src/trace_processor/rpc/rpc.cc - third_party/perfetto - Git at Google

 /*
  * Copyright (C) 2019 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 "src/trace_processor/rpc/rpc.h"

 #include <string.h>

 #include <vector>

 #include "perfetto/base/logging.h"
 #include "perfetto/base/time.h"
 #include "perfetto/ext/base/utils.h"
 #include "perfetto/protozero/scattered_heap_buffer.h"
 #include "perfetto/protozero/scattered_stream_writer.h"
 #include "perfetto/trace_processor/trace_processor.h"
 #include "src/protozero/proto_ring_buffer.h"
 #include "src/trace_processor/rpc/query_result_serializer.h"
 #include "src/trace_processor/tp_metatrace.h"

 #include "protos/perfetto/trace_processor/trace_processor.pbzero.h"

 namespace perfetto {
 namespace trace_processor {

 namespace {
 // Writes a "Loading trace ..." update every N bytes.
 constexpr size_t kProgressUpdateBytes = 50 * 1000 * 1000;
 using TraceProcessorRpcStream = protos::pbzero::TraceProcessorRpcStream;
 using RpcProto = protos::pbzero::TraceProcessorRpc;

 // Most RPC messages are either very small or a query results.
 // QueryResultSerializer splits rows into batches of approximately 128KB. Try
 // avoid extra heap allocations for the nominal case.
 constexpr auto kSliceSize =
     QueryResultSerializer::kDefaultBatchSplitThreshold + 4096;

 // Holds a trace_processor::TraceProcessorRpc pbzero message. Avoids extra
 // copies by doing direct scattered calls from the fragmented heap buffer onto
 // the RpcResponseFunction (the receiver is expected to deal with arbitrary
 // fragmentation anyways). It also takes care of prefixing each message with
 // the proto preamble and varint size.
 class Response {
  public:
   Response(int64_t seq, int method);
   Response(const Response&) = delete;
   Response& operator=(const Response&) = delete;
   RpcProto* operator->() { return msg_; }
   void Send(Rpc::RpcResponseFunction);

  private:
   RpcProto* msg_ = nullptr;

   // The reason why we use TraceProcessorRpcStream as root message is because
   // the RPC wire protocol expects each message to be prefixed with a proto
   // preamble and varint size. This happens to be the same serialization of a
   // repeated field (this is really the same trick we use between
   // Trace and TracePacket in trace.proto)
   protozero::HeapBuffered<TraceProcessorRpcStream> buf_;
 };

 Response::Response(int64_t seq, int method) : buf_(kSliceSize, kSliceSize) {
   msg_ = buf_->add_msg();
   msg_->set_seq(seq);
   msg_->set_response(static_cast<RpcProto::TraceProcessorMethod>(method));
 }

 void Response::Send(Rpc::RpcResponseFunction send_fn) {
   buf_->Finalize();
   for (const auto& slice : buf_.GetSlices()) {
     auto range = slice.GetUsedRange();
     send_fn(range.begin, static_cast<uint32_t>(range.size()));
   }
 }

 }  // namespace

 Rpc::Rpc(std::unique_ptr<TraceProcessor> preloaded_instance)
     : trace_processor_(std::move(preloaded_instance)),
       session_id_(base::Uuidv4()) {
   if (!trace_processor_)
     ResetTraceProcessor();
 }

 Rpc::Rpc() : Rpc(nullptr) {}
 Rpc::~Rpc() = default;

 void Rpc::ResetTraceProcessor() {
   trace_processor_ = TraceProcessor::CreateInstance(Config());
   bytes_parsed_ = bytes_last_progress_ = 0;
   t_parse_started_ = base::GetWallTimeNs().count();
   // Deliberately not resetting the RPC channel state (rxbuf_, {tx,rx}_seq_id_).
   // This is invoked from the same client to clear the current trace state
   // before loading a new one. The IPC channel is orthogonal to that and the
   // message numbering continues regardless of the reset.
 }

 void Rpc::OnRpcRequest(const void* data, size_t len) {
   rxbuf_.Append(data, len);
   for (;;) {
     auto msg = rxbuf_.ReadMessage();
     if (!msg.valid()) {
       if (msg.fatal_framing_error)
         rpc_response_fn_(nullptr, 0);  // Disconnect.
       break;
     }
     ParseRpcRequest(msg.start, msg.len);
   }
 }

 // [data, len] here is a tokenized TraceProcessorRpc proto message, without the
 // size header.
 void Rpc::ParseRpcRequest(const uint8_t* data, size_t len) {
   RpcProto::Decoder req(data, len);

   // We allow restarting the sequence from 0. This happens when refreshing the
   // browser while using the external trace_processor_shell --httpd.
   if (req.seq() != 0 && rx_seq_id_ != 0 && req.seq() != rx_seq_id_ + 1) {
     PERFETTO_ELOG("RPC request out of order. Expected %" PRId64
                   ", got %" PRId64,
                   rx_seq_id_ + 1, req.seq());
     rpc_response_fn_(nullptr, 0);  // Disconnect.
     return;
   }
   rx_seq_id_ = req.seq();

