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Thang Chung
Thang Chung

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WebAssembly, Docker container, Dapr, and Kubernetes better together - Part 3: Daprize the coffee backend services

#webassembly #kubernetes #docker #dapr

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Source code of this series can be found at https://github.com/thangchung/dapr-labs/tree/main/polyglot.

In this post, we will explore Dapr capabilities such as service invocation, pubsub, and state management. And we will use Dapr API for communicating as well as storing the data between polyglot applications (Rust - WASM/WASI with Spin and .NET with container approaches).

Overall Dapr components usage

Image description

1. Service invocation

We leverage Dapr .NET SDK to invoke product-api from counter-api.

// ref: https://github.com/thangchung/dapr-labs/blob/main/polyglot/counter-api/Infrastructure/ItemDaprGateway.cs#L14

var productAppName = config.GetValue("ProductCatalogAppDaprName", "product-api-dapr-http");
        logger.LogInformation("ProductCatalogAppDaprName: {0}", productAppName);

var httpResponseMessage = await daprClient.InvokeMethodAsync<List<ItemDto>>(
    HttpMethod.Get,
    productAppName,
    "v1-get-item-types");
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2. State management

As mentioned in previous part, we use Dapr state management for storing the state of counter-api (use Dapr .NET SDK), barista-api (use Dapr State Management API), and kitchen-api (use Dapr State Management API).

The sample code for storing data in counter-api is as follows:

// ref: https://github.com/thangchung/dapr-labs/blob/main/polyglot/counter-api/Activities/AddOrderActivity.cs#L44

await daprClient.SaveStateAsync("statestore", "order-list", new List<Guid> { order.Id });
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Or,

// ref: https://github.com/thangchung/dapr-labs/blob/main/polyglot/counter-api/UseCases/OrderFulfillmentQuery.cs#L46

var mulitpleStateResult = await daprClient.GetBulkStateAsync("statestore", orderGuidProcceed, parallelism: 1, cancellationToken: cancellationToken);
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Dapr component:

# ref: statestore.yaml

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: statestore
spec:
  type: state.redis
  version: v1
  metadata:
    - name: redisHost
      value: localhost:6379
    - name: redisPassword
      value: ""
    - name: actorStateStore
      value: "true"
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3. Pub/sub

Pub/sub is a popular pattern for Event-driven Architecture (EDA). In this application, we use both Dapr .NET SDK and Dapr pub/sub API.

Publish a message, see below

// ref: https://github.com/thangchung/dapr-labs/blob/main/polyglot/counter-api/Activities/AddOrderActivity.cs#L109

await daprClient.PublishEventAsync(
    "baristapubsub",
    nameof(BaristaOrderPlaced).ToLowerInvariant(),
    @event.Value);
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Or, in barista-api:

// ref: https://github.com/thangchung/dapr-labs/blob/main/polyglot/barista-api/src/lib.rs#L119

fn pub_order_updated(dapr_url: &str, pubsub_name: &str, topic: &str, e: BaristaOrderUpdated) {
    let url = format!("{}/v1.0/publish/{}/{}", dapr_url, pubsub_name, topic);
    println!("url: {}", url);

    let body = bytes::Bytes::from(json!(e).to_string());
    let result = spin_sdk::outbound_http::send_request(
        http::Request::builder()
            .header("Content-Type", "application/json")
            .method("POST")
            .uri(url)
            .body(Some(body))
            .unwrap(),
    );
}
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Subscribe a message, with .NET in counter-api:

// ref: https://github.com/thangchung/dapr-labs/blob/main/polyglot/counter-api/UseCases/OrderUpdatedCommand.cs#L15

builder.MapPost("/dapr_subscribe_BaristaOrderUpdated", async (BaristaOrderUpdated @event, ISender sender) =>
            await sender.Send(new OrderUpdatedCommand(
                    @event.OrderId,
                    @event.ItemLines)));
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Or, in Rust with barista-api:

// ref: https://github.com/thangchung/dapr-labs/blob/main/polyglot/barista-api/src/lib.rs#L71

router.post("/dapr_subscribe_BaristaOrdered", post_place_order_handler);
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Dapr components:

# barista_pubsub.yaml

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: baristapubsub
  namespace: default
spec:
  type: pubsub.redis
  version: v1
  metadata:
    - name: redisHost
      value: localhost:6379
    - name: redisPassword
      value: ""
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# kitchen_pubsub.yaml

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: kitchenpubsub
  namespace: default
spec:
  type: pubsub.redis
  version: v1
  metadata:
    - name: redisHost
      value: localhost:6379
    - name: redisPassword
      value: ""
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# barista_order_placed_subscription.yaml

apiVersion: dapr.io/v1alpha1
kind: Subscription
metadata:
  name: barista-ordered-subscription
spec:
  topic: baristaorderplaced
  route: /dapr_subscribe_BaristaOrdered
  pubsubname: baristapubsub
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# kitchen_order_placed_subscription.yaml

apiVersion: dapr.io/v1alpha1
kind: Subscription
metadata:
  name: kitchen-ordered-subscription
spec:
  topic: kitchenorderplaced
  route: /dapr_subscribe_KitchenOrdered
  pubsubname: kitchenpubsub
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# barista_updated_subscription.yaml

apiVersion: dapr.io/v1alpha1
kind: Subscription
metadata:
  name: barista-updated-subscription
spec:
  topic: baristaorderupdated
  route: /dapr_subscribe_BaristaOrderUpdated
  pubsubname: baristapubsub
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# kitchen_updated_subscription.yaml

apiVersion: dapr.io/v1alpha1
kind: Subscription
metadata:
  name: kitchen-updated-subscription
spec:
  topic: kitchenorderupdated
  route: /dapr_subscribe_KitchenOrderUpdated
  pubsubname: kitchenpubsub
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Set up and run Dapr apps

Now, let installing dapr in your local machine (Windows 11 - WSL2 - Ubuntu 22.04)

> wget -q https://raw.githubusercontent.com/dapr/cli/master/install/install.sh -O - | /bin/bash
> dapr init
> dapr --version
CLI version: 1.11.0
Runtime version: 1.11.2
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Create .env with content:

DAPR_URL=http://localhost:3500
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Run product-api 

> cd product-api && \
    spin build && \
    dapr run \
    --app-id productapi \
    --app-port 5001 \
    --resources-path ../components \
    --config ../components/daprConfig.yaml \
    -- spin up --listen 0.0.0.0:5001
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Run counter-api 

> dapr run \
    --app-id counterapi \
    --app-port 5002 \
    --dapr-http-port 3500 \
    --resources-path components \
    --config components/daprConfig.yaml \
    -- dotnet run --project counter-api/counter-api.csproj
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Run barista-api 

> cd barista-api && \
    spin build && \
    dapr run \
    --app-id baristaapi \
    --app-port 5003 \
    --resources-path ../components \
    --config ../components/daprConfig.yaml \
    -- spin up --listen 0.0.0.0:5003 --env DAPR_URL=${DAPR_URL}
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Run kitchen-api 

> cd kitchen-api && \
    spin build && \
    dapr run \
    --app-id kitchenaapi \
    --app-port 5004 \
    --resources-path ../components \
    --config ../components/daprConfig.yaml \
    -- spin up --listen 0.0.0.0:5004 --env DAPR_URL=${DAPR_URL}
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Go to Rest Client at client.local.http to play around with it.

Summary

In this part, we install and play around with Dapr CLI on the local machine. Next part, we will deploy it to Kubernetes (k3d), and it's going to be an interesting part of this series.

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