/
memorylimiter.go
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/
memorylimiter.go
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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
package memorylimiter // import "go.opentelemetry.io/collector/internal/memorylimiter"
import (
"context"
"errors"
"fmt"
"runtime"
"sync"
"sync/atomic"
"time"
"go.uber.org/zap"
"go.opentelemetry.io/collector/component"
"go.opentelemetry.io/collector/internal/iruntime"
)
const (
mibBytes = 1024 * 1024
// Minimum interval between forced GC when in soft limited mode. We don't want to
// do GCs too frequently since it is a CPU-heavy operation.
minGCIntervalWhenSoftLimited = 10 * time.Second
)
var (
// ErrDataRefused will be returned to callers of ConsumeTraceData to indicate
// that data is being refused due to high memory usage.
ErrDataRefused = errors.New("data refused due to high memory usage")
// ErrShutdownNotStarted indicates no memorylimiter has not start when shutdown
ErrShutdownNotStarted = errors.New("no existing monitoring routine is running")
// GetMemoryFn and ReadMemStatsFn make it overridable by tests
GetMemoryFn = iruntime.TotalMemory
ReadMemStatsFn = runtime.ReadMemStats
)
// MemoryLimiter is used to prevent out of memory situations on the collector.
type MemoryLimiter struct {
usageChecker memUsageChecker
memCheckWait time.Duration
ballastSize uint64
// mustRefuse is used to indicate when data should be refused.
mustRefuse *atomic.Bool
ticker *time.Ticker
lastGCDone time.Time
// The function to read the mem values is set as a reference to help with
// testing different values.
readMemStatsFn func(m *runtime.MemStats)
// Fields used for logging.
logger *zap.Logger
configMismatchedLogged bool
refCounterLock sync.Mutex
refCounter int
waitGroup sync.WaitGroup
closed chan struct{}
}
// NewMemoryLimiter returns a new memory limiter component
func NewMemoryLimiter(cfg *Config, logger *zap.Logger) (*MemoryLimiter, error) {
usageChecker, err := getMemUsageChecker(cfg, logger)
if err != nil {
return nil, err
}
logger.Info("Memory limiter configured",
zap.Uint64("limit_mib", usageChecker.memAllocLimit/mibBytes),
zap.Uint64("spike_limit_mib", usageChecker.memSpikeLimit/mibBytes),
zap.Duration("check_interval", cfg.CheckInterval))
return &MemoryLimiter{
usageChecker: *usageChecker,
memCheckWait: cfg.CheckInterval,
ticker: time.NewTicker(cfg.CheckInterval),
readMemStatsFn: ReadMemStatsFn,
logger: logger,
mustRefuse: &atomic.Bool{},
}, nil
}
// startMonitoring starts a single ticker'd goroutine per instance
// that will check memory usage every checkInterval period.
func (ml *MemoryLimiter) startMonitoring() {
ml.refCounterLock.Lock()
defer ml.refCounterLock.Unlock()
ml.refCounter++
if ml.refCounter == 1 {
ml.closed = make(chan struct{})
ml.waitGroup.Add(1)
go func() {
defer ml.waitGroup.Done()
for {
select {
case <-ml.ticker.C:
case <-ml.closed:
return
}
ml.CheckMemLimits()
}
}()
}
}
func (ml *MemoryLimiter) Start(_ context.Context, host component.Host) error {
extensions := host.GetExtensions()
for _, extension := range extensions {
if ext, ok := extension.(interface{ GetBallastSize() uint64 }); ok {
ml.ballastSize = ext.GetBallastSize()
break
}
}
ml.startMonitoring()
return nil
}
// Shutdown resets MemoryLimiter monitoring ticker and stop monitoring
func (ml *MemoryLimiter) Shutdown(context.Context) error {
ml.refCounterLock.Lock()
defer ml.refCounterLock.Unlock()
if ml.refCounter == 0 {
return ErrShutdownNotStarted
} else if ml.refCounter == 1 {
ml.ticker.Stop()
close(ml.closed)
ml.waitGroup.Wait()
}
ml.refCounter--
return nil
}
// MustRefuse returns if the caller should deny because memory has reached it's configured limits
func (ml *MemoryLimiter) MustRefuse() bool {
return ml.mustRefuse.Load()
}
func getMemUsageChecker(cfg *Config, logger *zap.Logger) (*memUsageChecker, error) {
memAllocLimit := uint64(cfg.MemoryLimitMiB) * mibBytes
memSpikeLimit := uint64(cfg.MemorySpikeLimitMiB) * mibBytes
if cfg.MemoryLimitMiB != 0 {
return newFixedMemUsageChecker(memAllocLimit, memSpikeLimit), nil
}
totalMemory, err := GetMemoryFn()
if err != nil {
return nil, fmt.Errorf("failed to get total memory, use fixed memory settings (limit_mib): %w", err)
}
logger.Info("Using percentage memory limiter",
zap.Uint64("total_memory_mib", totalMemory/mibBytes),
zap.Uint32("limit_percentage", cfg.MemoryLimitPercentage),
zap.Uint32("spike_limit_percentage", cfg.MemorySpikePercentage))
return newPercentageMemUsageChecker(totalMemory, uint64(cfg.MemoryLimitPercentage),
uint64(cfg.MemorySpikePercentage)), nil
}
func (ml *MemoryLimiter) readMemStats() *runtime.MemStats {
ms := &runtime.MemStats{}
ml.readMemStatsFn(ms)
// If proper configured ms.Alloc should be at least ml.ballastSize but since
// a misconfiguration is possible check for that here.
