SEARCH KEYWORD -- NIL CHECK


  A plugin to update last_error in Delayed Job

delayed_job is a process based asynchronous task processing gem which can be ran at background. It will fork the specified number of processes to execute the tasks asynchronously. The task status is usually stored in the database so that it can be easily integrated into a Rails application where asynchronous job execution is desired. Normally when a job fails to execute or error occurs, it would save the error into the database with the column last_error. Ideally all these will be handled b...

   RUBY,RUBY ON RAILS,DELAYED JOB,LAST_ERROR     2017-11-18 13:05:49

  Access control in Java -- doPrivileged

Previously we have introduced how Java performs permission check to protect resource access. What if sometimes we need to give some class the temporary access to some resource which it initially doesn't have? AccessController provides six doPrivileged methods to fulfill this requirement. These six methods have below signatures : static T doPrivileged(PrivilegedAction action)static T doPrivileged(PrivilegedAction action, AccessControlContext context)static T doPrivileged(PrivilegedExceptionA...

   JAVA,SECURITY,DOPRIVILEGED     2016-03-08 05:46:42

  Undefined property or variable in JavaScript

JavaScript is a weak type language, and also you can use a variable or property where it's undefined. If we don't have correct ways to check whether a property or variable is defined, we may get unexpected results when we try to access the,. How can we check whether a property or variable is undefined? This is actually a somewhat tricky question. Let's start off with some facts about undefined and then see what kind of function is consistent with the ones we care about. JavaScript attaches type...

   Property,Undefined,Array,JavaScript     2014-07-24 06:56:07

  Check file readability in Java

File operation is quite platform dependent. Although Java is a cross platform programming language, the file operation in Java is also platform dependent. The obvious evidence is the file permission check. In Java, we can call canRead(), canWrite() and canExecutable() to check whether the program can read, write or execute the file specified. However, on Windows, when we call canRead() on a File object, we may get unexpected result. Actually, on Windows, when we call canRead() on a File object, ...

   Java,Files,Readable,Check     2013-12-05 06:10:15

  First Chinese app on Google Glass : PM25.in

PM25.in is an open source PM2.5 project developed by BestApp. It retrieves PM2.5 data of different cities in China through a crawler and then processes the data retrieved. They also created an API which enables third parties to access these data. Now the team has built something new, they moved this project to Google Glass and developed the world's first Chinese Google Glass application -- PM25.in. Now users with Google Glass can check PM2.5 of different cities in China. The final effect on Goog...

   Google Glass,China,PM25.in,BestApp     2013-06-23 10:17:40

  Check mobile device using JavaScript

Sometimes developers want to know whether the user is using a mobile browser or a desktop browser so that they can build corresponding user experience. Although in many cases responsive web design would help solve component alignment issues, there are performance related considerations in some cases where some code should not be ran or some feature should not be available if user is on mobile browser. or vice versa This post will summarize a few ways which are commonly used to check whether a us...

   CHECK,MOBILE BROWSER,MOBILE DEVICE,JAVASCRIPT     2021-10-02 01:36:16

  Foursquare : 20 million users and 2 billion check-ins

Yesterday was the Foursquare third annual 4sqDay celebration (Four - squared open four square, ie April 16), this mobile phone service site which is based on user location information confirmed that their users reached 20 million and there were two billion check-ins.Foursquare was founded in 2009 and it is a mobile phone service website based on the user location information .It encourages mobile phone users to share their current geographic location and other information with others. In co...

   Fpoursquare,Check-in,4sqDay     2012-04-17 13:39:14

  Remote form submission

Remote form submission is way of submitting HTML forms from local to a particular remote server. This is used by many advertisers, spammers or even hackers to submit bad data to other websites in order to get what they want. They can write some automation scripts to help them do spamming. How can people do remote form submission and how to prevent this kind of attacks? Since a website can be accessed by almost every one, so one can save a local copy of a HTML form of a website through File->S...

   PHP,Security,Remote form submission     2013-07-14 01:04:49

  Server monitoring shell scripts

There are many open source server monitoring software such as cacti and nagios. Besides these, can we write our own shell scripts to monitor them? The shell scripts written by ourselves can fulfill our special requirements better and have a more detailed coverage. Below are some commonly used shell scripts used by Evangelist, an Oracle DBA. 1. Check network gateway traffic #!/bin/bash #network #Mike.Xu while : ; do time='date +%m"-"%d" "%k":"%M' day='date +%m"-"%d' rx_before='...

   Server monitor,CPU,memory,shell     2013-08-30 21:56:14

  Build a Kubectl Plugin from Scratch

by author The command-line tool kubectl is indispensable when using Kubernetes. You need it to query related Pod and Service information both in developing or performing some maintenance operations, such as events, scale, rolling update, etc. However, when using kubectl, there are many inconveniences. Though Kubernetes is officially maintaining kubectl¹, and you can submit the problems, improvement, and even PR in its Github Issues, you still have to wait long before its release. The m...

   KUBENETES,KUBECTL,PLUGIN,GOLANG     2020-12-02 03:43:16

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