'Play' function not working

d.russo · July 16, 2025, 2:40pm

Hello everyone.

To interact with Camunda in a local development environment, I’m using the Docker Compose version of Camunda (all the various modules described here). Among these, the one currently giving me a problem is the Web Modeler, which I’d like to use to build my application workflows.
I’m having trouble with the “play” functionality of a BPMN diagram.
I can successfully deploy and run it, but when I try to simulate the flow with “play,” I get an error, as shown in the image below:

As suggested in the error ‘The diagram failed to deploy. Please check the Output tab in the Implement mode for more details.’, my Output tab displays this message:

As you can see, the workflow should be configured correctly, as it only consists of a start and end step.

How should I proceed? Did I configure something incorrectly? Could the issue be related to the cache mentioned in the error message?
Thanks

nathan.loding · July 16, 2025, 3:16pm

Hi @d.russo, welcome to the forums! I assume you are using an alpha version of 8.8 with Docker? If so, I suspect you are encountering this bug:

github.com/camunda/camunda

Web Modeler fails silently with "Unable to create client cache [deploy-error]" if Zeebe is in none authentication mode

opened 04:44AM - 13 Jul 25 UTC

marciotex

kind/bug severity/low likelihood/unknown needs component label affects/8.8

### ### ### ### ### Description When using the Web Modeler (sel…f-managed via Docker Compose) with ZEEBE_AUTHENTICATION_MODE=none, attempting to deploy a BPMN process using the Play button results in the following error: Unable to create client cache [deploy-error] The Web Modeler is configured to use OAuth2 (Keycloak) and expects to authenticate against a Zeebe endpoint that accepts tokens. However, in none mode, Zeebe does not expect or accept any tokens. This causes the Web Modeler's internal client to fail — but the error message is not informative, and the UI gives no indication of what is wrong. This behavior: - causes confusion for users trying to run Zeebe in none mode for local development; - provides no actionable feedback; - is especially misleading because the Web Modeler UI and health checks appear to be working correctly. Environment: - Camunda 8.8.0-alpha6 (Docker Compose setup) - Web Modeler self-managed - Windows 10 with Docker Desktop I’m happy to submit a PR for this improvement. ### Steps to reproduce 1. Clone the [[Camunda Self-Managed Docker Compose setup](https://github.com/camunda/camunda)](https://github.com/camunda/camunda) or use your own based on the official example. 2. In your `.env` file, set: ``` ZEEBE_AUTHENTICATION_MODE=none ``` 3. Start the stack: ```bash docker compose up -d ``` 4. Open the Web Modeler at `http://localhost:8070` and log in (default user: `demo/demo`). 5. Create or open a BPMN diagram. 6. Click the **Play** button to deploy the model. 7. Observe the error message: ``` Unable to create client cache [deploy-error] ``` ### Current behavior When attempting to deploy a BPMN model from the Web Modeler using the **Play** button, the action fails with the following error displayed in the UI: ``` Unable to create client cache [deploy-error] ``` This happens when `ZEEBE_AUTHENTICATION_MODE` is set to `none` in the `.env` file (i.e., Zeebe is running without authentication). The Web Modeler attempts to authenticate with Zeebe using a token obtained from Keycloak, but Zeebe in `none` mode does not expect or accept tokens. As a result: * The internal Web Modeler client fails to initialize silently. * No meaningful explanation is provided to the user in the UI or logs. * All services appear healthy and responsive, making the issue difficult to trace. ### Expected behavior - A clear error message indicating that the selected cluster is not compatible with the configured authentication; - Or: validation during startup or cluster configuration that prevents selecting a Zeebe target with incompatible auth mode; - Or: fallback to unauthenticated deployment when none mode is used. ### Environment SM ### Version Camunda 8.8.0-alpha6 (Docker Compose setup) ### Rootcause The Web Modeler is designed to authenticate with Zeebe using OAuth2 tokens issued by Keycloak. This behavior is hardcoded into the Web Modeler when clusters are defined with `CAMUNDA_CLIENT_AUTH_METHOD=oidc`. However, when `ZEEBE_AUTHENTICATION_MODE=none` is configured on the Zeebe broker, it expects unauthenticated requests and rejects or ignores tokens. This causes a mismatch: * The Web Modeler client attempts to obtain and use a token for gRPC or REST communication. * Zeebe, expecting no authentication headers, fails the request or closes the connection silently. * The Modeler receives no usable response, and surfaces only a generic error (`Unable to create client cache [deploy-error]`) to the user. Since there is no validation of the authentication mode compatibility between Web Modeler and Zeebe, the user is left without feedback on the misconfiguration. ### Solution ideas - Improve error reporting on the Web Modeler side when a token is used against a none-mode Zeebe; - Or detect and warn the user that Web Modeler requires ZEEBE_AUTHENTICATION_MODE=identity. ### Dev -> QA handover #### 🔧 What was changed * Added validation and/or documentation to ensure users are warned when attempting to use Web Modeler with a Zeebe cluster configured in `ZEEBE_AUTHENTICATION_MODE=none`. * Clarified expected authentication modes during startup or cluster configuration. * Improved error message shown in the UI when authentication fails due to mode mismatch. #### 🧪 How to test 1. In `.env`, set: ``` ZEEBE_AUTHENTICATION_MODE=none ``` 2. Start the Camunda stack using Docker Compose: ```bash docker compose up -d ``` 3. Log in to Web Modeler at `http://localhost:8070` using the default user (`demo/demo`). 4. Create or open a BPMN diagram. 5. Click **Play** to deploy. **Expected QA Outcomes:** * The deployment does **not** succeed (since auth modes are incompatible). * A **clear, user-friendly error message** should explain the reason: > "Zeebe is running in `none` authentication mode, but this Web Modeler cluster requires OAuth2. Please configure Zeebe with `ZEEBE_AUTHENTICATION_MODE=identity`." * (Optional) If a validation mechanism was added during cluster registration, the Modeler should **prevent saving or selecting** a misconfigured cluster. #### ✅ Regression checklist * Deployment from Web Modeler still works as expected when Zeebe is in `identity` mode. * Other Modeler features (editing, saving, UI navigation) function normally regardless of auth mode. * No impact on Zeebe, Identity, or Keycloak container stability. ### Links _No response_

d.russo · July 17, 2025, 10:33am

yes it’s that’s my problem!

I resolve changing the env variabile ZEEBE_AUTHENTICATION_MODE=identity and with this the “play” work now.

I think it’s a bug of this version,
thanks so much for the suggestion!

nathan.loding · July 17, 2025, 3:01pm

@d.russo - it’s always a risk using an alpha release, because it’s known to be incomplete - but we appreciate the users who are using it and providing feedback so we can ensure the final release is as stable as possible!

d.russo · July 17, 2025, 3:43pm

I understand but i think i am using a released version, not alpha.

In my “.env” and my “docker-compose.yaml” files the version of Camunda is “8.7.x” it’s correct ?

nathan.loding · July 17, 2025, 3:46pm

@d.russo - oh, very interesting! Yes, if the .env says 8.7 then you’re on a stable release. I will make sure the team knows that this bug affects prior versions as well. Thanks for pointing this out!

system · July 24, 2025, 3:47pm

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