if ms.Alloc >= ml.ballastSize {
ms.Alloc -= ml.ballastSize
} else if !ml.configMismatchedLogged {
// This indicates misconfiguration. Log it once.
ml.configMismatchedLogged = true
ml.logger.Warn(`"size_mib" in ballast extension is likely incorrectly configured.`)
}
return ms
}
func memstatToZapField(ms *runtime.MemStats) zap.Field {
return zap.Uint64("cur_mem_mib", ms.Alloc/mibBytes)
}
func (ml *MemoryLimiter) doGCandReadMemStats() *runtime.MemStats {
runtime.GC()
ml.lastGCDone = time.Now()
ms := ml.readMemStats()
ml.logger.Info("Memory usage after GC.", memstatToZapField(ms))
return ms
}
// CheckMemLimits inspects current memory usage against threshold and toggle mustRefuse when threshold is exceeded
func (ml *MemoryLimiter) CheckMemLimits() {
ms := ml.readMemStats()
ml.logger.Debug("Currently used memory.", memstatToZapField(ms))
if ml.usageChecker.aboveHardLimit(ms) {
ml.logger.Warn("Memory usage is above hard limit. Forcing a GC.", memstatToZapField(ms))
ms = ml.doGCandReadMemStats()
}
// Remember current state.
wasRefusing := ml.mustRefuse.Load()
// Check if the memory usage is above the soft limit.
mustRefuse := ml.usageChecker.aboveSoftLimit(ms)
if wasRefusing && !mustRefuse {
// Was previously refusing but enough memory is available now, no need to limit.
ml.logger.Info("Memory usage back within limits. Resuming normal operation.", memstatToZapField(ms))
}
if !wasRefusing && mustRefuse {
// We are above soft limit, do a GC if it wasn't done recently and see if
// it brings memory usage below the soft limit.
if time.Since(ml.lastGCDone) > minGCIntervalWhenSoftLimited {
ml.logger.Info("Memory usage is above soft limit. Forcing a GC.", memstatToZapField(ms))
ms = ml.doGCandReadMemStats()
// Check the limit again to see if GC helped.
mustRefuse = ml.usageChecker.aboveSoftLimit(ms)
}
if mustRefuse {
ml.logger.Warn("Memory usage is above soft limit. Refusing data.", memstatToZapField(ms))
}
}
ml.mustRefuse.Store(mustRefuse)
}
type memUsageChecker struct {
memAllocLimit uint64
memSpikeLimit uint64
}
func (d memUsageChecker) aboveSoftLimit(ms *runtime.MemStats) bool {
return ms.Alloc >= d.memAllocLimit-d.memSpikeLimit
}
func (d memUsageChecker) aboveHardLimit(ms *runtime.MemStats) bool {
return ms.Alloc >= d.memAllocLimit
}
func newFixedMemUsageChecker(memAllocLimit, memSpikeLimit uint64) *memUsageChecker {
if memSpikeLimit == 0 {
// If spike limit is unspecified use 20% of mem limit.
memSpikeLimit = memAllocLimit / 5
}
return &memUsageChecker{
memAllocLimit: memAllocLimit,
memSpikeLimit: memSpikeLimit,
}
}
func newPercentageMemUsageChecker(totalMemory uint64, percentageLimit, percentageSpike uint64) *memUsageChecker {
return newFixedMemUsageChecker(percentageLimit*totalMemory/100, percentageSpike*totalMemory/100)
}