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  What is cache penetration, cache breakdown and cache avalanche?

When designing and developing highly available system, cache is an very important consideration. It is useful to cache some frequently accessed data so that they can be accessed quickly and also cache can protect the downstream system like DB from being hit too often.  To provide better cache design in large systems, some problems may need to be considered first. In this post, we will talk about some frequently discussed cache problems and mitigation plans. Cache penetration Cache penetrati...

   SYSTEM DESIGN,CACHE PENETRATION,CACHE BREAKDOWN,CACHE AVALANCHE     2020-04-10 08:43:00

  HeartBleed: Should C be blamed for the HeartBleed bug?

There is a discussion about the security of applications written in C on Hacker News recently after the report of HeartBleed bug in OpenSSL. In this discussion, some people are saying that the applications written in C are unsafe. It seems all or most of the faults should be laid on C. I think this is biased. The language itself should not be blamed.Safety is a relative term for programming languages. No language is absolutely safe. We claim some languages like Java and C# are safer than C/C++ b...

   C,HeartBleed,Analysis,Code review     2014-04-14 03:52:55

  What is the use of empty struct in GoLang

In Go, an empty struct struct{} is a struct with no fields that may appear to be of little use, but in reality, it can be useful in certain situations and become a simple and efficient solution in code. As a semaphore or lock Because the empty struct has no fields, it can be conveniently used to implement some concurrency control functions, such as mutex locks, read-write locks. We can use chan struct{} to implement an unbuffered channel for controlling concurrent access. package main import ( ...

   GOLANG,EMPTY STRUCT     2024-04-05 23:54:03

  Launch Java process programmatically in Java

In some cases while working on some automation testcase, developers would like to launch Java process programmatically so that the tests can be ran without manual intervention. Java provides such methods to achieve this. ProcessBuilder can be used to build a Java process which can be launched when everything is ready. Basically it can take a list of parameters which are similar to the command line options/arguments.  For example, if you want to launch a Java process, you can do followi...

   JAVA,PROCESSBUILDER,COMMAND LINE     2016-04-27 04:03:30

  What to put on whiteboard during an interview

As a programmer, you may go through different kinds of programming tests while interviewing for jobs. The most famous and difficult one may be the whiteboard test for lots of people. Usually the interviewer will give the candidate an algorithm problem or case study and ask the candidate to implement the algorithm with his/her favorite programming language. The code to be written is not too much but it requires the candidate to thoroughly consider different edge cases. So wha...

   TIPS,INTERVIEW,WHITEBOARD TEST     2014-08-29 20:34:52

  Handle NXDomain error when resolving IP address in Ruby DNS resolver

In another post, we covered how to resolve SystemStackError when resolving IP address in Ruby. In this post, we would cover another common issue where a NXDomain error is returned when resolving an IP address. The NXDomain error means that the queried domain name does not exist in the DNS. In Ruby, DNS resolver library will use /etc/resolv.conf by default get the name servers to resolve the domain name. There are multiple DNS name servers can be specified in /etc/resolv.conf with below format. ...

   RUBY,RUBY ON RAILS,NETWORK,DNS,NXDOMAIN     2017-07-16 01:39:23

  Create customized GitHub profile page

How long have you been using GitHub? Have you ever wondered whether one can customize his profile page with some fancy looking? Indeed GitHub allows developers to customize profile page through a secret repository. The secret is to create a repository with the same name as your GitHub username. And you will be granted into the work of customizing your own profile page. In this post, we will show a simple walk through on how to create it. Create secret repository As indicated by the term secret r...

   GITHUB,CUSTOMIZED PROFILE,SECRET REPOSITORY     2020-10-18 03:02:42

  Do you have this kind of comments in your source code?

Writing runnable code is the essential skill of a programmer, writing understandable comment is also a skill a programmer should acquire. There is some famous saying that bad comment is worth than no comment. Usually your code will be maintained by other people, if you provide them some difficult to understand or misguided comments, this will be nightmare to them. While at some other time, programmers may put some funny comments in their codes which may make others laugh. Today we...

   COMMENT,HUMOR     2016-08-01 10:25:14

  The evolving history of asynchronous operation in JavaScript

JavaScript is single threaded, it means there would be only one task running at any point of time. But this would slow down the overall program execution if there is long running task, hence asynchronous task execution is desired in complex cases. To achieve asynchronous task execution, there are a few options introduced in JavaScript. setTimeout/setInterval Event Promise Async/Await setTimeout/setInterval is one of the first mechanisms introduced in JavaScript to simulate asynchronous operati...

   JAVASCRIPT,ASYNC,PROMISE,AWAIT     2019-11-09 08:21:56

  How deep should unit test go?

There is a question on Stackoverflow which says "How deep are your unit tests?". It is asked by a guy named John Nolan. The question is not too new, but what catches me is the Best Answer given by Kent Beck, who is the creator of Extreme programming(XP) and Test Driven Development(TDD). Let's look at the question first. The thing I've found about TDD is that its takes time to get your tests set up and being naturally lazy I always want to write as little code as possible. The first thing I seem ...

   Unit test,TDD,XP     2012-09-03 10:11:27

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