   // The static cast is to prevent that the compiler breaks future proofness.
   const int req_type = static_cast<int>(req.request());
   static const char kErrFieldNotSet[] = "RPC error: request field not set";
   switch (req_type) {
     case RpcProto::TPM_APPEND_TRACE_DATA: {
       Response resp(tx_seq_id_++, req_type);
       auto* result = resp->set_append_result();
       if (!req.has_append_trace_data()) {
         result->set_error(kErrFieldNotSet);
       } else {
         protozero::ConstBytes byte_range = req.append_trace_data();
         util::Status res = Parse(byte_range.data, byte_range.size);
         if (!res.ok()) {
           result->set_error(res.message());
         }
       }
       resp.Send(rpc_response_fn_);
       break;
     }
     case RpcProto::TPM_FINALIZE_TRACE_DATA: {
       Response resp(tx_seq_id_++, req_type);
       NotifyEndOfFile();
       resp.Send(rpc_response_fn_);
       break;
     }
     case RpcProto::TPM_QUERY_STREAMING: {
       if (!req.has_query_args()) {
         Response resp(tx_seq_id_++, req_type);
         auto* result = resp->set_query_result();
         result->set_error(kErrFieldNotSet);
         resp.Send(rpc_response_fn_);
       } else {
         protozero::ConstBytes args = req.query_args();
         auto it = QueryInternal(args.data, args.size);
         QueryResultSerializer serializer(std::move(it));
         for (bool has_more = true; has_more;) {
           Response resp(tx_seq_id_++, req_type);
           has_more = serializer.Serialize(resp->set_query_result());
           resp.Send(rpc_response_fn_);
         }
       }
       break;
     }
     case RpcProto::TPM_QUERY_RAW_DEPRECATED: {
       Response resp(tx_seq_id_++, req_type);
       auto* result = resp->set_raw_query_result();
       if (!req.has_raw_query_args()) {
         result->set_error(kErrFieldNotSet);
       } else {
         protozero::ConstBytes args = req.raw_query_args();
         RawQueryInternal(args.data, args.size, result);
       }
       resp.Send(rpc_response_fn_);
       break;
     }
     case RpcProto::TPM_COMPUTE_METRIC: {
       Response resp(tx_seq_id_++, req_type);
       auto* result = resp->set_metric_result();
       if (!req.has_compute_metric_args()) {
         result->set_error(kErrFieldNotSet);
       } else {
         protozero::ConstBytes args = req.compute_metric_args();
         ComputeMetricInternal(args.data, args.size, result);
       }
       resp.Send(rpc_response_fn_);
       break;
     }
     case RpcProto::TPM_GET_METRIC_DESCRIPTORS: {
       Response resp(tx_seq_id_++, req_type);
       auto descriptor_set = trace_processor_->GetMetricDescriptors();
       auto* result = resp->set_metric_descriptors();
       result->AppendRawProtoBytes(descriptor_set.data(), descriptor_set.size());
       resp.Send(rpc_response_fn_);
       break;
     }
     case RpcProto::TPM_RESTORE_INITIAL_TABLES: {
       trace_processor_->RestoreInitialTables();
       Response resp(tx_seq_id_++, req_type);
       resp.Send(rpc_response_fn_);
       break;
     }
     case RpcProto::TPM_ENABLE_METATRACE: {
       trace_processor_->EnableMetatrace();
       Response resp(tx_seq_id_++, req_type);
       resp.Send(rpc_response_fn_);
       break;
     }
     case RpcProto::TPM_DISABLE_AND_READ_METATRACE: {
       Response resp(tx_seq_id_++, req_type);
       DisableAndReadMetatraceInternal(resp->set_metatrace());
       resp.Send(rpc_response_fn_);
       break;
     }
     default: {
       // This can legitimately happen if the client is newer. We reply with a
       // generic "unkown request" response, so the client can do feature
       // detection
       PERFETTO_DLOG("[RPC] Uknown request type (%d), size=%zu", req_type, len);
       Response resp(tx_seq_id_++, req_type);
       resp->set_invalid_request(
           static_cast<RpcProto::TraceProcessorMethod>(req_type));
       resp.Send(rpc_response_fn_);
       break;
     }
   }  // switch(req_type)
 }

 util::Status Rpc::Parse(const uint8_t* data, size_t len) {
   if (eof_) {
     // Reset the trace processor state if another trace has been previously
     // loaded.
     ResetTraceProcessor();
   }

   eof_ = false;
   bytes_parsed_ += len;
   MaybePrintProgress();

   if (len == 0)
     return util::OkStatus();

