我已经记不清距离上次大版本更新时什么时间了，好像很久很久了，自从去年（具体时间忘记了）Merb和Rails宣布合并推出Rails3后，N多人就在期待其发布的一天，终于，来了！

这次升级需要新装很多的gem，如下：

gem install tzinfo builder memcache-client rack rack-test rack-mount erubis mail text-format thor bundler i18n
gem install rails –pre

期间遇到一个错误：

Due to a rubygems bug, you must uninstall all older versions of bundler for 0.9 to work

然后这边有N多关于Rails3的资料供参考：

Rails 3 Tutorials & Blog Posts

• Edging your way towards Ruby 1.9.1 and Rails 3.0pre
• Unobtrusive JavaScript in Rails 3 by Zach Carter
• A Fresh Cup: Seed Data in Rails 3 tutorial – feature summary + code example by Mike Gunderloy.
• Rails3: Stepping off of the golden path slides by Matt Aimonetti
• Rails Magazine – RailsConf 2009 Edition page 5 has a section called The Unofficial Guide to What’s New in Rails 3 by Rupak Ganguly
• Jason Ting’s RailsConf 2009 Notes includes some basic notes about Rails 3
• Noel Rappin: Railsconf 09 – After the RailsConfening article
• Yehuda Katz: Railsconf Wrapup blog – contains links to jQuery talk by Katz at RailsConf 09
• How to Begin Playing With Rails 3 by Oscar Del Ben
• My Five Favorite Things About Rails 3 by Yehuda Katz
• Rails 3: The Great Decoupling by Yehuda Katz
• Rails Edge Architecture by Yehuda Katz
• How to Build Sinatra on Rails 3 by Yehuda Katz

Rails 3 Presentations & Conference Talks

• Yehuda: What to Expect in Rails 3.0 webcast recording
• Scotland on Rails: Yehuda on Rails & Merb Merge video. For more Scotland on Rails videos, check out this Ruby Inside post.
• Yehuda Katz on Rails 3 and beyond interview by Mark Coleman
• RailsConf: Yehuda – The Russian Doll Pattern video
• RailsConf 09: DHH Keynote video – DHH previews unobtrusive javascript, default escaping & more.

Rails 3 Books

• Rails 3 in Action by Yehuda Katz and Mike Gunderloy. Currently available is their Early Access Edition, which gives you access to chapters as they are written.
• Beginning Rails 3 by Jeffrey Allan Hardy , Cloves Carneiro Jr. & Rida Al Barazi

Rails 3 Commentary

• Internet News: Rails 3 Gets Supersized With Merb
• eWeek: Rubyists Unite Ruby on Rails and Merb to Merge in Rails 3
• CIO: Rails 3 to add security enhancement
• Yehuda Katz: Rails and Merb Merge
• RubyOnRails.org: Rails + Merb Merge Announcement

前段时间写了一篇《实例优化mysql配置文件my.cnf》，这几天看到效果非常明显，别的不说，单mysql cache_hits就很不错（之前竟然没注意到这个参数）

# Increase query_cache_size from 0 to 128M
query_cache_size=128M
# Increase query cache limit from 1048576 to 2M
query_cache_limit=2M

看到效果很明显，如下是munin的监控图：

如果你和我一样经常使用终端程序，这个小程序一定可以帮到你。他能将终端窗口变成类似雷神或CS那样的下拉窗口，非常酷。
可以从这里下载 http://visor.binaryage.com/
这个软件需要SIMBL ，如果你没有安装，要先安装这个。
http://www.culater.net/software/SIMBL/SIMBL.php

SIMBL (SIMple Bundle Loader) – pronounced like “symbol” or “cymbal” – enables hacks and plugins. For instance, SIMBL enables PithHelmet to enhance Safari.

之后将下载下来的文件解压，将解压后的文件拷贝至/Library/Application Support/SIMBL/Plugins，之后再重新启动你的终端你就可以看到效果了。 默认的快捷启动键是Ctrl+`
visor： http://visor.binaryage.com/

Installation

Install SIMBL and make sure you have latest SIMBL 0.9.x
Place Visor.bundle into ~/Library/Application Support/SIMBL/Plugins (create this directory if it does not exist)
Relaunch Terminal.app – You should now see the Visor Status Menu Item
Configure your keyboard trigger by selecting the Visor Status Menu Item -> Visor Preferences … and edit your keyboard hot-key
You can now trigger Visor with your hot-key from any application to get an instant terminal session.

To hide Visor, you can either:
re-trigger with your key-combo
optionally you can click off of the Visor window

TextMate中已经集成了SVN的Bundle，使用起来非常方便，要用Git的话也可以装Bundle，方法如下：

Installation

mkdir -p ~/Library/Application\ Support/TextMate/Bundles
cd ~/Library/Application\ Support/TextMate/Bundles
git clone git://github.com/jcf/git-tmbundle Git.tmbundle

restart teatmate and it’s done!

