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  Oracle released an urgent Java patch

On March 23, Oracle just released an urgent Java patch which is out of its normal update schedule. The security vulnerability is related to the Java SE running in web browsers on desktops. The CVE ID for this issue is CVE-2016-0636. With the unpatched Java, attackers can remotely exploit the target system without username and credentials. Successful exploits can impact the availability, integrity, and confidentiality of the user's system. When the user access pages containing malicious code...

   JAVA,SECURITY,ORACLE,NEWS     2016-03-25 08:39:59

  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

  Why accessing Java HashMap may cause infinite loop in concurrent environment

HashMap in Java is frequently used to handle key/value pairs. But it is not a good candidate to be used in concurrent environment where ConcurrentHashMap should be used instead. If used in concurrent environment, it may cause lots of unexpected behavior even including make the program getting into an infinite loop situation. To understand how this can happen, let's first discuss how HaspMap works internally. In this post we will use implementation of HashMap before Java 8 as example, Java 8 prov...

   JAVA,HASHMAP,INFINITE LOOP     2020-03-29 01:47:00

  Be careful when running knife vault command

While using Chef, one would frequently use knife commands which are used to manage resources on the Chef server. One can list all nodes, data bags, vault items and many other stuff on the Chef server. In this post, we would cover one command which may need your attention when using it -- knife vault. On Chef server, one can store data to data bags which can be accessed by registered clients. These data bags usually store the data in plain text format. In some cases, one would need to store data ...

   KNIFE VAULT,KNIFE DATA BAG,CHEF-VAULT,CHEF     2017-08-19 00:26:54

  Resolve high CPU usage issue caused by file_get_contents in PHP

Sometimes a Linux server which runs Nginx + PHP-CGI(php-fpm) web service may experience sudden system load increase and the CPU usage is around 100% for many php-cgi processes when checking with top command. If this happens, file_get_contents may be the cause if it's used in the PHP script. In lots of web applications, normally there are lots of API requests based on HTTP. Many PHP developers like to use file_get_contents("http://example.com/") to get the API response because it's simple to...

   PHP,FILE_GET_CONTENTS,PHP-CGI     2018-11-09 21:35:00

  Best practices of front end optimization

1. Use DocumentFragment or innerHTML to replace complex elements insertion DOM operation on browser is expensive. Although browser performance is improved much, multiple DOM elements insertion is still expensive and will affect the page load speed. Assume we have an ul element on our page, we now want to retrieve a JSON list using AJAX and then update the ul using JavaScript. Usually we may write it as : var list = document.querySelector('ul'); ajaxResult.items.forEach(function(item) { // ...

   JavaScript,Front end,Optimization,Tips     2013-07-06 11:26:27

  Run code with multiple files in the same main package in GoLang

To run a GoLang program, there needs to be a main() function defined. In some cases when developing some demo program which has multiple files and just wanna put them in the same main package and this folder is not in GOPATH, how to run the program? Let's say we have following folder structure where the main() function is defined in main.go. If you just run below command, it would fail to start to run the program and gives some error if some struct is defined in other files and being used. PS D...

   EXECUTABLE,GOLANG,MAIN PACKAGE,MULTIPLE FILE     2021-05-15 10:20:10

  An easy way to log client side information to server

JavaScript debug is a very troublesome thing in web application development. Because many web browsers will not notify you if there is any error in the JavaScript codes you write. They just silently fail and block the following codes execution. In order to debug JavaScript codes, we need a good log mechanism which will help us log the error information,, we often need to log errors in JavaScript codes to server for debug purpose in a production web application, What should we do? The first ...

   JavaScript log, Ajax,Image,Debug     2012-12-30 09:16:50

  How does computer boot up?

The whole boot process of computer can be summarized in 4 phases. 1. BIOS In the 70's  read-only memory(ROM) was invented. The boot program is written into ROM, the first thing the computer does is to read and execute this program when it's powered on. The program in this chip is called "Basic Input/Output System" (BIOS). 1.1 Power-On Self-Test The BIOS will first check whether the computer hardware can fulfill the basic conditions for booting up, this process is called Power-On Self-Test...

   Computer, boot, partition     2013-02-23 23:19:47

  Using public key authentication in SSH

SSH is a popular cryptographic network protocol for secure network service operation. It is frequently used in remote server login. For a system administrator or software developer, SSH is frequently used to access remote servers or development servers or testing servers etc.  To login with SSH, there are different authentication mechanisms : password, public key and interactive etc. If a remote server needs to be accessed frequently, password authentication may be too troublesome as p...

   LINUX,DEBUG,SSH,PUBLIC KEY     2016-09-10 05:55:46

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