Split raft/core/logger

cpp/include/raft/core/logger-ext.hpp

@@ -0,0 +1,128 @@
+/*
+ * Copyright (c) 2022-2023, NVIDIA CORPORATION.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+#include <memory>         // std::unique_ptr
+#include <string>         // std::string
+#include <unordered_map>  // std::unordered_map
+
+namespace raft {
+
+static const std::string RAFT_NAME = "raft";
+static const std::string default_log_pattern("[%L] [%H:%M:%S.%f] %v");
+
+/**
+ * @brief The main Logging class for raft library.
+ *
+ * This class acts as a thin wrapper over the underlying `spdlog` interface. The
+ * design is done in this way in order to avoid us having to also ship `spdlog`
+ * header files in our installation.
+ *
+ * @todo This currently only supports logging to stdout. Need to add support in
+ *       future to add custom loggers as well [Issue #2046]
+ */
+class logger {
+ public:
+  // @todo setting the logger once per process with
+  logger(std::string const& name_ = "");
+  /**
+   * @brief Singleton method to get the underlying logger object
+   *
+   * @return the singleton logger object
+   */
+  static logger& get(std::string const& name = "");
+
+  /**
+   * @brief Set the logging level.
+   *
+   * Only messages with level equal or above this will be printed
+   *
+   * @param[in] level logging level
+   *
+   * @note The log level will actually be set only if the input is within the
+   *       range [RAFT_LEVEL_TRACE, RAFT_LEVEL_OFF]. If it is not, then it'll
+   *       be ignored. See documentation of decisiontree for how this gets used
+   */
+  void set_level(int level);
+
+  /**
+   * @brief Set the logging pattern
+   *
+   * @param[in] pattern the pattern to be set. Refer this link
+   *                    https://github.com/gabime/spdlog/wiki/3.-Custom-formatting
+   *                    to know the right syntax of this pattern
+   */
+  void set_pattern(const std::string& pattern);
+
+  /**
+   * @brief Register a callback function to be run in place of usual log call
+   *
+   * @param[in] callback the function to be run on all logged messages
+   */
+  void set_callback(void (*callback)(int lvl, const char* msg));
+
+  /**
+   * @brief Register a flush function compatible with the registered callback
+   *
+   * @param[in] flush the function to use when flushing logs
+   */
+  void set_flush(void (*flush)());
+
+  /**
+   * @brief Tells whether messages will be logged for the given log level
+   *
+   * @param[in] level log level to be checked for
+   * @return true if messages will be logged for this level, else false
+   */
+  bool should_log_for(int level) const;
+  /**
+   * @brief Query for the current log level
+   *
+   * @return the current log level
+   */
+  int get_level() const;
+
+  /**
+   * @brief Get the current logging pattern
+   * @return the pattern
+   */
+  std::string get_pattern() const;
+
+  /**
+   * @brief Main logging method
+   *
+   * @param[in] level logging level of this message
+   * @param[in] fmt   C-like format string, followed by respective params
+   */
+  void log(int level, const char* fmt, ...);
+
+  /**
+   * @brief Flush logs by calling flush on underlying logger
+   */
+  void flush();
+
+  ~logger();
+
+ private:
+  logger();
+  // pimpl pattern:
+  // https://learn.microsoft.com/en-us/cpp/cpp/pimpl-for-compile-time-encapsulation-modern-cpp?view=msvc-170
+  class impl;
+  std::unique_ptr<impl> pimpl;
+  static inline std::unordered_map<std::string, std::shared_ptr<raft::logger>> log_map;
+};  // class logger
+
+};  // namespace raft