Frontend Microservices: Service Discovery and Communication Strategies

Mikrotjenestearkitekturen har revolusjonert backend-utvikling, og gjort det mulig for team å bygge skalerbare, robuste og uavhengig distribuerbare tjenester. Nå blir dette arkitektoniske mønsteret i økende grad tatt i bruk på frontenden, noe som gir opphav til frontend-mikrotjenester, også kjent som mikro-frontender. Denne artikkelen dykker ned i de avgjørende aspektene ved tjenesteoppdagelse og kommunikasjon innenfor en frontend-mikrotjenestearkitektur.

What are Frontend Microservices?

Frontend-mikrotjenester (eller mikro-frontender) er en arkitektonisk tilnærming der en frontend-applikasjon er dekomponert i mindre, uavhengig distribuerbare og vedlikeholdbare enheter. Hver mikro-frontend eies vanligvis av et eget team, noe som gir større autonomi, raskere utviklingssykluser og enklere skalering. I motsetning til monolittiske frontender, der alle funksjoner er tett koblet, fremmer mikro-frontender modularitet og løs kobling.

Benefits of Frontend Microservices:

• Independent Deployment: Teams can deploy their micro frontends without affecting other parts of the application, reducing deployment risks and enabling faster iterations.
• Technology Diversity: Each team can choose the best technology stack for their specific micro frontend, allowing for experimentation and innovation.
• Improved Scalability: Micro frontends can be scaled independently based on their specific needs, optimizing resource utilization.
• Increased Team Autonomy: Teams have full ownership of their micro frontends, leading to increased autonomy and faster decision-making.
• Easier Maintenance: Smaller codebases are easier to maintain and understand, reducing the risk of introducing bugs.

Challenges of Frontend Microservices:

• Increased Complexity: Managing multiple micro frontends can be more complex than managing a single monolithic frontend.
• Service Discovery and Communication: Implementing effective service discovery and communication mechanisms is crucial for the success of a micro frontend architecture.
• Shared Components: Managing shared components and dependencies across micro frontends can be challenging.
• Performance Optimization: Optimizing performance across multiple micro frontends requires careful consideration of loading strategies and data transfer mechanisms.
• Integration Testing: Integration testing can be more complex in a micro frontend architecture, as it requires testing the interaction between multiple independent units.

Service Discovery in Frontend Microservices

Tjenesteoppdagelse er prosessen med automatisk å finne og koble til tjenester i et distribuert system. I en frontend-mikrotjenestearkitektur er tjenesteoppdagelse avgjørende for å gjøre det mulig for mikro-frontender å kommunisere med hverandre og med backend-tjenester. Det finnes flere tilnærminger til tjenesteoppdagelse i frontend-mikrotjenester, hver med sine egne fordeler og ulemper.

Approaches to Service Discovery:

1. Static Configuration:

I denne tilnærmingen er plasseringen av hver mikro-frontend hardkodet i en konfigurasjonsfil eller miljøvariabel. Dette er den enkleste tilnærmingen, men det er også den minst fleksible. Hvis plasseringen av en mikro-frontend endres, må du oppdatere konfigurasjonsfilen og re-distribuere applikasjonen.

Example:

            const microFrontendConfig = {
  "productCatalog": "https://product-catalog.example.com",
  "shoppingCart": "https://shopping-cart.example.com",
  "userProfile": "https://user-profile.example.com"
};
            

              
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Pros:

• Simple to implement.

Cons:

• Not scalable.
• Requires redeployment for configuration changes.
• Not resilient to failures.

2. DNS-based Service Discovery:

Denne tilnærmingen bruker DNS til å løse plasseringen av mikro-frontender. Hver mikro-frontend er tildelt en DNS-post, og klienter kan bruke DNS-spørringer for å oppdage plasseringen. Denne tilnærmingen er mer fleksibel enn statisk konfigurasjon, siden du kan oppdatere DNS-postene uten å re-distribuere applikasjonen.

