Metadata.Operations.enqueueDeployment Callback not allowing Callouts

Question

I have a scenario where I am saving custom metadata for an external API configuration. I want to deploy all the metadata, then after the deploy job is done, make a callout to the API to verify the configuration is correct.

My callback class looks like this:

public with sharing class DeployCallback implements Metadata.DeployCallback {
  CallbackRunnable runnable;

  public DeployCallback() {
  }

  public DeployCallback(CallbackRunnable runnable) {
    this.runnable = runnable;
  }

  public void handleResult(
    Metadata.DeployResult result,
    Metadata.DeployCallbackContext context
  ) {
    Id deployJobId = context.getCallbackJobId();

    switch on (result.status) {
      when Succeeded {
        if (runnable != null && runnable.runOnSuccess)
          runnable.run();
      }
      when SucceededPartial {
        // The deployment succeeded, but some components might not have been successfully deployed. Check Metadata.DeployResult for more details.
        if (runnable != null && runnable.runOnSuccess)
          runnable.run();
      }
      when Failed {
        // Deployment was not successful
        if (runnable != null && runnable.runOnFail)
          runnable.run();
      }
      when Canceled {
        // Deployment was not successful
      }
      when Pending, InProgress, Canceling {
        // Queued or state changing
      }
    }
  }

  public virtual class CallbackRunnable {
    public Boolean runOnSuccess;
    public Boolean runOnFail;

    public CallbackRunnable() {
    }

    public virtual void run() {
    }
  }
}

My runnable implementation looks like this:

  private class APIConfigPostDeploy extends DeployCallback.CallbackRunnable {
    APIConfigPostDeploy() {
      this.runOnSuccess = true;
    }
    public override void run() {
      APIService apiService = new APIService();
      apiService.verifyConfigCallout();
    }
  }

The apiService.verifyConfigCallout() does a HTTP call using the settings that were just deployed.

And of course we are enqueueing the deploy job like this:

Metadata.Operations.enqueueDeployment(theMetadata, callback);

I keep getting the error:

Callout not allowed from this future method. Please enable callout by annotating the future method. eg: @Future(callout=true)

None of the methods in my call chain are future methods, and calling the apiService.verifyConfigCallout() directly works just fine. It only fails with this error when being called from within the deploy callback.

My assumption is that the Metadata.Operations does its callback as a future. I'm wondering if anyone has run into this and has a workaround?

Answer 1

Without documentation, it's kind of hard to tell, but the easiest solution would be to call a Queueable from your callback to make the callout. I realize this is a bit roundabout, but it should work with minimal modification to what you already have. Remember to use Database.AllowsCallouts on your Queueable to allow the callout to happen.