Why you should consider a Nginx reverse proxy for your Microservice

In the world of modern application development, microservices have emerged as a popular architectural pattern for building large, complex systems. By breaking an application down into smaller, loosely-coupled services that each implement a specific business capability, organizations can achieve greater agility, scalability, and maintainability compared to a traditional monolithic approach.

However, microservices also introduce new challenges around service discovery, load balancing, security, and more. This is where nginx, the popular open source web server and reverse proxy, can play a key role. By deploying nginx in front of your microservices, you can solve many of these challenges while also gaining additional benefits.

In this post, we‘ll take an in-depth look at why you should consider using nginx as part of your microservices architecture. We‘ll cover the core use cases and benefits, share example configurations, and discuss best practices to keep in mind as you get started.

What are Microservices?

Before diving into nginx itself, let‘s take a step back and define what we mean by "microservices". Microservices is an architectural style where an application is developed as a collection of small, autonomous services that are:

• Highly maintainable and testable
• Loosely coupled
• Independently deployable
• Organized around business capabilities
• Owned by small teams

Each microservice typically runs in its own process and communicates with other services via lightweight mechanisms like HTTP/REST or message queues. This is in contrast to the traditional "monolithic" style where an application is built as a single, large system.

While microservices can offer many benefits, they also come with additional complexity. As an application is broken down into more and more services, it becomes increasingly important to have solid strategies in place for cross-cutting concerns like:

• Service discovery: How do services find and communicate with each other?
• Load balancing: How do you distribute requests across multiple instances of a service?
• Security: How do you handle authentication, authorization, encryption, etc across services?
• Monitoring and logging: How do you gain visibility into the health and performance of all your services?

Using a reverse proxy like nginx at the edge of your microservices can help address many of these concerns. Let‘s look at some of the key benefits and use cases.

Benefits of Nginx in a Microservices Architecture

Reverse Proxy Routing

One of the most common ways to use nginx with microservices is as a reverse proxy to route external requests to the appropriate backend service. For example, you might have separate microservices for handling user authentication, product information, recommendations, shopping carts, orders, and more. Nginx can examine the URL of incoming requests and route them to the correct service based on a defined mapping.

A simple nginx configuration for this might look like:

http {
  upstream auth_service {
    server auth1.internal.example.com:8080;
    server auth2.internal.example.com:8080;
  }

  upstream products_service {
    server products1.internal.example.com:8080;
    server products2.internal.example.com:8080;
  }

  server {
    listen 80;
    server_name api.example.com;

    location /auth {
      proxy_pass http://auth_service;
    }

    location /products {
      proxy_pass http://products_service; 
    }
  }
}

Here, requests to api.example.com/auth will be forwarded to the auth microservice, while requests to api.example.com/products will go to the products microservice. The upstream blocks define groups of backend servers that can be referred to by name.

Using this approach, you can present a single cohesive API to clients while still maintaining the flexibility of a microservices architecture on the backend. Clients don‘t need to know anything about the individual services. If you need to refactor, scale, or change the implementation of a particular service, you can do so without impacting clients as long as you maintain a compatible API.

Load Balancing

Another key use case for nginx is load balancing requests across multiple instances of a service. This becomes increasingly important as you scale your microservices to handle a growing volume of traffic. With nginx, you can define an upstream group consisting of multiple backend servers. Nginx will then distribute requests across those servers according to the configured load balancing algorithm.

For example:

upstream products_service {
  server products1.example.com:8080;
  server products2.example.com:8080;
  server products3.example.com:8080;
}

By default, nginx will use a round-robin algorithm to cycle requests through the upstream servers in order. However, there are a number of other options available:

• least_conn: Send requests to the server with the least number of active connections
• ip_hash: Distribute requests based on a hash of the client IP, such that a given client will always go to the same backend server
• hash: Distribute requests based on a configurable hash key, such as a cookie or URL parameter
• random: Randomly choose a backend server for each request

You can also configure nginx to do passive health checks on the backend servers by looking at the status of responses (e.g. marking a server as "unhealthy" if it returns a certain number of errors). Unhealthy servers can be temporarily removed from the load balancing rotation.

With these load balancing capabilities, you can help ensure your microservices remain performant and available even as traffic grows. Being able to quickly scale the number of instances of a service and have nginx automatically handle the distribution of requests is a huge benefit.

SSL/TLS Termination

In most production deployments, you‘ll want to encrypt communication between clients and your API using SSL/TLS. With microservices, it usually makes sense to terminate the SSL connection at the nginx layer, rather than configuring SSL for each individual service.

By terminating SSL in nginx, you can:

• present a single SSL endpoint to clients
• centralize SSL configuration and credentials
• offload encryption overhead from your backend services
• continue using plain HTTP for communication between nginx and backend services

Here‘s what a basic nginx config with SSL termination might look like:

http {
  server {
    listen 443 ssl;
    server_name api.example.com;

    ssl_certificate /etc/nginx/certs/cert.pem;
    ssl_certificate_key /etc/nginx/certs/key.pem;

    location /auth {
      proxy_pass http://auth_service;
    }
  }
}

In this example, nginx listens on port 443 and presents the SSL certificate configured with the ssl_certificate and ssl_certificate_key directives. It then proxies decrypted requests to the auth_service over standard HTTP.

