Traffic management (routing, splitting) in Microservices - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is traffic routing in microservices?

Traffic routing is the process of directing incoming requests to specific microservice instances or versions based on rules like URL path, headers, or user location.

beginner

Explain traffic splitting in microservices.

Traffic splitting divides incoming requests between different versions or instances of a microservice, often used for gradual rollouts or A/B testing.

intermediate

Why use traffic splitting during deployments?

It helps test new versions with a small user group, reduces risk of failures, and allows quick rollback if issues arise.

intermediate

Name two common tools or technologies used for traffic management in microservices.

Service meshes like Istio and API gateways like Kong or NGINX are popular tools for routing and splitting traffic.

intermediate

What is a canary deployment in the context of traffic management?

A canary deployment sends a small percentage of traffic to a new version to monitor its behavior before full rollout.

What does traffic routing primarily depend on in microservices?

A Request attributes like URL or headers

B Database schema

C CPU usage of microservices

D User's screen resolution

Traffic routing uses request attributes such as URL paths or headers to decide where to send requests.

Which scenario best describes traffic splitting?

A Sending all traffic to one microservice version

B Dividing traffic between multiple microservice versions

C Blocking traffic from unknown users

D Encrypting traffic between services

Traffic splitting divides requests among different versions or instances.

What is the main benefit of canary deployments?

A Gradual testing of new versions with limited users

B Faster database queries

C Improved UI design

D Reducing server costs

Canary deployments allow testing new versions with a small user group before full rollout.

Which tool is commonly used for traffic management in microservices?

A Docker Compose

B MySQL

C React

D Istio

Istio is a service mesh that helps manage traffic routing and splitting.

Traffic routing rules can be based on which of the following?

A Operating system version

B Microservice memory size

C User location

D Time of day only

Routing can consider user location among other request attributes.

Describe how traffic routing and traffic splitting differ and how they work together in microservices.

Think about directing requests versus dividing requests.

Explain the benefits and risks of using traffic splitting during a microservice deployment.

Consider why splitting traffic helps and what could go wrong.

Practice

1. What is the main purpose of traffic routing in microservices architecture?

easy

A. To direct incoming requests to specific services based on rules

B. To store data persistently across services

C. To encrypt communication between services

D. To monitor service health and uptime

Solution

1. Step 1: Understand traffic routing

   Traffic routing means sending requests to the right service based on rules like URL path or user type.

2. Step 2: Identify the main purpose

   Routing helps control where requests go, ensuring they reach the correct microservice.

3. Final Answer:

   To direct incoming requests to specific services based on rules -> Option A

4. Quick Check:

   Routing = directing requests [OK]

Hint: Routing means sending requests to the right place [OK]

Common Mistakes:

• Confusing routing with data storage
• Thinking routing encrypts data
• Mixing routing with monitoring

2. Which of the following is a correct way to define a traffic splitting rule in a service mesh configuration?

easy

A. split:
- weight: 50
service: v1
- weight: 50
service: v2

B. route:
path: /api
service: v1

C. split:
- service: v1
- service: v2
- weight: 100

D. route:
weight: 100
service: v1
path: /home

Solution

1. Step 1: Understand traffic splitting syntax

   Traffic splitting uses weights to divide requests between service versions, e.g., 50% to v1 and 50% to v2.

2. Step 2: Identify correct syntax

   split: - weight: 50 service: v1 - weight: 50 service: v2 correctly assigns weights to services for splitting. Other options mix routing and splitting or have invalid weight placement.

3. Final Answer:

   split: - weight: 50 service: v1 - weight: 50 service: v2 -> Option A

4. Quick Check:

   Splitting uses weights per service [OK]

Hint: Splitting needs weights assigned to each service [OK]

Common Mistakes:

• Confusing routing rules with splitting rules
• Missing weights in splitting definitions
• Placing weights outside service entries

3. Given this traffic splitting configuration, what percentage of requests go to service v2?

split:
  - weight: 70
    service: v1
  - weight: 30
    service: v2

medium

A. 100%

B. 70%

C. 50%

D. 30%

Solution

1. Step 1: Read the weights for each service

   Service v1 has weight 70, and service v2 has weight 30.

2. Step 2: Calculate percentage for v2

   Total weight = 70 + 30 = 100. So, v2 gets 30/100 = 30% of requests.

3. Final Answer:

   30% -> Option D

4. Quick Check:

   Weight 30 means 30% traffic [OK]

Hint: Traffic % = service weight / total weight [OK]

Common Mistakes:

• Adding weights incorrectly
• Assuming equal split without weights
• Confusing service names

4. You have this routing rule:

route:
  path: /user
  service: user-service-v1
  weight: 100

But requests to /user/profile are not reaching user-service-v1. What is the likely problem?

medium

A. Service name is incorrect and causes failure

B. Weight should be split between multiple services

C. The path rule matches only exact /user, not subpaths like /user/profile

D. Routing rules cannot use path matching

Solution

1. Step 1: Analyze the path matching rule

   The rule matches exactly /user, but /user/profile is a subpath and may not match unless wildcard or prefix matching is used.

2. Step 2: Identify why requests fail

   Since /user/profile does not match exactly /user, requests do not route to user-service-v1.

3. Final Answer:

   The path rule matches only exact /user, not subpaths like /user/profile -> Option C

4. Quick Check:

   Exact path matching excludes subpaths [OK]

Hint: Exact path matches exclude subpaths unless wildcard used [OK]

Common Mistakes:

• Assuming weight must be split
• Blaming service name without checking
• Thinking routing ignores paths

5. You want to gradually roll out a new version of a payment service to 10% of users while keeping 90% on the old version. Which traffic management strategy is best suited for this?

hard

A. Use routing based on URL path to send 10% of requests to new service

B. Use traffic splitting with weights 90% to old and 10% to new service

C. Deploy both versions without traffic control and monitor errors

D. Use a load balancer that randomly sends requests without weights

Solution

1. Step 1: Understand gradual rollout needs

   Gradual rollout means controlling what percentage of users see the new version.

2. Step 2: Choose traffic management method

   Traffic splitting with weights allows precise control of request percentages to each version.

3. Step 3: Evaluate other options

   Routing by URL path cannot split traffic by percentage. Random load balancing lacks control. Deploying without control risks all users seeing new version.

4. Final Answer:

   Use traffic splitting with weights 90% to old and 10% to new service -> Option B

5. Quick Check:

   Splitting controls rollout percentages [OK]

Hint: Use weighted splitting for gradual rollout [OK]

Common Mistakes:

• Using URL path routing for percentage split
• Ignoring traffic control during rollout
• Relying on random load balancing