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Add ENVOY_LOG_PERIODIC #12961

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merged 7 commits into from
Sep 9, 2020
Merged

Add ENVOY_LOG_PERIODIC #12961

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42a4eba
Add ENVOY_LOG_PERIODIC
oschaaf Sep 2, 2020
85003d4
Review feedback
oschaaf Sep 4, 2020
aca8716
Amend comment
oschaaf Sep 4, 2020
541e555
Review feedback II
oschaaf Sep 4, 2020
15819e6
review feedback: uint64 where it's not implied
oschaaf Sep 8, 2020
cc387f0
Merge remote-tracking branch 'upstream/master' into envoy-log-periodic
oschaaf Sep 9, 2020
efbabc5
Fix platform issue, eliminate sleep() call.
oschaaf Sep 9, 2020
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44 changes: 35 additions & 9 deletions source/common/common/logger.h
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
#pragma once

#include <bitset>
#include <chrono>
#include <cstdint>
#include <memory>
#include <string>
Expand Down Expand Up @@ -403,9 +404,11 @@ template <Id id> class Loggable {

#define ENVOY_LOG_FIRST_N(LEVEL, N, ...) \
do { \
static auto* countdown = new std::atomic<uint64_t>(); \
if (countdown->fetch_add(1) < N) { \
ENVOY_LOG(LEVEL, ##__VA_ARGS__); \
if (ENVOY_LOG_COMP_LEVEL(ENVOY_LOGGER(), LEVEL)) { \
static auto* countdown = new std::atomic<uint64_t>(); \
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if (countdown->fetch_add(1) < N) { \
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The counter may eventually overflow. ;)

ENVOY_LOG(LEVEL, ##__VA_ARGS__); \
} \
} \
} while (0)

Expand All @@ -416,17 +419,40 @@ template <Id id> class Loggable {

#define ENVOY_LOG_EVERY_NTH(LEVEL, N, ...) \
do { \
static auto* count = new std::atomic<uint64_t>(); \
if ((count->fetch_add(1) % N) == 0) { \
ENVOY_LOG(LEVEL, ##__VA_ARGS__); \
if (ENVOY_LOG_COMP_LEVEL(ENVOY_LOGGER(), LEVEL)) { \
static auto* count = new std::atomic<uint64_t>(); \
if ((count->fetch_add(1) % N) == 0) { \
ENVOY_LOG(LEVEL, ##__VA_ARGS__); \
} \
} \
} while (0)

#define ENVOY_LOG_EVERY_POW_2(LEVEL, ...) \
do { \
static auto* count = new std::atomic<uint64_t>(); \
if (std::bitset<64>(1 + count->fetch_add(1)).count() == 1) { \
ENVOY_LOG(LEVEL, ##__VA_ARGS__); \
if (ENVOY_LOG_COMP_LEVEL(ENVOY_LOGGER(), LEVEL)) { \
static auto* count = new std::atomic<uint64_t>(); \
if (std::bitset<64>(1 + count->fetch_add(1)).count() == 1) { \
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How about this kind of thing:

auto bits = count->fetch_add(1);
if ( bits && !(bits & (bits-1)) )

The unsigned type here is fine.
Any bitwise && of any power of 2 with a number less by 1 will give 0. No need to involve std::bitset and we get rid of that magic number too.

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@oschaaf oschaaf Sep 4, 2020 •
edited
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I went with std::bitset because I think I remember it being compiled to something fast under the hood (__builtin_popcount?); but also - and this is probably subjective - I find it easier to grok. The +1 deserves a comment, e.g. // +1 because the first hit needs to be logged, but this imho this also wouldn't hurt with the -1 (or maybe the whole expression) in the variant you propose, depending on who the audience is?

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Ok. Let's leave it be for now, no problemo. bitset.count() is readable, true.
Yes, __builtin_popcount for GCC and for LLVM it's a similar thing; which translates, depending on the platform, into about 2-3 cpu intructions, or into Kernighan’s algorithm (latter is slower than this little trick).

