feat: Pattern ingesters add a limiter for high eviction rate (#13464)

Author: cyriltovena

docs/sources/shared/configuration.md

@@ -583,7 +583,17 @@ pattern_ingester:
   # first flush check is delayed by a random time up to 0.8x the flush check
   # period. Additionally, there is +/- 1% jitter added to the interval.
   # CLI flag: -pattern-ingester.flush-check-period
-  [flush_check_period: <duration> | default = 30s]
+  [flush_check_period: <duration> | default = 1m]
+
+  # The maximum number of detected pattern clusters that can be created by
+  # streams.
+  # CLI flag: -pattern-ingester.max-clusters
+  [max_clusters: <int> | default = 300]
+
+  # The maximum eviction ratio of patterns per stream. Once that ratio is
+  # reached, the stream will throttled pattern detection.
+  # CLI flag: -pattern-ingester.max-eviction-ratio
+  [max_eviction_ratio: <float> | default = 0.25]
 
   # Configures the metric aggregation and storage behavior of the pattern
   # ingester.

pkg/pattern/chunk/util.go

@@ -8,7 +8,7 @@ import (
 
 const (
 	TimeResolution = model.Time(int64(time.Second*10) / 1e6)
-	MaxChunkTime   = 1 * time.Hour
+	MaxChunkTime   = 15 * time.Minute
 )
 
 func TruncateTimestamp(ts, step model.Time) model.Time { return ts - ts%step }

pkg/pattern/drain/drain.go

@@ -36,13 +36,14 @@ import (
 )
 
 type Config struct {
-	maxNodeDepth    int
-	LogClusterDepth int
-	SimTh           float64
-	MaxChildren     int
-	ExtraDelimiters []string
-	MaxClusters     int
-	ParamString     string
+	maxNodeDepth     int
+	LogClusterDepth  int
+	SimTh            float64
+	MaxChildren      int
+	ExtraDelimiters  []string
+	MaxClusters      int
+	ParamString      string
+	MaxEvictionRatio float64
 }
 
 func createLogClusterCache(maxSize int, onEvict func(int, *LogCluster)) *LogClusterCache {
@@ -60,29 +61,13 @@ type LogClusterCache struct {
 }
 
 func (c *LogClusterCache) Values() []*LogCluster {
-	values := make([]*LogCluster, 0)
-	for _, key := range c.cache.Keys() {
-		if value, ok := c.cache.Peek(key); ok {
-			values = append(values, value)
-		}
-	}
-	return values
+	return c.cache.Values()
 }
 
 func (c *LogClusterCache) Set(key int, cluster *LogCluster) {
 	c.cache.Add(key, cluster)
 }
 
-func (c *LogClusterCache) Iterate(fn func(*LogCluster) bool) {
-	for _, key := range c.cache.Keys() {
-		if value, ok := c.cache.Peek(key); ok {
-			if !fn(value) {
-				return
-			}
-		}
-	}
-}
-
 func (c *LogClusterCache) Get(key int) *LogCluster {
 	cluster, ok := c.cache.Get(key)
 	if !ok {
@@ -140,10 +125,11 @@ func DefaultConfig() *Config {
 		// Both SimTh and MaxClusterDepth impact branching factor: the greater
 		// MaxClusterDepth and SimTh, the less the chance that there will be
 		// "similar" clusters, but the greater the footprint.
-		SimTh:       0.3,
-		MaxChildren: 15,
-		ParamString: `<_>`,
-		MaxClusters: 300,
+		SimTh:            0.3,
+		MaxChildren:      15,
+		ParamString:      `<_>`,
+		MaxClusters:      300,
+		MaxEvictionRatio: 0.25,
 	}
 }
 
