Ambassador pattern in Microservices - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define an ambassador service that proxies requests to the main service.

Microservices

class AmbassadorService {
    constructor(targetService) {
        this.targetService = targetService;
    }

    handleRequest(request) {
        return this.targetService.[1](request);
    }
}

Drag options to blanks, or click blank then click option'

AproxyRequest

BsendRequest

CprocessRequest

DhandleRequest

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name that does not exist on the target service.

Confusing the ambassador's own method with the target service's method.

The ambassador service forwards the request by calling handleRequest on the target service.

2fill in blank

medium

Complete the code to add logging in the ambassador before forwarding the request.

Microservices

class AmbassadorService {
    handleRequest(request) {
        console.log('Forwarding request:', [1]);
        return this.targetService.handleRequest(request);
    }
}

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Athis

Brequest

CtargetService

Drequest.data

Attempts:

3 left

💡 Hint

Common Mistakes

Logging this instead of the request.

Logging a property that may not exist like request.data.

Logging the entire request object helps track what is being forwarded.

3fill in blank

hard

Fix the error in the ambassador's retry logic to handle failed requests.

Microservices

async handleRequest(request) {
    let attempts = 0;
    while (attempts < [1]) {
        try {
            return await this.targetService.handleRequest(request);
        } catch (error) {
            attempts++;
        }
    }
    throw new Error('Max retries reached');
}

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AmaxRetries

B'3'

C3

DretryCount

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a number for the retry limit.

Using variables that are not defined in the scope.

The retry limit should be a number literal like 3 to control the loop correctly.

4fill in blank

hard

Fill both blanks to implement a timeout mechanism in the ambassador pattern.

Microservices

async handleRequest(request) {
    const controller = new AbortController();
    const timeoutId = setTimeout(() => controller.[1](), [2]);
    try {
        return await this.targetService.handleRequest({ ...request, signal: controller.signal });
    } finally {
        clearTimeout(timeoutId);
    }
}

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Aabort

Bcancel

C5000

D10000

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-existent method like cancel().

Setting an unreasonably long timeout like 10000 without explanation.

The AbortController uses the abort() method to cancel requests after a timeout of 5000 milliseconds.

5fill in blank

hard

Fill all three blanks to create a caching layer in the ambassador to reduce load on the main service.

Microservices

class AmbassadorService {
    constructor(targetService) {
        this.targetService = targetService;
        this.cache = new Map();
    }

    async handleRequest(request) {
        const key = JSON.stringify([1]);
        if (this.cache.has(key)) {
            return this.cache.get(key);
        }
        const response = await this.targetService.handleRequest([2]);
        this.cache.set(key, [3]);
        return response;
    }
}

Drag options to blanks, or click blank then click option'

Arequest

Cresponse

Drequest.data

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent variables for the cache key and request forwarding.

Caching the request instead of the response.

The cache key is created from the request. The request is forwarded as is, and the response is cached for future use.