Microservices architecture has revolutionized the way software developers approach building applications by breaking down a monolithic codebase into smaller, independently deployable services. One of the fundamental aspects of implementing microservices is choosing the right type of server to host them. Tomcat, a popular choice due to its robustness and light footprint, can be used in two distinct modes: Embedded and Standalone. Understanding the differences between these two can significantly influence how you design and deploy your microservices.

Overview of Tomcat Server Deployment Modes

Embedded Tomcat

Embedded Tomcat refers to integrating the Tomcat server directly into your application, usually packaged as part of a Spring Boot or similar framework application. This approach means that the application itself starts the server and manages its lifecycle.

Key Characteristics

• Ease of Deployment: With Embedded Tomcat, your application and Tomcat server are bundled together, resulting in a single executable JAR or WAR file. This can simplify DevOps processes as you deal with fewer moving parts.
• Configuration: Configuration is typically done programmatically or through application properties, offering greater flexibility and less dependence on external configuration files.
• Resource Management: Since the application controls the server, it can optimize resource usage for specific application needs, potentially leading to better performance.
• Portability: Applications using Embedded Tomcat are often more portable, leveraging Docker and similar container technologies to make deployments consistent across environments.

Standalone Tomcat

On the other hand, Standalone Tomcat means the Tomcat server is installed separately from the application and the application is deployed to it following standard web application deployment procedures.

Key Characteristics

• Separation of Concerns: By separating the server from application management, operations teams can manage each independently for tasks like scaling, monitoring, and updating.
• Stability and Maturity: Standalone Tomcat has a long history and broad adoption, providing a stable and mature environment that might benefit applications with complex deployment requirements.
• Configuration Complexity: Typically, configuration is handled through XML configuration files like `server.xml`, which might require a deeper understanding of Tomcat’s operation.
• Standardization: Organizations with large infrastructures may prefer standardized server configurations to maintain consistency, making standalone Tomcat a familiar choice.

Technical Exploitations

Deployment Speed

Embedded Tomcat generally leads to faster deployments as the entire application, including the server, is initiated at once. In contrast, Standalone Tomcat requires initializing and preparing the server environment before deploying the application, adding steps to the deployment lifecycle.

Operational Flexibility

Embedded Tomcat tends to offer more operational flexibility. For example, developers can change server configurations directly as part of the application's properties. However, with Standalone Tomcat, any change in server configurations might require a restart of the server, causing potential downtime.

Monitoring and Logging

Standalone Tomcat often provides more extensive monitoring and logging features already integrated into many organizational structures. Embedded Tomcat applications must implement additional monitoring strategies, often relying on application-level monitoring tools.

Example: Using Embedded Tomcat with Spring Boot

Consider a microservice application built with Spring Boot:

• The `SpringApplication.run()` method starts the embedded Tomcat server with the application.
• Configuration aspects like server port changes can be managed in `application.properties`: