Targets

Apply resiliency policies to apps, components and actors

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.

Diagram showing service invocation resiliency

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

Components

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.
  • Invoking an output binding.

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

Diagram showing service invocation resiliency
spec:
  targets:
    components:
      myStateStore:
        outbound:
          retry: retryForever
          circuitBreaker: simpleCB
Inbound

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

  • Subscriptions when delivering a message.
  • Input bindings.

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

Diagram showing service invocation resiliency
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.

Diagram showing service invocation resiliency
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, you can specify whether circuit breaking state should be scoped to:

  • An individual actor ID.
  • All actors across the actor type.
  • Both.

Specify circuitBreakerScope with values id, type, or both.

You can specify a cache size for the number of circuit breakers to keep in memory. Do this by specifying circuitBreakerCacheSize and providing an integer value, e.g. 5000.

Example

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

Last modified April 6, 2022: PR feedback (3f5b4887)