nraj

[nraj]

Node installation on a screwed up OSX env.

Cleaning up development env. on Mac

1. Remove any traces of node and family

Excellent set of instructions given here:

http://stackoverflow.com/questions/11177954/how-do-i-completely-uninstall-node-js-and-reinstall-from-beginning-mac-os-x

2. Use homebrew and nothing else to start fresh.

See instructions at -

http://thechangelog.com/install-node-js-with-homebrew-on-os-x/

3. brew update

If that fails, then

cd $(brew --repository) git reset --hard FETCH_HEAD

4. brew doctor

Per the recommendations of doc, I ended up -

   - upgrading  xCode

   - brew prune to mend broken symlinks

   - brew installing missing - brew missing

   - brew install openssl. 

5. fix the path by setting at higher priority local installations instead of system's 

echo export PATH='/usr/local/bin:$PATH' >> ~/.bash_profile

6. Finally, the nirvana -

brew install node

[nraj]

Mount | Sharing bet Windows & Linux server

Libraries to be installed are samba-client, samba-common, cifs-utils

yum install samba-client samba-common cifs-utils

Create directory for shared drive 

sudo mkdir -p /mnt/sharedDrive

Mount the Windows drive on CentOS server

sudo mount -t cifs //machinename/shareName -o username=<username>,password=<password> /mnt/sharedDrive

View a list of mounted drives

cat /proc/mounts

Un-mount an existing mounted drive

umount /mnt/sharedDrive

To permanently remove the share

rm -rf /mnt/sharedDrive

To mount a DFS share, add following in /etc/request-key.conf file

create cifs.spnego * * /usr/sbin/cifs.upcall -c %k create dns_resolver * * /usr/sbin/cifs.upcall %k

DFS share mount may not work using cifs-utils since its valid for CentOS-6 (or later) only

View the available shares on a non-DFS machine like so-

smbclient -L '//machinename' -U ieams/nraj

Incase of non-DFS share mounting, one can use IP if machine name mounting doesnt work.

Reference: http://www.cyberciti.biz/faq/mounting-windows-partition-onto-ubuntu-linux/ http://mikemstech.blogspot.in/2012/10/how-to-mount-dfs-share-in-linux.html

http://wiki.centos.org/TipsAndTricks/WindowsShares

http://www.thatsquality.com/articles/mounting-windows-smb-file-shares-using-cifs

[nraj]

Custom format for excel dates

select cell

right click and select format

choose Cutsom

In the type textbox, give the custom format that you want from the abbreviations found in the reference site.

Ref: http://office.microsoft.com/en-in/excel-help/format-a-date-the-way-you-want-HA102809474.aspx

[nraj]

Common *nix commands

Archive

To view contents of a zip file without unzipping -

unzip -l status-api.zip | less

Such and other Utility commands with gz files -

http://www.cyberciti.biz/tips/decompress-and-expand-text-files.html

[nraj]

- tmux

- Rename window

ctrl a + ,

- Check out all bindings

ctrl a + ?

- Split current window into vertical panes

ctrl a + %

- Split current window into horizontal panes

ctrl a + "

- Switch to next pane

ctrl a + o

- toggle between horizontal and vertical layouts

ctrl a + <spacebar>

- Maximize the current pane

ctrl a + z

- restore the current pane to its original size

ctrl a + z

Ref: https://gist.github.com/MohamedAlaa/2961058

http://blog.hawkhost.com/2010/06/28/tmux-the-terminal-multiplexer/

[nraj]

/home/localadmin/.forever/*.log {

  monthly       # how often to rotate

  rotate 12     # max num of log files to keep

  missingok     # don't panic if the log file doesn't exist

  notifempty    # ignore empty files

  compress      # compress rotated log file with gzip

  sharedscripts # no idea what it does, but it's in all examples

  copytruncate  # needed for forever to work properly

  dateext       # adds date to filename

  create 775 apache apache

  dateformat %Y-%m-%d.

}

[nraj]

Mysql server fails to start [error : 28]

 sudo service mysqld start

Timeout error occurred trying to start MySQL Daemon.

