Why Traffic management (routing, splitting) in Microservices? - Purpose & Use Cases

The Big Idea

What if you could control millions of user requests smoothly without lifting a finger?

The Scenario

Imagine you run a busy restaurant where customers come in and you have to decide which chef cooks their meal. Without a system, you shout orders randomly, hoping the right chef gets the right dish. Sometimes orders pile up, some chefs get overwhelmed, and others stand idle.

The Problem

Manually directing traffic in a microservices setup is like shouting orders in a noisy kitchen. It's slow, mistakes happen often, and you can't easily balance the load. This leads to delays, unhappy users, and wasted resources.

The Solution

Traffic management with routing and splitting acts like a smart kitchen manager. It automatically directs requests to the right service or splits traffic between versions smoothly. This keeps everything balanced, efficient, and easy to control.

Before vs After

✗ Before

if (userRequest.type == 'A') {
  serviceA.handle(userRequest);
} else {
  serviceB.handle(userRequest);
}

✓ After

router.route(userRequest).to('serviceA', 0.7).to('serviceB', 0.3)

What It Enables

It enables seamless updates, load balancing, and fault isolation without downtime or manual chaos.

Real Life Example

When a new app version is released, traffic splitting lets 10% of users try it first while 90% stay on the stable version, catching issues early without affecting everyone.

Key Takeaways

Manual routing is slow and error-prone in complex systems.

Traffic management automates directing and splitting requests efficiently.

This leads to better performance, safer updates, and happier users.

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