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[BUG] Configuration subscription stops permanently after the daprd sidecar restarts

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
68/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
grpc, python
Domain
api, backend

Research direction

Start in dapr/clients/grpc/_response.py with ConfigurationWatcher, then trace subscribe_configuration() in both dapr.clients.DaprClient and dapr.aio.clients.DaprClient. Reproduce the stream failure by restarting daprd, and verify that both subscription paths recover and deliver later updates without restarting the application.

Written by the indexing model from the issue text.

Description

kind/bug

Expected Behavior

DaprClient.subscribe_configuration() keeps delivering configuration updates for the lifetime of the client.
If the daprd sidecar process exits and comes back (for example an OOM kill of the sidecar container while the application container keeps running), the SDK should re-establish SubscribeConfigurationAlpha1 against the new sidecar and continue calling the handler. Updates that happened while the sidecar was down should be visible on the new subscription, or the application should at least be able to observe that the previous stream ended.
Unary calls such as get_configuration() already work again once the new sidecar is listening. The long-lived configuration subscription should recover the same way.

Actual Behavior

The subscription works after a fresh application start. After daprd restarts, the handler is never called again. The application process stays healthy, so a Kubernetes pod is not recreated, and dynamic config updates are silently lost until the application process itself restarts.
ConfigurationWatcher in dapr/clients/grpc/_response.py reads SubscribeConfigurationAlpha1 on a daemon thread. When the stream raises, the thread prints to stdout and returns:

except Exception:
    print(f'{self.store_name} configuration watcher for keys {self.keys} stopped.')
    pass

There is no retry. subscribe_configuration() does not retain the ConfigurationWatcher, so nothing is left to start a new stream. The failure is not reported through the Python logger, and the returned subscription id belongs to the dead sidecar.
Seen with dapr Python SDK 1.18.3. Both dapr.clients.DaprClient.subscribe_configuration and dapr.aio.clients.DaprClient.subscribe_configuration use this watcher.

Steps to Reproduce the Problem

  1. Run an app with a configuration.redis component and the Python SDK 1.18.3.
  2. Subscribe once at startup:
from dapr.clients import DaprClient
def handler(subscription_id, response):
    print("update", subscription_id, {k: v.value for k, v in response.items.items()})
with DaprClient() as client:
    subscription_id = client.subscribe_configuration(
        store_name="configstore",
        keys=["my-key"],
        handler=handler,
    )
    print("subscribed", subscription_id)
    # keep the process alive
  1. Confirm a config change invokes handler.
  2. Restart only daprd. In Kubernetes this is a sidecar OOM (OOMKilled) while the app container keeps the same process. Locally, stop and start the daprd process without restarting the app.
  3. Change my-key again after daprd is healthy.
    handler is not called. Stdout may contain {store} configuration watcher for keys [...] stopped. Recreating the app process makes updates work again until the next sidecar restart.

Release Note

RELEASE NOTE: FIX Reconnect configuration subscriptions after the Dapr sidecar stream drops.

Dominant language
Python
Stars
273
Forks
155
Avg merge
3d 13h
Merged PRs (30d)
11

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