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federate: Fix PeekBack usage

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In most cases, there is no sample at `maxt`, so `PeekBack` has to be
used. So far, `PeekBack` did not return a float histogram, and we
disregarded even any returned normal histogram. This fixes both, and
also tweaks the unit test to discover the problem (by using an earlier
timestamp than "now" for the samples in the TSDB).

Signed-off-by: beorn7 <beorn@grafana.com>
This commit is contained in:
beorn7 2023-01-12 15:20:50 +01:00 committed by Ganesh Vernekar
parent b4e15899d1
commit d121db7a65
No known key found for this signature in database
GPG key ID: F056451B52F1DC34
4 changed files with 17 additions and 11 deletions
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6
storage/buffer.go
View file

@ -68,9 +68,11 @@ func (b *BufferedSeriesIterator) ReduceDelta(delta int64) bool {
// PeekBack returns the nth previous element of the iterator. If there is none buffered,
// ok is false.
func (b *BufferedSeriesIterator) PeekBack(n int) (t int64, v float64, h *histogram.Histogram, ok bool) {
func (b *BufferedSeriesIterator) PeekBack(n int) (
t int64, v float64, h *histogram.Histogram, fh *histogram.FloatHistogram, ok bool,
) {
s, ok := b.buf.nthLast(n)
return s.t, s.v, s.h, ok
return s.t, s.v, s.h, s.fh, ok
}
// Buffer returns an iterator over the buffered data. Invalidates previously

2
storage/buffer_test.go
View file

@ -107,7 +107,7 @@ func TestBufferedSeriesIterator(t *testing.T) {
require.Equal(t, ev, v, "value mismatch")
}
prevSampleEq := func(ets int64, ev float64, eok bool) {
ts, v, _, ok := it.PeekBack(1)
ts, v, _, _, ok := it.PeekBack(1)
require.Equal(t, eok, ok, "exist mismatch")
require.Equal(t, ets, ts, "timestamp mismatch")
require.Equal(t, ev, v, "value mismatch")

12
web/federate.go
View file

@ -116,7 +116,8 @@ Loop:
var (
t int64
v float64
h *histogram.FloatHistogram
h *histogram.Histogram
fh *histogram.FloatHistogram
ok bool
)
valueType := it.Seek(maxt)
@ -124,12 +125,15 @@ Loop:
case chunkenc.ValFloat:
t, v = it.At()
case chunkenc.ValFloatHistogram, chunkenc.ValHistogram:
t, h = it.AtFloatHistogram()
t, fh = it.AtFloatHistogram()
default:
t, v, _, ok = it.PeekBack(1)
t, v, h, fh, ok = it.PeekBack(1)
if !ok {
continue Loop
}
if h != nil {
fh = h.ToFloat()
}
}
// The exposition formats do not support stale markers, so drop them. This
// is good enough for staleness handling of federated data, as the
@ -141,7 +145,7 @@ Loop:
vec = append(vec, promql.Sample{
Metric: s.Labels(),
Point: promql.Point{T: t, V: v, H: h},
Point: promql.Point{T: t, V: v, H: fh},
})
}
if ws := set.Warnings(); len(ws) > 0 {

8
web/federate_test.go
View file

@ -340,16 +340,16 @@ func TestFederationWithNativeHistograms(t *testing.T) {
l := labels.FromStrings("__name__", "test_metric", "foo", fmt.Sprintf("%d", i))
expL := labels.FromStrings("__name__", "test_metric", "instance", "", "foo", fmt.Sprintf("%d", i))
if i%3 == 0 {
_, err = app.Append(0, l, 101*60*1000, float64(i*100))
_, err = app.Append(0, l, 100*60*1000, float64(i*100))
expVec = append(expVec, promql.Sample{
Point: promql.Point{T: 101 * 60 * 1000, V: float64(i * 100)},
Point: promql.Point{T: 100 * 60 * 1000, V: float64(i * 100)},
Metric: expL,
})
} else {
hist.ZeroCount++
_, err = app.AppendHistogram(0, l, 101*60*1000, hist.Copy(), nil)
_, err = app.AppendHistogram(0, l, 100*60*1000, hist.Copy(), nil)
expVec = append(expVec, promql.Sample{
Point: promql.Point{T: 101 * 60 * 1000, H: hist.ToFloat()},
Point: promql.Point{T: 100 * 60 * 1000, H: hist.ToFloat()},
Metric: expL,
})
}