2 * Copyright 2016 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.
21 #include <glog/logging.h>
23 #ifndef FB_LOG_EVERY_MS
25 * Issues a LOG(severity) no more often than every
26 * milliseconds. Example:
28 * FB_LOG_EVERY_MS(INFO, 10000) << "At least ten seconds passed"
29 * " since you last saw this.";
31 * The implementation uses for statements to introduce variables in
32 * a nice way that doesn't mess surrounding statements. It is thread
33 * safe. Non-positive intervals will always log.
35 #define FB_LOG_EVERY_MS(severity, milli_interval) \
36 for (decltype(milli_interval) FB_LEM_once = 1, \
37 FB_LEM_interval = (milli_interval); \
39 for (::std::chrono::milliseconds::rep FB_LEM_prev, FB_LEM_now = \
40 FB_LEM_interval <= 0 ? 0 : \
41 ::std::chrono::duration_cast< ::std::chrono::milliseconds>( \
42 ::std::chrono::system_clock::now().time_since_epoch() \
45 for (static ::std::atomic< ::std::chrono::milliseconds::rep> \
46 FB_LEM_hist; FB_LEM_once; FB_LEM_once = 0) \
47 if (FB_LEM_interval > 0 && \
48 (FB_LEM_now - (FB_LEM_prev = \
49 FB_LEM_hist.load(std::memory_order_acquire)) < \
51 !FB_LEM_hist.compare_exchange_strong(FB_LEM_prev,FB_LEM_now))) {\