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SEARCH KEYWORD -- Distributed system

  How Query Optimizer Works in RDBMS

In a previous post, we discussed how the various relational operators are implemented in relational database systems. If you have read that post, you probably still remember that there are a few alternative implementations for every operator. Thus, how should RDBMS determine which algorithm (or implementation) to use? Obviously, to optimize the performance for any query, RDBMS has to select the correct the algorithm based on the query. It would not be desirable to always use the same algori...

   DATABASE,DATABASE DESIGN,DATABASE OPTIMIZATION     2019-04-20 07:26:32

  CASSANDRA data model

Cassandra is an open source distributed database, it combines dynamic key/value and column oriented feature of Bigtable. Features of Cassandra are: Flexible schema, no need to design schema first, it's very convenient to add or delete strings Support range search on keys High usability, extensible. The single node error will not affect the cluster. We can think Cassandra's data model as a 4 or 5 dimensional Hash. COLUMN Columns is the smallest data unit in Cassandra, it is a 3 dimensional data...

   Cassandra,database,sort     2013-06-08 22:07:40

  Recursive class initialization in Java

When a Java class is referenced and initialized, it has to go through the loading and linking first. Once the loading and linking complete successfully. The class will be initialized. The static variables and constant variables will be initialized during this process. Once the class is initialized, it is ready for use. If when class A is initialized and it is referencing a class B, the class B will also get initialized. But what will happen if class B is referencing class A as well? This is call...

   Java,JVM,class initialization,static final     2015-04-15 21:04:29

  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

  What kind of automated testing does Facebook do?

We do several kinds of testing. Some specifics:For our PHP code, we have a suite of a few thousand test classes using the PHPUnit framework. They range in complexity from simple true unit tests to large-scale integration tests that hit our production backend services. The PHPUnit tests are run both by developers as part of their workflow and continuously by an automated test runner on dedicated hardware. Our developer tools automatically use code coverage data to run tests that cover the ...

   Facebook,Testing,PHP,Automated testing     2012-02-28 08:10:10

  Yes, Virginia, Scala is hard

Let me first say that I am a Scala lover and have been a Scala champion for almost 5 years.  I've written books and articles on Scala.  I've worked with dozens of companies that have launched Scala and Lift projects.  I've code reviewed many dozens of Scala projects.I used to think that Scala was easy.  It was, and continues to be, a cure for some of the numerous problems with Java.  From the "stuff that's hard or impossible in Java is simple in Scala," Scala is a very e...

   Scala,OOP,FP,function programming,hard,idiom     2011-11-08 08:47:43

  Oracle released an urgent Java patch

On March 23, Oracle just released an urgent Java patch which is out of its normal update schedule. The security vulnerability is related to the Java SE running in web browsers on desktops. The CVE ID for this issue is CVE-2016-0636. With the unpatched Java, attackers can remotely exploit the target system without username and credentials. Successful exploits can impact the availability, integrity, and confidentiality of the user's system. When the user access pages containing malicious code...

   JAVA,SECURITY,ORACLE,NEWS     2016-03-25 08:39:59

  Hexadecimal and long in Java

Today I encountered a hexadecimal operation problem when I was implementing a bit reverse function for integer type. Basically in the implementation, there is an operation which is to do the bit operation & between one long integer and a hexadecimal number 0x00000000FFFFFFFFF. I was expecting that the high 32 bits of the long integer will be zeroed. But unfortunately I didn't get the expected result. The basic implementation is: long num=0x00F0_0000; num = (num>>16) | (num<<16); ...

   Hexadecimal,long,Java,bitwise operation     2014-06-18 23:44:32

  How to write good requirements

Requirements are pretty ubiquitous in the embedded world. They are used to define tasks, help coordinate large development efforts, and to communicate the behavior of the desired end product between the developers and the customer. When done right, requirements can be very useful. Unfortunately, if you spend much time working in the embedded world you quickly discover that there are a lot of bad requirements. And then when you try to go fix them, you quickly discover that writing good req...

   Requirement gathering,Good requirement     2012-02-18 12:53:15

  How Kafka achieves high throughput low latency

Kafka is a message streaming system with high throughput and low latency. It is widely adopted in lots of big companies. A well configured Kafka cluster can achieve super high throughput with millions of concurrent writes. How Kafka can achieve this? This post will try to explain some technologies used by Kafka. Page cache + Disk sequential write Every time when Kafka receives a record, it will write it to disk file eventually. But if it writes to disk every time it receives a record, it would ...

   BIG DATA,KAFKA     2019-03-08 09:42:57

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