InAppPurchase thread safety

MacOSX and iOS
1

Hi,

It seems some InAppPurchase listener callback happen on threads that are not the juce message thread. For example, I was trying to call ‘restoreProductsBoughtList’ on a device with no internet access. At that point, ‘purchasesListRestored’ is called for my InAppPurchases::Listener with the ‘Product query failed’ error, but not from the message thread ( JUCE_ASSERT_MESSAGE_MANAGER_IS_LOCKED asserts).

It can be silenced by replacing:

                       case PendingProductInfoRequest::Type::query:
                            t.owner.listeners.call ([&] (Listener& l)
                            {
                                l.purchasesListRestored ({}, false, NEEDS_TRANS ("Product query failed") + errorDetails);
                            });

                        break;

with

                       case PendingProductInfoRequest::Type::query:
                          MessageManager::callAsync ([&t, errorDetails]
                          {
                            t.owner.listeners.call ([errorDetails] (Listener& l)
                            {
                                l.purchasesListRestored ({}, false, NEEDS_TRANS ("Product query failed") + errorDetails);
                            });
                          });
                            break;

Maybe the other places where listeners are called should be reviewed in order to ensure that we stay on the message thread.

2

probably related: the red warning in SKProductsRequestDelegate | Apple Developer Documentation

Responses received by the SKProductsRequestDelegate may not be returned on a specific thread. If you make assumptions about which queue will handle delegate responses, you may encounter unintended performance and compatibility issues in the future.

3

(bump)

4

the issue is still there btw. I’m wrapping the juce InAppPurchase::Listener with MessageManager::callAsync in order to avoid issues:

struct SafeJuceInAppPurchasesListener {
  using Product = juce::InAppPurchases::Product;
  using PurchaseInfo = juce::InAppPurchases::Listener::PurchaseInfo;
private:
  struct UnsafeListener : public juce::InAppPurchases::Listener {
    SafeJuceInAppPurchasesListener *owner;
    UnsafeListener(SafeJuceInAppPurchasesListener *owner) : owner(owner) {}

    static void callAsyncIfNotOnMessageThread(std::function<void()> fn) {
      if (juce::MessageManager::getInstance()->isThisTheMessageThread()) {
        fn();
      } else {
        juce::MessageManager::callAsync(std::move(fn));
      }
    }

    void productsInfoReturned (const Array<Product>& products) override {
      callAsyncIfNotOnMessageThread([this, products]() { owner->productsInfoReturned(products); });
    }
    void productPurchaseFinished (const PurchaseInfo& info, bool success, const String& statusDescription) override {
      callAsyncIfNotOnMessageThread([this, info, success, statusDescription]() {
        owner->productPurchaseFinished(info, success, statusDescription);
      });
    }
    void purchasesListRestored (const Array<PurchaseInfo> &info, bool success, const String& statusDescription) override {
      callAsyncIfNotOnMessageThread([this, info, success, statusDescription]() {
        owner->purchasesListRestored(info, success, statusDescription);
      });
    }
  };
  UnsafeListener juce_listener{this};
public:
  juce::InAppPurchases::Listener *getUnsafeListener() { return &juce_listener; }
  virtual void productsInfoReturned (const Array<Product>& /*products*/) {}
  virtual void productPurchaseFinished (const PurchaseInfo&, bool /*success*/, const String& /*statusDescription*/) {}
  virtual void purchasesListRestored (const Array<PurchaseInfo>&, bool /*success*/, const String& /*statusDescription*/) {}
};
2 Likes
5

Bumping as I would really like the JUCE team to investigate thread safety of iOS in-app purchase code. Most of my iOS crash logs in Xcode are still something like that (happening in a thread that is not the message thread), so the workaround I previously posted is not enough:

std::__1::vector<std::__1::unique_ptr<juce::InAppPurchases::Pimpl::PendingProductInfoRequest, std::__1::default_delete<juce::InAppPurchases::Pimpl::PendingProductInfoRequest>>, std::__1::allocator<... + 72
0x0000000101099f68 juce::InAppPurchases::Pimpl::Class::Class()::'lambda'(objc_object*, objc_selector*, SKProductsRequest*, SKProductsResponse*)::operator()(objc_object*, objc_selector*, SKProductsRequest*, SKProducts... + 304
0x0000000101099fa0 juce::InAppPurchases::Pimpl::Class::Class()::'lambda'(objc_object*, objc_selector*, SKProductsRequest*, SKProductsResponse*)::__invoke(objc_object*, objc_selector*, SKProductsRequest*, SKProductsRe... + 36