Starting MySQL:                                            [FAILED]

Logs /var/log/mysqld :

mysqld  Error: unable to create temporary file; errno: 28

Can't start server : Bind on unix socket: No space left on device

1. Check /tmp for permissions and space availability

2. df -h

Filesystem            Size  Used Avail Use% Mounted on

/dev/xvd               37G   35G  0M    100% /

...

tmpfs                 2.0G     0  2.0G   0% /dev/shm

Now, /tmp is under / which has 0 M available and is 100% used.

3. ls -lrt /tmp . Its lined up with loads of RackMultipart files

Reason: Paperclip Issue 

Check the no. of such files 

> ls -lrt /tmp/RackMultipart* | wc -l

> 297

4. Remove these files 

rm -f /tmp/RackMultipart*

5. Try again

sudo service mysqld start

Starting MySQL:                                            [  OK  ]

sudo service mysqld status

mysqld (pid 17048) is running...

Ref: http://man.chinaunix.net/database/manual_MySQL/manual_Problems.html

[nraj]

Linux Drives / Partitions /Volumes

Straight from this SO Issue

A drive is a physical block disk. For example: /dev/sda.

A partition A drive can be divided into some logic block disk. These logic block disk are named partition. For example: /dev/sda1, /dev/sda2.

A volume is also a logic block disk. Volume is a concept involved with partition. A volume can contain many partition. You can take a look at LVM project to understand the concept of a volume.http://sourceware.org/lvm2/.

For example: vg0/lvol0

[nraj]

Tmux installation on CentOS

Install libevent which is a pre-req for tmux installation

wget https://github.com/downloads/libevent/libevent/libevent-2.0.21-stable.tar.gz

sudo tar xzvf libevent-2.0.21-stable.tar.gz

cd libevent-2.0.21-stable

sudo ./configure && make

 sudo make install

    2. Now install tmux by downloading from http://tmux.sourceforge.net/

sudo tar xzvf tmux-1.8.tar.gz

cd tmux-1.8

sudo ./configure && make

sudo make install

     3. Confirm tmux installation like so -

whereis tmux

      4. If you get the following error after installation -

tmux: error while loading shared libraries: libevent-2.0.so.5: cannot open shared object file: No such file or directory

       Solution:

sudo vi ~/.bashrc

       Append 

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:"/usr/local/lib"

source ~/.bashrc

Ref: http://superuser.com/questions/324613/installing-a-library-locally-in-home-directory-but-program-doesnt-recognize-it

[nraj]

NODE JS package manager- npm install <options>

npm install <tarball file> npm install <tarball url> npm install <folder> npm install <pkg> npm install <pkg>@<tag> npm install <pkg>@<version> npm install <pkg>@<version range> Ref: http://npmjs.org/doc/install.html

[nraj]

How to check if a CentOS port is open

nmap -sT -O localhost

 cat /etc/services | grep smtp

netstat -anp | grep 25

lsof -i | grep 25

telnet myserver.com 25

netstat -tuplen

  Ref: http://www.centos.org/docs/5/html/5.2/Deployment_Guide/s1-server-ports.html

[nraj]

Unicode UTF-8 Issue with YII and MSSQL framework

Error : QLSTATE[HY000]: General error: 20018 Unicode data in a Unicode-only collation or ntext data cannot be sent to clients using DB-Library (such as ISQL) or ODBC version 3.7 or earlier.

Diagnosis:

The requisite encoding UTF-8 is not getting set.

Application Stack:

MS SQL

YII framework

PHP

Red Hat

Fixes at all levels of application stack:

1. MSSQL - Checked at the database level, SQL data is getting stored and retrieved without any issues.

2. YII - ini_set('mssql.charset', 'UTF-8'); in index.php

3. PHP - in /etc/php.ini,

   default_charset = "UTF-8"    mssql.charset = "UTF-8"

4. Red Hat Server

In /etc/freetds.conf -

ensure in teh global settings if dedicated server else have a separate section with these setting for your application instance

[global]      host = servername      client charset = UTF-8      tds version = 8.0      text size = 20971520

References:

- http://www.yiiframework.com/wiki/16/how-to-set-up-unicode/

- Basics: http://blog.goosoftware.co.uk/2012/12/05/how-ascii-lost-and-unicode-won/