In the TextMate preferences, advanced tab, shell variables, set the TM_GIT variable to point to your installation of git (ie /usr/local/bin/git)
Many shortcuts are available from the Git-shortcut (Ctrl-Shift-G). Subversion commands are Command-Option-g. Less frequent commands are accessed via the menu.
Update your bundle by running the “Update Git Bundle” command.

To install a new theme, select one of the .tmTheme links listed below, download it to your desktop and double-click on the file. This will place it in ~/Library/Application Support/TextMate/Themes, at which point the new theme will appear in the list found in Preferences → Fonts & Colors. This will also set it as the active theme. (Once the theme is installed, you may remove the .tmTheme from your desktop.)

Rails Envy TextMate Theme
http://railsenvy.com/2008/9/18/rails-envy-textmate-theme

User Submitted Themes
http://wiki.macromates.com/Themes/UserSubmittedThemes

WP终于发布了android的客户端，以后可以随时发表博客了。
这个客户端还真不赖。

mysql数据库也像ORACLE数据库一样，可以动态的修改参数，可以修改会话级变量只对当前会话产生影响；也可以修改全局变量，对所有新连接的会话都产生影响。

修改会话级变量
用show variables 命令查看当前参数的值,like ‘pattern’用于模式匹配，查找指定的参数

mysql> show variables like ‘%sort_buffer_size%’;
+—————————+————+
| Variable_name | Value |
+—————————+————+
| sort_buffer_size | 6291448 |
+—————————+————+
1 rows in set (0.00 sec)

用set SESSION命令设置会话级变量的新值

mysql> set SESSION sort_buffer_size=7000000;
Query OK, 0 rows affected (0.00 sec)

–修改会话级变量对当前会话来说立刻生效
mysql> show variables like ‘%sort_buffer_size%’;
+—————————+————+
| Variable_name | Value |
+—————————+————+
| sort_buffer_size | 7000000 |
+—————————+————+
1 rows in set (0.00 sec)

mysql> exit
Bye
退出重新连接后，此参数恢复原值
[root@devdbc_stb root]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 40 to server version: 5.0.37-log

Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the buffer.

mysql> show variables like ‘%sort_buffer_size%’;
+—————————+————+
| Variable_name | Value |
+—————————+————+
| sort_buffer_size | 6291448 |
+—————————+————+
1 rows in set (0.00 sec)

修改全局变量
[root@devdbc_stb root]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 40 to server version: 5.0.37-log

Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the buffer.

mysql> show variables like ‘%sort_buffer_size%’;
+—————————+————+
| Variable_name | Value |
+—————————+————+
| sort_buffer_size | 6291448 |
+—————————+————+
1 rows in set (0.00 sec)

用set GLOBAL 命令设置全局变量

mysql> set GLOBAL sort_buffer_size = 7000000;
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like ‘%sort_buffer_size%’;
+—————————+————+
| Variable_name | Value |
+—————————+————+
| sort_buffer_size | 6291448 |
+—————————+————+
1 rows in set (0.00 sec)
当前此参数的值并不发生变化，先退出，然后重新连进去
mysql> exit
Bye
[root@devdbc_stb root]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 41 to server version: 5.0.37-log

Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the buffer.

mysql> show variables like ‘%sort_buffer_size%’;
+—————————+————+
| Variable_name | Value |
+—————————+————+
| sort_buffer_size | 7000000 |
+—————————+————+
1 rows in set (0.00 sec)
新的参数值生效

一直以来，只要我看到explain出来的结果有“Using filesort ”，我就要想方设法的优化和改善，因为我以前以为这个的意思就是使用文件系统来排序（那该多慢呀！），其实不是这样的。
在mysqlperformanceblog上看到一篇文章《What does Using filesort mean in MySQL?》其中作者说自己每次面世的时候都会问“what does Using filesort mean in EXPLAIN,” 结果没有一个人回答的是对的，结果让其比较郁闷，就写了这个文章说明：

The usual answer is something like “rows are being placed into a temporary table which is too big to fit in memory, so it gets sorted on disk.” Unfortunately, this is not the same thing. First of all, this is Using temporary. Secondly, temporary tables may go to disk if they are too big, but EXPLAIN doesn’t show that. (If I interview you, I might ask you what “too big” means, or I might ask you the other reason temporary tables go to disk!)

通常的解释是：选择出来的记录太多了，需要排序时内存中放不下了，所以会存储在磁盘中，并通过操作磁盘的文件的方式来排序。但是呢，这是不对的。

The truth is, filesort is badly named. Anytime a sort can’t be performed from an index, it’s a filesort. It has nothing to do with files. Filesort should be called “sort.” It is quicksort at heart.

