Targets

Targets

Named policies are applied to targets. Dapr supports three target types that apply all Dapr building block APIs:

• apps
• components
• actors

Apps

With the apps target, you can apply retry, timeout, and circuitBreaker policies to service invocation calls between Dapr apps. Under targets/apps, policies are applied to each target service’s app-id. The policies are invoked when a failure occurs in communication between sidecars, as shown in the diagram below.

Dapr provides built-in service invocation retries, so any applied retry policies are additional.

Example of policies to a target app with the app-id “appB”:

specs:
  targets:
    apps:
      appB: # app-id of the target service
        timeout: general
        retry: general
        circuitBreaker: general

组件

With the components target, you can apply retry, timeout and circuitBreaker policies to component operations.

Policies can be applied for outbound operations (calls to the Dapr sidecar) and/or inbound (the sidecar calling your app).

Outbound

outbound operations are calls from the sidecar to a component, such as:

• Persisting or retrieving state.
• Publishing a message on a PubSub component.
• Invoking an output binding.

Some components may have built-in retry capabilities and are configured on a per-component basis.

spec:
  targets:
    components:
      myStateStore:
        outbound:
          retry: retryForever
          circuitBreaker: simpleCB

Inbound

inbound operations are calls from the sidecar to your application, such as:

• PubSub subscriptions when delivering a message.
• Input bindings.

Some components may have built-in retry capabilities and are configured on a per-component basis.

spec:
  targets:
    components:
      myInputBinding:
        inbound: 
          timeout: general
          retry: general
          circuitBreaker: general

PubSub

In a PubSub target/component, you can specify both inbound and outbound operations.

spec:
  targets:
    components:
      myPubsub:
        outbound:
          retry: pubsubRetry
          circuitBreaker: pubsubCB
        inbound: # inbound only applies to delivery from sidecar to app
          timeout: general
          retry: general
          circuitBreaker: general

Actors

With the actors target, you can apply retry, timeout, and circuitBreaker policies to actor operations.

When using a circuitBreaker policy for the actors target, you can specify how circuit breaking state should be scoped by using circuitBreakerScope:

• id: an individual actor ID
• type: all actors of a given actor type
• both: both of the above

You can also specify a cache size for the number of circuit breakers to keep in memory with the circuitBreakerCacheSize property, providing an integer value, e.g. 5000.

Example

spec:
  targets:
    actors:
      myActorType:
        timeout: general
        retry: general
        circuitBreaker: general
        circuitBreakerScope: both
        circuitBreakerCacheSize: 5000

下一步

Try out one of the Resiliency quickstarts:

• Resiliency: Service-to-service
• Resiliency: State Management