Web Services Creation

Friday, April 13, 2018

ExecJS::RuntimeError: SyntaxError: Unexpected token punc «(», expected punc «:»

I got this error when deploy Rails app to production server.
This error will be raised if your javasctripts on assets include ES6 syntax.

These steps will fix the probrem.

Update uglifier
bundle update uglifier
Modify config/environments/production.rb
from
config.assets.js_compressor = :uglifier
to
config.assets.js_compressor = Uglifier.new(harmony: true)

https://github.com/lautis/uglifier/issues/116#issuecomment-347386669

Tuesday, April 19, 2016

Screen resolutions and image ratios of Android devices

The base resolution(1.0) is mdpi, and ratios of other resolutions are below.
ldpi = 0.75
mdpi = 1.00
hdpi = 1.5
xhdpi = 2.0
xxhdpi = 3.0
xxxhdpi = 4.0

Width for each resolution of an image which width is 100px
ldpi = 75px
mdpi = 100px
hdpi = 150px
xhdpi = 200px
xxhdpi = 300px
xxxhdpi = 400px

Supporting Multiple Screens | Android Developers

Thursday, March 19, 2015

Couldn't connect to Docker daemon at http+unix://var/run/docker.sock - is it running?

Docker Compose raise error below.

$ docker-compose up Couldn't connect to Docker daemon at http+unix://var/run/docker.sock - is it running? If it's at a non-standard location, specify the URL with the DOCKER_HOST environment variable.

$(docker-machine env MACHINE NAME) solved the problem.

$(docker-machine env dev)

Saturday, March 7, 2015

docker-machine hang at Waiting for VM to start...

I've installed docker-machin on Mac OSX(10.8.5), and it hangs up at Waiting for VM to start... when start docker machine.
Then I've upgraded Virtual Box to 4.3.24 and rm stacked docker-machine and created a new docker-machine.
That solved the problem

http://stackoverflow.com/questions/27614056/osx-boot2docker-hangs-on-waiting-for-vm-and-docker-daemon-to-start#28782567

Saturday, September 21, 2013

Install NTP on CentOS

Install NTP

sudo yum install ntp

Start NT

sudo /etc/init.d/ntpd start

Configure NTP servers
Select NTP server which close to your location from area list.
http://support.ntp.org/bin/view/Servers/NTPPoolServers

sudo vi /etc/ntp.conf

Replace default NTP servers.

server 0.centos.pool.ntp.org
server 1.centos.pool.ntp.org
server 2.centos.pool.ntp.org
to
server 0.north-america.pool.ntp.org
server 1.north-america.pool.ntp.org
server 2.north-america.pool.ntp.org
server 3.north-america.pool.ntp.org

Restart NTP

sudo /etc/init.d/ntp stop sudo /etc/init.d/ntp start

Check sync status.

ntpstat
unsynchronised
time server re-starting
polling server every 64 s

If just started NTP, it won't start synchronize, it will take 10 or more minutes to start syncronizing.
If successfully synchorised, you will see messages like this.

synchronised to NTP server (180.235.254.234) at stratum 3
time correct to within 30 ms
polling server every 64 s

Configure automatic run. at booting.

sudo /sbin/chkconfig ntpd on
sudo /sbin/chkconfig --list
ntpd ntpd 0:off 1:off 2:on 3:on 4:on 5:on 6:off

Note. NTP uses UDP port 123 to synchronize.
If you have filtered this port, you have to open port 123.
To open this port you can open with the following iptables arguments.

-I INPUT -p udp --dport 123 -j ACCEPT
-I OUTPUT -p udp --sport 123 -j ACCEPT

Thursday, June 2, 2011

Random search in Rails

#MySQL
User.find(:all,'RAND()',:limit =>5)
#PostgreSQL,SQLite
User.find(:all,'RANDOM()',:limit =>5)

Wednesday, June 1, 2011

Installing Zen Coding eclipse plugin

Select menu
Help > Install New Software ... > and add http://zen-coding.ru/eclipse/updates/ into location column.

Check Zen Coding for Eclipse and proceed

After instaling finished, type html > Ctrl(command) + E and it will converted <html></html> if installing successfully finished.