Example:

Assuming you have DNS records configured like this:

• product-catalog.microfrontends.example.com IN A 192.0.2.10
• shopping-cart.microfrontends.example.com IN A 192.0.2.11

Your frontend code might look like this:

            const microFrontendUrls = {
  "productCatalog": `http://${new URL("product-catalog.microfrontends.example.com").hostname}`,
  "shoppingCart": `http://${new URL("shopping-cart.microfrontends.example.com").hostname}`
};
            

              
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Pros:

• More flexible than static configuration.
• Can be integrated with existing DNS infrastructure.

Cons:

• Requires managing DNS records.
• Can be slow to propagate changes.
• Relies on DNS infrastructure availability.

3. Service Registry:

Denne tilnærmingen bruker et dedikert tjenesteregister for å lagre plasseringen av mikro-frontender. Mikro-frontender registrerer seg selv i tjenesteregisteret når de starter opp, og klienter kan spørre tjenesteregisteret for å oppdage plasseringen. Dette er den mest dynamiske og robuste tilnærmingen, siden tjenesteregisteret automatisk kan oppdage og fjerne usunne mikro-frontender.

Popular service registries include:

• Consul
• Eureka
• etcd
• ZooKeeper

Example (using Consul):

First, a micro frontend registers itself with Consul upon startup. This typically involves providing the micro frontend's name, IP address, port, and any other relevant metadata.

            // Example using Node.js and the 'node-consul' library
const consul = require('consul')({
  host: 'consul.example.com', // Consul server address
  port: 8500
});

const serviceRegistration = {
  name: 'product-catalog',
  id: 'product-catalog-1',
  address: '192.168.1.10',
  port: 3000,
  check: {
    http: 'http://192.168.1.10:3000/health',
    interval: '10s',
    timeout: '5s'
  }
};

consul.agent.service.register(serviceRegistration, function(err) {
  if (err) throw err;
  console.log('Registered with Consul');
});
            

              
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Then, other micro frontends or the main application can query Consul to discover the location of the product catalog service.

            consul.agent.service.list(function(err, result) {
  if (err) throw err;
  const productCatalogService = Object.values(result).find(service => service.Service === 'product-catalog');

  if (productCatalogService) {
    const productCatalogUrl = `http://${productCatalogService.Address}:${productCatalogService.Port}`;
    console.log('Product Catalog URL:', productCatalogUrl);
  } else {
    console.log('Product Catalog service not found');
  }
});
            

              
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Pros:

• Highly dynamic and resilient.
• Supports health checks and automatic failover.
• Provides a central point of control for service management.

Cons:

• Requires deploying and managing a service registry.
• Adds complexity to the architecture.

4. API Gateway:

En API-gateway fungerer som et enkelt inngangspunkt for alle forespørsler til backend-tjenestene. Den kan håndtere tjenesteoppdagelse, ruting, autentisering og autorisasjon. I sammenheng med frontend-mikrotjenester kan API-gatewayen brukes til å rute forespørsler til den aktuelle mikro-frontenden basert på URL-banen eller andre kriterier. API Gateway abstraherer kompleksiteten til de enkelte tjenestene fra klienten. Selskaper som Netflix og Amazon bruker API Gateways i stor grad.

Example:

Let's imagine you're using a reverse proxy like Nginx as an API Gateway. You can configure Nginx to route requests to different micro frontends based on the URL path.

            # nginx configuration

http {
  upstream product_catalog {
    server product-catalog.example.com:8080;
  }

  upstream shopping_cart {
    server shopping-cart.example.com:8081;
  }

  server {
    listen 80;

    location /product-catalog/ {
      proxy_pass http://product_catalog/;
    }

    location /shopping-cart/ {
      proxy_pass http://shopping_cart/;
    }
  }
}
            

              
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In this configuration, requests to `/product-catalog/*` are routed to the `product_catalog` upstream, and requests to `/shopping-cart/*` are routed to the `shopping_cart` upstream. The upstream blocks define the backend servers that handle the requests.

Pros:

• Centralized entry point for all requests.
• Handles routing, authentication, and authorization.
• Simplifies service discovery for clients.

Cons:

• Can become a bottleneck if not properly scaled.
• Adds complexity to the architecture.
• Requires careful configuration and management.

