PyLogAppender.h

/*
 * This file is part of log.
 *
 * Developed for the LSST Data Management System.
 * This product includes software developed by the LSST Project
 * (https://www.lsst.org).
 * See the COPYRIGHT file at the top-level directory of this distribution
 * for details of code ownership.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 
#ifndef LSST_LOG_PYLOGAPPENDER_H
#define LSST_LOG_PYLOGAPPENDER_H
 
// Python header has to be first to avoid compilation warnings
#include "Python.h"
 
#include <cstdint>
#include <map>
#include <mutex>
#include <string>
 
// Base class header
#include "log4cxx/appenderskeleton.h"
 
#include "log4cxx/helpers/object.h"
#include "PyObjectPtr.h"
 
namespace lsst::log::detail {
 
// This needs to be here for all LOG4CXX macros to work
using namespace log4cxx;

class PyLogAppender : public AppenderSkeleton {
public:
 
    DECLARE_LOG4CXX_OBJECT(PyLogAppender)
    BEGIN_LOG4CXX_CAST_MAP()
            LOG4CXX_CAST_ENTRY(PyLogAppender)
            LOG4CXX_CAST_ENTRY_CHAIN(AppenderSkeleton)
    END_LOG4CXX_CAST_MAP()
 
    // Make an instance
    PyLogAppender();
 
    // we do not support copying
    PyLogAppender(const PyLogAppender&) = delete;
    PyLogAppender& operator=(const PyLogAppender&) = delete;

    void append(const spi::LoggingEventPtr& event, log4cxx::helpers::Pool& p) override;

    void close() override;

    bool requiresLayout() const override;

    void setOption(const LogString &option, const LogString &value) override;
 
private:
 
    // cache entry type
    struct LRUEntry {
        PyObjectPtr logger;
        uint32_t age = 0;
    };
 
    using LRUCache = std::map<std::string, LRUEntry>;
 
    PyObjectPtr _getLogger;  // logging.getLogger() method
    PyObjectPtr _mdc_class;  // lsst.log.MDCDict class
    std::mutex _cache_mutex;
    uint32_t _lru_age = 0;
    LRUCache _cache;  // LRU cache for loggers
};
 
} // namespace lsst::log::detail
 
#endif // LSST_LOG_PYLOGAPPENDER_H