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service-to-component-resiliency.md

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Dapr Resiliency: State Managment

In this QuickStart, you will run a microservice application that continuously persists and retrieves state via Dapr's state management API. When operations to the state store begin to fail, Dapr resiliency policies are applied.

Visit the documentation about Dapr resiliency link for more information

This quickstart includes one service:

  • Client service order-processor
  • Redis component spec statestore.yaml
  • Resiliency spec resiliency.yaml

Run the client service with Dapr and resiliency enabled

  1. Navigate to the app directory, install dependencies, and run the service with resiliency:

C# example:

cd ../state_management/csharp/sdk/order-processor
dotnet restore
dotnet build
dapr run --app-id order-processor --resources-path ../../../resources/ -- dotnet run

Go example:

cd ../state_management/go/sdk/order-processor
go build .
dapr run --app-id order-processor --resources-path ../../../resources -- go run .

Java example:

cd ../state_management/java/sdk/order-processor
mvn clean install
dapr run --app-id order-processor --resources-path ../../../resources/ -- java -jar target/OrderProcessingService-0.0.1-SNAPSHOT.jar

JavaScript example:

cd ../state_management/javascript/sdk/order-processor
npm install
dapr run --app-id order-processor  --resources-path ../../../resources/ -- npm start

Python example:

cd ../state_management/python/sdk/order-processor
pip3 install -r requirements.txt
dapr run --app-id order-processor  --resources-path ../../../resources/ -- python3

Expected output:

== APP == Saving Order:  { orderId: '1' }
== APP == Getting Order:  { orderId: '1' }
== APP == Saving Order:  { orderId: '2' }
== APP == Getting Order:  { orderId: '2' }
== APP == Saving Order:  { orderId: '3' }
== APP == Getting Order:  { orderId: '3' }
== APP == Saving Order:  { orderId: '4' }
== APP == Getting Order:  { orderId: '4' }

Simulate a component failure by stopping the Redis container instance

In a new terminal window, stop the Redis container that's running on your machine:

docker stop dapr_redis

Observe retry and circuit breaker policies are applied:

Policies defined in the resiliency.yaml spec:

retryForever:
  policy: constant
  duration: 5s
  maxRetries: -1

circuitBreakers:
  simpleCB:
  maxRequests: 1
  timeout: 5s
  trip: consecutiveFailures >= 5

Applied policies:

INFO[0006] Error processing operation component[statestore] output. Retrying...
INFO[0026] Circuit breaker "simpleCB-statestore" changed state from closed to open
INFO[0031] Circuit breaker "simpleCB-statestore" changed state from open to half-open
INFO[0031] Circuit breaker "simpleCB-statestore" changed state from half-open to open

Simulate the component recovering by restarting the Redis container instance:

docker start dapr_redis

Observe orders have resumed sequentially

INFO[0036] Recovered processing operation component[statestore] output.
== APP == Saving Order:  { orderId: '5' }
== APP == Getting Order:  { orderId: '5' }
== APP == Saving Order:  { orderId: '6' }
== APP == Getting Order:  { orderId: '6' }
== APP == Saving Order:  { orderId: '7' }
== APP == Getting Order:  { orderId: '7' }
== APP == Saving Order:  { orderId: '8' }
== APP == Getting Order:  { orderId: '8' }
== APP == Saving Order:  { orderId: '9' }
== APP == Getting Order:  { orderId: '9' }

Stop the app with Dapr

dapr stop --app-id order-processor