5. Backend for Frontend (BFF):

Backend for Frontend (BFF)-mønsteret innebærer å opprette en separat backend-tjeneste for hver frontend. Hver BFF er ansvarlig for å samle data fra flere backend-tjenester og skreddersy responsen til de spesifikke behovene til frontenden. I en mikro-frontend-arkitektur kan hver mikro-frontend ha sin egen BFF, noe som forenkler datahenting og reduserer kompleksiteten i frontend-koden. Denne tilnærmingen er spesielt nyttig når du har å gjøre med forskjellige typer klienter (f.eks. web, mobil) som krever forskjellige dataformater eller aggregeringer.

Example:

Imagine a web application and a mobile app both need to display product details, but they require slightly different data and formatting. Instead of having the frontend directly call multiple backend services and handle the data transformation itself, you create a BFF for each frontend.

The web BFF might aggregate data from the `ProductCatalogService`, `ReviewService`, and `RecommendationService` and return a response optimized for display on a large screen. The mobile BFF, on the other hand, might only fetch the most essential data from the `ProductCatalogService` and `ReviewService` to minimize data usage and optimize performance on mobile devices.

Pros:

• Optimized for specific frontend needs.
• Reduces complexity on the frontend.
• Enables independent evolution of frontends and backends.

Cons:

• Requires developing and maintaining multiple backend services.
• Can lead to code duplication if not properly managed.
• Increases operational overhead.

Communication Strategies in Frontend Microservices

Når mikro-frontender er oppdaget, må de kommunisere med hverandre for å gi en sømløs brukeropplevelse. Det finnes flere kommunikasjonsmønstre som kan brukes i en frontend-mikrotjenestearkitektur.

Communication Patterns:

1. Direct Communication:

I dette mønsteret kommuniserer mikro-frontender direkte med hverandre ved hjelp av HTTP-forespørsler eller andre protokoller. Dette er det enkleste kommunikasjonsmønsteret, men det kan føre til tett kobling og økt kompleksitet. Det kan også føre til ytelsesproblemer hvis mikro-frontender er plassert i forskjellige nettverk eller regioner.

Example:

One micro frontend (e.g., a product listing micro frontend) needs to display the current user's shopping cart count, which is managed by another micro frontend (the shopping cart micro frontend). The product listing micro frontend can directly make an HTTP request to the shopping cart micro frontend to retrieve the cart count.

            // In the product listing micro frontend:

async function getCartCount() {
  const response = await fetch('https://shopping-cart.example.com/cart/count');
  const data = await response.json();
  return data.count;
}

// ... display the cart count in the product listing

            

              
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Pros:

• Simple to implement.

Cons:

• Tight coupling between micro frontends.
• Increased complexity.
• Potential performance issues.
• Difficult to manage dependencies.

2. Events (Publish/Subscribe):

I dette mønsteret kommuniserer mikro-frontender med hverandre ved å publisere og abonnere på hendelser. Når en mikro-frontend publiserer en hendelse, mottar alle andre mikro-frontender som abonnerer på den hendelsen et varsel. Dette mønsteret fremmer løs kobling og lar mikro-frontender reagere på endringer i andre deler av applikasjonen uten å kjenne detaljene i disse endringene.

Example:

When a user adds an item to the shopping cart (managed by the shopping cart micro frontend), it publishes an event called "cartItemAdded". The product listing micro frontend, which is subscribed to this event, updates the displayed cart count without directly calling the shopping cart micro frontend.

            // Shopping Cart Micro Frontend (Publisher):

function addItemToCart(item) {
  // ... add item to cart
  publishEvent('cartItemAdded', { itemId: item.id });
}

function publishEvent(eventName, data) {
  // ... publish the event using a message broker or custom event bus
}

// Product Listing Micro Frontend (Subscriber):

subscribeToEvent('cartItemAdded', (data) => {
  // ... update the displayed cart count based on the event data
});

function subscribeToEvent(eventName, callback) {
  // ... subscribe to the event using a message broker or custom event bus
}
            

              
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Pros:

• Loose coupling between micro frontends.
• Increased flexibility.
• Improved scalability.

Cons:

• Requires implementing a message broker or event bus.
• Can be difficult to debug.
• Eventual consistency can be a challenge.

