JSON: add a thread local memory resource ptr

The resource and its heap will be used by a stateless allocator for all
parse operations.

The heap is initialized at engine shard initialization.

Signed-off-by: Abhijat Malviya <[email protected]>

Author: abhijat

src/core/json/json_object.cc

@@ -11,6 +11,10 @@ using namespace std;
 
 namespace dfly {
 
+void InitJSONTLHeap(PMR_NS::memory_resource* mr) {
+  detail::tl_mr = mr;
+}
+
 optional<JsonType> JsonFromString(string_view input, PMR_NS::memory_resource* mr) {
   error_code ec;
   auto JsonErrorHandler = [](json_errc ec, const ser_context&) {

src/core/json/json_object.h

@@ -21,6 +21,14 @@
 
 namespace dfly {
 
+namespace detail {
+
+inline thread_local PMR_NS::memory_resource* tl_mr = nullptr;
+
+}
+
+void InitJSONTLHeap(PMR_NS::memory_resource* mr);
+
 using JsonType = jsoncons::pmr::json;
 
 // Build a json object from string. If the string is not legal json, will return nullopt

src/server/engine_shard.cc

@@ -422,6 +422,7 @@ void EngineShard::InitThreadLocal(ProactorBase* pb) {
 
   CompactObj::InitThreadLocal(shard_->memory_resource());
   SmallString::InitThreadLocal(data_heap);
+  InitJSONTLHeap(shard_->memory_resource());
 
   shard_->shard_search_indices_ = std::make_unique<ShardDocIndices>();
 }