   // TraceProcessor needs take ownership of the memory chunk.
   std::unique_ptr<uint8_t[]> data_copy(new uint8_t[len]);
   memcpy(data_copy.get(), data, len);
   return trace_processor_->Parse(std::move(data_copy), len);
 }

 void Rpc::NotifyEndOfFile() {
   trace_processor_->NotifyEndOfFile();
   eof_ = true;
   MaybePrintProgress();
 }

 void Rpc::MaybePrintProgress() {
   if (eof_ || bytes_parsed_ - bytes_last_progress_ > kProgressUpdateBytes) {
     bytes_last_progress_ = bytes_parsed_;
     auto t_load_s =
         static_cast<double>(base::GetWallTimeNs().count() - t_parse_started_) /
         1e9;
     fprintf(stderr, "\rLoading trace %.2f MB (%.1f MB/s)%s",
             static_cast<double>(bytes_parsed_) / 1e6,
             static_cast<double>(bytes_parsed_) / 1e6 / t_load_s,
             (eof_ ? "\n" : ""));
     fflush(stderr);
   }
 }

 void Rpc::Query(const uint8_t* args,
                 size_t len,
                 QueryResultBatchCallback result_callback) {
   auto it = QueryInternal(args, len);
   QueryResultSerializer serializer(std::move(it));

   std::vector<uint8_t> res;
   for (bool has_more = true; has_more;) {
     has_more = serializer.Serialize(&res);
     result_callback(res.data(), res.size(), has_more);
     res.clear();
   }
 }

 Iterator Rpc::QueryInternal(const uint8_t* args, size_t len) {
   protos::pbzero::RawQueryArgs::Decoder query(args, len);
   std::string sql = query.sql_query().ToStdString();
   PERFETTO_DLOG("[RPC] Query < %s", sql.c_str());
   PERFETTO_TP_TRACE("RPC_QUERY",
                     [&](metatrace::Record* r) { r->AddArg("SQL", sql); });

   return trace_processor_->ExecuteQuery(sql.c_str());
 }

 std::vector<uint8_t> Rpc::RawQuery(const uint8_t* args, size_t len) {
   protozero::HeapBuffered<protos::pbzero::RawQueryResult> result;
   RawQueryInternal(args, len, result.get());
   return result.SerializeAsArray();
 }

 void Rpc::RawQueryInternal(const uint8_t* args,
                            size_t len,
                            protos::pbzero::RawQueryResult* result) {
   using ColumnValues = protos::pbzero::RawQueryResult::ColumnValues;
   using ColumnDesc = protos::pbzero::RawQueryResult::ColumnDesc;

   protos::pbzero::RawQueryArgs::Decoder query(args, len);
   std::string sql = query.sql_query().ToStdString();
   PERFETTO_DLOG("[RPC] RawQuery < %s", sql.c_str());
   PERFETTO_TP_TRACE("RPC_RAW_QUERY",
                     [&](metatrace::Record* r) { r->AddArg("SQL", sql); });

   auto it = trace_processor_->ExecuteQuery(sql.c_str());

   // This vector contains a standalone protozero message per column. The problem
   // it's solving is the following: (i) sqlite iterators are row-based; (ii) the
   // RawQueryResult proto is column-based (that was a poor design choice we
   // should revisit at some point); (iii) the protozero API doesn't allow to
   // begin a new nested message before the previous one is completed.
   // In order to avoid the interleaved-writing, we write each column in a
   // dedicated heap buffer and then we merge all the column data at the end,
   // after having iterated all rows.
   std::vector<protozero::HeapBuffered<ColumnValues>> cols(it.ColumnCount());

   // This constexpr is to avoid ODR-use of protozero constants which are only
   // declared but not defined. Putting directly UNKONWN in the vector ctor
   // causes a linker error in the WASM toolchain.
   static constexpr auto kUnknown = ColumnDesc::UNKNOWN;
   std::vector<ColumnDesc::Type> col_types(it.ColumnCount(), kUnknown);
   uint32_t rows = 0;

   for (; it.Next(); ++rows) {
     for (uint32_t col_idx = 0; col_idx < it.ColumnCount(); ++col_idx) {
       auto& col = cols[col_idx];
       auto& col_type = col_types[col_idx];

       using SqlValue = trace_processor::SqlValue;
       auto cell = it.Get(col_idx);
       if (col_type == ColumnDesc::UNKNOWN) {
         switch (cell.type) {
           case SqlValue::Type::kLong:
             col_type = ColumnDesc::LONG;
             break;
           case SqlValue::Type::kString:
             col_type = ColumnDesc::STRING;
             break;
           case SqlValue::Type::kDouble:
             col_type = ColumnDesc::DOUBLE;
             break;
           case SqlValue::Type::kBytes:
             col_type = ColumnDesc::STRING;
             break;
           case SqlValue::Type::kNull:
             break;
         }
       }

       // If either the column type is null or we still don't know the type,
       // just add null values to all the columns.
       if (cell.type == SqlValue::Type::kNull ||
           col_type == ColumnDesc::UNKNOWN) {
         col->add_long_values(0);
         col->add_string_values("[NULL]");
         col->add_double_values(0);
         col->add_is_nulls(true);
         continue;
       }

