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_
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.
34 #define FB_LOG_EVERY_MS(severity, milli_interval) \
35 for (bool FB_LEM_once = true; FB_LEM_once; ) \
36 for (const auto FB_LEM_now = ::std::chrono::system_clock::now(); \
38 for (static ::std::chrono::system_clock::time_point FB_LEM_last; \
39 FB_LEM_once; FB_LEM_once = false) \
40 if (FB_LEM_now - FB_LEM_last < \
41 ::std::chrono::milliseconds(milli_interval)) { \
43 (FB_LEM_last = FB_LEM_now, LOG(severity))
47 #endif // FOLLY_LOGGING_H_