2 * Copyright 2014 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 #ifndef FOLLY_LOGGING_H_
18 #define FOLLY_LOGGING_H_
22 #include <glog/logging.h>
24 #ifndef FB_LOG_EVERY_MS
26 * Issues a LOG(severity) no more often than every
27 * milliseconds. Example:
29 * FB_LOG_EVERY_MS(INFO, 10000) << "At least ten seconds passed"
30 * " since you last saw this.";
32 * The implementation uses for statements to introduce variables in
33 * a nice way that doesn't mess surrounding statements. It is thread
36 #define FB_LOG_EVERY_MS(severity, milli_interval) \
37 for (bool FB_LEM_once = true; FB_LEM_once; ) \
38 for (::std::chrono::milliseconds::rep FB_LEM_prev, FB_LEM_now = \
39 ::std::chrono::duration_cast< ::std::chrono::milliseconds>( \
40 ::std::chrono::system_clock::now().time_since_epoch() \
43 for (static ::std::atomic< ::std::chrono::milliseconds::rep> \
44 FB_LEM_hist; FB_LEM_once; FB_LEM_once = false) \
45 if (FB_LEM_now - (FB_LEM_prev = \
46 FB_LEM_hist.load(std::memory_order_acquire)) < \
48 !FB_LEM_hist.compare_exchange_strong(FB_LEM_prev, FB_LEM_now)) { \
54 #endif // FOLLY_LOGGING_H_