An application server is a software platform that provides an environment for running and managing applications. It acts as an intermediary between end users/clients and the backend systems or databases. The primary purpose of an application server is to host, manage, and deliver applications to clients over a network.
An application server serves as middleware, enabling communication and integration between various components of an application, such as web servers, databases, and business logic.
Examples of popular application servers include Apache Tomcat, JBoss (WildFly), IBM WebSphere Application Server, Oracle WebLogic Server, and Microsoft Internet Information Services (IIS). These servers support different programming languages, frameworks, and application types, such as Java, ASP .NET, and PHP.
There are several reasons why application servers are used in modern application architectures:
Overall, using an application server simplifies development, improves application performance and scalability, enhances security, and provide centralized management and monitoring capabilities. This is why application servers are essential components in modern application deployments.
Application servers often host the middleware components of an application. A web server often receives and directs requests to an application server which then handles the business logic of the application. To be scalable, application servers implement multi-threading. Requests can execute in parallel using individual threads.
While a web server serves static content (pages, files, images, videos, and the like) only, an application server serves dynamic content (implemented using JSPs, servlets, etc). Many application servers also support similar capabilities as web servers (HTTP processing, caching of static content, etc.) and this makes the distinction with web servers less apparent.
Since application servers are important components of a web application architecture, it is essential that they be monitored. All key components of application servers must be monitored. The runtime engine – Java, .NET, etc. – must also be monitored. Workloads to the different application server components and their responsiveness must be tracked. Unfortunately, there is no standard mechanism for monitoring different application servers. Even when they support the same protocol – e.g., Java Management Extensions – the attributes to be monitored vary from one application server to another.