Microservicessystem_design~12 mins

Liveness and readiness probes in Microservices - Architecture Diagram

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System Overview - Liveness and readiness probes

This system uses liveness and readiness probes to monitor microservices health. Liveness probes check if a service is alive and should be restarted if not. Readiness probes check if a service is ready to accept traffic, ensuring smooth user experience.

Architecture Diagram

User
  |
  v
Load Balancer
  |
  v
API Gateway
  |
  v
+------------------+      +------------------+
| Microservice A    |<---->| Liveness Probe   |
| (with Readiness)  |      +------------------+
+------------------+
        |
        v
+------------------+
| Database         |
+------------------+

Components

User

client

Sends requests to the system

Load Balancer

load_balancer

Distributes incoming requests to API Gateway instances

API Gateway

api_gateway

Routes requests to microservices and performs health checks

Microservice A

service

Handles business logic; has liveness and readiness probes

Liveness Probe

health_check

Checks if Microservice A is alive; triggers restart if failed

Readiness Probe

health_check

Checks if Microservice A is ready to serve traffic

Database

database

Stores persistent data used by Microservice A

Request Flow - 9 Hops

User → Load Balancer

Load Balancer → API Gateway

API Gateway → Readiness Probe

API Gateway → Microservice A

Microservice A → Database

Microservice A → API Gateway

API Gateway → Load Balancer

Load Balancer → User

Liveness Probe → Microservice A

Failure Scenario

Component Fails:Microservice A

Impact:If Microservice A crashes, liveness probe detects failure and triggers restart. Readiness probe marks service as not ready, so no traffic is sent to it.

Mitigation:Orchestrator restarts Microservice A automatically. Load balancer and API Gateway stop sending traffic until readiness probe reports ready.

Architecture Quiz - 3 Questions

Test your understanding

Which probe ensures the service is ready to accept user traffic?

ALiveness probe

BReadiness probe

CLoad balancer health check

DDatabase connectivity check

Design Principle

Using liveness and readiness probes separates concerns of service health and traffic readiness. This improves system reliability by restarting unhealthy services and preventing traffic to services not ready to serve, ensuring smooth user experience.