[Backport] [ML] Remove allocators from cache after usage

docs/CHANGELOG.asciidoc

@@ -28,6 +28,13 @@
 
 //=== Regressions
 
+== {es} version 7.17.23
+
+=== Enhancements
+
+* Improve memory allocation management for JSON processing to reduce memory usage. 
+  (See {ml-pull}#2678[2678].)
+
 == {es} version 7.17.16
 
 === Enhancements

include/api/CJsonOutputWriter.h

@@ -266,6 +266,9 @@ class API_EXPORT CJsonOutputWriter {
     //! \p allocatorName A unique identifier for the allocator
     void pushAllocator(const std::string& allocatorName);
 
+    //! remove the allocator
+    void removeAllocator(const std::string& allocatorName);
+
     //! revert to using the previous allocator for JSON output processing
     void popAllocator();
 

include/core/CRapidJsonWriterBase.h

@@ -162,6 +162,15 @@ class CRapidJsonWriterBase
         return allocator;
     }
 
+    //! remove an allocator from the cache
+    void removeAllocator(const std::string& allocatorName) {
+        auto allocator = m_AllocatorCache.find(allocatorName);
+        if (allocator != m_AllocatorCache.end()) {
+            allocator->second.reset();
+            m_AllocatorCache.erase(allocator);
+        }
+    }
+
     rapidjson::MemoryPoolAllocator<>& getRawAllocator() const {
         return this->getAllocator()->get();
     }

include/core/CScopedRapidJsonPoolAllocator.h

@@ -32,14 +32,18 @@ class CScopedRapidJsonPoolAllocator {
     //! \p allocatorName Unique identifier for the allocator
     //! \p jsonOutputWriter JSON output writer that will make use of the allocator
     CScopedRapidJsonPoolAllocator(const std::string& allocatorName, T& writer)
-        : m_Writer(writer) {
+        : m_Writer(writer), m_AllocatorName(allocatorName) {
         m_Writer.pushAllocator(allocatorName);
     }
 
-    ~CScopedRapidJsonPoolAllocator() { m_Writer.popAllocator(); }
+    ~CScopedRapidJsonPoolAllocator() {
+        m_Writer.popAllocator();
+        m_Writer.removeAllocator(m_AllocatorName);
+    }
 
 private:
     T& m_Writer;
+    std::string m_AllocatorName;
 };
 }
 }

lib/api/CJsonOutputWriter.cc

@@ -825,6 +825,10 @@ void CJsonOutputWriter::pushAllocator(const std::string& allocatorName) {
     m_Writer.pushAllocator(allocatorName);
 }
 
+void CJsonOutputWriter::removeAllocator(const std::string& allocatorName) {
+    m_Writer.removeAllocator(allocatorName);
+}
+
 void CJsonOutputWriter::popAllocator() {
     m_Writer.popAllocator();
 }