[discourse] Error getting boolean flag

[markphelps]

Originally posted by leonardo on Discourse

Hey Flipt folks!

I’m integrating Flipt in our FastAPI backend using gRPC. Everything works fine but I have a problem getting a boolean flag. I’m building a service class with a method similar to this:

def evaluate_bool(self, flag_key: str, entity_id: str) -> bool:
        client = self.get_client() # This create a channel with an interceptor that inject the AuthToken, and return the Flipt Stub
        response = client.Evaluate(
            EvaluationRequest(
                flag_key=flag_key,
                entity_id=entity_id,
                context={},
                namespace_key=app_settings.FLIPT_NAMESPACE,
            ),
        )
        ...

If the flag_key is a variant, the response is expected depending on the entity_id. But if the flag is a boolean, I’m getting this error:

grpc._channel._InactiveRpcError: <_InactiveRpcError of RPC that terminated with:
        status = StatusCode.INVALID_ARGUMENT
        details = "flag type BOOLEAN_FLAG_TYPE invalid"
        debug_error_string = "UNKNOWN:Error received from peer  {created_time:"2024-09-11T13:55:10.76349593+00:00", grpc_status:3, grpc_message:"flag type BOOLEAN_FLAG_TYPE invalid"}"

This is my configuration:

version: "1.4"
namespace:
  key: production
  name: Production
flags:
- key: test-key
  name: test-sync-edited
  type: BOOLEAN_FLAG_TYPE
  enabled: false
  rollouts:
  - segment:
      key: internal-users
      value: true
- key: another-thing
  name: another-thing
  type: VARIANT_FLAG_TYPE
  enabled: true
  variants:
  - default: true
    key: t1
  - key: t2
  rules:
  - segment: internal-users
    distributions:
    - variant: t2
      rollout: 100
- key: boolean-flag
  name: Boolean Flag
  type: BOOLEAN_FLAG_TYPE
  enabled: false
segments:
- key: internal-users
  name: internal-users
  constraints:
  - type: ENTITY_ID_COMPARISON_TYPE
    property: entityId
    operator: eq
    value: leo.david
  match_type: ALL_MATCH_TYPE

The flag that I’m using and getting the error is test-key. I noticed that the enabled field is False, but I can’t change it in the UI, I don’t see any button.

Flipt is a great platform! Thank you so much for building it!

[dosubot[bot]]

The error happens because the flag you’re evaluating (test-key) is not enabled. In Flipt, the enabled field controls whether a flag is active and can be evaluated—if it’s set to false, evaluation is skipped or short-circuited, which can result in errors like the one you’re seeing.

The reason you can’t change the enabled field in the UI is likely because the UI disables this control when the app is in read-only mode, or possibly due to how boolean flags are handled in the form logic. For boolean flags, the toggle for enabling/disabling is sometimes linked to the default value toggle, and both can be disabled if the app is read-only or if the flag type was recently changed, which resets the enabled status and disables editing it in the UI.

To resolve this, make sure the flag is enabled in your configuration or check if your Flipt instance is running in read-only mode, which would prevent changes in the UI. Once the flag is enabled, the evaluation via gRPC should work as expected.

Reference: Flipt UI flag form logic

To reply, just mention @dosu.

---

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[markphelps]

Reply from george on Discourse:

Hey @leonardo ! Sorry you’re running into issues.

This looks like it is using our older Evaluation API, which only support variant type flags. There is a new evaluation specific protobuf set of definitions to generate from, if you want to go this way:

  <a href="https://github.com/flipt-io/flipt/blob/de7ee01bd2d166f8d5e6632cb761ebb182552617/rpc/flipt/evaluation/evaluation.proto#L88-L101" target="_blank" rel="noopener nofollow ugc">github.com</a>

flipt-io/flipt/blob/de7ee01bd2d166f8d5e6632cb761ebb182552617/rpc/flipt/evaluation/evaluation.proto#L88-L101

<pre class="onebox"><code class="lang-proto">
  <ol class="start lines" start="88" style="counter-reset: li-counter 87 ;">
      <li>service EvaluationService {</li>
      <li>  rpc Boolean(EvaluationRequest) returns (BooleanEvaluationResponse) {</li>
      <li>    option (google.api.http) = {post: "/evaluate/v1/boolean" body: "*"};</li>
      <li>    option (gnostic.openapi.v3.operation) = {operation_id: "evaluateBoolean"};</li>
      <li>  }</li>
      <li>  rpc Variant(EvaluationRequest) returns (VariantEvaluationResponse) {</li>
      <li>    option (google.api.http) = {post: "/evaluate/v1/variant" body: "*"};</li>
      <li>    option (gnostic.openapi.v3.operation) = {operation_id: "evaluateVariant"};</li>
      <li>  }</li>
      <li>  rpc Batch(BatchEvaluationRequest) returns (BatchEvaluationResponse) {</li>
      <li>    option (google.api.http) = {post: "/evaluate/v1/batch" body: "*"};</li>
      <li>    option (gnostic.openapi.v3.operation) = {operation_id: "evaluateBatch"};</li>
      <li>  }</li>
      <li>}</li>
  </ol>
</code></pre>

In this situation, you need to use the Boolean specific evaluation RPC.

Are you using one of our pre-built clients? or something hand generated?

[markphelps]

Reply from leonardo on Discourse:

Hey @george!

I see the issue now . I’m installing the proto definitions from buf using:

pip install flipt-io-flipt-grpc-python --extra-index-url https://buf.build/gen/python
pip install flipt-io-flipt-protocolbuffers-python --extra-index-url https://buf.build/gen/python

But in the Python definitions, I don’t see any EvaluationService. Are that dependencies updated? Where I can find that pre-built clients?

Thanks in advance for your help!

[markphelps]

Reply from george on Discourse:

Ahh amazing, let me find out if we can get these other APIs published to buf too.

We have a range of clients in different languages. The main repos are:

Server-Side Eval: GitHub - flipt-io/flipt-server-sdks: Flipt Server-Side SDKs

Client-Side Eval: GitHub - flipt-io/flipt-client-sdks: Flipt Client-Side Evaluation SDKs

The client-side evaluators run evaluations in your application, so no network hop in your code FYI. These are the most performant ones for your application.

The server-side SDKs mostly support HTTP only (apart from Go).

[markphelps]

Reply from george on Discourse:

So we are publishing the evaluation API to buf, but I am unsure how to get the magic python install for just this sub package:

  <a href="https://buf.build/flipt-io/flipt/docs/main:flipt.evaluation" target="_blank" rel="noopener nofollow ugc">buf.build</a>

Buf Schema Registry

Explore protobuf schemas within the BSR

[markphelps]

Reply from leonardo on Discourse:

Hey George! Sorry for my late response. I changed our implementation to use the Python Client-Side lib, and it works really fine! Great use of FFI!

Thank you so much for your help!

[markphelps]

Reply from george on Discourse:

That is great to hear @leonardo ! Let us know how well you get on with it.

If you’re interested too, we just launched our cloud product (https://flipt.cloud), which works with or without (you decide) the open-source version. If that happens to pique your interest, we would love your feedback!