@@ -152,10 +138,17 @@ func New(config *Config, format string, metrics *Metrics) *Drain {
 		panic("depth argument must be at least 3")
 	}
 	config.maxNodeDepth = config.LogClusterDepth - 2
-	var evictFn func(int, *LogCluster)
-	if metrics != nil {
-		evictFn = func(int, *LogCluster) { metrics.PatternsEvictedTotal.Inc() }
+
+	d := &Drain{
+		config:               config,
+		rootNode:             createNode(),
+		metrics:              metrics,
+		maxAllowedLineLength: 3000,
+		format:               format,
 	}
+
+	limiter := newLimiter(config.MaxEvictionRatio)
+
 	var tokenizer LineTokenizer
 	switch format {
 	case FormatJSON:
@@ -165,16 +158,20 @@ func New(config *Config, format string, metrics *Metrics) *Drain {
 	default:
 		tokenizer = newPunctuationTokenizer()
 	}
-
-	d := &Drain{
-		config:               config,
-		rootNode:             createNode(),
-		idToCluster:          createLogClusterCache(config.MaxClusters, evictFn),
-		metrics:              metrics,
-		tokenizer:            tokenizer,
-		maxAllowedLineLength: 3000,
-		format:               format,
-	}
+	d.idToCluster = createLogClusterCache(config.MaxClusters, func(int, *LogCluster) {
+		if metrics != nil {
+			if d.pruning {
+				metrics.PatternsPrunedTotal.Inc()
+			} else {
+				metrics.PatternsEvictedTotal.Inc()
+			}
+		}
+		if !d.pruning {
+			limiter.Evict()
+		}
+	})
+	d.tokenizer = tokenizer
+	d.limiter = limiter
 	return d
 }
 
@@ -189,6 +186,8 @@ type Drain struct {
 	format               string
 	tokens               []string
 	state                interface{}
+	limiter              *limiter
+	pruning              bool
 }
 
 func (d *Drain) Clusters() []*LogCluster {
@@ -200,6 +199,9 @@ func (d *Drain) TrainTokens(tokens []string, stringer func([]string) string, ts
 }
 
 func (d *Drain) Train(content string, ts int64) *LogCluster {
+	if !d.limiter.Allow() {
+		return nil
+	}
 	if len(content) > d.maxAllowedLineLength {
 		return nil
 	}
@@ -325,7 +327,9 @@ func (d *Drain) pruneTree(node *Node) int {
 }
 
 func (d *Drain) Delete(cluster *LogCluster) {
+	d.pruning = true
 	d.idToCluster.cache.Remove(cluster.id)
+	d.pruning = false
 }
 
 func (d *Drain) treeSearch(rootNode *Node, tokens []string, simTh float64, includeParams bool) *LogCluster {

pkg/pattern/drain/limiter.go

@@ -0,0 +1,51 @@
+package drain
+
+import (
+	"time"
+)
+
+type limiter struct {
+	added         int64
+	evicted       int64
+	maxPercentage float64
+	blockedUntil  time.Time
+}
+
+func newLimiter(maxPercentage float64) *limiter {
+	return &limiter{
+		maxPercentage: maxPercentage,
+	}
+}
+
+func (l *limiter) Allow() bool {
+	if !l.blockedUntil.IsZero() {
+		if time.Now().Before(l.blockedUntil) {
+			return false
+		}
+		l.reset()
+	}
+	if l.added == 0 {
+		l.added++
+		return true
+	}
+	if float64(l.evicted)/float64(l.added) > l.maxPercentage {
+		l.block()
+		return false
+	}
+	l.added++
+	return true
+}
+
+func (l *limiter) Evict() {
+	l.evicted++
+}
+
+func (l *limiter) reset() {
+	l.added = 0
+	l.evicted = 0
+	l.blockedUntil = time.Time{}
+}
+
+func (l *limiter) block() {
+	l.blockedUntil = time.Now().Add(10 * time.Minute)
+}

