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  What is Hystrix and How does Hystrix work

Background In distributed systems, there is one effect where the unavailability of one service or some services will lead to the service unavailability of the whole system, this is called service avalanche effect. A common way to prevent service avalanche is do manual service fallback, in fact Hystrix also provides another option beside this. Definition of Service Avalanche Effect Service avalanche effect is a kind of effect where the service provider fails to provide service which causes t...

   AVALANCHE EFFECT,HYSTRIX,DISTRIBUTED SYSTEM     2019-02-04 06:00:38

  A trick of building multithreaded application on Solaris

Firstly, Let’s see a simple multithreaded application: #include <stdio.h> #include <pthread.h> #include <errno.h> void *thread1_func(void *p_arg) { errno = 0; sleep(3); errno = 1; printf("%s exit, errno is %d\n", (char*)p_arg, errno); } void *thread2_func(void *p_arg) { errno = 0; sleep(5); printf("%s exit, errno is %d\n", (char*)p_arg, errno); } int main(void) { pthread_t t1, t2; ...

   C, Solaris     2014-10-14 02:59:40

  Content based HTTP Cache

Browsers may cache the webpages we visited, when user types a URL on the address bar, the browser may cache the webpage returned from server while displaying it. If there is no update on the webpage, then next time when the browser requests the same page, it will not download the page again, instead it will load the cached page. If the website explicitly specify that the page is updated, then the browser will download the page again from the server. What's HTTP Cache? You may be familiar with th...

   HTTP Cache,Web crawler     2013-05-24 05:12:59

  var in JavaScript

Geoff published an article sometime ago--"How one missing var ruined our launch". This article described one case where MelonCard uses Node.js as their backend system, suddenly there was a small registration peak period--50-100 people registered concurrently, then the entire website stopped responding and many other strange problems showed up. When they were investigating the source of the problem, they found one missing var in the following code.app.all(‘/apps/:user_id/status’, fun...

   JavaScript,Scope,variable     2012-05-26 12:35:36

  Install multiple versions of Go

As a developer, there might be need in some cases to have multiple versions of Go installed. One may test out some new features of the latest version of Go but also wanna maintain a stable version of Go for daily development purpose. How to maintain multiple versions of Go? The GoLang official website has provided a way to maintain multiple versions of Go by using go get to install the different versions of Go. Below are steps: Download a normal version of Go and install it Go to the Go release...

   MULTIPLE VERSION,GO BINARY,GO VERSION     2021-05-16 02:01:46

  The internals of slice in GoLang

There are 3 components of slice:a) Pointer: Points to the start position of slice in the underlying array;b) length (type is int): the number of the valid elements of the slice;b) capacity (type is int): the total number of slots of the slice. Check the following code: package main import ( "fmt" "unsafe" ) func main() { var s1 []int fmt.Println(unsafe.Sizeof(s1)) } The result is 24 on my 64-bit system (The pointer and int both occupy 8 bytes). In the next example, I will use gdb to poke t...

   GOLANG,SLICE     2019-06-30 02:55:22

  PHP advisory file lock : flock

When we process a file in PHP, we may often need to acquire a lock so that other scripts cannot edit the same file at the same time. There is a flock() function in PHP which can help us lock the file we want to process. But there is one issue we should take care. Recently, ffb encountered one issue while he was trying to lock a file handle. The codes are below: $filename = "/tmp/lock.txt";      $fp = fopen($filename, "r+");   if (!$fp...

   flock(),advisory locking,PHP     2013-04-23 11:42:48

  New function signal.NotifyContext in GoLang 1.16

os/signal package in GoLang may not be frequently used but it provides some good features like Shutdown() which can be used to gracefully shutdown a running HTTP server. func (srv *Server) Shutdown(ctx context.Context) error With this function, there is no need to use third party library to gracefully shutdown HTTP server. How is it being used? package main import ( "context" "fmt" "net/http" "os" "os/signal" "time" ) func main() { server := http.Server{ Addr: ":8080", } http.Handl...

   GOLANG,NOTIFYCONTEXT,GRACEFUL SHUTDOWN     2021-06-19 01:07:10

  CSS position explained

CSS has two very important properties on determining the position of an element in webpage: display and position. display is used to determine how elements are grouped and displayed on the page. While position is used to determine the exact position of an element on a page. And this post would explain position property in detail. position is used to determine the exact position of an element on a page. It has five possible values. static relative absolute fixed sticky sticky is supported start...

   CSS,STICKY,CSS3     2019-11-22 19:57:52

  You should publish your contributions of Open Source, even it’s not required

Although many Open Source projects don’t require you publish the modifications of them, I still propose you should make the changes open. The reasons are as following: (1) For other people: the out-of-box Open Source projects save your time and money, and you get benefit from them. You should not only take, but also need to give! Only if everyone shares his code, document, or whatever related, the Open Source projects can grow up healthy. (2) For yourself: You release your code can actuall...

       2017-07-18 03:53:05

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