Merge branch 'main' into add-example-for-customlabels
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commit
86cdda8cb1
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@ -1,5 +1,11 @@
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## Unreleased
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* [BUGFIX] histograms: Fix possible data race when appending exemplars vs metrics gather. #1623
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## 1.20.3 / 2024-09-05
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* [BUGFIX] histograms: Fix possible data race when appending exemplars. #1608
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## 1.20.2 / 2024-08-23
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* [BUGFIX] promhttp: Unset Content-Encoding header when data is uncompressed. #1596
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@ -844,9 +844,7 @@ func (h *histogram) Write(out *dto.Metric) error {
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}}
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}
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// If exemplars are not configured, the cap will be 0.
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// So append is not needed in this case.
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if cap(h.nativeExemplars.exemplars) > 0 {
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if h.nativeExemplars.isEnabled() {
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h.nativeExemplars.Lock()
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his.Exemplars = append(his.Exemplars, h.nativeExemplars.exemplars...)
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h.nativeExemplars.Unlock()
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@ -1658,10 +1656,17 @@ func addAndResetCounts(hot, cold *histogramCounts) {
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type nativeExemplars struct {
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sync.Mutex
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ttl time.Duration
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// Time-to-live for exemplars, it is set to -1 if exemplars are disabled, that is NativeHistogramMaxExemplars is below 0.
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// The ttl is used on insertion to remove an exemplar that is older than ttl, if present.
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ttl time.Duration
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exemplars []*dto.Exemplar
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}
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func (n *nativeExemplars) isEnabled() bool {
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return n.ttl != -1
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}
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func makeNativeExemplars(ttl time.Duration, maxCount int) nativeExemplars {
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if ttl == 0 {
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ttl = 5 * time.Minute
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@ -1673,6 +1678,7 @@ func makeNativeExemplars(ttl time.Duration, maxCount int) nativeExemplars {
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if maxCount < 0 {
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maxCount = 0
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ttl = -1
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}
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return nativeExemplars{
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@ -1682,20 +1688,18 @@ func makeNativeExemplars(ttl time.Duration, maxCount int) nativeExemplars {
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}
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func (n *nativeExemplars) addExemplar(e *dto.Exemplar) {
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if cap(n.exemplars) == 0 {
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if !n.isEnabled() {
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return
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}
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n.Lock()
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defer n.Unlock()
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// The index where to insert the new exemplar.
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var nIdx int = -1
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// When the number of exemplars has not yet exceeded or
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// is equal to cap(n.exemplars), then
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// insert the new exemplar directly.
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if len(n.exemplars) < cap(n.exemplars) {
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var nIdx int
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for nIdx = 0; nIdx < len(n.exemplars); nIdx++ {
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if *e.Value < *n.exemplars[nIdx].Value {
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break
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@ -1705,17 +1709,46 @@ func (n *nativeExemplars) addExemplar(e *dto.Exemplar) {
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return
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}
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if len(n.exemplars) == 1 {
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// When the number of exemplars is 1, then
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// replace the existing exemplar with the new exemplar.
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n.exemplars[0] = e
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return
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}
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// From this point on, the number of exemplars is greater than 1.
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// When the number of exemplars exceeds the limit, remove one exemplar.
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var (
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rIdx int // The index where to remove the old exemplar.
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ot = time.Time{} // Oldest timestamp seen. Initial value doesn't matter as we replace it due to otIdx == -1 in the loop.
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otIdx = -1 // Index of the exemplar with the oldest timestamp.
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ot = time.Now() // Oldest timestamp seen.
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otIdx = -1 // Index of the exemplar with the oldest timestamp.
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md = -1.0 // Logarithm of the delta of the closest pair of exemplars.
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md = -1.0 // Logarithm of the delta of the closest pair of exemplars.
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mdIdx = -1 // Index of the older exemplar within the closest pair.
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cLog float64 // Logarithm of the current exemplar.
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pLog float64 // Logarithm of the previous exemplar.
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// The insertion point of the new exemplar in the exemplars slice after insertion.
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// This is calculated purely based on the order of the exemplars by value.
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// nIdx == len(n.exemplars) means the new exemplar is to be inserted after the end.
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nIdx = -1
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// rIdx is ultimately the index for the exemplar that we are replacing with the new exemplar.
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// The aim is to keep a good spread of exemplars by value and not let them bunch up too much.
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// It is calculated in 3 steps:
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// 1. First we set rIdx to the index of the older exemplar within the closest pair by value.
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// That is the following will be true (on log scale):
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// either the exemplar pair on index (rIdx-1, rIdx) or (rIdx, rIdx+1) will have
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// the closest values to each other from all pairs.
