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  Solve Hibernate "Too many connections" issue in MySQL

When working with Hibernate and MySQL, sometimes some exceptions will be thrown after sometime. The exception may seem like : java.sql.SQLException: Data source rejected establishment of connection, message from server: "Too many connections" This means there are too many active connections on the MySQL, you can use SHOW STATUS LIKE '%Threads_connected%'; to check the active connections to MySQL. If you want to change the maximum connections allowed to MySQL. You can execute: set global max_co...

   MySQL,Hibernate,Clos     2013-09-04 22:20:49

  About tmpfs

tmpfs is another confusing name in Linux kernel, its implementation is in mm/shmem.c, shmem has no relation to tmpfs at first glance although we know tmpfs is based on memory. We can understand why we use this name by seeing where this is used. In a desktop Linux system, tmpfs is loaded usually: % grep tmpfs /proc/mountsdevtmpfs /dev devtmpfs rw,seclabel,nosuid,relatime,size=1958956k,nr_inodes=489739,mode=755 0 0tmpfs /dev/shm tmpfs rw,seclabel,nosuid,nodev,relatime 0 0tmpfs /run tmpfs rw,seclab...

   tmpfs,Linux,file system     2013-06-14 12:10:56

  bash network interface

Some of us may have seen /dev/tcp/<host>/<port> before, is this a special file system implemented in some BSD kernel? Because there is no /dev/tcp in Linux. Actually, this one is implemented in bash. We no need to rely on wget,nc to do network connection. It's very easy to use this interface: bash-4.2$ cat </dev/tcp/time.nist.gov/13 56188 12-09-18 15:34:26 50 0 0 733.5 UTC(NIST) * bash-4.2$ exec 3<>/dev/tcp/www.w3.org/80 bash-4.2$ echo -e "GET / HTTP/1.0\n\n" >&3 b...

   Bash,Network interface,/dev/tcp     2013-07-20 00:57:52

  When can Chinese buy fresh food online?

Farmigo is an online agricultural marketing platform. Farmers can post their own products, people can directly purchase their favorite ingredients on it. Farmigo promises that fresh ingredients will be sent to the designated location within 48 hours, but the price is 20-30% cheaper than the supermarket.In other words, Farmigo itself does not sell agricultural products, it just plays a platform intermediary role. Their advantages to attract consumers are fresh ingredients supply, home delivery a...

   Agriculture, Online sales, B2B     2012-12-12 13:37:03

  Java Cipher encryption/decryption example

In Java, Cipher is the API for doing data encryption/decryption. Many cryptographic algorithms such as AES, DES, RC4 etc can be specified when creating Cipher instance. The Cipher instance calls the underlying algorithm specific implementation to do the actual encryption/decryption.  Before doing the encryption/decryption, a key needs to be created and it will be used to do the encryption/decryption. A sample program for performing all these is : import java.security.Key; import javax.cryp...

   Java, Java Security, Cipher, Example, Sample     2015-08-14 07:07:10

  Facebook : App Center is more suitable for developers

Facebook recently announced that they will release their own app store named App Center. It will be released in a few weeks. At the same time, Facebook also released the introduction page of the App Center, it introduces to developers the process of app submission and the standards of app approval.Facebook allows developer to provide charged apps via App Center. Since it has over 900 million active users globally, so many developers are willing to develop apps on this platform. Facebook will dec...

   Facebook,App Center,Introduction     2012-05-13 01:03:56

  Origin of Windows blue screen

Many of you from old ages might see the classical blue Windows blue screen before.Do you still remember the most famous Windows blue screen incident during a presentation of a Windows 98 beta by Bill Gates at COMDEX on April 20 1998. But do you know the history of blue screen? John Vert, an ex-Windoes NT kernel guy, shared the story on Quora.  Back in 1991 John Vert wrote the original code for Windows NT 3.1 that put the video screen back into text mode and the routines to put text on it (a...

   Windows blue screen,History     2013-07-24 09:25:16

  Supervisord, God and Monit, which one to choose?

With the popularity of Docker, more and more service have been moved into docker containers and they are easy to build up and maintain for each atomic service(though it's a bit complex to maintain multiple docker containers which contain different service to form a complete solution). Ideally, each docker container should only contain one service which has only one running process. However, in reality there would be cases multiple processes would run in one single docker container and there is a...

   DEVOPS,MONIT,SUPERVISORD,GOD,DOCKER     2017-11-25 12:28:11

  4 asynchronous programming methods in JavaScript

You may know the execution environment of JavaScript is single threaded. The so called single thread means only one task can be running at any time, if there are many tasks, they need to be in a queue and wait for the previous task to be completed. The advantage of this mode is it's easy to implement and the execution environment is relative simple; the disadvantage is that if one task takes long time, the tasks following it must wait in the queue and this will delay other tasks consequently. Th...

   JAVASCRIPT,ASYNCHRONOUS PROGRAMMING, EVENT MODEL,PROMISE     2012-12-25 00:55:47

  Will Weibo's IPO be a success?

The Chinese version of Twitter -- Weibo is going to launch its IPO today on NASDAQ. The stock code is "WB" and its target price per share is set to $17. The total funds it's going to raise is around $328.44 million. Weibo claims it's the first Chinese SNS media to be listed on NASDAQ. Goldman Sachs and Credit Suisse are the joint lead underwriter of the IPO. They have gained one option from Weibo for validity of 30 days to buy 2.52 million shares of ADS. One interesting thing is Goldman Sachs ...

   Weibo,NASDAQ,IPO     2014-04-17 07:33:42

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