       // Cast the sqlite value to the type of the column.
       switch (col_type) {
         case ColumnDesc::LONG:
           PERFETTO_CHECK(cell.type == SqlValue::Type::kLong ||
                          cell.type == SqlValue::Type::kDouble);
           if (cell.type == SqlValue::Type::kLong) {
             col->add_long_values(cell.long_value);
           } else /* if (cell.type == SqlValue::Type::kDouble) */ {
             col->add_long_values(static_cast<int64_t>(cell.double_value));
           }
           col->add_is_nulls(false);
           break;
         case ColumnDesc::STRING: {
           if (cell.type == SqlValue::Type::kBytes) {
             col->add_string_values("<bytes>");
           } else {
             PERFETTO_CHECK(cell.type == SqlValue::Type::kString);
             col->add_string_values(cell.string_value);
           }
           col->add_is_nulls(false);
           break;
         }
         case ColumnDesc::DOUBLE:
           PERFETTO_CHECK(cell.type == SqlValue::Type::kLong ||
                          cell.type == SqlValue::Type::kDouble);
           if (cell.type == SqlValue::Type::kLong) {
             col->add_double_values(static_cast<double>(cell.long_value));
           } else /* if (cell.type == SqlValue::Type::kDouble) */ {
             col->add_double_values(cell.double_value);
           }
           col->add_is_nulls(false);
           break;
         case ColumnDesc::UNKNOWN:
           PERFETTO_FATAL("Handled in if statement above.");
       }
     }  // for(col)
   }    // for(row)

   // Write the column descriptors.
   for (uint32_t col_idx = 0; col_idx < it.ColumnCount(); ++col_idx) {
     auto* descriptor = result->add_column_descriptors();
     std::string col_name = it.GetColumnName(col_idx);
     descriptor->set_name(col_name.data(), col_name.size());
     descriptor->set_type(col_types[col_idx]);
   }

   // Merge the column values.
   for (uint32_t col_idx = 0; col_idx < it.ColumnCount(); ++col_idx) {
     std::vector<uint8_t> col_data = cols[col_idx].SerializeAsArray();
     result->AppendBytes(protos::pbzero::RawQueryResult::kColumnsFieldNumber,
                         col_data.data(), col_data.size());
   }

   util::Status status = it.Status();
   result->set_num_records(rows);
   if (!status.ok())
     result->set_error(status.c_message());
   PERFETTO_DLOG("[RPC] RawQuery > %d rows (err: %d)", rows, !status.ok());
 }

 std::string Rpc::GetCurrentTraceName() {
   return trace_processor_->GetCurrentTraceName();
 }

 void Rpc::RestoreInitialTables() {
   trace_processor_->RestoreInitialTables();
   session_id_ = base::Uuidv4();
 }

 std::vector<uint8_t> Rpc::ComputeMetric(const uint8_t* args, size_t len) {
   protozero::HeapBuffered<protos::pbzero::ComputeMetricResult> result;
   ComputeMetricInternal(args, len, result.get());
   return result.SerializeAsArray();
 }

 void Rpc::ComputeMetricInternal(const uint8_t* data,
                                 size_t len,
                                 protos::pbzero::ComputeMetricResult* result) {
   protos::pbzero::ComputeMetricArgs::Decoder args(data, len);
   std::vector<std::string> metric_names;
   for (auto it = args.metric_names(); it; ++it) {
     metric_names.emplace_back(it->as_std_string());
   }

   PERFETTO_TP_TRACE("RPC_COMPUTE_METRIC", [&](metatrace::Record* r) {
     for (const auto& metric : metric_names) {
       r->AddArg("Metric", metric);
       r->AddArg("Format", std::to_string(args.format()));
     }
   });

   PERFETTO_DLOG("[RPC] ComputeMetrics(%zu, %s), format=%d", metric_names.size(),
                 metric_names.empty() ? "" : metric_names.front().c_str(),
                 args.format());
   switch (args.format()) {
     case protos::pbzero::ComputeMetricArgs::BINARY_PROTOBUF: {
       std::vector<uint8_t> metrics_proto;
       util::Status status =
           trace_processor_->ComputeMetric(metric_names, &metrics_proto);
       if (status.ok()) {
         result->set_metrics(metrics_proto.data(), metrics_proto.size());
       } else {
         result->set_error(status.message());
       }
       break;
     }
     case protos::pbzero::ComputeMetricArgs::TEXTPROTO: {
       std::string metrics_string;
       util::Status status = trace_processor_->ComputeMetricText(
           metric_names, TraceProcessor::MetricResultFormat::kProtoText,
           &metrics_string);
       if (status.ok()) {
         result->set_metrics_as_prototext(metrics_string);
       } else {
         result->set_error(status.message());
       }
       break;
     }
   }
 }

 void Rpc::EnableMetatrace() {
   trace_processor_->EnableMetatrace();
 }

 std::vector<uint8_t> Rpc::DisableAndReadMetatrace() {
   protozero::HeapBuffered<protos::pbzero::DisableAndReadMetatraceResult> result;
   DisableAndReadMetatraceInternal(result.get());
   return result.SerializeAsArray();
 }

 void Rpc::DisableAndReadMetatraceInternal(
     protos::pbzero::DisableAndReadMetatraceResult* result) {
   std::vector<uint8_t> trace_proto;
   util::Status status = trace_processor_->DisableAndReadMetatrace(&trace_proto);
   if (status.ok()) {
     result->set_metatrace(trace_proto.data(), trace_proto.size());
   } else {
     result->set_error(status.message());
   }
 }

 std::string Rpc::GetSessionId() {
   return session_id_.ToPrettyString();
 }

 }  // namespace trace_processor
 }  // namespace perfetto
	/*
	* Copyright (C) 2019 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 "src/trace_processor/rpc/rpc.h"