3. Shared State:

I dette mønsteret deler mikro-frontender en felles tilstand som er lagret på et sentralt sted, for eksempel en nettleserkake, lokal lagring eller en delt database. Mikro-frontender kan få tilgang til og endre den delte tilstanden, slik at de kan kommunisere med hverandre indirekte. Dette mønsteret er nyttig for å dele små mengder data, men det kan føre til ytelsesproblemer og datainkonsistenser hvis det ikke administreres riktig. Vurder å bruke et tilstandsadministrasjonsbibliotek som Redux eller Vuex for å administrere delt tilstand.

Example:

Micro frontends might share the user's authentication token stored in a cookie. Each micro frontend can access the cookie to verify the user's identity without needing to directly communicate with an authentication service.

            // Setting the authentication token (e.g., in the authentication micro frontend)

document.cookie = "authToken=your_auth_token; path=/";

// Accessing the authentication token (e.g., in other micro frontends)

function getAuthToken() {
  const cookies = document.cookie.split(';');
  for (let i = 0; i < cookies.length; i++) {
    const cookie = cookies[i].trim();
    if (cookie.startsWith('authToken=')) {
      return cookie.substring('authToken='.length);
    }
  }
  return null;
}

const authToken = getAuthToken();
if (authToken) {
  // ... use the auth token to authenticate the user
}
            

              
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Pros:

• Simple to implement for small amounts of data.

Cons:

• Can lead to performance issues.
• Data inconsistencies can occur.
• Difficult to manage state changes.
• Security risks if not handled carefully (e.g., storing sensitive data in cookies).

4. Window Events (Custom Events):

Micro frontends can communicate using custom events dispatched on the `window` object. This allows micro frontends to interact even if they are loaded in different iframes or web components. It's a browser-native approach, but requires careful management of event names and data formats to avoid conflicts and maintain consistency.

Example:

            // Micro Frontend A (Publisher)

const event = new CustomEvent('custom-event', { detail: { message: 'Hello from Micro Frontend A' } });
window.dispatchEvent(event);

// Micro Frontend B (Subscriber)

window.addEventListener('custom-event', (event) => {
  console.log('Received event:', event.detail.message);
});
            

              
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Pros:

• Native browser support.
• Relatively simple to implement for basic communication.

Cons:

• Global namespace can lead to conflicts.
• Difficult to manage complex event structures.
• Limited scalability for large applications.
• Requires careful coordination between teams to avoid naming collisions.

5. Module Federation (Webpack 5):

Module federation allows a JavaScript application to dynamically load code from another application at runtime. It enables sharing code and dependencies between different micro frontends without needing to publish and consume npm packages. This is a powerful approach for building composable and extensible frontends, but it requires careful planning and configuration.

Example:

Micro Frontend A (Host) loads a component from Micro Frontend B (Remote).

            // Micro Frontend A (webpack.config.js)

const ModuleFederationPlugin = require('webpack/lib/container/ModuleFederationPlugin');

module.exports = {
  // ... other webpack configurations
  plugins: [
    new ModuleFederationPlugin({
      name: 'MicroFrontendA',
      remotes: {
        'MicroFrontendB': 'MicroFrontendB@http://localhost:3001/remoteEntry.js',
      },
      shared: ['react', 'react-dom'], // Share dependencies to avoid duplicates
    }),
  ],
};

// Micro Frontend A (Component)

import React from 'react';
import RemoteComponent from 'MicroFrontendB/Component';

const App = () => {
  return (
    

      
Micro Frontend A
      
    
  );
};

export default App;

// Micro Frontend B (webpack.config.js)

const ModuleFederationPlugin = require('webpack/lib/container/ModuleFederationPlugin');

module.exports = {
  // ... other webpack configurations
  plugins: [
    new ModuleFederationPlugin({
      name: 'MicroFrontendB',
      exposes: {
        './Component': './src/Component',
      },
      shared: ['react', 'react-dom'],
    }),
  ],
};

// Micro Frontend B (src/Component.js)

import React from 'react';

const Component = () => {
  return 
Hello from Micro Frontend B!
;
};

export default Component;
            

              
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Pros:

• Code sharing and reuse without npm packages.
• Dynamic loading of components at runtime.
• Improved build times and deployment efficiency.

