Service discovery concept in Microservices - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to register a service instance with the discovery server.

Microservices

discovery_client.register_service('[1]', '10.0.0.1', 8080)

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

Aservice_id

Bservice_name

Cservice_port

Dservice_address

Attempts:

3 left

💡 Hint

Common Mistakes

Using IP address or port as the service identifier.

Confusing service ID with service name.

The first argument should be the service name to identify the service in the discovery system.

2fill in blank

medium

Complete the code to discover the address of a service instance.

Microservices

address = discovery_client.get_service_address('[1]')

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

Ainstance_id

Bservice_port

Cservice_name

Dnode_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using instance ID instead of service name.

Using port number or node ID which are not keys for discovery.

You need to provide the service name to get the address of one of its instances.

3fill in blank

hard

Fix the error in the service registration code to include health check.

Microservices

discovery_client.register_service('payment-service', '10.0.0.5', 9090, health_check='[1]')

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

Ahttp://10.0.0.5:9090/health

B10.0.0.5:9090

C/health

Dhealth

Attempts:

3 left

💡 Hint

Common Mistakes

Providing only a path or IP without protocol.

Using a keyword instead of a URL.

The health check URL must be a full HTTP URL so the discovery server can call it to check service health.

4fill in blank

hard

Fill both blanks to create a dictionary of service instances filtered by status.

Microservices

healthy_services = {id: info for id, info in services.items() if info['[1]'] == '[2]'}

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

Astatus

Bhealthy

Caddress

Dactive

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'address' as a key for filtering.

Using 'active' instead of 'healthy' as status value.

We filter services where the status key equals healthy to get only healthy instances.

5fill in blank

hard

Fill all three blanks to implement a simple client-side load balancer picking a random healthy instance.

Microservices

import random

instances = discovery_client.get_service_instances('[1]')
healthy = [i for i in instances if i['[2]'] == '[3]']
selected = random.choice(healthy)

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

Aorder-service

Bstatus

Chealthy

Daddress

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong service name.

Filtering by wrong key or value.

Not filtering before choosing randomly.

We get instances of 'order-service', filter by 'status' equal to 'healthy', then pick one randomly.

Practice

1. What is the main purpose of service discovery in a microservices architecture?

easy

A. To help services find and communicate with each other automatically

B. To store user data securely

C. To manage database transactions

D. To handle user authentication

Solution

1. Step 1: Understand the role of service discovery

   Service discovery allows microservices to locate each other dynamically without hardcoding addresses.

2. Step 2: Identify the correct purpose

   It is not about data storage, transactions, or authentication but about service communication.

3. Final Answer:

   To help services find and communicate with each other automatically -> Option A

4. Quick Check:

   Service discovery = automatic service location [OK]

Hint: Service discovery = finding services automatically [OK]

Common Mistakes:

• Confusing service discovery with data storage
• Thinking it manages user authentication
• Assuming it handles database transactions

2. Which of the following is a common component used in service discovery for microservices?

easy

A. Load balancer

B. Service registry

C. API gateway

D. Database shard

Solution

1. Step 1: Identify components related to service discovery

   A service registry keeps track of available service instances and their locations.

2. Step 2: Differentiate from other components

   Load balancers distribute traffic, API gateways manage requests, and database shards split data, but none perform service discovery.

3. Final Answer:

   Service registry -> Option B

4. Quick Check:

   Service registry = key for service discovery [OK]

Hint: Service registry stores service locations [OK]

Common Mistakes:

• Confusing load balancer with service registry
• Mixing API gateway with service discovery
• Thinking database shards help find services

3. Consider this simplified service discovery flow:

1. Service A queries the registry for Service B's address.
2. Registry returns Service B's current IP and port.
3. Service A connects to Service B using the returned address.
4. Service B processes the request and responds.

What happens if Service B changes its IP but the registry is not updated?

medium

A. Service B will notify Service A directly

B. Service A will automatically find the new IP

C. The registry will redirect Service A to the new IP

D. Service A will connect to the old IP and fail

Solution

1. Step 1: Analyze the flow when registry is outdated

   If the registry has an old IP, Service A uses that wrong address to connect.

2. Step 2: Understand consequences of stale registry data

   Service A cannot find Service B at the old IP, so connection fails; no automatic update or redirection occurs.

3. Final Answer:

   Service A will connect to the old IP and fail -> Option D

4. Quick Check:

   Stale registry = failed connection [OK]

Hint: Outdated registry causes failed connections [OK]

Common Mistakes:

• Assuming automatic IP update without registry refresh
• Thinking services notify each other directly
• Believing registry redirects requests automatically

4. A developer notices that service discovery is failing because services cannot find each other. The registry is running, but services do not register themselves. What is the most likely cause?

medium

A. The registry database is full

B. Network latency is too high

C. Services are not sending heartbeat or registration requests to the registry

D. Services are using incorrect API versions

Solution

1. Step 1: Identify why services are missing in registry

   Services must actively register or send heartbeats to the registry to be discoverable.

2. Step 2: Eliminate other causes

   Full database or network latency might cause delays but not complete absence; API version mismatch affects communication, not registration.

3. Final Answer:

   Services are not sending heartbeat or registration requests to the registry -> Option C

4. Quick Check:

   Missing registration = discovery failure [OK]

Hint: Services must register to be discoverable [OK]

Common Mistakes:

• Blaming network latency for missing registrations
• Assuming registry storage limits cause missing services
• Confusing API version issues with registration problems

5. In a large microservices system with many instances starting and stopping frequently, which service discovery approach best supports scalability and fault tolerance?

hard

A. Using a centralized service registry with periodic health checks and automatic deregistration

B. Hardcoding service IPs in each microservice configuration

C. Using DNS-based service discovery without health checks

D. Relying on client-side caching of service addresses without updates

Solution

1. Step 1: Evaluate scalability and fault tolerance needs

   Frequent changes require dynamic updates and health checks to avoid stale info and failures.

2. Step 2: Compare approaches

   Centralized registry with health checks keeps accurate service info; hardcoding or caching causes stale data; DNS without health checks misses failures.

3. Final Answer:

   Using a centralized service registry with periodic health checks and automatic deregistration -> Option A

4. Quick Check:

   Dynamic registry + health checks = scalable, fault tolerant [OK]

Hint: Dynamic registry with health checks scales best [OK]

Common Mistakes:

• Hardcoding IPs causing poor scalability
• Ignoring health checks leading to stale data
• Relying on caching without updates