connect with ssh to a linux (debian- ubuntu) server you get the following error:

bash: warning: setlocale: LC_ALL: cannot change locale (en_GB.UTF-8)

Solution

The reason is that the server is missing the en_US locale that your client is trying to use to connect to the server.
Login to the server and by using sudo (or su) run the following to install the missing en_US locale and make sure that you leave default to ‘None’ as described here:

dpkg-reconfigure locales