chore(cache): max entries type int -> uint

internal/config/settings/lru.go

@@ -1,9 +1,6 @@
 package settings
 
 import (
-	"errors"
-	"fmt"
-
 	"github.com/qdm12/gosettings"
 	"github.com/qdm12/gotree"
 )
@@ -12,21 +9,15 @@ type CacheLRU struct {
 	// MaxEntries is the number of maximum entries
 	// to keep in the LRU cache. It defaults to 10e4
 	// if letf unset.
-	MaxEntries int
+	MaxEntries uint
 }
 
 func (c *CacheLRU) setDefaults() {
 	const defaultMaxEntries = 10e4
 	c.MaxEntries = gosettings.DefaultNumber(c.MaxEntries, defaultMaxEntries)
 }
 
-var ErrMaxEntriesNegative = errors.New("max entries must be positive")
-
 func (c *CacheLRU) validate() error {
-	if c.MaxEntries < 0 {
-		return fmt.Errorf("%w: %d", ErrMaxEntriesNegative, c.MaxEntries)
-	}
-
 	return nil
 }
 

internal/config/sources/env/cache.go

@@ -3,6 +3,7 @@ package env
 import (
 	"errors"
 	"fmt"
+	"math"
 	"os"
 	"strconv"
 	"strings"
@@ -23,18 +24,26 @@ func readCache() (settings settings.Cache, err error) {
 
 var ErrCacheLRUMaxEntries = errors.New("invalid value for max entries of the LRU cache")
 
-func getLRUCacheMaxEntries() (maxEntries int, err error) {
+func getLRUCacheMaxEntries() (maxEntries uint, err error) {
 	s := os.Getenv("CACHE_LRU_MAX_ENTRIES")
 	if s == "" {
 		return 0, nil
 	}
 
-	maxEntries, err = strconv.Atoi(s)
-	if err != nil {
+	const base, bits = 10, 64
+	maxEntriesUint64, err := strconv.ParseUint(s, base, bits)
+	switch {
+	case err != nil:
 		return 0, fmt.Errorf("environment variable CACHE_LRU_MAX_ENTRIES: %w", err)
-	} else if maxEntries < 1 {
-		return 0, fmt.Errorf("%w: must be strictly positive: %d",
-			ErrCacheLRUMaxEntries, maxEntries)
+	case maxEntries == 0:
+		return 0, fmt.Errorf("%w: cannot be zero", ErrCacheLRUMaxEntries)
+	case maxEntries > math.MaxInt:
+		// down the call stack, maxEntries is converted to int
+		// for a map size, and the max int depends on the platform.
+		return 0, fmt.Errorf("%w: %s must be less than %d",
+			ErrCacheLRUMaxEntries, s, math.MaxInt)
 	}
+
+	maxEntries = uint(maxEntriesUint64)
 	return maxEntries, nil
 }

pkg/cache/lru/lru.go

@@ -11,7 +11,7 @@ import (
 
 type LRU struct {
 	// Configuration
-	maxEntries int
+	maxEntries uint
 
 	// State
 	kv         map[string]*list.Element
@@ -70,7 +70,7 @@ func (l *LRU) Add(request, response *dns.Msg) {
 		response: responseCopy,
 	}
 
-	if l.maxEntries > 0 && l.linkedList.Len() == l.maxEntries {
+	if l.maxEntries > 0 && l.linkedList.Len() == int(l.maxEntries) {
 		l.removeOldest()
 	}
 

pkg/cache/lru/settings.go

@@ -10,7 +10,7 @@ import (
 type Settings struct {
 	// MaxEntries is the maximum number of request<->response pairs
 	// to be stored in the cache. It defaults to 10e4 if left unset.
-	MaxEntries int
+	MaxEntries uint
 	// Metrics is the metrics interface to record metric information
 	// for the cache. It defaults to a No-Op metric implementation.
 	Metrics metrics.Interface

pkg/cache/lru/settings_test.go

@@ -12,6 +12,6 @@ func Test_Settings_SetDefaults(t *testing.T) {
 	settings := Settings{}
 	settings.SetDefaults()
 
-	assert.Greater(t, settings.MaxEntries, 1)
+	assert.Greater(t, settings.MaxEntries, uint(1))
 	assert.NotNil(t, settings.Metrics)
 }

pkg/cache/metrics/interface.go

@@ -23,7 +23,7 @@ type Interface interface {
 	CacheHitInc()
 	CacheMissInc()
 	CacheExpiredInc()
-	CacheMaxEntriesSet(maxEntries int)
+	CacheMaxEntriesSet(maxEntries uint)
 }
 
 type Settings struct {

pkg/cache/metrics/noop/metrics.go

@@ -7,13 +7,13 @@ func New() (metrics *Metrics) {
 	return new(Metrics)
 }
 
-func (m *Metrics) SetCacheType(string)    {}
-func (m *Metrics) CacheInsertInc()        {}
-func (m *Metrics) CacheRemoveInc()        {}
-func (m *Metrics) CacheMoveInc()          {}
-func (m *Metrics) CacheGetEmptyInc()      {}
-func (m *Metrics) CacheInsertEmptyInc()   {}
-func (m *Metrics) CacheHitInc()           {}
-func (m *Metrics) CacheMissInc()          {}
-func (m *Metrics) CacheExpiredInc()       {}
-func (m *Metrics) CacheMaxEntriesSet(int) {}
+func (m *Metrics) SetCacheType(string)     {}
+func (m *Metrics) CacheInsertInc()         {}
+func (m *Metrics) CacheRemoveInc()         {}
+func (m *Metrics) CacheMoveInc()           {}
+func (m *Metrics) CacheGetEmptyInc()       {}
+func (m *Metrics) CacheInsertEmptyInc()    {}
+func (m *Metrics) CacheHitInc()            {}
+func (m *Metrics) CacheMissInc()           {}
+func (m *Metrics) CacheExpiredInc()        {}
+func (m *Metrics) CacheMaxEntriesSet(uint) {}

pkg/cache/metrics/prometheus/gauges.go

@@ -24,6 +24,6 @@ func newGauges(settings prom.Settings) (g *gauges, err error) {
 	return g, nil
 }
 
-func (g *gauges) CacheMaxEntriesSet(maxEntries int) {
+func (g *gauges) CacheMaxEntriesSet(maxEntries uint) {
 	g.maxEntries.Set(float64(maxEntries))
 }