1/*
2 * Copyright 2012-present Facebook, Inc.
3 *
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
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
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.
15 */
16
17#pragma once
18
19#include <atomic>
20#include <chrono>
21
22#include <glog/logging.h>
23
24#ifndef FB_LOG_EVERY_MS
25/**
26 * Issues a LOG(severity) no more often than every
27 * milliseconds. Example:
28 *
29 * FB_LOG_EVERY_MS(INFO, 10000) << "At least ten seconds passed"
30 * " since you last saw this.";
31 *
32 * The implementation uses for statements to introduce variables in
33 * a nice way that doesn't mess surrounding statements. It is thread
34 * safe. Non-positive intervals will always log.
35 */
36#define FB_LOG_EVERY_MS(severity, milli_interval) \
37 for (decltype(milli_interval) FB_LEM_once = 1, \
38 FB_LEM_interval = (milli_interval); \
39 FB_LEM_once;) \
40 for (::std::chrono::milliseconds::rep FB_LEM_prev, \
41 FB_LEM_now = FB_LEM_interval <= 0 \
42 ? 0 \
43 : ::std::chrono::duration_cast<::std::chrono::milliseconds>( \
44 ::std::chrono::system_clock::now().time_since_epoch()) \
45 .count(); \
46 FB_LEM_once;) \
47 for (static ::std::atomic<::std::chrono::milliseconds::rep> FB_LEM_hist; \
48 FB_LEM_once; \
49 FB_LEM_once = 0) \
50 if (FB_LEM_interval > 0 && \
51 (FB_LEM_now - \
52 (FB_LEM_prev = \
53 FB_LEM_hist.load(std::memory_order_acquire)) < \
54 FB_LEM_interval || \
55 !FB_LEM_hist.compare_exchange_strong(FB_LEM_prev, FB_LEM_now))) { \
56 } else \
57 LOG(severity)
58
59#endif
60