Sidecar Pattern Architecture

Sidecar Pattern Architecture

In this tutorial, we are going to discuss about the Sidecar Pattern Architecture. The Sidecar Pattern is an architectural design pattern commonly used in microservices architectures to address cross-cutting concerns by deploying auxiliary services alongside primary services. These auxiliary services, known as sidecars, run in separate processes or containers but are tightly coupled to the primary services, sharing the same lifecycle and often residing on the same host.

Sidecar Pattern Architecture
Architecture Components

1. Primary Service

  • The main application or service that provides the core business functionality.
  • Typically runs in its own container or process.

2. Sidecar Service

  • An auxiliary service that provides additional capabilities such as logging, monitoring, networking, and security.
  • Runs in a separate container or process but is closely integrated with the primary service.
  • Shares the same lifecycle and environment as the primary service.

3. Shared Resources

  • File Systems: Both services might share volumes for logging or configuration files.
  • Network Interfaces: Typically, sidecars and primary services share the same network namespace, enabling them to communicate over localhost.
  • Environment Variables: Shared configurations can be accessed via environment variables.
    Communication and Integration
    • Inter-Process Communication (IPC): Sidecars often communicate with the primary service through IPC mechanisms such as shared memory, Unix domain sockets, or HTTP calls.
    • Shared Network Namespace: In containerized environments, sidecars and primary services often share the same network namespace, allowing direct communication over localhost.
    The Containerized Confluence

    One of the most distinctive features of the Sidecar Pattern’s architecture is its use of containers. The main application and its sidecar are deployed together in the same container, allowing them to share resources and communicate efficiently. This shared environment enables them to operate as a single unit while maintaining their individuality.

    Sidecars Galore: A Multifaceted Approach

    In the architecture of the Sidecar Pattern, you are not restricted to one sidecar per main application. In fact, you can have multiple sidecars, each addressing a specific functionality. This allows you to modularize your application, making it easier to manage and scale.

    Imagine a motorbike equipped with multiple sidecars – one for extra storage, one for an extra passenger, and one equipped with navigation aids. Each sidecar serves a distinct purpose, yet they all contribute to a smooth and efficient ride!

    The Network Navigator

    In the Sidecar Pattern architecture, the sidecar also plays an instrumental role in network communication. It intercepts all incoming and outgoing network traffic from the main application, effectively acting as a proxy. This means it can handle responsibilities such as load balancing, circuit breaking, and security, leaving the main application free to focus on delivering the primary service.

    The Lifespan Link

    The sidecar and the main application, while separate entities, share the same lifespan in the Sidecar Pattern architecture. This means they are created, deployed, and destroyed together. This synchronized lifespan ensures that the main application always has its sidecar at its side, ready to serve.

    Sidecar Pattern: Bringing Theory to Practice with an Example

    In this section, we’ll bring the Sidecar Pattern to life, showing you just how it operates in a real-world scenario.

    Creating the Main Application

    First things first, we need an application. Let’s create a simple Java web application. This application will expose a RESTful API and will serve as our main application.

    Here is a simple Java web service using Spring Boot:

    import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class MainApplication {

  public static void main(String[] args) {
    SpringApplication.run(MainApplication.class, args);
  }

  @GetMapping("/api")
  public String getData() {
    return "Hello, Sidecar!";
  }
}

    This web service will return the string “Hello, Sidecar!” whenever we hit the “/api” endpoint.

    Introducing the Sidecar

    Now that we have our main application, it’s time to introduce the sidecar. In our case, let’s create a sidecar that will log every request to our “/api” endpoint. For simplicity, our sidecar will also be a Java application:

    import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class LoggingSidecar {

  public static void main(String[] args) {
    SpringApplication.run(LoggingSidecar.class, args);
  }

  @GetMapping("/log")
  public String logRequest() {
    System.out.println("Request received at /api endpoint");
    return "Logged!";
  }
}

    This sidecar will print a log message every time the “/log” endpoint is hit. We’ll use this endpoint to log requests to our main application’s “/api” endpoint.

    Making the Sidecar and Main Application Work Together

    Now, let’s make our main application and sidecar work together. We need to modify our main application to call the “/log” endpoint of the sidecar whenever the “/api” endpoint is hit.

    We’ll use RestTemplate, a Spring utility class for calling RESTful services:

    import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@RestController
public class MainApplication {

  private RestTemplate restTemplate = new RestTemplate();

  public static void main(String[] args) {
    SpringApplication.run(MainApplication.class, args);
  }

  @GetMapping("/api")
  public String getData() {
    ResponseEntity<String> response = restTemplate.getForEntity("http://localhost:8081/log", String.class);
    System.out.println("Response from sidecar: " + response.getBody());
    return "Hello, Sidecar!";
  }
}

    Now, whenever the “/api” endpoint of our main application is hit, it will call the “/log” endpoint of our sidecar. The sidecar will log the request, and the main application will continue to process the request.

    Keep in Mind: The Docker Factor

    Remember, the sidecar and the main application need to be deployed within the same container to achieve the benefits of the Sidecar Pattern. While our Java example didn’t cover this aspect, in a production scenario, you’d use a container platform like Docker to deploy the main application and the sidecar in the same container.

    You’d also likely use Kubernetes as an orchestration tool to manage the deployment and scaling of your application and its sidecar. Kubernetes also has built-in support for sidecar containers, making it an ideal tool for implementing the Sidecar Pattern Architecture.

    Conclusion

    The Sidecar Pattern provides a modular and flexible approach to managing cross-cutting concerns in microservices architectures. By offloading these concerns to sidecar services, you can achieve a clean separation of concerns, enhance reusability, and maintain consistency across your microservices. This pattern is particularly well-suited for containerized environments and is a foundational element of service mesh architectures.

    That’s all about the Sidecar Pattern Architecture. If you have any queries or feedback, please write us email at contact@waytoeasylearn.com. Enjoy learning, Enjoy Microservices..!!.!!

    Sidecar Pattern Architecture
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