But you're right. To follow readibility guidelines i should've suggested a lambda at least here, sth like auto is_exactly_one_bit_set = [](const uint64_t bits) { return bits && !(bits & (bits-1)); };.

ENVOY_LOG(LEVEL, ##__VA_ARGS__); \
} \
} \
} while (0)

// This is to get us to pass the format check. We reference a real-world time source here.
// We'd have to introduce a singleton for a time source here, and consensus was that avoiding
// that is preferable.
using t_logclock = std::chrono::steady_clock; // NOLINT

#define ENVOY_LOG_PERIODIC(LEVEL, CHRONO_DURATION, ...) \
do { \
if (ENVOY_LOG_COMP_LEVEL(ENVOY_LOGGER(), LEVEL)) { \
static auto* last_hit = new std::atomic<uint64_t>(); \
auto last = last_hit->load(); \
const auto now = t_logclock::now().time_since_epoch().count(); \
if ((now - last) > \
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std::chrono::duration_cast<std::chrono::nanoseconds>(CHRONO_DURATION).count() && \
last_hit->compare_exchange_strong(last, now)) { \
ENVOY_LOG(LEVEL, ##__VA_ARGS__); \
} \
} \
} while (0)

Expand Down
22 changes: 18 additions & 4 deletions test/common/common/log_macros_test.cc
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
#include <chrono>
#include <functional>
#include <iostream>
#include <string>
Expand All @@ -15,6 +16,8 @@

namespace Envoy {

using namespace std::chrono_literals;

class TestFilterLog : public Logger::Loggable<Logger::Id::filter> {
public:
void logMessage() {
Expand Down Expand Up @@ -148,6 +151,7 @@ TEST(Logger, SparseLogMacros) {
void logSomethingThrice() { ENVOY_LOG_FIRST_N(error, 3, "foo4 '{}'", evaluations()++); }
void logEverySeventh() { ENVOY_LOG_EVERY_NTH(error, 7, "foo5 '{}'", evaluations()++); }
void logEveryPow2() { ENVOY_LOG_EVERY_POW_2(error, "foo6 '{}'", evaluations()++); }
void logEverySecond() { ENVOY_LOG_PERIODIC(error, 1s, "foo7 '{}'", evaluations()++); }
std::atomic<int32_t>& evaluations() { MUTABLE_CONSTRUCT_ON_FIRST_USE(std::atomic<int32_t>); };
};
constexpr uint32_t kNumThreads = 100;
Expand Down Expand Up @@ -185,11 +189,21 @@ TEST(Logger, SparseLogMacros) {
// We should log on 2, 4, 8, 16, 32, 64, which means we can expect to add 6 more evaluations.
EXPECT_EQ(27, helper.evaluations());

spamCall([&helper]() { helper.logEverySecond(); }, kNumThreads);
// First call ought to evaluate.
EXPECT_EQ(28, helper.evaluations());

// We expect one log entry / second. Therefore each spamCall ought to result in one
// more evaluation. This depends on real time and not sim time, hopefully 1 second
// is enough to not introduce flakes in practice.
sleep(1);
spamCall([&helper]() { helper.logEverySecond(); }, kNumThreads);
EXPECT_EQ(29, helper.evaluations());

spamCall([&helper]() { helper.logSomethingBelowLogLevelOnce(); }, kNumThreads);
// Without fine-grained logging, we shouldn't observe additional argument evaluations
// for log lines below the configured log level.
// TODO(#12885): fancy logger shouldn't always evaluate variadic macro arguments.
EXPECT_EQ(::Envoy::Logger::Context::useFancyLogger() ? 28 : 27, helper.evaluations());
// We shouldn't observe additional argument evaluations for log lines below the configured
// log level.
EXPECT_EQ(29, helper.evaluations());
}

TEST(RegistryTest, LoggerWithName) {
Expand Down