	#include <string.h>

	#include <vector>

	#include "perfetto/base/logging.h"
	#include "perfetto/base/time.h"
	#include "perfetto/ext/base/utils.h"
	#include "perfetto/protozero/scattered_heap_buffer.h"
	#include "perfetto/protozero/scattered_stream_writer.h"
	#include "perfetto/trace_processor/trace_processor.h"
	#include "src/protozero/proto_ring_buffer.h"
	#include "src/trace_processor/rpc/query_result_serializer.h"
	#include "src/trace_processor/tp_metatrace.h"

	#include "protos/perfetto/trace_processor/trace_processor.pbzero.h"

	namespace perfetto {
	namespace trace_processor {

	namespace {
	// Writes a "Loading trace ..." update every N bytes.
	constexpr size_t kProgressUpdateBytes = 50 * 1000 * 1000;
	using TraceProcessorRpcStream = protos::pbzero::TraceProcessorRpcStream;
	using RpcProto = protos::pbzero::TraceProcessorRpc;

	// Most RPC messages are either very small or a query results.
	// QueryResultSerializer splits rows into batches of approximately 128KB. Try
	// avoid extra heap allocations for the nominal case.
	constexpr auto kSliceSize =
	QueryResultSerializer::kDefaultBatchSplitThreshold + 4096;

	// Holds a trace_processor::TraceProcessorRpc pbzero message. Avoids extra
	// copies by doing direct scattered calls from the fragmented heap buffer onto
	// the RpcResponseFunction (the receiver is expected to deal with arbitrary
	// fragmentation anyways). It also takes care of prefixing each message with
	// the proto preamble and varint size.
	class Response {
	public:
	Response(int64_t seq, int method);
	Response(const Response&) = delete;
	Response& operator=(const Response&) = delete;
	RpcProto* operator->() { return msg_; }
	void Send(Rpc::RpcResponseFunction);

	private:
	RpcProto* msg_ = nullptr;

	// The reason why we use TraceProcessorRpcStream as root message is because
	// the RPC wire protocol expects each message to be prefixed with a proto
	// preamble and varint size. This happens to be the same serialization of a
	// repeated field (this is really the same trick we use between
	// Trace and TracePacket in trace.proto)
	protozero::HeapBuffered<TraceProcessorRpcStream> buf_;
	};

	Response::Response(int64_t seq, int method) : buf_(kSliceSize, kSliceSize) {
	msg_ = buf_->add_msg();
	msg_->set_seq(seq);
	msg_->set_response(static_cast<RpcProto::TraceProcessorMethod>(method));
	}

	void Response::Send(Rpc::RpcResponseFunction send_fn) {
	buf_->Finalize();
	for (const auto& slice : buf_.GetSlices()) {
	auto range = slice.GetUsedRange();
	send_fn(range.begin, static_cast<uint32_t>(range.size()));
	}
	}

	} // namespace

	Rpc::Rpc(std::unique_ptr<TraceProcessor> preloaded_instance)
	: trace_processor_(std::move(preloaded_instance)),
	session_id_(base::Uuidv4()) {
	if (!trace_processor_)
	ResetTraceProcessor();
	}

	Rpc::Rpc() : Rpc(nullptr) {}
	Rpc::~Rpc() = default;

	void Rpc::ResetTraceProcessor() {
	trace_processor_ = TraceProcessor::CreateInstance(Config());
	bytes_parsed_ = bytes_last_progress_ = 0;
	t_parse_started_ = base::GetWallTimeNs().count();
	// Deliberately not resetting the RPC channel state (rxbuf_, {tx,rx}_seq_id_).
	// This is invoked from the same client to clear the current trace state
	// before loading a new one. The IPC channel is orthogonal to that and the
	// message numbering continues regardless of the reset.
	}

	void Rpc::OnRpcRequest(const void* data, size_t len) {
	rxbuf_.Append(data, len);
	for (;;) {
	auto msg = rxbuf_.ReadMessage();
	if (!msg.valid()) {
	if (msg.fatal_framing_error)
	rpc_response_fn_(nullptr, 0); // Disconnect.
	break;
	}
	ParseRpcRequest(msg.start, msg.len);
	}
	}

	// [data, len] here is a tokenized TraceProcessorRpc proto message, without the
	// size header.
	void Rpc::ParseRpcRequest(const uint8_t* data, size_t len) {
	RpcProto::Decoder req(data, len);

	// We allow restarting the sequence from 0. This happens when refreshing the
	// browser while using the external trace_processor_shell --httpd.
	if (req.seq() != 0 && rx_seq_id_ != 0 && req.seq() != rx_seq_id_ + 1) {
	PERFETTO_ELOG("RPC request out of order. Expected %" PRId64
	", got %" PRId64,
	rx_seq_id_ + 1, req.seq());
	rpc_response_fn_(nullptr, 0); // Disconnect.
	return;
	}
	rx_seq_id_ = req.seq();

