Files
cc-metric-collector/pkg/multiChanTicker/multiChanTicker.go
moebiusband 3d4c464166 Fix metric timeseries gaps on nodes with many cores
On nodes with >300 cores, one interval's burst of per-hwthread metrics
overran the fixed 200-slot channels. With blocking sends at every hop,
sink back-pressure propagated to the collectors, the collection round
exceeded the interval, and time.Ticker silently dropped the missed
ticks - whole intervals were skipped without any log message.

- multiChanTicker: deliver ticks non-blockingly and warn when a
  consumer misses a tick instead of stalling all consumers; guard the
  channel list with a mutex (data race with AddChannel)
- collectorManager: run the collection round detached from the tick
  loop, skip-and-warn when a round is still running, log per-collector
  and per-round durations at debug level, close serial collectors on
  shutdown
- metricRouter: buffer the interval timestamp channel and drain it
  before stamping, so metrics never carry the previous interval's
  timestamp; warn when the collector input channel is full at tick time
- main: scale the inter-manager channels to max(200, 24*NumCPU),
  overridable with the new optional channel_buffer_size config option
- add first unit tests for ticker, collector manager and router

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
2026-07-07 21:18:16 +02:00

84 lines
2.0 KiB
Go

// Copyright (C) NHR@FAU, University Erlangen-Nuremberg.
// All rights reserved. This file is part of cc-lib.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
// additional authors:
// Holger Obermaier (NHR@KIT)
package multiChanTicker
import (
"fmt"
"sync"
"time"
cclog "github.com/ClusterCockpit/cc-lib/v2/ccLogger"
)
type multiChanTicker struct {
ticker *time.Ticker
mutex sync.Mutex // protects channels, which is appended to while the tick goroutine iterates it
channels []chan time.Time
done chan bool
}
type MultiChanTicker interface {
Init(duration time.Duration)
AddChannel(channel chan time.Time)
Close()
}
func (t *multiChanTicker) Init(duration time.Duration) {
t.ticker = time.NewTicker(duration)
t.done = make(chan bool)
go func() {
done := func() {
close(t.done)
cclog.ComponentDebug("MultiChanTicker", "DONE")
}
for {
select {
case <-t.done:
done()
return
case ts := <-t.ticker.C:
cclog.ComponentDebug("MultiChanTicker", "Tick", ts)
t.mutex.Lock()
for i, c := range t.channels {
// Non-blocking send: a consumer that has not yet read the
// previous tick must not stall the ticker, otherwise
// time.Ticker silently drops fires for ALL consumers
select {
case c <- ts:
default:
cclog.ComponentWarn("MultiChanTicker", fmt.Sprintf("consumer %d did not read previous tick, dropping tick %v", i, ts))
}
}
t.mutex.Unlock()
}
}
}()
}
func (t *multiChanTicker) AddChannel(channel chan time.Time) {
if cap(channel) == 0 {
cclog.ComponentWarn("MultiChanTicker", "unbuffered channel registered, ticks may be dropped if the consumer is not ready")
}
t.mutex.Lock()
t.channels = append(t.channels, channel)
t.mutex.Unlock()
}
func (t *multiChanTicker) Close() {
cclog.ComponentDebug("MultiChanTicker", "CLOSE")
t.done <- true
// wait for close of channel t.done
<-t.done
}
func NewTicker(duration time.Duration) MultiChanTicker {
t := &multiChanTicker{}
t.Init(duration)
return t
}