Consolidating SSL configuration in your nginx proxy helps simplify management and reduces the burden on individual services to handle encryption. It‘s one less thing each service team needs to worry about.

API Gateway

As you start to build out a larger microservices architecture, you may find that you need more than just a simple reverse proxy. This is where the concept of an "API Gateway" comes into play. An API Gateway acts as a single entry point for all client requests, handling common tasks like:

• authentication and authorization
• rate limiting and throttling
• request and response transformation
• caching
• API composition and aggregation

Nginx can serve as the foundation for building your own lightweight API Gateway. By leveraging third-party modules and the lua scripting language, you can implement many of these API Gateway features directly in your nginx configuration.

For example, to add basic API key authentication to an endpoint:

location /api {
  access_by_lua_block {
    local api_key = ngx.var.arg_api_key
    if api_key ~= "my_secret_key" then
      ngx.exit(ngx.HTTP_UNAUTHORIZED)
    end
  }

  proxy_pass http://my_service;
}

Or to cache responses from a backend service:

http {
  proxy_cache_path /data/nginx/cache keys_zone=my_cache:10m;

  server {
    location /api {
      proxy_cache my_cache;
      proxy_cache_valid 200 10m;
      proxy_cache_use_stale error timeout invalid_header updating http_500 http_502 http_503 http_504;

      proxy_pass http://my_service;
    }
  }  
}

These are just a couple simple examples, but they demonstrate the flexibility and power of using nginx as an API Gateway. You can implement all sorts of logic to shape traffic and enforce policies across your microservices.

That said, for more complex API Gateway scenarios you may want to look at API management products like Kong, Apigee, or Amazon API Gateway that are built on top of nginx. These can provide higher level configuration, richer policy support, developer portals, and other features that go beyond what you would want to build yourself in nginx.

Alternatives to Nginx

While nginx is a popular and powerful choice for a microservices reverse proxy, there are certainly other options to consider as well. Some other common open source proxies include:

• HAProxy: Another widely used open source TCP/HTTP load balancer. It has a reputation for being extremely fast and efficient, especially for TCP-based services.
• Envoy: A more recent proxy originally developed at Lyft. It has a focus on dynamic configuration and integrates well with service meshes like Istio and Consul.
• Traefik: A modern HTTP reverse proxy with automatic service discovery, support for multiple orchestration backends, and a polished web UI.

In the end, the "right" proxy for your organization will depend on your specific needs and existing technology stack. Nginx‘s combination of performance, stability, flexibility, and rich feature set make it a solid default choice for many. But it‘s worth evaluating some of these other options, especially if you have more unique requirements.

Nginx Deployment Best Practices

As you implement nginx as part of your microservices stack, there are a few best practices to keep in mind:

• Ensure you have a well-defined strategy for rolling out configuration changes to your nginx fleet. Common approaches include using configuration management tools like Ansible or Puppet, templating configs with Consul Template or confd, or deploying nginx as an immutable Docker container.

• Implement a robust monitoring and alerting system around your nginx proxies. Some key metrics to watch include requests per second, error rates, latency, and resource utilization. You can use open source tools like Prometheus, Grafana, and the nginx VTS module or paid solutions like Datadog, New Relic, and NGINX Amplify to help monitor performance.

• Plan ahead for how you will handle SSL/TLS certificate management, especially if you expect to have a large number of certificates. Approaches like using a certificate management service (e.g. Let‘s Encrypt) or delegating to a service mesh can help simplify the process.

• Understand the high availability and failover story for your nginx deployment. At a minimum you‘ll likely want to run multiple nginx instances behind a layer-4 load balancer. For more mission critical workloads, consider an active/passive or active/active HA configuration with something like Keepalived or a managed solution like Amazon‘s Elastic Load Balancer.

• Carefully tune your nginx configuration for optimal performance. Some key settings include worker processes, connections, keepalive, buffers, and timeouts. Use tools like AB or wrk to load test your environment and experiment with different values.

By following these practices, you can help ensure your nginx reverse proxy is reliable, performant, and easy to manage as a core part of your microservices architecture.

Conclusion

As microservices continue to grow in popularity, nginx is well positioned to serve as a foundational element of many organizations‘ deployment stacks. Its reverse proxy and load balancing capabilities help solve some of the most common challenges teams face as they build and scale distributed, service-based applications. It can also serve as a lightweight API gateway, providing authentication, rate limiting, and other cross-cutting concerns.

While there are many proxies to choose from, nginx stands out for its rich feature set, excellent performance, and massive community support. If you‘re not already using nginx with your microservices, it‘s definitely worth taking the time to explore and evaluate.

Hopefully this post has given you a solid overview of nginx‘s role in a microservices architecture, along with some practical tips to help you get started. As with any technology, the best approach is to start small, experiment, and iterate. Begin by configuring nginx as a basic reverse proxy, then start to layer in more advanced functionality like load balancing, SSL termination, and caching as your needs evolve.

Above all, remember that your reverse proxy is a critical component of your application delivery stack. Invest the time to thoroughly test your configuration, monitor its behavior in production, and keep it up-to-date. With the right approach, nginx can be a powerful ally in your journey towards a successful microservices architecture.