	// The static cast is to prevent that the compiler breaks future proofness.
	const int req_type = static_cast<int>(req.request());
	static const char kErrFieldNotSet[] = "RPC error: request field not set";
	switch (req_type) {
	case RpcProto::TPM_APPEND_TRACE_DATA: {
	Response resp(tx_seq_id_++, req_type);
	auto* result = resp->set_append_result();
	if (!req.has_append_trace_data()) {
	result->set_error(kErrFieldNotSet);
	} else {
	protozero::ConstBytes byte_range = req.append_trace_data();
	util::Status res = Parse(byte_range.data, byte_range.size);
	if (!res.ok()) {
	result->set_error(res.message());
	}
	}
	resp.Send(rpc_response_fn_);
	break;
	}
	case RpcProto::TPM_FINALIZE_TRACE_DATA: {
	Response resp(tx_seq_id_++, req_type);
	NotifyEndOfFile();
	resp.Send(rpc_response_fn_);
	break;
	}
	case RpcProto::TPM_QUERY_STREAMING: {
	if (!req.has_query_args()) {
	Response resp(tx_seq_id_++, req_type);
	auto* result = resp->set_query_result();
	result->set_error(kErrFieldNotSet);
	resp.Send(rpc_response_fn_);
	} else {
	protozero::ConstBytes args = req.query_args();
	auto it = QueryInternal(args.data, args.size);
	QueryResultSerializer serializer(std::move(it));
	for (bool has_more = true; has_more;) {
	Response resp(tx_seq_id_++, req_type);
	has_more = serializer.Serialize(resp->set_query_result());
	resp.Send(rpc_response_fn_);
	}
	}
	break;
	}
	case RpcProto::TPM_QUERY_RAW_DEPRECATED: {
	Response resp(tx_seq_id_++, req_type);
	auto* result = resp->set_raw_query_result();
	if (!req.has_raw_query_args()) {
	result->set_error(kErrFieldNotSet);
	} else {
	protozero::ConstBytes args = req.raw_query_args();
	RawQueryInternal(args.data, args.size, result);
	}
	resp.Send(rpc_response_fn_);
	break;
	}
	case RpcProto::TPM_COMPUTE_METRIC: {
	Response resp(tx_seq_id_++, req_type);
	auto* result = resp->set_metric_result();
	if (!req.has_compute_metric_args()) {
	result->set_error(kErrFieldNotSet);
	} else {
	protozero::ConstBytes args = req.compute_metric_args();
	ComputeMetricInternal(args.data, args.size, result);
	}
	resp.Send(rpc_response_fn_);
	break;
	}
	case RpcProto::TPM_GET_METRIC_DESCRIPTORS: {
	Response resp(tx_seq_id_++, req_type);
	auto descriptor_set = trace_processor_->GetMetricDescriptors();
	auto* result = resp->set_metric_descriptors();
	result->AppendRawProtoBytes(descriptor_set.data(), descriptor_set.size());
	resp.Send(rpc_response_fn_);
	break;
	}
	case RpcProto::TPM_RESTORE_INITIAL_TABLES: {
	trace_processor_->RestoreInitialTables();
	Response resp(tx_seq_id_++, req_type);
	resp.Send(rpc_response_fn_);
	break;
	}
	case RpcProto::TPM_ENABLE_METATRACE: {
	trace_processor_->EnableMetatrace();
	Response resp(tx_seq_id_++, req_type);
	resp.Send(rpc_response_fn_);
	break;
	}
	case RpcProto::TPM_DISABLE_AND_READ_METATRACE: {
	Response resp(tx_seq_id_++, req_type);
	DisableAndReadMetatraceInternal(resp->set_metatrace());
	resp.Send(rpc_response_fn_);
	break;
	}
	default: {
	// This can legitimately happen if the client is newer. We reply with a
	// generic "unkown request" response, so the client can do feature
	// detection
	PERFETTO_DLOG("[RPC] Uknown request type (%d), size=%zu", req_type, len);
	Response resp(tx_seq_id_++, req_type);
	resp->set_invalid_request(
	static_cast<RpcProto::TraceProcessorMethod>(req_type));
	resp.Send(rpc_response_fn_);
	break;
	}
	} // switch(req_type)
	}

	util::Status Rpc::Parse(const uint8_t* data, size_t len) {
	if (eof_) {
	// Reset the trace processor state if another trace has been previously
	// loaded.
	ResetTraceProcessor();
	}

	eof_ = false;
	bytes_parsed_ += len;
	MaybePrintProgress();

	if (len == 0)
	return util::OkStatus();

