jit_executor_context_pool.h

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/*
 * Copyright (c) 2024, 2025, Oracle and/or its affiliates.
 *
 * This program is free software; you can redistribute it and/or modify
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 * as published by the Free Software Foundation.
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
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#ifndef ROUTER_SRC_JIT_EXECUTOR_INCLUDE_MYSQLROUTER_JIT_EXECUTOR_CONTEXT_POOL_H_
#define ROUTER_SRC_JIT_EXECUTOR_INCLUDE_MYSQLROUTER_JIT_EXECUTOR_CONTEXT_POOL_H_
 
#include <atomic>
#include <condition_variable>
#include <deque>
#include <functional>
#include <memory>
#include <mutex>
#include <stdexcept>
#include <string>
#include <thread>
#include <vector>
 
#include "mysql/harness/logging/logging.h"
#include "mysql/harness/mpsc_queue.h"
#include "mysql/harness/scoped_callback.h"
#include "mysqlrouter/jit_executor_context.h"
#include "mysqlrouter/jit_executor_context_handle.h"
#include "mysqlrouter/jit_executor_value.h"
#include "mysqlrouter/polyglot_file_system.h"
 
namespace jit_executor {
 
IMPORT_LOG_FUNCTIONS()
 
class PooledContextHandle;
class CommonContext;
class ContextPool final {
 public:
  ContextPool(CommonContext *common_context);
 
  ~ContextPool();
 
  std::shared_ptr<PooledContextHandle> get_context();
  void teardown();
 
 private:
  friend class PooledContextHandle;
  void release(IContext *ctx);
  void release_thread();
 
  void increase_active_items(bool created);
  void decrease_active_items(bool destroyed);
 
  bool can_create();
  IContext *create();
  void destroy(IContext *ctx);
 
  void do_release(IContext *ctx);
  void discard(IContext *ctx);
  void do_teardown();
  IContext *create(size_t id);
  IContext *get();
 
  CommonContext *m_common_context;
  mysql_harness::WaitingMPSCQueue<IContext *> m_release_queue;
  std::unique_ptr<std::thread> m_release_thread;
 
  std::mutex m_mutex;
  std::condition_variable m_item_availability;
  bool m_teardown = false;
  std::deque<IContext *> m_items;
  size_t m_created_items = 0;               // total created contexts
  size_t m_active_items = 0;                // alive contexts
  std::atomic<size_t> m_running_items = 0;  // contexts in use
  std::atomic<size_t> m_queued_items = 0;   // contexts in the release queue
 
  std::atomic_bool m_forbid_context_creation = false;
};
 
/**
 * A wrapper that will return a context to the pool as soon as it is released
 */
class PooledContextHandle : public IContextHandle {
 public:
  PooledContextHandle(ContextPool *pool, IContext *ctx)
      : m_pool{pool}, m_context{ctx} {}
  ~PooledContextHandle() override { m_pool->release(m_context); }
 
  IContext *get() override { return m_context; }
 
 private:
  ContextPool *m_pool;
  IContext *m_context;
};
 
}  // namespace jit_executor
 
#endif  // ROUTER_SRC_JIT_EXECUTOR_INCLUDE_MYSQLROUTER_JIT_EXECUTOR_CONTEXT_POOL_H_