Your browser will redirect pdf architect 4 torrent your requested content shortly. Web applications scalability is a common problem most of the web architect face.
Any internet facing web application may require to be highly scalable due to heavy load of traffic. Now a days, developing a smart web application is much more than creating dynamic Web pages. Irrespective of programming languages like Java, PHP, . NET, Python, Ruby or others, these challenges are faced by software architects everyday. In this decade, lot of distributed web applications are being developed that can utilize the resources from multiple machines, by separating the application functionality into manageable group of tasks that can be deployed in a distribute systems. There are numerous benefits to dividing applications this way, some of the most important are re-usability, scalability, and manageability. What Do You Mean By High Availability?
Having better service capacity with high availability and low latency is mission critical for almost all businesses. Availability means the ability of the application user to access the system, If a user cannot access the application, it is assumed unavailable. High Availability means the application will be available, without interruption. Achieving high availability for a application is not always a easy task. Availability is commonly expressed as a percentage of uptime in a given year. Scalability is the ability of a system, network, or process to handle a growing amount of load by adding more resources. This involves adding more resources to the existing nodes.
For example, adding more RAM, Storage or processing power. This involves adding more nodes to support more users. If we add resources to the system It should increase the ability of application to take more load in a proportional manner of added resources. An ideal application should be able to serve high level of load in less resources. However, in practical, linearly scalable system may be the best option achievable. A cluster is group of computer machines that can individually run a software. Why Do You Need Clustering?
By creating a cluster of more than one machine, we can reduce the chances of our service going un-available in case one of the machine fails. However it in not very likely in case you have many machines and they are located at different location or supported by their own resources. What Is Middle Tier Clustering? Middle tier clustering is just a cluster that is used for service the middle tier in a application.
Failure of middle tier can cause multiple clients and systems to fail, therefore its one of the approaches to do clustering at the middle tier of a application. In general any application that has a business logic that can be shared across multiple client can use a middle tier cluster for high availability. Load balancing is simple technique for distributing workloads across multiple machines or clusters. The most common and simple load balancing algorithm is Round Robin. In this type of load balancing the request is divided in circular order ensuring all machines get equal number of requests and no single machine is overloaded or underloaded. Avoid overload and under-load of any machines.
What Do You Mean By ‘session Affinity’? Sticky session or a session affinity technique another popular load balancing technique that requires a user session to be always served by a allocated machine. This can be avoided by always serving a particular user session request from one machine. The machine is associated with a session as soon as the session is created. All the requests in a particular session are always redirected to the associated machine. This ensures the user data is only at one machine and load is also shared. In Java world, this is typically done by using jsessionid cookie.
The cookie is sent to the client for the first request and every subsequent request by client must be containing that same cookie to identify the session. What Are The Issues With Sticky Session? This may cause strange behavior for the users who use no cookie based browsers. What Is IP Address Affinity Technique For Load Balancing?
IP address affinity is another popular way to do load balancing. This approach can be really easy to implement since IP address is always available in a HTTP request header and no additional settings need to be performed. However there is a down side of this approach. NATed IP address is really common, in fact anytime you are browsing from a office network its likely that you and all your coworkers are using same NATed IP address. Fail over means switching to another machine when one of the machine fails.