	// TraceProcessor needs take ownership of the memory chunk.
	std::unique_ptr<uint8_t[]> data_copy(new uint8_t[len]);
	memcpy(data_copy.get(), data, len);
	return trace_processor_->Parse(std::move(data_copy), len);
	}

	void Rpc::NotifyEndOfFile() {
	trace_processor_->NotifyEndOfFile();
	eof_ = true;
	MaybePrintProgress();
	}

	void Rpc::MaybePrintProgress() {
	if (eof_ \|\| bytes_parsed_ - bytes_last_progress_ > kProgressUpdateBytes) {
	bytes_last_progress_ = bytes_parsed_;
	auto t_load_s =
	static_cast<double>(base::GetWallTimeNs().count() - t_parse_started_) /
	1e9;
	fprintf(stderr, "\rLoading trace %.2f MB (%.1f MB/s)%s",
	static_cast<double>(bytes_parsed_) / 1e6,
	static_cast<double>(bytes_parsed_) / 1e6 / t_load_s,
	(eof_ ? "\n" : ""));
	fflush(stderr);
	}
	}

	void Rpc::Query(const uint8_t* args,
	size_t len,
	QueryResultBatchCallback result_callback) {
	auto it = QueryInternal(args, len);
	QueryResultSerializer serializer(std::move(it));

	std::vector<uint8_t> res;
	for (bool has_more = true; has_more;) {
	has_more = serializer.Serialize(&res);
	result_callback(res.data(), res.size(), has_more);
	res.clear();
	}
	}

	Iterator Rpc::QueryInternal(const uint8_t* args, size_t len) {
	protos::pbzero::RawQueryArgs::Decoder query(args, len);
	std::string sql = query.sql_query().ToStdString();
	PERFETTO_DLOG("[RPC] Query < %s", sql.c_str());
	PERFETTO_TP_TRACE("RPC_QUERY",
	[&](metatrace::Record* r) { r->AddArg("SQL", sql); });

	return trace_processor_->ExecuteQuery(sql.c_str());
	}

	std::vector<uint8_t> Rpc::RawQuery(const uint8_t* args, size_t len) {
	protozero::HeapBuffered<protos::pbzero::RawQueryResult> result;
	RawQueryInternal(args, len, result.get());
	return result.SerializeAsArray();
	}

	void Rpc::RawQueryInternal(const uint8_t* args,
	size_t len,
	protos::pbzero::RawQueryResult* result) {
	using ColumnValues = protos::pbzero::RawQueryResult::ColumnValues;
	using ColumnDesc = protos::pbzero::RawQueryResult::ColumnDesc;

	protos::pbzero::RawQueryArgs::Decoder query(args, len);
	std::string sql = query.sql_query().ToStdString();
	PERFETTO_DLOG("[RPC] RawQuery < %s", sql.c_str());
	PERFETTO_TP_TRACE("RPC_RAW_QUERY",
	[&](metatrace::Record* r) { r->AddArg("SQL", sql); });

	auto it = trace_processor_->ExecuteQuery(sql.c_str());

	// This vector contains a standalone protozero message per column. The problem
	// it's solving is the following: (i) sqlite iterators are row-based; (ii) the
	// RawQueryResult proto is column-based (that was a poor design choice we
	// should revisit at some point); (iii) the protozero API doesn't allow to
	// begin a new nested message before the previous one is completed.
	// In order to avoid the interleaved-writing, we write each column in a
	// dedicated heap buffer and then we merge all the column data at the end,
	// after having iterated all rows.
	std::vector<protozero::HeapBuffered<ColumnValues>> cols(it.ColumnCount());

	// This constexpr is to avoid ODR-use of protozero constants which are only
	// declared but not defined. Putting directly UNKONWN in the vector ctor
	// causes a linker error in the WASM toolchain.
	static constexpr auto kUnknown = ColumnDesc::UNKNOWN;
	std::vector<ColumnDesc::Type> col_types(it.ColumnCount(), kUnknown);
	uint32_t rows = 0;

	for (; it.Next(); ++rows) {
	for (uint32_t col_idx = 0; col_idx < it.ColumnCount(); ++col_idx) {
	auto& col = cols[col_idx];
	auto& col_type = col_types[col_idx];

	using SqlValue = trace_processor::SqlValue;
	auto cell = it.Get(col_idx);
	if (col_type == ColumnDesc::UNKNOWN) {
	switch (cell.type) {
	case SqlValue::Type::kLong:
	col_type = ColumnDesc::LONG;
	break;
	case SqlValue::Type::kString:
	col_type = ColumnDesc::STRING;
	break;
	case SqlValue::Type::kDouble:
	col_type = ColumnDesc::DOUBLE;
	break;
	case SqlValue::Type::kBytes:
	col_type = ColumnDesc::STRING;
	break;
	case SqlValue::Type::kNull:
	break;
	}
	}

	// If either the column type is null or we still don't know the type,
	// just add null values to all the columns.
	if (cell.type == SqlValue::Type::kNull \|\|
	col_type == ColumnDesc::UNKNOWN) {
	col->add_long_values(0);
	col->add_string_values("[NULL]");
	col->add_double_values(0);
	col->add_is_nulls(true);
	continue;
	}