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// For example, suppose the values are distributed like this:
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// |-----------x-------------x----------------x----x-----|
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// ^--rIdx as this is older.
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// Or like this:
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// |-----------x-------------x----------------x----x-----|
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// ^--rIdx as this is older.
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// 2. If there is an exemplar that expired, then we simple reset rIdx to that index.
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// 3. We check if by inserting the new exemplar we would create a closer pair at
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// (nIdx-1, nIdx) or (nIdx, nIdx+1) and set rIdx to nIdx-1 or nIdx accordingly to
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// keep the spread of exemplars by value; otherwise we keep rIdx as it is.
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rIdx = -1
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cLog float64 // Logarithm of the current exemplar.
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pLog float64 // Logarithm of the previous exemplar.
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)
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for i, exemplar := range n.exemplars {
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@ -1726,7 +1759,7 @@ func (n *nativeExemplars) addExemplar(e *dto.Exemplar) {
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}
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// Find the index at which to insert new the exemplar.
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if *e.Value <= *exemplar.Value && nIdx == -1 {
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if nIdx == -1 && *e.Value <= *exemplar.Value {
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nIdx = i
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}
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@ -1738,11 +1771,13 @@ func (n *nativeExemplars) addExemplar(e *dto.Exemplar) {
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}
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diff := math.Abs(cLog - pLog)
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if md == -1 || diff < md {
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// The closest exemplar pair is at index: i-1, i.
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// Choose the exemplar with the older timestamp for replacement.
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md = diff
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if n.exemplars[i].Timestamp.AsTime().Before(n.exemplars[i-1].Timestamp.AsTime()) {
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mdIdx = i
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rIdx = i
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} else {
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mdIdx = i - 1
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rIdx = i - 1
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}
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}
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@ -1753,8 +1788,12 @@ func (n *nativeExemplars) addExemplar(e *dto.Exemplar) {
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if nIdx == -1 {
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nIdx = len(n.exemplars)
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}
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// Here, we have the following relationships:
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// n.exemplars[nIdx-1].Value < e.Value (if nIdx > 0)
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// e.Value <= n.exemplars[nIdx].Value (if nIdx < len(n.exemplars))
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if otIdx != -1 && e.Timestamp.AsTime().Sub(ot) > n.ttl {
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// If the oldest exemplar has expired, then replace it with the new exemplar.
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rIdx = otIdx
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} else {
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// In the previous for loop, when calculating the closest pair of exemplars,
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@ -1764,23 +1803,26 @@ func (n *nativeExemplars) addExemplar(e *dto.Exemplar) {
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if nIdx > 0 {
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diff := math.Abs(elog - math.Log(n.exemplars[nIdx-1].GetValue()))
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if diff < md {
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// The value we are about to insert is closer to the previous exemplar at the insertion point than what we calculated before in rIdx.
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// v--rIdx
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// |-----------x-n-----------x----------------x----x-----|
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// nIdx-1--^ ^--new exemplar value
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// Do not make the spread worse, replace nIdx-1 and not rIdx.
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md = diff
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mdIdx = nIdx
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if n.exemplars[nIdx-1].Timestamp.AsTime().Before(e.Timestamp.AsTime()) {
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mdIdx = nIdx - 1
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}
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rIdx = nIdx - 1
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}
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}
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if nIdx < len(n.exemplars) {
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diff := math.Abs(math.Log(n.exemplars[nIdx].GetValue()) - elog)
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if diff < md {
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mdIdx = nIdx
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if n.exemplars[nIdx].Timestamp.AsTime().Before(e.Timestamp.AsTime()) {
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mdIdx = nIdx
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}
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// The value we are about to insert is closer to the next exemplar at the insertion point than what we calculated before in rIdx.
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// v--rIdx
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// |-----------x-----------n-x----------------x----x-----|
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// new exemplar value--^ ^--nIdx
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// Do not make the spread worse, replace nIdx-1 and not rIdx.
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rIdx = nIdx
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}
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}
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rIdx = mdIdx
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}
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// Adjust the slice according to rIdx and nIdx.
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@ -1049,10 +1049,14 @@ func TestNativeHistogramConcurrency(t *testing.T) {
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go func(vals []float64) {
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start.Wait()
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for _, v := range vals {
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for i, v := range vals {
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// An observation every 1 to 10 seconds.
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atomic.AddInt64(&ts, rand.Int63n(10)+1)
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his.Observe(v)
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if i%2 == 0 {
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his.Observe(v)
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} else {
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his.(ExemplarObserver).ObserveWithExemplar(v, Labels{"foo": "bar"})
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}
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}
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end.Done()
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}(vals)
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