Retry Policy to Not Trigger For POST Requests

Question

Is it possible to configure the resiliency policy in Dapr to not perform a retry when the HTTP request is POST? The Polly library in .NET, for example, allows fine-grained configuration of retry and circuit breaker policies. Is it possible to do the same in Dapr?

apiVersion: dapr.io/v1alpha1
kind: Resiliency
metadata:
  name: resiliency-policy
scopes:
  - shoppingbasket
spec:
  policies:
    retries:
      operation:
        policy: constant
        duration: 5s
        maxRetries: 3

    circuitBreakers:
      serviceCB:
        maxRequests: 1
        timeout: 30s
        trip: consecutiveFailures >= 3

  targets:
    apps:
      discount:
        retry: operation
        circuitBreaker: serviceCB

Peter Csala · Accepted Answer · 2024-05-30 10:02:52Z

1

Dapr is written in Golang so it does not use Polly under the hood.

It has a slightly different trigger concept:

In Polly you can define when should the retry policy/strategy handle the outcome of the given operation.
In Dapr a retry could be triggered whenever a given operation returns an abnormal state. Here you can find some examples.

In one of the github issues they call out the following:

You're correct that it retries on any error, including 4xx responses. For the initial version of resiliency, we took the approach of more retries is better than no retries. In the future, we may add in additional filters/scenarios that you can trigger a retry off of. I know there were plans to add in more CEL level expressions for Phase 2 of resiliency.

In the proposal PR you can see some mentioning about conditional retries:

 apis:
    invoke:
      - match: appId == "appB"
        # Nested rules: Prevent duplicative checks in rules.
        # Its likely that controler-gen does not support this
        # but apiextensionsv1.JSON can be used as workaround.
        rules:
          - match:
              request.method == "GET" &&
              request.metadata.count > 1000
            timeout: largeResponse
            retry: largeResponse
          - match:
              request.path == "/someOperation"
            retry: someOperation

Unfortunately Phase 2 did not happen yet as far as I know. There is one related open PR: https://github.com/dapr/dapr/pull/7132.

edited May 30, 2024 at 10:02

answered May 30, 2024 at 9:18

Peter Csala

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5 Comments

Sohlae Over a year ago

Thank you Peter for your answer, but what is considered an abnormal state? Is it any status code >= 400? Is it a transient fault? Or perhaps both?

Peter Csala Over a year ago

@Sohlae 408 ( Request Timeout ), 429 ( Too many requests ) and 5xx are considered transient Http codes.

Sohlae Over a year ago

Peter Csala, so basically, phase 1 of the retry and CB policies only applies to transient HTTP codes, is my assumption correct?

Peter Csala Over a year ago

@Sohlae There is a What errors in Dapr are retriable or permanent? section in the github issue. Even though it mentions a couple of status codes but does not explicitly articulate which one is considered as retryable and which one is non-retryable. So I'm not entirely sure that your assumption is correct.

Sohlae Over a year ago

Okay, thank you.

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