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  Supercolliding a PHP array

Did you know that inserting 2^16 = 65536 specially crafted values into a normal PHP array can take 30 seconds? Normally this would take only 0.01 seconds. This is the code to reproduce it: <?php echo '<pre>'; $size = pow(2, 16); // 16 is just an example, could also be 15 or 17 $startTime = microtime(true); $array = array(); for ($key = 0, $maxKey = ($size - 1) * $size; $key <= $maxKey; $key += $size) { $array[$key] = 0; } $endTime = microtime(true); echo 'Inserting...

   PHP,Array,hashtable,Slow,Colliding     2011-12-29 09:02:01

  Service discovery with etcd

In previous post, we have talked about etcd and its usage. This post we will cover how to implement server discovery with etcd. Service discovery is to solve one of the most commonly seen scenarios in distributed system where how to find the corresponding target service to talk to. In short, it is to find some server which one can talk to based on some service name. A complete service discovery system include below three key functions: Service registration: A service must register itself to so...

   ETCD,SERVICE DISCOVERY,DEMO,TUTORIAL     2021-03-08 05:36:29

  The Greatest Regex Trick Ever (Simplified)

There is a post which is really hot recently which showcased a best ever regular expression trick. In this post, it provides a trick which can be adapted to situations where one wants to match some patterns desired and exclude the patterns undesired. In simple, the trick is : Pattern not desired | (Pattern desired) Then taking the group 1 match of the capturing group of matched. This group will contain the strings matching the desired patterns. Have to say this trick is really neat and brilliant...

   REGULAR EXPRESSION,PROGRAMMING,JAVA     2015-10-01 21:59:05

  A guide on installing and running Clickhouse on macOS

ClickHouse is a high-performance open-source columnar database management system developed by Yandex. Here are some of the key features of ClickHouse: Columnar storage: ClickHouse uses a columnar storage format, which allows it to efficiently store and retrieve data by column, rather than by row. This results in much faster query performance, especially for analytical and aggregate queries. Real-time data processing: ClickHouse is designed to handle real-time data processing and can handle bill...

   CLICKHOUSE,MACOS     2023-02-15 06:04:55

  C Preprocessor Hell

Lisp programmers should stop reading right now because they'll likely suffer severe injury of the jaw muscles as they laugh themselves silly at how hard it is to do some things in C. The C language has a pre-processor (typically called cpp) that is both infuriating and powerful. How powerful is usually best described as 'just too little' and it has happened more than once that I found myself almost - but not quite - able to do what I wanted to do. The frustration can run very deep at ti...

   C,Preprocessor,Lisp,Hell     2012-01-19 10:22:31

  Top 10 PHP Best Security Practices for Sys Admins

PHP is widely used for various of web development. However, misconfigured server-side scripting would create all sorts of problem. And here are php security best practices that you should aware when configuring PHP securely. Nowadays most of the web servers are operated under Linux environment (like: Ubuntu, Debian...etc). Hence, in the following article, I am going to use list top 10 ways to enhance PHP Security Best Practices under Linux environment. My sample setup for PHP Security Tips: D...

   PHP,code security,System admin,Advice,Best practice     2012-02-01 00:04:37

  A simple tutorial on writing Java native program

Java provides Java Native Interface(JNI) to enable developers to write programs which can utilize the underlying native libraries of the operating system. The benefits of writing native code are that they normally provide better performance compared to Java codes. Sometimes if you want to utilize some system specific functions you may also want to use JNI. One main drawback of writing native code is that your application may not be platform independent anymore. This is not what Java is desi...

   Java native interface, JNI, Native code, Sample     2015-08-15 08:28:15

  How Do I Enable Remote Access To MySQL Database Server?

By default remote access to MySQL database server is disabled for security reasons. However, some time you need to provide remote access to database server from home or a web server. If you want to remotely access to the database server from the web server or home, follow this quick tutorial.MySQL Remote AccessYou need type the following commands which will allow remote connections.Step # 1: Login Using SSH (if server is outside your data center)First, login over ssh to remote MySQL database ser...

   MySQL,Remote access,Enable,Host or webdomain     2011-10-31 00:31:41

  Python threads: communication and stopping

A very common doubt developers new to Python have is how to use its threads correctly. Specifically, a large amount of questions on StackOverflow show that people struggle most with two aspects: How to stop / kill a threadHow to safely pass data to a thread and back I already have a blog post touching on these issues right here, but I feel it’s too task-specific for sockets, and a more basic and general post would be appropriate. I assume the reader has a basic familiarity with Pytho...

   Python,Multithreading,Communication,Synchronize     2011-12-28 07:38:32

  Why exception would be thrown when deleting element while looping through HashMap in Java

HashMap and other Collection types are frequently used in Java application programming. This post will explain why exception would be thrown when deleting element with Map.remove() while looping through a Map using Iterator. This issue would also occur to other Collection types such as Set, List. Below is a sample code snippet demonstrating the exception thrown. Map<String,String> map = Collections.synchronizedMap(new TreeMap<String,String>()); map.put("key1","value1"); map.put("ke...

   JAVA,HASHMAP,CONCURRENTMODIFICATIONEXCEPTION     2018-06-30 12:49:09

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