mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-12-16 19:32:07 +00:00
236 lines
8.6 KiB
C++
236 lines
8.6 KiB
C++
#include "QueryProfiler.h"
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#include <random>
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#include <common/Pipe.h>
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#include <common/phdr_cache.h>
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#include <common/config_common.h>
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#include <Common/StackTrace.h>
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#include <common/StringRef.h>
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#include <common/logger_useful.h>
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#include <Common/CurrentThread.h>
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#include <Common/Exception.h>
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#include <Common/thread_local_rng.h>
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#include <IO/WriteHelpers.h>
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#include <IO/WriteBufferFromFileDescriptor.h>
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namespace ProfileEvents
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{
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extern const Event QueryProfilerCannotWriteTrace;
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extern const Event QueryProfilerSignalOverruns;
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}
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namespace DB
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{
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extern LazyPipe trace_pipe;
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namespace
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{
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/** Write to file descriptor but drop the data if write would block or fail.
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* To use within signal handler. Motivating example: a signal handler invoked during execution of malloc
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* should not block because some mutex (or even worse - a spinlock) may be held.
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*/
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class WriteBufferDiscardOnFailure : public WriteBufferFromFileDescriptor
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{
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protected:
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void nextImpl() override
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{
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size_t bytes_written = 0;
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while (bytes_written != offset())
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{
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ssize_t res = ::write(fd, working_buffer.begin() + bytes_written, offset() - bytes_written);
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if ((-1 == res || 0 == res) && errno != EINTR)
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{
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ProfileEvents::increment(ProfileEvents::QueryProfilerCannotWriteTrace);
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break; /// Discard
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}
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if (res > 0)
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bytes_written += res;
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}
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}
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public:
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using WriteBufferFromFileDescriptor::WriteBufferFromFileDescriptor;
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~WriteBufferDiscardOnFailure() override {}
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};
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/// Normally query_id is a UUID (string with a fixed length) but user can provide custom query_id.
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/// Thus upper bound on query_id length should be introduced to avoid buffer overflow in signal handler.
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constexpr size_t QUERY_ID_MAX_LEN = 1024;
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thread_local size_t write_trace_iteration = 0;
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void writeTraceInfo(TimerType timer_type, int /* sig */, siginfo_t * info, void * context)
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{
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/// Quickly drop if signal handler is called too frequently.
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/// Otherwise we may end up infinitelly processing signals instead of doing any useful work.
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++write_trace_iteration;
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if (info && info->si_overrun > 0)
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{
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/// But pass with some frequency to avoid drop of all traces.
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if (write_trace_iteration % info->si_overrun == 0)
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{
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ProfileEvents::increment(ProfileEvents::QueryProfilerSignalOverruns, info->si_overrun);
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}
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else
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{
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ProfileEvents::increment(ProfileEvents::QueryProfilerSignalOverruns, info->si_overrun + 1);
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return;
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}
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}
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constexpr size_t buf_size = sizeof(char) + // TraceCollector stop flag
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8 * sizeof(char) + // maximum VarUInt length for string size
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QUERY_ID_MAX_LEN * sizeof(char) + // maximum query_id length
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sizeof(UInt8) + // number of stack frames
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sizeof(StackTrace::Frames) + // collected stack trace, maximum capacity
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sizeof(TimerType) + // timer type
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sizeof(UInt32); // thread_number
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char buffer[buf_size];
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WriteBufferDiscardOnFailure out(trace_pipe.fds_rw[1], buf_size, buffer);
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StringRef query_id = CurrentThread::getQueryId();
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query_id.size = std::min(query_id.size, QUERY_ID_MAX_LEN);
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UInt32 thread_number = CurrentThread::get().thread_number;
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const auto signal_context = *reinterpret_cast<ucontext_t *>(context);
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const StackTrace stack_trace(signal_context);
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writeChar(false, out);
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writeStringBinary(query_id, out);
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size_t stack_trace_size = stack_trace.getSize();
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size_t stack_trace_offset = stack_trace.getOffset();
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writeIntBinary(UInt8(stack_trace_size - stack_trace_offset), out);
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for (size_t i = stack_trace_offset; i < stack_trace_size; ++i)
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writePODBinary(stack_trace.getFrames()[i], out);
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writePODBinary(timer_type, out);
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writePODBinary(thread_number, out);
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out.next();
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}
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[[maybe_unused]] const UInt32 TIMER_PRECISION = 1e9;
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}
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namespace ErrorCodes
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{
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extern const int CANNOT_MANIPULATE_SIGSET;
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extern const int CANNOT_SET_SIGNAL_HANDLER;
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extern const int CANNOT_CREATE_TIMER;
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extern const int CANNOT_SET_TIMER_PERIOD;
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extern const int CANNOT_DELETE_TIMER;
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}
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template <typename ProfilerImpl>
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QueryProfilerBase<ProfilerImpl>::QueryProfilerBase(const Int32 thread_id, const int clock_type, UInt32 period, const int pause_signal_)
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: log(&Logger::get("QueryProfiler"))
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, pause_signal(pause_signal_)
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{
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#if USE_INTERNAL_UNWIND_LIBRARY
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/// Sanity check.
