Approach for scalability in software as a service

Abstract

Software as a Service (SaaS) is a software service delivery model. Software is centrally hosted on cloud infrastructure and delivered as a service through the Internet. Scalability is one of the major issues in SaaS. One of the ways to achieve scalability is to use proper caching mechanism. Memcached is a well known, high performance < key, value > distributed cache used for the Internet applications. High frequently used data and costly data (takes more time to decompress) is stored in memcached server node. Data is not persistent in memcached server node. The data is lost if memcached server node fails. In memcached server node, data is not durable. Durability of high frequently used data and costly data should be high. To achieve availability and durability of stored data is very difficult in pool of memcached server nodes. Frequency of data being accessed, data that takes more time to decompress and number of write operations in pool of memcached server nodes are the characteristics that needs to be considered in order to decide the durability of the data.

To achieve high durability, data needs to be replicated among several memcached server nodes. Based on the term durability, data is replicated among several memcached server nodes. Data replication is done by memcacheS server node. MemcacheS server node acts as a central entity which supports read and write operations to memcached server nodes. In write operation, memcacheS server node creates replication of data in available memcached server nodes according to durability. When memcached client node needs data for particular key, it sends request to memcacheS server node. MemcacheS server node provides information of owner memcached server nodes. Memcached client node requests the data for particular key and gets the value of the data. Durable data storage provides high availability of the data. Performed set of experiments are based on the proposed approach. After failure of any memcached server node, value of stored data could be retrieved from other memcached server node with durability of data more than 1. The results indicate that, availability of data is increased, as it can be fetched from other memcached server nodes too. Durable data storage provides high availability of the data. The proposed approach. is helpful in dynamic web application and Software as a Service (SaaS) applications where time to satisfy millions of requests is critical issue.