tips & tricks

Tips

Delete large number of files:
 ls|xargs -L 1000 rm

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Maintenace page for Rails

RewriteEngine on

RewriteCond %{DOCUMENT_ROOT}/../tmp/stop.txt -f
RewriteCond %{SCRIPT_FILENAME} !-f
RewriteCond %{SCRIPT_FILENAME} !503.html

RewriteRule ^.*$ /503.html [L]

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Mysql 

Innodb by default stores all tables in one big file and continues to grow. To better handle growth
store tables in separate files. This setting will be applied only to databases *created* after the 
setting has been applied. So backup the database, drop database, add the setting, restart mysql server 
and import backup to apply it to existing database

[mysqld]
innodb_file_per_table

Also to reclaim space from unwanted tables do
truncate table table_name; optimize table table_name
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Apache X-Sendfile

https://tn123.org/mod_xsendfile/
apxs2 -cia mod_xsendfile.c

in virtualhost definition

XSendFile on
XSendFilePath path

By default Xsendfile is off and the path includes document root and below. Define the path to include 
the main directory of the rails app to server files stored in non public folders

Rails 2.3.x definition
send_file file_location, :filename => filename, :x_sendfile => ENV['RAILS_ENV'] == 'production' , 
   :type => 'application/pdf'

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lzma file
try
tar --lzma -xvf filename.tar.lzma
OR
unxz filename.lzma

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Emulating slow links

I have done two simple scripts to configure my firewall automatically. They will slow down the http port (80) to a crawl. I do not handle the SSL port for https traffic, but it’s easily achieved by duplicating the script content and adjusting the parameters.

Here are the scripts. The first one, that slows down everything:


#!/bin/sh

/sbin/ipfw add 100 pipe 1 ip from any 80 to any out
/sbin/ipfw add 200 pipe 2 ip from any 80 to any in
/sbin/ipfw pipe 1 config bw 128Kbit/s queue 64Kbytes delay 250ms
/sbin/ipfw pipe 2 config bw 128Kbit/s queue 64Kbytes delay 250ms

And the one that brings your network back to normally:


#!/bin/sh

/sbin/ipfw delete 100
/sbin/ipfw delete 200