YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

// Licensed to the Apache Software Foundation (ASF) under one

// or more contributor license agreements.  See the NOTICE file

// distributed with this work for additional information

// regarding copyright ownership.  The ASF licenses this file

// to you 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.

//

// The following only applies to changes made to this file as part of YugaByte development.

//

// Portions Copyright (c) YugaByte, Inc.

//

// 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.

//

// This header defines the following macro:

//

// VLOG_AND_TRACE(category, vlevel)

//

//   Write a log message to VLOG(vlevel) as well as the current

//   trace event buffer as an "INSTANT" trace event type. If the

//   given vlog level is not enabled, this will still result in a

//   trace buffer entry.

//

//   The provided 'category' should be a trace event category, which

//   allows the users to filter which trace events to enable.

//   For example:

//

//    VLOG_AND_TRACE("my_subsystem", 1) << "This always shows up in trace buffers "

//        << "but only shows up in the log if VLOG(1) level logging is enabled.";

//

//   Most VLOG(1) level log messages are reasonable to use this macro.

//   Note that there is slightly more overhead to this macro as opposed

//   to just using VLOG(1).

//

//   Note that, like VLOG(n), this macro avoids evaluating its arguments unless

//   either trace recording or VLOG(n) is enabled. In the case that both are enabled,

//   the arguments are only evaluated once.

//

#ifndef YB_DEBUG_TRACE_LOGGING_H

#define YB_DEBUG_TRACE_LOGGING_H

#include <glog/logging.h>

#include <string>

#include "yb/gutil/macros.h"

#include "yb/util/debug/trace_event.h"

// The inner workings of these macros are a bit arcane:

// - We make use of the fact that a block can be embedded within a ternary expression.

//   This allows us to determine whether the trace event is enabled before we decide

//   to evaluate the arguments.

// - We have to use google::LogMessageVoidify so that we can put 'void(0)' on one side

//   of the ternary expression and the log stream on the other. This technique is

//   cribbed from glog/logging.h.

#define VLOG_AND_TRACE_INTERNAL(category, vlevel) \

  yb::debug::TraceVLog(__FILE__, __LINE__, category, VLOG_IS_ON(vlevel)).stream()

#define VLOG_AND_TRACE(category, vlevel)                              \

  !( {                                                                \

      bool enabled;                                                   \

      TRACE_EVENT_CATEGORY_GROUP_ENABLED(category, &enabled);         \

      enabled || VLOG_IS_ON(vlevel);                                  \

    } ) ? static_cast<void>(0) :                                      \

          google::LogMessageVoidify() & VLOG_AND_TRACE_INTERNAL(category, vlevel)

namespace yb {

namespace debug {

class TraceVLog {

 public:

  TraceVLog(const char* file, int line, const char* category, bool do_vlog)

    : sink_(category),

      google_msg_(file, line, google::GLOG_INFO, &sink_, do_vlog) {

  }

  std::ostream& stream() {

    return google_msg_.stream();

  }

 private:

  class TraceLogSink : public google::LogSink {

   public:

    explicit TraceLogSink(const char* category) : category_(category) {}

    void send(google::LogSeverity severity, const char* full_filename,

              const char* base_filename, int line,

              const struct ::tm* tm_time, const char* message,

              size_t message_len) override {

      // Rather than calling TRACE_EVENT_INSTANT here, we have to do it from

      // the destructor. This is because glog holds its internal mutex while

      // calling send(). So, if we try to use TRACE_EVENT here, and --trace_to_console

      // is enabled, then we'd end up calling back into glog when its lock is already

      // held. glog isn't re-entrant, so that causes a crash.

      //

      // By just storing the string here, and then emitting the trace in the dtor,

      // we defer the tracing until the google::LogMessage has destructed and the

      // glog lock is available again.

      str_ = ToString(severity, base_filename, line,

                      tm_time, message, message_len);

    }

    virtual ~TraceLogSink() {

      TRACE_EVENT_INSTANT1(category_, "vlog", TRACE_EVENT_SCOPE_THREAD,

                           "msg", str_);

    }

   private:

    const char* const category_;

    std::string str_;

  };

  TraceLogSink sink_;

  google::LogMessage google_msg_;

};

} // namespace debug

} // namespace yb

#endif /* YB_DEBUG_TRACE_LOGGING_H */