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4a7fde922f
This change takes the EvEndOfGeneration event and promotes it to a real event that appears in the trace. This allows the trace parser to unambiguously identify truncated traces vs. broken traces. It also makes a lot of the logic around parsing simpler, because there's no more batch spilling necessary. Fixes #73904. Change-Id: I37c359b32b6b5f894825aafc02921adeaacf2595 Reviewed-on: https://go-review.googlesource.com/c/go/+/693398 Reviewed-by: Carlos Amedee <carlos@golang.org> Reviewed-by: Michael Pratt <mpratt@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
88 lines
2.2 KiB
Go
88 lines
2.2 KiB
Go
// Copyright 2025 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package trace
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import (
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"fmt"
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"internal/trace/tracev2"
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)
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// timestamp is an unprocessed timestamp.
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type timestamp uint64
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type batch struct {
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time timestamp
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gen uint64
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data []byte
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}
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// readBatch copies b and parses the trace batch header inside.
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// Returns the batch, bytes read, and an error.
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func readBatch(b []byte) (batch, uint64, error) {
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if len(b) == 0 {
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return batch{}, 0, fmt.Errorf("batch is empty")
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}
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data := make([]byte, len(b))
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copy(data, b)
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// Read batch header byte.
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if typ := tracev2.EventType(b[0]); typ == tracev2.EvEndOfGeneration {
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if len(b) != 1 {
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return batch{}, 1, fmt.Errorf("unexpected end of generation in batch of size >1")
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}
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return batch{data: data}, 1, nil
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}
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if typ := tracev2.EventType(b[0]); typ != tracev2.EvEventBatch && typ != tracev2.EvExperimentalBatch {
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return batch{}, 1, fmt.Errorf("expected batch event, got event %d", typ)
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}
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total := 1
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b = b[1:]
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// Read the generation
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gen, n, err := readUvarint(b)
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if err != nil {
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return batch{}, uint64(total + n), fmt.Errorf("error reading batch gen: %w", err)
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}
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total += n
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b = b[n:]
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// Read the M (discard it).
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_, n, err = readUvarint(b)
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if err != nil {
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return batch{}, uint64(total + n), fmt.Errorf("error reading batch M ID: %w", err)
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}
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total += n
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b = b[n:]
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// Read the timestamp.
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ts, n, err := readUvarint(b)
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if err != nil {
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return batch{}, uint64(total + n), fmt.Errorf("error reading batch timestamp: %w", err)
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}
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total += n
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b = b[n:]
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// Read the size of the batch to follow.
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size, n, err := readUvarint(b)
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if err != nil {
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return batch{}, uint64(total + n), fmt.Errorf("error reading batch size: %w", err)
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}
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if size > tracev2.MaxBatchSize {
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return batch{}, uint64(total + n), fmt.Errorf("invalid batch size %d, maximum is %d", size, tracev2.MaxBatchSize)
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}
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total += n
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total += int(size)
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if total != len(data) {
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return batch{}, uint64(total), fmt.Errorf("expected complete batch")
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}
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data = data[:total]
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// Return the batch.
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return batch{
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gen: gen,
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time: timestamp(ts),
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data: data,
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}, uint64(total), nil
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}
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