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if (!hasPHDRCache())
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throw Exception("QueryProfiler cannot be used without PHDR cache, that is not available for TSan build", ErrorCodes::NOT_IMPLEMENTED);
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/// Too high frequency can introduce infinite busy loop of signal handlers. We will limit maximum frequency (with 1000 signals per second).
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if (period < 1000000)
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period = 1000000;
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struct sigaction sa{};
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sa.sa_sigaction = ProfilerImpl::signalHandler;
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sa.sa_flags = SA_SIGINFO | SA_RESTART;
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if (sigemptyset(&sa.sa_mask))
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throwFromErrno("Failed to clean signal mask for query profiler", ErrorCodes::CANNOT_MANIPULATE_SIGSET);
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if (sigaddset(&sa.sa_mask, pause_signal))
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throwFromErrno("Failed to add signal to mask for query profiler", ErrorCodes::CANNOT_MANIPULATE_SIGSET);
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if (sigaction(pause_signal, &sa, previous_handler))
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throwFromErrno("Failed to setup signal handler for query profiler", ErrorCodes::CANNOT_SET_SIGNAL_HANDLER);
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try
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{
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struct sigevent sev;
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sev.sigev_notify = SIGEV_THREAD_ID;
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sev.sigev_signo = pause_signal;
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#if defined(__FreeBSD__)
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sev._sigev_un._threadid = thread_id;
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#else
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sev._sigev_un._tid = thread_id;
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#endif
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if (timer_create(clock_type, &sev, &timer_id))
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throwFromErrno("Failed to create thread timer", ErrorCodes::CANNOT_CREATE_TIMER);
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/// Randomize offset as uniform random value from 0 to period - 1.
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/// It will allow to sample short queries even if timer period is large.
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/// (For example, with period of 1 second, query with 50 ms duration will be sampled with 1 / 20 probability).
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/// It also helps to avoid interference (moire).
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UInt32 period_rand = std::uniform_int_distribution<UInt32>(0, period)(thread_local_rng);
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struct timespec interval{.tv_sec = period / TIMER_PRECISION, .tv_nsec = period % TIMER_PRECISION};
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struct timespec offset{.tv_sec = period_rand / TIMER_PRECISION, .tv_nsec = period_rand % TIMER_PRECISION};
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struct itimerspec timer_spec = {.it_interval = interval, .it_value = offset};
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if (timer_settime(timer_id, 0, &timer_spec, nullptr))
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throwFromErrno("Failed to set thread timer period", ErrorCodes::CANNOT_SET_TIMER_PERIOD);
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}
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catch (...)
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{
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tryCleanup();
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throw;
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}
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#else
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UNUSED(thread_id);
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UNUSED(clock_type);
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UNUSED(period);
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UNUSED(pause_signal);
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throw Exception("QueryProfiler cannot work with stock libunwind", ErrorCodes::NOT_IMPLEMENTED);
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#endif
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}
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template <typename ProfilerImpl>
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QueryProfilerBase<ProfilerImpl>::~QueryProfilerBase()
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{
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tryCleanup();
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}
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template <typename ProfilerImpl>
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void QueryProfilerBase<ProfilerImpl>::tryCleanup()
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{
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if (timer_id != nullptr && timer_delete(timer_id))
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LOG_ERROR(log, "Failed to delete query profiler timer " + errnoToString(ErrorCodes::CANNOT_DELETE_TIMER));
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if (previous_handler != nullptr && sigaction(pause_signal, previous_handler, nullptr))
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LOG_ERROR(log, "Failed to restore signal handler after query profiler " + errnoToString(ErrorCodes::CANNOT_SET_SIGNAL_HANDLER));
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}
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template class QueryProfilerBase<QueryProfilerReal>;
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template class QueryProfilerBase<QueryProfilerCpu>;
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QueryProfilerReal::QueryProfilerReal(const Int32 thread_id, const UInt32 period)
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: QueryProfilerBase(thread_id, CLOCK_REALTIME, period, SIGUSR1)
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{}
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void QueryProfilerReal::signalHandler(int sig, siginfo_t * info, void * context)
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{
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writeTraceInfo(TimerType::Real, sig, info, context);
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}
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QueryProfilerCpu::QueryProfilerCpu(const Int32 thread_id, const UInt32 period)
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: QueryProfilerBase(thread_id, CLOCK_THREAD_CPUTIME_ID, period, SIGUSR2)
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{}
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void QueryProfilerCpu::signalHandler(int sig, siginfo_t * info, void * context)
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{
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writeTraceInfo(TimerType::Cpu, sig, info, context);
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}
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}
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