InstanceSharedPtr ManagerImpl::get(const std::string& name, SingletonFactoryCb cb, bool pin) {

  ASSERT_IS_MAIN_OR_TEST_THREAD();

  ENVOY_BUG(Registry::FactoryRegistry<Registration>::getFactory(name) != nullptr,

            "invalid singleton name '" + name + "'. Make sure it is registered.");

  auto existing_singleton = singletons_[name].lock();

  if (existing_singleton == nullptr) {

    InstanceSharedPtr singleton = cb();

    singletons_[name] = singleton;

    if (pin && singleton != nullptr) {

      pinned_singletons_.push_back(singleton);

    }

    return singleton;

  } else {

    return existing_singleton;

  }

}