How-To: Share state between applications

Choose different strategies for sharing state between different applications

Introduction

Dapr offers developers different ways to share state between applications.

Different architectures might have different needs when it comes to sharing state. For example, in one scenario you may want to encapsulate all state within a given application and have Dapr manage the access for you. In a different scenario, you may need to have two applications working on the same state be able to get and save the same keys.

To enable state sharing, Dapr supports the following key prefixes strategies:

• appid - This is the default strategy. the appid prefix allows state to be managed only by the app with the specified appid. All state keys will be prefixed with the appid, and are scoped for the application.

• name - This setting uses the name of the state store component as the prefix. Multiple applications can share the same state for a given state store.

• none - This setting uses no prefixing. Multiple applications share state across different state stores.

Specifying a state prefix strategy

To specify a prefix strategy, add a metadata key named keyPrefix on a state component:

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: statestore
  namespace: production
spec:
  type: state.redis
  version: v1
  metadata:
  - name: keyPrefix
    value: <key-prefix-strategy>

Examples

The following examples will show you how state retrieval looks like with each of the supported prefix strategies:

appid (default)

A Dapr application with app id myApp is saving state into a state store named redis:

curl -X POST http://localhost:3500/v1.0/state/redis \
  -H "Content-Type: application/json"
  -d '[
        {
          "key": "darth",
          "value": "nihilus"
        }
      ]'

The key will be saved as myApp||darth.

name

A Dapr application with app id myApp is saving state into a state store named redis:

curl -X POST http://localhost:3500/v1.0/state/redis \
  -H "Content-Type: application/json"
  -d '[
        {
          "key": "darth",
          "value": "nihilus"
        }
      ]'

The key will be saved as redis||darth.

none

A Dapr application with app id myApp is saving state into a state store named redis:

curl -X POST http://localhost:3500/v1.0/state/redis \
  -H "Content-Type: application/json"
  -d '[
        {
          "key": "darth",
          "value": "nihilus"
        }
      ]'

The key will be saved as darth.

Last modified February 16, 2021: Merge pull request #1235 from dapr/update-v0.11 (b4e9fbb)