The metadata checkpointing in HDFS is done by the Secondary NameNode to merge the fsimage and the edits log files periodically and keep edits log size within a limit. For various reasons, the checkpointing by the Secondary NameNode may fail. For one example, HDFS SecondaraNameNode log shows errors in its log as follows. 2017-08-06 10:54:14,488…
Making a career choice is difficult. And, if you have decided on becoming a programmer, the difficulty is just beginning. The most important thing is to first decide the language that you want to learn and this is often the most difficult decision. The good part is that you know you need to focus on…
This post is about the Spring Shell technology and its use in java. Experts of java development India have shared their best knowledge in this post for Spring Shell with the community people. If you have anything to ask, do it at the end. Technology: It is command line tool for Java applications to interact…
In this tutorial, Microsoft Dynamics CRM India experts will teach you how to filter salutation based on Gender field in MS CRM. You can follow the step-by-step guide shared in this post to avail the results. Description- According to the requirement we need to filter salutation based on gender in contact entity. For this we…
In this post, java development India based experts will explain the concept of Quartz. You will also learn the method of setting up the Quartz in this article. You can ask experts if anything bothers you. Technology Quartz is the open source Java technology for scheduling background jobs. If we want to execute the task…
Hadoop 2 or YARN is the new version of Hadoop. It adds the yarn resource manager in addition to the HDFS and MapReduce components. Hadoop MapReduce is a programming model and software framework for writing applications, which is an open-source variant of MapReduce designed and implemented by Google initially for processing and generating large data…
1，Java抛弃了头文件、预处理机制、goto语句和多维数组。 2，Java不支持指针。 3，Java抛弃了联合体和结构体。 4，Java不支持独立函数。所有函数必须在类中声明。 5，Java不支持多重继承，可以使用接口模拟多重继承。 6，Java不支持运算符重载。 7，Java中布尔型不再用整数来代替。 8，Java中主函数必须有一个字符串类型的参数。 Java抛弃的C++中的这些机制和结构多数都是“危险”的，减少了语言的复杂性，增强了安全性，虽然在一定程度上减少了其灵活性。
Vim provides some basic formatting commands. A combination of these commands with the editing commands will make the programmer happy. A list of basic text formatting commands in Vim: = is an operator that formats/indents text. i{ is a text object that specifies the surrounding code block. It should be used together with v, =,…
一个基于Java Applet的浏览器端远程系统资源监视器，使用Socket从网络主机上读取信息然后在browser上动态显示出来。是当年我在实验室中一个项目中做的贡献部分. 这个演示程序中使用的是正态分布生成的数据。 截图一张：
OCaml is an interesting functional language. There are lots learning materials on the Internet. I compile a list of resources for OCaml learning and reference. Recommended OCaml learning and reference material Online book of Real World OCaml by Yaron Minsky, Anil Madhavapeddy, Jason Hickey. A very good tutorial by Jason Hickey: http://www.cs.caltech.edu/courses/cs134/cs134b/book.pdf. The OCaml system…
How to call a function in .dll from Java on Windows is introduced in this post with an example. Platforms used: OS: Microsoft Windows XP [5.1.2600] C to .dll compiler: MS Visual Studio 2008 JDK: java -version java version “1.6.0_05” Java(TM) SE Runtime Environment (build 1.6.0_05-b13) Java HotSpot(TM) Client VM (build 10.0-b19, mixed mode, sharing)…
We use tomcat as the container used for instructions in the post. 1) Download the driver mysql-connector-java-*.*.*-bin.jar and put it into WEB-INF/lib/, and remember to restart tomcat. 2) The example code as follows. String driverName=”com.mysql.jdbc.Driver”; String userName=”username”; String userPasswd=”password”; String dbName=”dbname”; String tableName=”tablename”; String url=”jdbc:mysql://localhost/”+dbName+”?user=”+userName+”&password=”+userPasswd; Class.forName(“com.mysql.jdbc.Driver”).newInstance(); Connection conn=DriverManager.getConnection(url); Statement statement = conn.createStatement(); String sql=”SELECT *…
TeraSort is one of Hadoop’s widely used benchmarks. Hadoop’s distribution contains both the input generator and sorting implementations: the TeraGen generates the input and TeraSort conducts the sorting. Here, we provide a short tutorial for using the Hadoop TeraSort benchmark. TeraGen generates random data that can be used as input data for a subsequent running…
Update: If you are new to Hadoop and trying to install one. Please check the newer version: Hadoop Installation Tutorial (Hadoop 2.x). Hadoop mainly consists of two parts: Hadoop MapReduce and HDFS. Hadoop MapReduce is a programming model and software framework for writing applications, which is an open-source variant of MapReduce that is initially designed…
After [[hadoop-installation-tutorial|installing Hadoop]], we usually run some benchmark programs to test whether the system works well. In the post of the Hadoop install tutorial, we show a very simple to grep strings from a simple sets of files. In this post, we introduce the Sort for testing and benchmarking Hadoop. The Sort program is also…
This post lists pitfalls and lessons learning when configuring and tuning Hadoop. Hadoop with IPv6 Hadoo doesn’t support IPv6 currently (up to 0.20.2 and 0.21.0): Hadoop and IPv6. The performance of the cluster may suffer from turning IPv6 on in clusters: mail archive. One good practice is to disable IPv6 on servers in the Hadoop…
Hadoop is designed to run on [[hadoop-installation-tutorial|hundreds to thousands of computers]] inside cluster. However, Hadoop is configured to run things in a non-distributed mode as a single Java process by default. This is specially useful for debugging since distributed debugging is really a nightmare. This post introduces how to set up a standalone Hadoop environment….