Behavioral Patterns

Blackboard

The Blackboard pattern provides a central repository (the Blackboard) of information that multiple, independent Knowledge Sources can access, modify, and react to. A Controller selects which Knowledge Sources are relevant at any given time based on the current state of the Blackboard, and applies their expertise to …

Request-Reply

behavioral messaging

The Request-Reply pattern is a fundamental communication pattern where one party (the client) sends a request to another party (the service) and waits for a response (the reply). It’s a synchronous interaction style, meaning the client blocks until the reply is received. This pattern is commonly used in …

Front Controller

behavioral web application

The Front Controller pattern provides a centralized entry point for all requests coming into a web application. Instead of having each servlet or controller directly handle requests, all requests are initially dispatched to a single controller – the Front Controller. This controller then determines the appropriate …

Mediator

behavioral communication

The Mediator pattern defines an object that encapsulates how a set of objects interact. This mediator promotes loose coupling by preventing objects from referring to each other explicitly and lets the mediation logic vary independently of the interacting objects. Instead of components communicating directly, they …

Transactional Consumer

behavioral integration reliability

The Transactional Consumer pattern ensures that messages received from a message broker are processed reliably and atomically. It handles message consumption within a database transaction, allowing for either complete processing of a message batch or a full rollback in case of failure. This prevents partial updates and …

Idempotent Receiver

behavioral integration resilience

The Idempotent Receiver is a pattern used in distributed systems to ensure that a receiver can safely reprocess the same message multiple times without causing unintended side effects. This is crucial in scenarios where message delivery is not guaranteed – a message might be retried due to network issues or receiver …

Plug-in

behavioral extensibility

The Plug-in pattern defines a framework where software functionality can be extended without modifying the core application code. It achieves this by defining extension points—interfaces or abstract classes—that allow third-party developers or internal teams to add features dynamically. These extensions, known as …

Scheduler-Agent-Supervisor

behavioral concurrency distributed systems

The Scheduler-Agent-Supervisor pattern addresses the challenge of reliably executing tasks in a distributed or concurrent environment. A Scheduler is responsible for creating and assigning tasks to Agents. Agents execute these tasks and report their status. A Supervisor independently monitors the Agents and, if an …

Rate Limiting

behavioral resilience microservices

Rate limiting is a technique used to control the rate at which users or systems can access a resource. This is crucial for preventing abuse, ensuring service availability, and protecting backend systems from overload. By limiting the number of requests within a specific timeframe, rate limiting helps to maintain a …

Cache Aside

behavioral performance

The Cache Aside pattern is a caching technique where the application first checks if the requested data exists in the cache. If it does, the cache returns the data immediately. If the data is not in the cache (a “cache miss”), the application retrieves it from the database, stores a copy in the cache for …