正解是，filesort这个名字有问题，容易给人误解，在mysql中，任何不能通过index进行的sort都称之为filesort，这里的filesort和文件没有任何关系，应该称之为“sort”而不是“filesort”，它的内部实现就是快速排序。

参考资料：
What does Using filesort mean in MySQL?

http://www.mysqlperformanceblog.com/2009/03/05/what-does-using-filesort-mean-in-mysql/

How MySQL executes ORDER BY

http://s.petrunia.net/blog/?p=24

发现VARIABLES里有个max_length_for_sort_data，其值是1024，感觉很小，如下

mysql> SHOW VARIABLES like “%sort%”;
+—————————+————+
| Variable_name | Value |
+—————————+————+
| max_length_for_sort_data | 1024 |
| max_sort_length | 1024 |
| myisam_max_sort_file_size | 2146435072 |
| myisam_sort_buffer_size | 67108864 |
| sort_buffer_size | 8388608 |
+—————————+————+
5 rows in set (0.00 sec)

不晓得是做啥用的，查了下资料：

http://forge.mysql.com/wiki/MySQL_Internals_Algorithms

Using the modified filesort algorithm, the tuples are longer than the pairs used in the original method, and fewer of them fit in the sort buffer (the size of which is given by sort_buffer_size). As a result, it is possible for the extra I/O to make the modified approach slower, not faster. To avoid a slowdown, the optimization is used only if the total size of the extra columns in the sort tuple does not exceed the value of the max_length_for_sort_data system variable. (A symptom of setting the value of this variable too high is that you should see high disk activity and low CPU activity.)

mysql的filesort有两个方法,MySQL 4.1之前是使用方法A, 之后版本会使用改进的算法B, 但使用方法B的前提是列长度的值小于max_length_for_sort_data, 但我们系统中的列的长度的值会大于1024. 因此也就是说在sort的时候, 是在使用方法A, 而方法A的性能比较差

这些天给我们的一个产品的服务器端加上了memcached，发现性能相当好，在newrelic上监控到每个请求差不多能稳定在100ms以下，开上10个ruby实例，每分钟处理几千个请求不是问题，但是耶发现munin的监控，MYSQL在过期缓冲的时候还是又慢查询，因为我有个表应该又100W的数据了。

晓得MYSQL默认的一些配置不合适，只是一直没来得及调整，今天查了下资料，讲相关的配置调整了下，调整后的如下，如果你是又这方面的经验，发现不合理的还请指出，谢谢。
机器配置：
CentOS release 5.3，CPU（Intel(R) Xeon(R) CPU L5420 @ 2.50GHz） RAM 3G，disk 200G

my.cnf配置

# Example MySQL config file for large systems.
#
# This is for a large system with memory = 512M where the system runs mainly
# MySQL.
#
# You can copy this file to
# /etc/my.cnf to set global options,
# mysql-data-dir/my.cnf to set server-specific options (in this
# installation this directory is /var/lib/mysql) or
# ~/.my.cnf to set user-specific options.
#
# In this file, you can use all long options that a program supports.
# If you want to know which options a program supports, run the program
# with the “–help” option.

# The following options will be passed to all MySQL clients
[client]
port = 3306
socket = /var/lib/mysql/mysql.sock

# Here follows entries for some specific programs

# The MySQL server
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
skip-locking

# By default, the wait_timeout value is 28800. Unless you want MySQL to keep waiting for 28800 seconds (480 minutes or 8 hours),
# please decrease its value according to your application needs.
wait_timeout=60
# Increase connect_timeout from 5 to 10
connect_timeout=10
# Decrease interactive_timeout from 28800 to 100
interactive_timeout=120
# Increase join_buffer_size from 131072 to 1M
join_buffer_size=1M
# Increase query_cache_size from 0 to 128M
query_cache_size=32M
# Increase query cache limit from 1048576 to 2M
query_cache_limit=2M
# Increase max allowed packet size from 1M to 16M
max_allowed_packet=2M
# Increase table cache cache from 256 to 1024
table_cache=1024
# Increase sort buffer size from 1M
sort_buffer_size=2M
# Increase read buffer size from 1M
read_buffer_size=2M
# Increase read_rnd_buffer_size to 4M
read_rnd_buffer_size=4M

#Other settings
sort_buffer_size=8M
key_buffer = 256M
key_buffer_size=64M
myisam_sort_buffer_size = 64M
thread_cache_size = 8
# Try number of CPU’s*2 for thread_concurrency
thread_concurrency = 2

# Don’t listen on a TCP/IP port at all. This can be a security enhancement,
# if all processes that need to connect to mysqld run on the same host.
# All interaction with mysqld must be made via Unix sockets or named pipes.
# Note that using this option without enabling named pipes on Windows
# (via the “enable-named-pipe” option) will render mysqld useless!
#
#skip-networking

# Disable Federated by default
skip-federated

old_passwords=1

#for slow queries
log-slow-queries = /var/log/mysql-slow.log
long_query_time = 3

[mysqldump]
quick
max_allowed_packet = 16M

[mysql]
no-auto-rehash
# Remove the next comment character if you are not familiar with SQL
#safe-updates

[isamchk]
key_buffer = 128M
sort_buffer_size = 128M
read_buffer = 2M
write_buffer = 2M

[myisamchk]
key_buffer = 128M
sort_buffer_size = 128M
read_buffer = 2M
write_buffer = 2M

[mysqlhotcopy]
interactive-timeout

[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid