Enable 'get_my_shard' API for UDL

include/cascade/detail/service_impl.hpp

@@ -335,6 +335,54 @@ uint32_t ServiceClient<CascadeTypes...>::get_number_of_shards (
     return get_number_of_shards(opm.subgroup_type_index,opm.subgroup_index);
 }
 
+template <typename... CascadeTypes>
+template <typename SubgroupType>
+int32_t ServiceClient<CascadeTypes...>::get_my_shard(uint32_t subgroup_index) const {
+    if (!is_external_client()) {
+        return group_ptr->template get_my_shard<SubgroupType>(subgroup_index);
+    } else {
+        return -1;
+    }
+}
+
+template <typename... CascadeTypes>
+template <typename FirstType,typename SecondType, typename...RestTypes>
+int32_t ServiceClient<CascadeTypes...>::type_recursive_get_my_shard (
+        uint32_t type_index,uint32_t subgroup_index) const {
+    if (type_index == 0) {
+        return this->template get_my_shard<FirstType>(subgroup_index);
+    } else {
+        return this->template type_recursive_get_number_of_shards<SecondType,RestTypes...>(type_index-1,subgroup_index);
+    }
+}
+
+template <typename... CascadeTypes>
+template <typename LastType>
+int32_t ServiceClient<CascadeTypes...>::type_recursive_get_my_shard (
+        uint32_t type_index, uint32_t subgroup_index) const {
+    if (type_index == 0) {
+        return this->template get_my_shard<LastType>(subgroup_index);
+    } else {
+        throw derecho::derecho_exception(std::string(__PRETTY_FUNCTION__) + " type index is out of boundary");
+    }
+}
+
+template <typename... CascadeTypes>
+int32_t ServiceClient<CascadeTypes...>::get_my_shard (
+        uint32_t subgroup_type_index, uint32_t subgroup_index) const {
+    return this->template type_recursive_get_my_shard<CascadeTypes...>(subgroup_type_index,subgroup_index);
+}
+
+template <typename... CascadeTypes>
+int32_t ServiceClient<CascadeTypes...>::get_my_shard (
+        const std::string& object_pool_pathname) {
+    auto opm = find_object_pool(object_pool_pathname);
+    if (!opm.is_valid() || opm.is_null() || opm.deleted) {
+        throw derecho::derecho_exception("Failed to find object_pool:" + object_pool_pathname);
+    }
+    return get_my_shard(opm.subgroup_type_index,opm.subgroup_index);
+}
+
 template <typename... CascadeTypes>
 template <typename SubgroupType>
 void ServiceClient<CascadeTypes...>::set_member_selection_policy(uint32_t subgroup_index,uint32_t shard_index,

include/cascade/service.hpp

@@ -603,6 +603,9 @@ namespace cascade {
          *                              shard index.
          * - get_number_of_subgroups    returns the number of subgroups of a given type
          * - get_number_of_shards       returns the number of shards of a given subgroup
+         * - get_my_shard               returns the shard number that this node is a member of in the specific
+         *                              subgroup (by subgroup type and index), or -1 if this node is not a member
+         *                              of any shard in the specified subgroup.
          * During view change, the Client might experience failure if the member is gone. In such a case, the client needs
          * refresh its local member cache by calling get_shard_members.
          */
@@ -657,6 +660,31 @@ namespace cascade {
          * @param[in] object_pool_pathname  - the object pool name
          */
         uint32_t get_number_of_shards(const std::string& object_pool_pathname);
+
+        template <typename SubgroupType>
+        int32_t get_my_shard(uint32_t subgroup_index) const;
+    protected:
+        template <typename FirstType,typename SecondType, typename...RestTypes>
+        int32_t type_recursive_get_my_shard(uint32_t type_index, uint32_t subgroup_index) const;
+        template <typename LastType>
+        int32_t type_recursive_get_my_shard(uint32_t type_index, uint32_t subgroup_index) const;
+    public:
+        /**
+         * @fn int32_t get_my_shard(uint32_t subgroup_type_index, uint32_t subgroup_index) const
+         * @brief find the shard I belong to, given the subgroup specified by type and index.
+         * @param[in]   subgroup_type_index     - the type index of the subgroup type.
+         * @param[in]   subgroup_index          - the subgroup index in the given type.
+         * @return  The number of the shard, or -1 if current node is not in the specified subgroup.
+         */
+        int32_t get_my_shard(uint32_t subgroup_type_index, uint32_t subgroup_index) const;
+
+        /**
+         * @fn int32_t get_my_shard(const std::string& object_pool_pathname)
+         * @brief find the shard I belong to, given the object pool specified by object pool path name.
+         * @param[in]   object_pool_pathname    - the object pool path name.
+         * @return  The number of the shard, or -1 if current node is not in the specified subgroup.
+         */
+        int32_t get_my_shard(const std::string& object_pool_pathname);
 
         /**
          * Member selection policy control API.

src/applications/tests/user_defined_logic/console_printer_udl.cpp

@@ -26,6 +26,13 @@ class ConsolePrinterOCDPO: public OffCriticalDataPathObserver {
                               uint32_t worker_id) override {
         std::cout << "[console printer ocdpo]: I(" << worker_id << ") received an object with key=" << key_string 
                   << ", matching prefix=" << key_string.substr(0,prefix_length) << std::endl;
+        auto* typed_ctxt = dynamic_cast<DefaultCascadeContextType*>(ctxt);
+        std::string prefix = key_string.substr(0,prefix_length);
+        std::cout << "[console printer ocdpo]: my shard @" 
+                  << prefix 
+                  << " is:" 
+                  << typed_ctxt->get_service_client_ref().get_my_shard(prefix)
+                  << std::endl;
     }
 
     static std::shared_ptr<OffCriticalDataPathObserver> ocdpo_ptr;