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  Break down defer statements in GoLang

Basic Concepts What are the characteristics of the deferred statement defer in Go language? When is it usually used? The deferred statement(defer statement) in Go language has the following characteristics: Deferred Execution: Deferred statements are executed before the function containing them exits, regardless of whether the function returns normally or encounters an exception. Last In, First Out (LIFO): If there are multiple deferred statements, they are executed in the order of last in, f...

   DEFER,GOLANG     2024-02-10 21:56:10

  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

  Will nil == nil be true in GoLang

There is some interview question may ask whether nil == nil be true in GoLang. Wil it be true. false or compilation error? To know the answer, some knowledge about nil in GoLang needs to be explained first. nil definition According to Go's official documentation, the definition of nil is // nil is a predeclared identifier representing the zero value for a // pointer, channel, func, interface, map, or slice type. var nil Type // Type must be a pointer, channel, func, interface, map, or slice type...

   GOLANG,NIL,NIL EXPLANATION     2021-08-08 02:54:15

  Ruby net-scp cannot scp multiple files with asterisk(*)

net-ssh/net-scp is a Ruby gem which can be used to scp files between different *nix machines. It's similar to how the *nix scp command. It can be used to scp a file or a directory. However, it seems it has some problem to scp multiple files using pattern *. For example, below script is supposed to download all files from remote directory to local directory: require 'net/scp' host = 'testmachine' login = 'testaccount' password = "testpassword" remote_path = '/tmp/remote...

   NET-SCP,RUBY,ASTERISK,MULTIPLE FILES     2016-10-20 03:00:13

  Install and setup Kafka on Windows

Kafka has become a very popular distributed message delivery service which decouples different services while making message delivery between service easy, fast and reliable. In this post, we will walk through how to install and set up Kafka on Windows. Pre-requisite Java Apache ZooKeeper Installation Go to Kafka's download link and download the latest stable release, we downloaded 2.2.0 as of this writing. After downloading, copy the installation file to some folder and unzip it.  Sinc...

   KAFKA,STREAM,USER GUIDE     2019-06-01 02:12:07

  Apple.com is down

UPDATE : The service is back now! Apple.com is now inaccessible. It shows below "Access denied" message on its official site. It is still unknown why the service is down. And there is no ETA on when the service will be back to normal. From the error message, some people think this happens because Apple uses Akamai's security product and the security policy in place is violated. It's basically a WAF. The big issue is it takes 45 minutes for changes to propagate through Akamai's network. So, you ...

   IPHONE 6S,IPHONE 6S PLUS,APPLE     2015-09-12 00:50:17

  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

  A C++ program puzzle

Recently I came across a question asked by wang2191195 on a Chinese IT forum CSDN which asks about a C++ program puzzle. He has a code snippet which cannot be compiled. The code is:#include <cstdlib> #include <iostream> using namespace std; class Base{ public: virtual void func(){ cout << "Base::func()" << endl; } virtual int func( int num ){ cout << "Base::func( int " << num << " )" << endl; return 0; ...

   C++,Puzzle,Hide,Overload     2012-05-13 02:31:26

  Run JavaScript in GoLang

In some cases, there might be some JavaScript code needs to be ran in a GoLang project. Fortunately, there are a few libraries which support running JavaScript in GoLang. The most famous one would be v8. This is a Go API for the famous v8 JavaScript engine originally developed for the Chrominum project and the foundation of NodeJS. In this post, we will show some simple steps to get v8 working in a GoLang program on MacOS. First you need to install the package so that you can import it. Run...

   GOLANG,JAVASCRIPT,V8     2019-05-16 07:40:38

  PHP to get access token for Twitter app

Previously we wrote an article about getting access token for Facebook app--PHP to get access token for Facebook app. Today we will introduce how to get access token for Twitter app using PHP. Since now Twitter is also using OAuth 2.0 to allow some web apps to access some users information on behalf of one user. They provided some APIs for developers to easily get them integrated with their own websites. The first step to get all these done is how to get the access token, the access token seems ...

   Twitter,OAuth,access token,PHP     2013-03-03 03:49:26

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