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TSDB: Allocate series ID after seriesLifecycleCallback

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This callback is not used by Prometheus, but in downstream projects it
is wasteful to allocate an ID only to abandon it.

Remove lengthy commment which I feel is distracting from the flow.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
This commit is contained in:
Bryan Boreham 2025-10-17 11:04:34 +01:00
parent 2852c9c431
commit 42b52ecc4b
3 changed files with 10 additions and 11 deletions
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15
tsdb/head.go
View File

@ -1738,24 +1738,23 @@ func (*Head) String() string {
}
func (h *Head) getOrCreate(hash uint64, lset labels.Labels, pendingCommit bool) (*memSeries, bool, error) {
// Just using `getOrCreateWithID` below would be semantically sufficient, but we'd create
// a new series on every sample inserted via Add(), which causes allocations
// and makes our series IDs rather random and harder to compress in postings.
s := h.series.getByHash(hash, lset)
if s != nil {
return s, false, nil
}
// Optimistically assume that we are the first one to create the series.
id := chunks.HeadSeriesRef(h.lastSeriesID.Inc())
return h.getOrCreateWithID(id, hash, lset, pendingCommit)
return h.getOrCreateWithOptionalID(0, hash, lset, pendingCommit)
}
func (h *Head) getOrCreateWithID(id chunks.HeadSeriesRef, hash uint64, lset labels.Labels, pendingCommit bool) (*memSeries, bool, error) {
// If id is zero, one will be allocated.
func (h *Head) getOrCreateWithOptionalID(id chunks.HeadSeriesRef, hash uint64, lset labels.Labels, pendingCommit bool) (*memSeries, bool, error) {
if preCreationErr := h.series.seriesLifecycleCallback.PreCreation(lset); preCreationErr != nil {
return nil, false, preCreationErr
}
if id == 0 {
// Note this id is wasted in the case where a concurrent operation creates the same series first.
id = chunks.HeadSeriesRef(h.lastSeriesID.Inc())
}
shardHash := uint64(0)
if h.opts.EnableSharding {

2
tsdb/head_test.go
View File

@ -1152,7 +1152,7 @@ func TestHead_KeepSeriesInWALCheckpoint(t *testing.T) {
{
name: "keep series still in the head",
prepare: func(t *testing.T, h *Head) {
_, _, err := h.getOrCreateWithID(chunks.HeadSeriesRef(existingRef), existingLbls.Hash(), existingLbls, false)
_, _, err := h.getOrCreateWithOptionalID(chunks.HeadSeriesRef(existingRef), existingLbls.Hash(), existingLbls, false)
require.NoError(t, err)
},
expected: true,

4
tsdb/head_wal.go
View File

@ -255,7 +255,7 @@ Outer:
switch v := d.(type) {
case []record.RefSeries:
for _, walSeries := range v {
mSeries, created, err := h.getOrCreateWithID(walSeries.Ref, walSeries.Labels.Hash(), walSeries.Labels, false)
mSeries, created, err := h.getOrCreateWithOptionalID(walSeries.Ref, walSeries.Labels.Hash(), walSeries.Labels, false)
if err != nil {
seriesCreationErr = err
break Outer
@ -1590,7 +1590,7 @@ func (h *Head) loadChunkSnapshot() (int, int, map[chunks.HeadSeriesRef]*memSerie
localRefSeries := shardedRefSeries[idx]
for csr := range rc {
series, _, err := h.getOrCreateWithID(csr.ref, csr.lset.Hash(), csr.lset, false)
series, _, err := h.getOrCreateWithOptionalID(csr.ref, csr.lset.Hash(), csr.lset, false)
if err != nil {
errChan <- err
return