-  http://stackoverflow.com/questions/1322421/php-sql-server-how-to-set-charset-for-connection

- http://www.craig-edmonds.com/solved-php-mssql-unicode-encoding-issues/

[nraj]

JavaScript - Numeric to String()

On Javascript console, try this -

12.toString();

SyntaxError: Unexpected token ILLEGAL

So to get string counterpart of a JavaScript number, use any of the the following options-

Number.prototype.toString.call(12); "12" OR 12..toString();

  OR

  (12).toString();

  Reference:

http://stackoverflow.com/questions/4046342/why-dont-number-literals-have-access-to-number-methods

http://stackoverflow.com/questions/6853865/usage-of-tostring-in-javascript

[nraj]

SVN Branch merge

Create a branch

svn copy http://proj_base_svn_url/trunk http://proj_base_svn_url/branches/rel-1.3.3/

Checkout branch as a new instance to work upon -

svn checkout http://proj_base_svn_url/branches/rel-1.3.3/  proj_rel133

Work on the newly created branch and keep checking the changes back to the parent SVN branch

Keep merging the branch code with trunk regularly to avoid numerous conflicts at the last moment.

svn merge ^/trunk

build and test

Once satisfied with the merge, commit the branch code back to SVN

svn commit -m "Comiting changes pertaining to branch merge with trunk"

Branch -Trunk merge

When the branch is ready to be merged back into trunk

cd proj_trunk

Get the trunk to latest state

svn update

Merge branch code into trunk

svn merge --reintegrate ^/branches/rel-1.3.3

In case there are conflicts, revert the merge like so -

svn revert -R .

If merge goes well, commit back the merge code into SVN

svn commit -m "branch 1.3.3. merged with trunk"

[nraj]

Regex escape of special characters in JavaScript/NodeJs

Escape your regex containing \ ^ $ * + ? . ( ) | { } [ ] like so:

function escapeRegExp(str) {

  return str.replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g, "\\$&")

}

OR

RegExp.escape = function(text) {

  return text.replace(/[-[\]{}()*+?.,\\^$|#\s]/g, "\\$&");

};

return str.replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g, "\\$&")ex documentation on Mozillaerflow solution 1

Stackoverflow solution 2

[nraj]

Rails - JSON encoding performance analysis

Scrutinize problem piece of code - 

Rather than using Ruby array manipulation functions on activerecord objects fetched, try to use the sql filter, order, group etc. via AREL

at = User.arel_table   

at1 = Object2.includes(:class3).where(at[:attribute1].lower.matches("%#{search_text.downcase}%"))

     2. While querying, include all the nested objects for eager loading.       Dramatic difference it makes - 

users = User.includes(:addresses => [{:countries => :city}, :designations]).where('id in (?) AND active = 1', user_ids)

    3. Now optimize the json encoding process - 

 Use Yajl library. Install like so

# Gemfile

gem 'yajl-ruby', :require => "yajl"

Use Yajl library

Ensure the engine used :

> MultiJson.engine

  Installation might give an error about Notifier, update your ruby gems - 

gem update --system

  4. Other JSON builders could also be chosen -

Representative

Tokamak

Builder

JSONify

Argonaut

JSON Builder

RABL

References:

https://groups.google.com/forum/?fromgroups=#!topic/rails-oceania/kGHfiHU3GG4

http://stackoverflow.com/questions/10451722/what-is-the-fastest-way-to-render-json-in-rails

Use Yajl library for JSON processing -

# Gemfile gem 'yajl-ruby', :require => "yajl"

Options

https://github.com/mdub/representative

https://github.com/inem/tequila https://github.com/abril/tokamak https://github.com/jbr/argonaut

http://engineering.gomiso.com/2011/05/16/if-youre-using-to_json-youre-doing-it-wrong/

[nraj]

Escape Mysql keywords in mysqli

How to escape and use historical tables/columns with reserved names in mysql command line -

mysql> select count(*) from keys;

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'keys' at line 1

Use Backticks like so:

mysql> select count(*) from `keys`;

Ref: http://stackoverflow.com/questions/7380156/is-key-a-reserved-word-in-mysqli-im-getting-an-error