liblog: add IF_ALOG_RATELIMIT
IF_ALOG_RATELIMIT()
ALOGE("Only one message globally using IF_ALOG_RATELIMIT()"
" in the process may appear ever ten seconds,"
" (%s)", strerror(errno));
static time_t last; /* initial state zero */
IF_ALOG_RATELIMIT_LOCAL(60, &last)
ALOGE("Only one message locally may appear every minute,"
" (%s)", strerror(errno));
These new calls are guaranteed not to affect the value of a
non-zero errno to simplify logging of errors. However, the
ALOGE calls in the above examples may update the errno value
upon their return.
Test: gTest liblog-unit-tests --gtest_filter=liblog.__android_log_ratelimit
Bug: 33535908
Change-Id: Id8cc192fc7d14504ffd418933cf88ae945c089f2
diff --git a/liblog/log_ratelimit.cpp b/liblog/log_ratelimit.cpp
new file mode 100644
index 0000000..dfd4b8f
--- /dev/null
+++ b/liblog/log_ratelimit.cpp
@@ -0,0 +1,86 @@
+/*
+** Copyright 2016, The Android Open Source Project
+**
+** 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.
+*/
+
+#include <errno.h>
+#include <pthread.h>
+#include <time.h>
+
+#include <log/log.h>
+
+#include "log_portability.h"
+
+// Global default if 'last' argument in __android_log_ratelimit is NULL
+static time_t g_last_clock;
+// Global above can not deal well with callers playing games with the
+// seconds argument, so we will also hold on to the maximum value
+// ever provided and use that to gain consistency. If the caller
+// provides their own 'last' argument, then they can play such games
+// of varying the 'seconds' argument to their pleasure.
+static time_t g_last_seconds;
+static const time_t last_seconds_default = 10;
+static const time_t last_seconds_max = 24 * 60 * 60; // maximum of a day
+static const time_t last_seconds_min = 2; // granularity
+// Lock to protect last_clock and last_seconds, but also 'last'
+// argument (not NULL) as supplied to __android_log_ratelimit.
+static pthread_mutex_t lock_ratelimit = PTHREAD_MUTEX_INITIALIZER;
+
+// if last is NULL, caller _must_ provide a consistent value for
+// seconds, otherwise we will take the maximum ever issued and hold
+// on to that. Preserves value of non-zero errno. Return -1 if we
+// can not acquire a lock, 0 if we are not to log a message, and 1
+// if we are ok to log a message. Caller should check > 0 for true.
+LIBLOG_ABI_PUBLIC int __android_log_ratelimit(time_t seconds, time_t* last) {
+ int save_errno = errno;
+
+ // Two reasons for trylock failure:
+ // 1. In a signal handler. Must prevent deadlock
+ // 2. Too many threads calling __android_log_ratelimit.
+ // Bonus to not print if they race here because that
+ // dovetails the goal of ratelimiting. One may print
+ // and the others will wait their turn ...
+ if (pthread_mutex_trylock(&lock_ratelimit)) {
+ if (save_errno) errno = save_errno;
+ return -1;
+ }
+
+ if (seconds == 0) {
+ seconds = last_seconds_default;
+ } else if (seconds < last_seconds_min) {
+ seconds = last_seconds_min;
+ } else if (seconds > last_seconds_max) {
+ seconds = last_seconds_max;
+ }
+
+ if (!last) {
+ if (g_last_seconds > seconds) {
+ seconds = g_last_seconds;
+ } else if (g_last_seconds < seconds) {
+ g_last_seconds = seconds;
+ }
+ last = &g_last_clock;
+ }
+
+ time_t now = time(NULL);
+ if ((now == (time_t)-1) || ((*last + seconds) > now)) {
+ pthread_mutex_unlock(&lock_ratelimit);
+ if (save_errno) errno = save_errno;
+ return 0;
+ }
+ *last = now;
+ pthread_mutex_unlock(&lock_ratelimit);
+ if (save_errno) errno = save_errno;
+ return 1;
+}