VictoriaMetrics/lib/streamaggr/last.go
Roman Khavronenko 7cb894a777
lib/streamaggr: reduce number of inuse objects (#6402)
The main change is getting rid of interning of sample key. It was
discovered that for cases with many unique time series aggregated by
vmagent interned keys could grow up to hundreds of millions of objects.
This has negative impact on the following aspects:
1. It slows down garbage collection cycles, as GC has to scan all inuse
objects periodically. The higher is the number of inuse objects, the
longer it takes/the more CPU it takes.
2. It slows down the hot path of samples aggregation where each key
needs to be looked up in the map first.

The change makes code more fragile, but suppose to provide performance
optimization for heavy-loaded vmagents with stream aggregation enabled.

---------

Signed-off-by: hagen1778 <roman@victoriametrics.com>
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
2024-06-07 15:45:52 +02:00

87 lines
1.9 KiB
Go

package streamaggr
import (
"strings"
"sync"
"github.com/VictoriaMetrics/VictoriaMetrics/lib/fasttime"
)
// lastAggrState calculates output=last, e.g. the last value over input samples.
type lastAggrState struct {
m sync.Map
}
type lastStateValue struct {
mu sync.Mutex
last float64
timestamp int64
deleted bool
}
func newLastAggrState() *lastAggrState {
return &lastAggrState{}
}
func (as *lastAggrState) pushSamples(samples []pushSample) {
for i := range samples {
s := &samples[i]
outputKey := getOutputKey(s.key)
again:
v, ok := as.m.Load(outputKey)
if !ok {
// The entry is missing in the map. Try creating it.
v = &lastStateValue{
last: s.value,
timestamp: s.timestamp,
}
vNew, loaded := as.m.LoadOrStore(strings.Clone(outputKey), v)
if !loaded {
// The new entry has been successfully created.
continue
}
// Use the entry created by a concurrent goroutine.
v = vNew
}
sv := v.(*lastStateValue)
sv.mu.Lock()
deleted := sv.deleted
if !deleted {
if s.timestamp >= sv.timestamp {
sv.last = s.value
sv.timestamp = s.timestamp
}
}
sv.mu.Unlock()
if deleted {
// The entry has been deleted by the concurrent call to flushState
// Try obtaining and updating the entry again.
goto again
}
}
}
func (as *lastAggrState) flushState(ctx *flushCtx, resetState bool) {
currentTimeMsec := int64(fasttime.UnixTimestamp()) * 1000
m := &as.m
m.Range(func(k, v interface{}) bool {
if resetState {
// Atomically delete the entry from the map, so new entry is created for the next flush.
m.Delete(k)
}
sv := v.(*lastStateValue)
sv.mu.Lock()
last := sv.last
if resetState {
// Mark the entry as deleted, so it won't be updated anymore by concurrent pushSample() calls.
sv.deleted = true
}
sv.mu.Unlock()
key := k.(string)
ctx.appendSeries(key, "last", currentTimeMsec, last)
return true
})
}