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internal/trace/v2: don't enforce batch order on Ms

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Currently the trace parser enforces that the timestamps for a series of
a batches on the same M come in order. We cannot actually assume this in
general because we don't trust timestamps. The source of truth on the
batch order is the order in which they were emitted. If that's wrong, it
should quickly become evident in the trace.

For #60773.
For #64061.

Change-Id: I7d5a407c9568dd1ce0b79d51b2b538ed6072b26d
Reviewed-on: https://go-review.googlesource.com/c/go/+/541695
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
This commit is contained in:
Michael Anthony Knyszek 2023-11-10 18:48:41 +00:00 committed by Gopher Robot
parent acc8cb6a5f
commit e8298c09b1
1 changed files with 5 additions and 9 deletions
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14
src/internal/trace/v2/generation.go
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@ -95,15 +95,11 @@ func readGeneration(r *bufio.Reader, spill *spilledBatch) (*generation, *spilled
if g.freq == 0 {
return nil, nil, fmt.Errorf("no frequency event found")
}
for _, batches := range g.batches {
sorted := slices.IsSortedFunc(batches, func(a, b batch) int {
return cmp.Compare(a.time, b.time)
})
if !sorted {
// TODO(mknyszek): Consider just sorting here.
return nil, nil, fmt.Errorf("per-M streams are out-of-order")
}
}
// N.B. Trust that the batch order is correct. We can't validate the batch order
// by timestamp because the timestamps could just be plain wrong. The source of
// truth is the order things appear in the trace and the partial order sequence
// numbers on certain events. If it turns out the batch order is actually incorrect
// we'll very likely fail to advance a partial order from the frontier.
// Compactify stacks and strings for better lookup performance later.
g.stacks.compactify()