Dapr Event Bridge

@purista/dapr-sdk provides a Dapr-oriented bridge and state/config/secret adapters. Use it when you operate in a polyglot environment or want Dapr’s sidecar model for transport abstraction.

Architecture

flowchart TB
    subgraph App["PURISTA Application"]
        S1["User Service"]
        S2["Order Service"]
    end
    subgraph Dapr["Dapr Sidecar"]
        PUB["Pub/Sub"]
        INV["Service Invocation"]
    end
    subgraph Infra["Infrastructure"]
        B1["Redis"]
        B2["RabbitMQ"]
        B3["Kafka"]
    end
    S1 <-->|HTTP/gRPC| Dapr
    S2 <-->|HTTP/gRPC| Dapr
    Dapr <-->|component| B1
    Dapr <-->|component| B2
    Dapr <-->|component| B3

PURISTA services talk to the Dapr sidecar. The sidecar handles routing, retries, and broker connectivity.

Setup

import { DaprEventBridge } from '@purista/dapr-sdk'

const eventBridge = new DaprEventBridge({
  clientConfig: {
    daprHost: 'localhost',
    daprPort: '3500',
  },
})

Delivery semantics

Semantics depend on the Dapr pub/sub component and broker backend:

Always verify your concrete component behavior in integration tests.

Command invocation

For Dapr invoke paths, timeout behavior is owned by the Dapr sidecar/client request lifecycle. PURISTA forwards TTL from invoke calls but does not emulate broker-style command retries.

Stream support

PURISTA stream runtime (openStream) is currently not implemented for the Dapr bridge.

Startup order

Use the sequence required for Dapr endpoint discovery:

// 1. Create bridge (do not start yet)
const eventBridge = new DaprEventBridge(config)

// 2. Create and start service
const myService = await myV1Service.getInstance(eventBridge)
await myService.start()

// 3. Start bridge (registers endpoints with Dapr)
await eventBridge.start()

Dapr stores

The Dapr SDK also provides store adapters:

import { DaprStateStore, DaprSecretStore } from '@purista/dapr-sdk'

const builder = new ServiceBuilder(myServiceInfo)
  .addStateStore(DaprStateStore)
  .addSecretStore(DaprSecretStore)

Reliability recommendations

• Document and version-control Dapr component/resiliency specs
• Validate duplicate handling in command/subscription side effects
• Test sidecar restarts and service readiness ordering
• Verify shutdown behavior with the same readiness probes used in production

When to choose Dapr

Next: Event Bridges overview to compare all bridge options.