--- type: docs title: "Quickstart: Resiliency" linkTitle: "Resiliency" weight: 72 description: "Get started with Dapr's resiliency capabilities" --- Diagram showing the resiliency applied to Dapr APIs {{% alert title="Note" color="primary" %}} Resiliency is currently a preview feature. {{% /alert %}} In this Quickstart, you will observe Dapr resiliency capabilities by simulating a system failure. You will execute 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. The resiliency policies used in this example are defined and applied via the [resiliency spec]() located in the components directory. ### Pre-requisites For this example, you will need: - [Dapr CLI and initialized environment](https://docs.dapr.io/getting-started). - [Latest Node.js installed](https://nodejs.org/download/). - [Docker Desktop](https://www.docker.com/products/docker-desktop) ### Step 1: Set up the environment Clone the [sample provided in the Quickstarts repo](https://github.com/dapr/quickstarts/tree/master/resiliency). ```bash git clone https://github.com/dapr/quickstarts.git ``` In a terminal window, navigate to the `order-processor` directory. ```bash cd quickstart/resiliency/javascript/order-processor ``` Install dependencies ```bash npm install ``` ### Step 2: Run the application with resiliency enabled Run the `order-processor` service alongside a Dapr sidecar. The `--config` parameter applies a Dapr configuration that enables the resiliency feature. The resilency spec is located in the components directory and is automatically discovered by the Dapr sidecar when run in standalone mode. ```bash dapr run --app-id order-processor --config ../config.yaml --components-path ../components/ -- npm start ``` Once the application has started, the `order-processor`service writes and reads `orderId` key/value pairs to the `statestore` redis instance [defined in the `statestore.yaml` component]({{< ref "#statestoreyaml-component-file" >}}). ```bash == 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' } ``` While the application is running continue to the next section. ### Step 3: Introduce a fault For example purposes, you will simulate a fault by stopping the Redis container that was initalized when executing `dapr init` on your development machine. The Redis instance is configured as the state store component for the order-processor microservice. Once the redis instance is stopped, write and read operations from the order-processor service will begin to fail. Since the `statestore` component is definied as a target in the resiliency spec applied to the order-processor service, all failed requests will apply retry and circuit breaker policies: ```yaml targets: components: statestore: outbound: retry: retryForever circuitBreaker: simpleCB ``` ```bash docker stop dapr_redis ``` Once the first request fails, the retry policy titled `retryForever` is applied: ```bash INFO[0006] Error processing operation component[statestore] output. Retrying... ``` ```yaml retryForever: policy: constant maxInterval: 5s maxRetries: -1 ``` Retries will continue for each failed request indefinitely, while waiting 5 seconds in between trying again. Once 5 consecutive retries have failed, the circuit breaker policy `simpleCB` is tripped and the breaker opens haulting all requests: ```bash INFO[0026] Circuit breaker "simpleCB-statestore" changed state from closed to open ``` ```yaml circuitBreakers: simpleCB: maxRequests: 1 timeout: 5s trip: consecutiveFailures >= 5 ``` After 5 seconds has surpassed, the circuit breaker will switch to a half-open state allowing one request through to verify if the fault has been resolved. If the request continues to fail, the circuit will trip back to the open state. This behavior will continue for as long as the Redis container is stopped. ```bash 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 INFO[0036] Circuit breaker "simpleCB-statestore" changed state from open to half-open INFO[0036] Circuit breaker "simpleCB-statestore" changed state from half-open to closed ``` ### Step 3: Remove the fault Restart the redis container on your machine and the application will recover seamlessly, picking up where it left off with writing and reading orders to the Redis state store component. ```bash docker start dapr_redis ``` ```bash 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' } ``` ## Tell us what you think! We're continuously working to improve our Quickstart examples and value your feedback. Did you find this quickstart helpful? Do you have suggestions for improvement? Join the discussion in our [discord channel](https://discord.com/channels/778680217417809931/953427615916638238). ## Next steps Visit [this](https://docs.dapr.io/operations/resiliency/resiliency-overview//) link for more information about Dapr resiliency. {{< button text="Explore Dapr tutorials >>" page="getting-started/tutorials/_index.md" >}}