Meet Yii

The name Yii is an acronym for Yes, it is, and is pronounced as Yee or (ji:). Yii is a high-performance, component-based, web application framework written in PHP5.

This article by Jeffrey Winesett, author of Web Application Development with Yii and PHP, provides you with a brief history of Yii, an introduction to the Model View Controller (MVC) application architecture, and you are introduced to the typical request life cycle as it makes its way from the end user through the application, and finally as a response back to the end user.

HBase Administration, Performance Tuning

Performance is one of the most interesting characteristics of an HBase cluster's behavior. It is a challenging operation for administrators, because performance tuning requires deep understanding of not only HBase but also of Hadoop, Java Virtual Machine Garbage Collection (JVM GC), and important tuning parameters of an operating system.

The structure of a typical HBase cluster is shown in the following diagram:

There are several components in the cluster—the ZooKeeper cluster, the HBase master node , region servers, the Hadoop Distributed File System(HDFS) and the HBase client.

The ZooKeeper cluster acts as a coordination service for the entire HBase cluster, handling master selection, root region server lookup, node registration, and so on. The master node does not do heavy tasks. Its job includes region allocation and failover, log splitting, and load balancing. Region servers hold the actual regions; they handle I/O requests to the hosting regions, flush the in-memory data store (MemStore) to HDFS, and split and compact regions. HDFS is the place where HBase stores its data files (StoreFile) and write ahead logs (WAL). We usually have an HBase region server running on the same machine as the HDFS DataNode, but it is not mandatory.

The HBase client provides APIs to access the HBase cluster. To communicate with the cluster, clients need to find the region server holding a specific row key range; this is called region lookups. HBase has two system tables to support region lookups—the -ROOT- table and the .META. table.

The -ROOT-table is used to refer to regions in the .META.table, while the .META.table holds references to all user regions. First, the clients query ZooKeeper to find the -ROOT-table location (the region server where it is deployed); they then query the -ROOT-table, and subsequently the .META.table, to find the region server holding a specific region. Clients also cache region locations to avoid querying ZooKeeper, -ROOT-, and .META.tables every time. With this background knowledge, we will describe how to tune HBase to gain better performance, in this article.

Besides HBase itself, other tuning points include Hadoop configurations, the JVM garbage collection settings, and the OS kernel parameters. These are as important as tuning HBase itself. We will also include recipes to tune these configurations, in this article.

In this article, by Yifeng Jiang, author of HBase Administration Cookbook, we will cover:

• Setting up Hadoop to spread disk I/O
• Using a network topology script to make the Hadoop rack-aware
• Mounting disks with noatimeand nodiratime
• Setting vm.swappinessto 0 to avoid swap
• Java GC and HBase heap settings
• Using compression
• Managing compactions
• Managing a region split

Ajax: Basic Utilities

In this article by Milan Sedliak, author of PHP Ajax we will learn how to build the basic Ajax forms. We will try to understand where we can use Ajax methodology and where we can't. There are a lot of ways in which we can use Ajax. Here are some "best" practices based on user experience and the performance of the specific system. Ajax makes our lives easier, faster, and better; how and where to use it is up to us.

In this article, we will cover the following topics:

• Validating a form using Ajax
• Creating an autosuggest control
• Making form wizards
• Uploading a file using Ajax
• Creating a five star rating system

Yii 1.1: Using Zii Components

Yii is a very flexible and high-performance application development framework written in PHP. It helps building web applications from small ones to large-scale enterprise applications. The framework name stands for Yes It Is.

In this article by Alexander Makarov, author of Yii 1.1 Application Development Cookbook, we will cover:

• Using data providers
• Using grids
• Using lists
• Creating custom grid columns