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#include "tracing/node_trace_buffer.h"
#include <memory>
#include "util-inl.h"
namespace node {
namespace tracing {
InternalTraceBuffer::InternalTraceBuffer(size_t max_chunks, uint32_t id,
Agent* agent)
: flushing_(false), max_chunks_(max_chunks),
agent_(agent), id_(id) {
chunks_.resize(max_chunks);
}
TraceObject* InternalTraceBuffer::AddTraceEvent(uint64_t* handle) {
Mutex::ScopedLock scoped_lock(mutex_);
// Create new chunk if last chunk is full or there is no chunk.
if (total_chunks_ == 0 || chunks_[total_chunks_ - 1]->IsFull()) {
auto& chunk = chunks_[total_chunks_++];
if (chunk) {
chunk->Reset(current_chunk_seq_++);
} else {
chunk = std::make_unique<TraceBufferChunk>(current_chunk_seq_++);
}
}
auto& chunk = chunks_[total_chunks_ - 1];
size_t event_index;
TraceObject* trace_object = chunk->AddTraceEvent(&event_index);
*handle = MakeHandle(total_chunks_ - 1, chunk->seq(), event_index);
return trace_object;
}
TraceObject* InternalTraceBuffer::GetEventByHandle(uint64_t handle) {
Mutex::ScopedLock scoped_lock(mutex_);
if (handle == 0) {
// A handle value of zero never has a trace event associated with it.
return nullptr;
}
size_t chunk_index, event_index;
uint32_t buffer_id, chunk_seq;
ExtractHandle(handle, &buffer_id, &chunk_index, &chunk_seq, &event_index);
if (buffer_id != id_ || chunk_index >= total_chunks_) {
// Either the chunk belongs to the other buffer, or is outside the current
// range of chunks loaded in memory (the latter being true suggests that
// the chunk has already been flushed and is no longer in memory.)
return nullptr;
}
auto& chunk = chunks_[chunk_index];
if (chunk->seq() != chunk_seq) {
// Chunk is no longer in memory.
return nullptr;
}
return chunk->GetEventAt(event_index);
}
void InternalTraceBuffer::Flush(bool blocking) {
{
Mutex::ScopedLock scoped_lock(mutex_);
if (total_chunks_ > 0) {
flushing_ = true;
for (size_t i = 0; i < total_chunks_; ++i) {
auto& chunk = chunks_[i];
for (size_t j = 0; j < chunk->size(); ++j) {
TraceObject* trace_event = chunk->GetEventAt(j);
// Another thread may have added a trace that is yet to be
// initialized. Skip such traces.
// https://github.com/nodejs/node/issues/21038.
if (trace_event->name()) {
agent_->AppendTraceEvent(trace_event);
}
}
}
total_chunks_ = 0;
flushing_ = false;
}
}
agent_->Flush(blocking);
}
uint64_t InternalTraceBuffer::MakeHandle(
size_t chunk_index, uint32_t chunk_seq, size_t event_index) const {
return ((static_cast<uint64_t>(chunk_seq) * Capacity() +
chunk_index * TraceBufferChunk::kChunkSize + event_index) << 1) + id_;
}
void InternalTraceBuffer::ExtractHandle(
uint64_t handle, uint32_t* buffer_id, size_t* chunk_index,
uint32_t* chunk_seq, size_t* event_index) const {
*buffer_id = static_cast<uint32_t>(handle & 0x1);
handle >>= 1;
*chunk_seq = static_cast<uint32_t>(handle / Capacity());
size_t indices = handle % Capacity();
*chunk_index = indices / TraceBufferChunk::kChunkSize;
*event_index = indices % TraceBufferChunk::kChunkSize;
}
NodeTraceBuffer::NodeTraceBuffer(size_t max_chunks,
Agent* agent, uv_loop_t* tracing_loop)
: tracing_loop_(tracing_loop),
buffer1_(max_chunks, 0, agent),
buffer2_(max_chunks, 1, agent) {
current_buf_.store(&buffer1_);
flush_signal_.data = this;
int err = uv_async_init(tracing_loop_, &flush_signal_,
NonBlockingFlushSignalCb);
CHECK_EQ(err, 0);
exit_signal_.data = this;
err = uv_async_init(tracing_loop_, &exit_signal_, ExitSignalCb);
CHECK_EQ(err, 0);
}
NodeTraceBuffer::~NodeTraceBuffer() {
uv_async_send(&exit_signal_);
Mutex::ScopedLock scoped_lock(exit_mutex_);
while (!exited_) {
exit_cond_.Wait(scoped_lock);
}
}
TraceObject* NodeTraceBuffer::AddTraceEvent(uint64_t* handle) {
// If the buffer is full, attempt to perform a flush.
if (!TryLoadAvailableBuffer()) {
// Assign a value of zero as the trace event handle.
// This is equivalent to calling InternalTraceBuffer::MakeHandle(0, 0, 0),
// and will cause GetEventByHandle to return NULL if passed as an argument.
*handle = 0;
return nullptr;
}
return current_buf_.load()->AddTraceEvent(handle);
}
TraceObject* NodeTraceBuffer::GetEventByHandle(uint64_t handle) {
return current_buf_.load()->GetEventByHandle(handle);
}
bool NodeTraceBuffer::Flush() {
buffer1_.Flush(true);
buffer2_.Flush(true);
return true;
}
// Attempts to set current_buf_ such that it references a buffer that can
// write at least one trace event. If both buffers are unavailable this
// method returns false; otherwise it returns true.
bool NodeTraceBuffer::TryLoadAvailableBuffer() {
InternalTraceBuffer* prev_buf = current_buf_.load();
if (prev_buf->IsFull()) {
uv_async_send(&flush_signal_); // trigger flush on a separate thread
InternalTraceBuffer* other_buf = prev_buf == &buffer1_ ?
&buffer2_ : &buffer1_;
if (!other_buf->IsFull()) {
current_buf_.store(other_buf);
} else {
return false;
}
}
return true;
}
// static
void NodeTraceBuffer::NonBlockingFlushSignalCb(uv_async_t* signal) {
NodeTraceBuffer* buffer = static_cast<NodeTraceBuffer*>(signal->data);
if (buffer->buffer1_.IsFull() && !buffer->buffer1_.IsFlushing()) {
buffer->buffer1_.Flush(false);
}
if (buffer->buffer2_.IsFull() && !buffer->buffer2_.IsFlushing()) {
buffer->buffer2_.Flush(false);
}
}
// static
void NodeTraceBuffer::ExitSignalCb(uv_async_t* signal) {
NodeTraceBuffer* buffer =
ContainerOf(&NodeTraceBuffer::exit_signal_, signal);
// Close both flush_signal_ and exit_signal_.
uv_close(reinterpret_cast<uv_handle_t*>(&buffer->flush_signal_),
[](uv_handle_t* signal) {
NodeTraceBuffer* buffer =
ContainerOf(&NodeTraceBuffer::flush_signal_,
reinterpret_cast<uv_async_t*>(signal));
uv_close(reinterpret_cast<uv_handle_t*>(&buffer->exit_signal_),
[](uv_handle_t* signal) {
NodeTraceBuffer* buffer =
ContainerOf(&NodeTraceBuffer::exit_signal_,
reinterpret_cast<uv_async_t*>(signal));
Mutex::ScopedLock scoped_lock(buffer->exit_mutex_);
buffer->exited_ = true;
buffer->exit_cond_.Signal(scoped_lock);
});
});
}
} // namespace tracing
} // namespace node
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