Retention: switch number of days type uint16 -> float32

This allows specifying less than a day as threshold.
That is especially useful if history doesn't mattter as much as disk space.

internal/config/config.go

@@ -55,8 +55,8 @@ type Flags struct {
 
 // RetentionConfig defines configuration for history retention.
 type RetentionConfig struct {
-	HistoryDays uint16                   `yaml:"history-days"`
-	SlaDays     uint16                   `yaml:"sla-days"`
+	HistoryDays float32                  `yaml:"history-days"`
+	SlaDays     float32                  `yaml:"sla-days"`
 	Interval    time.Duration            `yaml:"interval" default:"1h"`
 	Count       uint64                   `yaml:"count" default:"5000"`
 	Options     history.RetentionOptions `yaml:"options"`

pkg/icingadb/history/retention.go

@@ -11,6 +11,7 @@ import (
 	"github.com/icinga/icingadb/pkg/icingaredis/telemetry"
 	"github.com/pkg/errors"
 	"go.uber.org/zap"
+	"math"
 	"time"
 )
 
@@ -95,7 +96,7 @@ var RetentionStatements = []retentionStatement{{
 }}
 
 // RetentionOptions defines the non-default mapping of history categories with their retention period in days.
-type RetentionOptions map[string]uint16
+type RetentionOptions map[string]float32
 
 // Validate checks constraints in the supplied retention options and
 // returns an error if they are violated.
@@ -120,8 +121,8 @@ func (o RetentionOptions) Validate() error {
 type Retention struct {
 	db          *database.DB
 	logger      *logging.Logger
-	historyDays uint16
-	slaDays     uint16
+	historyDays float32
+	slaDays     float32
 	interval    time.Duration
 	count       uint64
 	options     RetentionOptions
@@ -129,7 +130,7 @@ type Retention struct {
 
 // NewRetention returns a new Retention.
 func NewRetention(
-	db *database.DB, historyDays, slaDays uint16, interval time.Duration,
+	db *database.DB, historyDays, slaDays float32, interval time.Duration,
 	count uint64, options RetentionOptions, logger *logging.Logger,
 ) *Retention {
 	return &Retention{
@@ -156,7 +157,7 @@ func (r *Retention) Start(ctx context.Context) error {
 	errs := make(chan error, 1)
 
 	for _, stmt := range RetentionStatements {
-		var days uint16
+		var days float32
 		switch stmt.RetentionType {
 		case RetentionHistory:
 			if d, ok := r.options[stmt.Category]; ok {
@@ -168,7 +169,7 @@ func (r *Retention) Start(ctx context.Context) error {
 			days = r.slaDays
 		}
 
-		if days < 1 {
+		if days <= 0 {
 			r.logger.Debugf("Skipping history retention for category %s", stmt.Category)
 			continue
 		}
@@ -177,12 +178,21 @@ func (r *Retention) Start(ctx context.Context) error {
 			fmt.Sprintf("Starting history retention for category %s", stmt.Category),
 			zap.Uint64("count", r.count),
 			zap.Duration("interval", r.interval),
-			zap.Uint16("retention-days", days),
+			zap.Float32("retention-days", days),
 		)
 
 		stmt := stmt
 		periodic.Start(ctx, r.interval, func(tick periodic.Tick) {
-			olderThan := tick.Time.AddDate(0, 0, -int(days))
+			olderThan := tick.Time
+			wholeDays, dayFraction := math.Modf(float64(days))
+
+			if wholeDays > 0 {
+				olderThan = olderThan.AddDate(0, 0, -int(wholeDays))
+			}
+
+			if dayFraction > 0 {
+				olderThan = olderThan.Add(-time.Duration(dayFraction * float64(24*time.Hour)))
+			}
 
 			r.logger.Debugf("Cleaning up historical data for category %s from table %s older than %s",
 				stmt.Category, stmt.Table, olderThan)