Cons:

• Requires Webpack 5 or later.
• Can be complex to configure.
• Version compatibility issues with shared dependencies can arise.

6. Web Components:

Web Components are a set of web standards that allow you to create reusable custom HTML elements with encapsulated styling and behavior. They provide a platform-agnostic way to build micro frontends that can be integrated into any web application, regardless of the underlying framework. While offering excellent encapsulation, they may require additional tooling or frameworks to handle complex state management or data binding scenarios.

Example:

            // Micro Frontend A (Web Component)

class MyCustomElement extends HTMLElement {
  constructor() {
    super();
    this.attachShadow({ mode: 'open' }); // Encapsulated shadow DOM
    this.shadowRoot.innerHTML = `
      
      
Hello from Web Component!
    `;
  }
}

customElements.define('my-custom-element', MyCustomElement);

// Using the Web Component in any HTML page


            

              
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Pros:

• Framework-agnostic and reusable across different applications.
• Encapsulated styling and behavior.
• Standardized web technology.

Cons:

• Can be verbose to write without a helper library.
• May require polyfills for older browsers.
• State management and data binding can be more complex compared to framework-based solutions.

Choosing the Right Strategy

Den beste tjenesteoppdagelses- og kommunikasjonsstrategien for din frontend-mikrotjenestearkitektur avhenger av flere faktorer, inkludert:

• The size and complexity of your application. For smaller applications, a simple approach like static configuration or direct communication may be sufficient. For larger, more complex applications, a more robust approach like a service registry or event-driven architecture is recommended.
• The level of autonomy required by your teams. If teams need to be highly autonomous, a loosely coupled communication pattern like events is preferred. If teams can coordinate more closely, a more tightly coupled pattern like direct communication may be acceptable.
• The performance requirements of your application. Some communication patterns, like direct communication, can be more performant than others, like events. However, the performance benefits of direct communication may be offset by the increased complexity and tight coupling.
• Your existing infrastructure. If you already have a service registry or message broker in place, it makes sense to leverage that infrastructure for your frontend microservices.

Best Practices

Her er noen anbefalte fremgangsmåter du bør følge når du implementerer tjenesteoppdagelse og kommunikasjon i din frontend-mikrotjenestearkitektur:

• Keep it simple. Start with the simplest approach that meets your needs and gradually increase complexity as required.
• Favor loose coupling. Loose coupling makes your application more flexible, resilient, and easier to maintain.
• Use a consistent communication pattern. Using a consistent communication pattern across your micro frontends makes your application easier to understand and debug.
• Monitor your services. Monitor the health and performance of your micro frontends to ensure that they are functioning correctly.
• Implement robust error handling. Handle errors gracefully and provide informative error messages to users.
• Document your architecture. Document the service discovery and communication patterns used in your application to help other developers understand and maintain it.

Conclusion

Frontend-mikrotjenester tilbyr betydelige fordeler når det gjelder skalerbarhet, vedlikeholdbarhet og teamautonomi. Imidlertid krever implementering av en vellykket mikro-frontend-arkitektur nøye vurdering av tjenesteoppdagelses- og kommunikasjonsstrategier. Ved å velge de riktige tilnærmingene og følge anbefalte fremgangsmåter, kan du bygge en robust og fleksibel frontend som oppfyller behovene til brukerne dine og utviklingsteamene dine.

The key to successful implementation of micro frontends lies in understanding the trade-offs between different service discovery and communication patterns. While static configuration offers simplicity, it lacks the dynamism of a service registry. Direct communication may seem straightforward but can lead to tight coupling, whereas event-driven architectures promote loose coupling but introduce complexity in terms of message brokering and eventual consistency. Module federation offers a powerful way to share code but requires a modern build toolchain. Similarly, web components provide a standardized approach, however they may need to be complemented by frameworks when managing state and data binding.

Ultimately, the optimal choice depends on the specific requirements of the project, the team's expertise, and the overall architectural goals. A well-planned strategy, combined with adherence to best practices, can result in a robust and scalable micro frontend architecture that delivers a superior user experience.