pkg/pattern/drain/limiter_test.go

@@ -0,0 +1,70 @@
+package drain
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestNewLimiter(t *testing.T) {
+	maxPercentage := 0.5
+	l := newLimiter(maxPercentage)
+	require.NotNil(t, l, "expected non-nil limiter")
+	require.Equal(t, maxPercentage, l.maxPercentage, "expected maxPercentage to match")
+	require.Equal(t, int64(0), l.added, "expected added to be 0")
+	require.Equal(t, int64(0), l.evicted, "expected evicted to be 0")
+	require.True(t, l.blockedUntil.IsZero(), "expected blockedUntil to be zero")
+}
+
+func TestLimiterAllow(t *testing.T) {
+	maxPercentage := 0.5
+	l := newLimiter(maxPercentage)
+
+	// Test allowing when no evictions
+	require.True(t, l.Allow(), "expected Allow to return true initially")
+
+	// Test allowing until evictions exceed maxPercentage
+	for i := 0; i < 2; i++ {
+		require.True(t, l.Allow(), "expected Allow to return true %d", i)
+		l.Evict()
+	}
+
+	// Evict to exceed maxPercentage
+	l.Evict()
+	require.False(t, l.Allow(), "expected Allow to return false after evictions exceed maxPercentage")
+
+	// Test blocking time
+	require.False(t, l.blockedUntil.IsZero(), "expected blockedUntil to be set")
+
+	// Fast forward time to simulate block duration passing
+	l.blockedUntil = time.Now().Add(-1 * time.Minute)
+	require.True(t, l.Allow(), "expected Allow to return true after block duration")
+}
+
+func TestLimiterEvict(t *testing.T) {
+	l := newLimiter(0.5)
+	l.Evict()
+	require.Equal(t, int64(1), l.evicted, "expected evicted to be 1")
+	l.Evict()
+	require.Equal(t, int64(2), l.evicted, "expected evicted to be 2")
+}
+
+func TestLimiterReset(t *testing.T) {
+	l := newLimiter(0.5)
+	l.added = 10
+	l.evicted = 5
+	l.blockedUntil = time.Now().Add(10 * time.Minute)
+	l.reset()
+	require.Equal(t, int64(0), l.added, "expected added to be 0")
+	require.Equal(t, int64(0), l.evicted, "expected evicted to be 0")
+	require.True(t, l.blockedUntil.IsZero(), "expected blockedUntil to be zero")
+}
+
+func TestLimiterBlock(t *testing.T) {
+	l := newLimiter(0.5)
+	l.block()
+	require.False(t, l.blockedUntil.IsZero(), "expected blockedUntil to be set")
+	require.False(t, l.Allow())
+	require.True(t, l.blockedUntil.After(time.Now()), "expected blockedUntil to be in the future")
+}

pkg/pattern/drain/metrics.go

@@ -29,6 +29,7 @@ func DetectLogFormat(line string) string {
 
 type Metrics struct {
 	PatternsEvictedTotal  prometheus.Counter
+	PatternsPrunedTotal   prometheus.Counter
 	PatternsDetectedTotal prometheus.Counter
 	TokensPerLine         prometheus.Observer
 	StatePerLine          prometheus.Observer

pkg/pattern/ingester.go

@@ -23,6 +23,7 @@ import (
 	"github.com/grafana/loki/v3/pkg/logproto"
 	"github.com/grafana/loki/v3/pkg/logql/syntax"
 	"github.com/grafana/loki/v3/pkg/pattern/clientpool"
+	"github.com/grafana/loki/v3/pkg/pattern/drain"
 	"github.com/grafana/loki/v3/pkg/pattern/metric"
 	"github.com/grafana/loki/v3/pkg/util"
 	util_log "github.com/grafana/loki/v3/pkg/util/log"
@@ -39,6 +40,8 @@ type Config struct {
 	ClientConfig      clientpool.Config     `yaml:"client_config,omitempty" doc:"description=Configures how the pattern ingester will connect to the ingesters."`
 	ConcurrentFlushes int                   `yaml:"concurrent_flushes"`
 	FlushCheckPeriod  time.Duration         `yaml:"flush_check_period"`
+	MaxClusters       int                   `yaml:"max_clusters,omitempty" doc:"description=The maximum number of detected pattern clusters that can be created by streams."`
+	MaxEvictionRatio  float64               `yaml:"max_eviction_ratio,omitempty" doc:"description=The maximum eviction ratio of patterns per stream. Once that ratio is reached, the stream will throttled pattern detection."`
 