	// Cast the sqlite value to the type of the column.
	switch (col_type) {
	case ColumnDesc::LONG:
	PERFETTO_CHECK(cell.type == SqlValue::Type::kLong \|\|
	cell.type == SqlValue::Type::kDouble);
	if (cell.type == SqlValue::Type::kLong) {
	col->add_long_values(cell.long_value);
	} else /* if (cell.type == SqlValue::Type::kDouble) */ {
	col->add_long_values(static_cast<int64_t>(cell.double_value));
	}
	col->add_is_nulls(false);
	break;
	case ColumnDesc::STRING: {
	if (cell.type == SqlValue::Type::kBytes) {
	col->add_string_values("<bytes>");
	} else {
	PERFETTO_CHECK(cell.type == SqlValue::Type::kString);
	col->add_string_values(cell.string_value);
	}
	col->add_is_nulls(false);
	break;
	}
	case ColumnDesc::DOUBLE:
	PERFETTO_CHECK(cell.type == SqlValue::Type::kLong \|\|
	cell.type == SqlValue::Type::kDouble);
	if (cell.type == SqlValue::Type::kLong) {
	col->add_double_values(static_cast<double>(cell.long_value));
	} else /* if (cell.type == SqlValue::Type::kDouble) */ {
	col->add_double_values(cell.double_value);
	}
	col->add_is_nulls(false);
	break;
	case ColumnDesc::UNKNOWN:
	PERFETTO_FATAL("Handled in if statement above.");
	}
	} // for(col)
	} // for(row)

	// Write the column descriptors.
	for (uint32_t col_idx = 0; col_idx < it.ColumnCount(); ++col_idx) {
	auto* descriptor = result->add_column_descriptors();
	std::string col_name = it.GetColumnName(col_idx);
	descriptor->set_name(col_name.data(), col_name.size());
	descriptor->set_type(col_types[col_idx]);
	}

	// Merge the column values.
	for (uint32_t col_idx = 0; col_idx < it.ColumnCount(); ++col_idx) {
	std::vector<uint8_t> col_data = cols[col_idx].SerializeAsArray();
	result->AppendBytes(protos::pbzero::RawQueryResult::kColumnsFieldNumber,
	col_data.data(), col_data.size());
	}

	util::Status status = it.Status();
	result->set_num_records(rows);
	if (!status.ok())
	result->set_error(status.c_message());
	PERFETTO_DLOG("[RPC] RawQuery > %d rows (err: %d)", rows, !status.ok());
	}

	std::string Rpc::GetCurrentTraceName() {
	return trace_processor_->GetCurrentTraceName();
	}

	void Rpc::RestoreInitialTables() {
	trace_processor_->RestoreInitialTables();
	session_id_ = base::Uuidv4();
	}

	std::vector<uint8_t> Rpc::ComputeMetric(const uint8_t* args, size_t len) {
	protozero::HeapBuffered<protos::pbzero::ComputeMetricResult> result;
	ComputeMetricInternal(args, len, result.get());
	return result.SerializeAsArray();
	}

	void Rpc::ComputeMetricInternal(const uint8_t* data,
	size_t len,
	protos::pbzero::ComputeMetricResult* result) {
	protos::pbzero::ComputeMetricArgs::Decoder args(data, len);
	std::vector<std::string> metric_names;
	for (auto it = args.metric_names(); it; ++it) {
	metric_names.emplace_back(it->as_std_string());
	}

	PERFETTO_TP_TRACE("RPC_COMPUTE_METRIC", [&](metatrace::Record* r) {
	for (const auto& metric : metric_names) {
	r->AddArg("Metric", metric);
	r->AddArg("Format", std::to_string(args.format()));
	}
	});

	PERFETTO_DLOG("[RPC] ComputeMetrics(%zu, %s), format=%d", metric_names.size(),
	metric_names.empty() ? "" : metric_names.front().c_str(),
	args.format());
	switch (args.format()) {
	case protos::pbzero::ComputeMetricArgs::BINARY_PROTOBUF: {
	std::vector<uint8_t> metrics_proto;
	util::Status status =
	trace_processor_->ComputeMetric(metric_names, &metrics_proto);
	if (status.ok()) {
	result->set_metrics(metrics_proto.data(), metrics_proto.size());
	} else {
	result->set_error(status.message());
	}
	break;
	}
	case protos::pbzero::ComputeMetricArgs::TEXTPROTO: {
	std::string metrics_string;
	util::Status status = trace_processor_->ComputeMetricText(
	metric_names, TraceProcessor::MetricResultFormat::kProtoText,
	&metrics_string);
	if (status.ok()) {
	result->set_metrics_as_prototext(metrics_string);
	} else {
	result->set_error(status.message());
	}
	break;
	}
	}
	}

	void Rpc::EnableMetatrace() {
	trace_processor_->EnableMetatrace();
	}

	std::vector<uint8_t> Rpc::DisableAndReadMetatrace() {
	protozero::HeapBuffered<protos::pbzero::DisableAndReadMetatraceResult> result;
	DisableAndReadMetatraceInternal(result.get());
	return result.SerializeAsArray();
	}

	void Rpc::DisableAndReadMetatraceInternal(
	protos::pbzero::DisableAndReadMetatraceResult* result) {
	std::vector<uint8_t> trace_proto;
	util::Status status = trace_processor_->DisableAndReadMetatrace(&trace_proto);
	if (status.ok()) {
	result->set_metatrace(trace_proto.data(), trace_proto.size());
	} else {
	result->set_error(status.message());
	}
	}

	std::string Rpc::GetSessionId() {
	return session_id_.ToPrettyString();
	}

	} // namespace trace_processor
	} // namespace perfetto