 	MetricAggregation metric.AggregationConfig `yaml:"metric_aggregation,omitempty" doc:"description=Configures the metric aggregation and storage behavior of the pattern ingester."`
 	// For testing.
@@ -53,7 +56,9 @@ func (cfg *Config) RegisterFlags(fs *flag.FlagSet) {
 
 	fs.BoolVar(&cfg.Enabled, "pattern-ingester.enabled", false, "Flag to enable or disable the usage of the pattern-ingester component.")
 	fs.IntVar(&cfg.ConcurrentFlushes, "pattern-ingester.concurrent-flushes", 32, "How many flushes can happen concurrently from each stream.")
-	fs.DurationVar(&cfg.FlushCheckPeriod, "pattern-ingester.flush-check-period", 30*time.Second, "How often should the ingester see if there are any blocks to flush. The first flush check is delayed by a random time up to 0.8x the flush check period. Additionally, there is +/- 1% jitter added to the interval.")
+	fs.DurationVar(&cfg.FlushCheckPeriod, "pattern-ingester.flush-check-period", 1*time.Minute, "How often should the ingester see if there are any blocks to flush. The first flush check is delayed by a random time up to 0.8x the flush check period. Additionally, there is +/- 1% jitter added to the interval.")
+	fs.IntVar(&cfg.MaxClusters, "pattern-ingester.max-clusters", drain.DefaultConfig().MaxClusters, "The maximum number of detected pattern clusters that can be created by the pattern ingester.")
+	fs.Float64Var(&cfg.MaxEvictionRatio, "pattern-ingester.max-eviction-ratio", drain.DefaultConfig().MaxEvictionRatio, "The maximum eviction ratio of patterns per stream. Once that ratio is reached, the stream will be throttled for pattern detection.")
 }
 
 func (cfg *Config) Validate() error {
@@ -85,6 +90,7 @@ type Ingester struct {
 
 	metrics      *ingesterMetrics
 	chunkMetrics *metric.ChunkMetrics
+	drainCfg     *drain.Config
 }
 
 func New(
@@ -97,6 +103,10 @@ func New(
 	chunkMetrics := metric.NewChunkMetrics(registerer, metricsNamespace)
 	registerer = prometheus.WrapRegistererWithPrefix(metricsNamespace+"_", registerer)
 
+	drainCfg := drain.DefaultConfig()
+	drainCfg.MaxClusters = cfg.MaxClusters
+	drainCfg.MaxEvictionRatio = cfg.MaxEvictionRatio
+
 	i := &Ingester{
 		cfg:          cfg,
 		logger:       log.With(logger, "component", "pattern-ingester"),
@@ -106,6 +116,7 @@ func New(
 		instances:    make(map[string]*instance),
 		flushQueues:  make([]*util.PriorityQueue, cfg.ConcurrentFlushes),
 		loopQuit:     make(chan struct{}),
+		drainCfg:     drainCfg,
 	}
 	i.Service = services.NewBasicService(i.starting, i.running, i.stopping)
 	var err error
@@ -357,6 +368,7 @@ func (i *Ingester) GetOrCreateInstance(instanceID string) (*instance, error) { /
 			i.logger,
 			i.metrics,
 			i.chunkMetrics,
+			i.drainCfg,
 			i.cfg.MetricAggregation,
 		)
 		if err != nil {

pkg/pattern/ingester_test.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/grafana/loki/v3/pkg/logproto"
 	"github.com/grafana/loki/v3/pkg/logql/syntax"
+	"github.com/grafana/loki/v3/pkg/pattern/drain"
 	"github.com/grafana/loki/v3/pkg/pattern/iter"
 	"github.com/grafana/loki/v3/pkg/pattern/metric"
 
@@ -28,6 +29,7 @@ func setup(t *testing.T) *instance {
 		log.NewNopLogger(),
 		newIngesterMetrics(nil, "test"),
 		metric.NewChunkMetrics(nil, "test"),
+		drain.DefaultConfig(),
 		metric.AggregationConfig{
 			Enabled: true,
 		},