[#234] pool: Update token expiration check in cache

Signed-off-by: Marina Biryukova <m.biryukova@yadro.com>

pool/cache.go

@@ -11,19 +11,20 @@ import (
 type sessionCache struct {
 	cache         *lru.Cache[string, *cacheValue]
 	currentEpoch  atomic.Uint64
+	tokenDuration uint64
 }
 
 type cacheValue struct {
 	token session.Object
 }
 
-func newCache() (*sessionCache, error) {
+func newCache(tokenDuration uint64) (*sessionCache, error) {
 	cache, err := lru.New[string, *cacheValue](100)
 	if err != nil {
 		return nil, err
 	}
 
-	return &sessionCache{cache: cache}, nil
+	return &sessionCache{cache: cache, tokenDuration: tokenDuration}, nil
 }
 
 // Get returns a copy of the session token from the cache without signature
@@ -66,8 +67,12 @@ func (c *sessionCache) updateEpoch(newEpoch uint64) {
 
 func (c *sessionCache) expired(val *cacheValue) bool {
 	epoch := c.currentEpoch.Load()
-	// use epoch+1 (clear cache beforehand) to prevent 'expired session token' error right after epoch tick
-	return val.token.ExpiredAt(epoch + 1)
+	preExpiredDur := c.tokenDuration / 2
+	if preExpiredDur == 0 {
+		preExpiredDur = 1
+	}
+
+	return val.token.ExpiredAt(epoch + preExpiredDur)
 }
 
 func (c *sessionCache) Epoch() uint64 {

pool/cache_test.go

@@ -20,7 +20,7 @@ func TestSessionCache_GetUnmodifiedToken(t *testing.T) {
 		require.False(t, tok.VerifySignature(), extra)
 	}
 
-	cache, err := newCache()
+	cache, err := newCache(0)
 	require.NoError(t, err)
 
 	cache.Put(key, target)

pool/pool.go

@@ -1947,7 +1947,7 @@ type innerPool struct {
 }
 
 const (
-	defaultSessionTokenExpirationDuration = 100 // in blocks
+	defaultSessionTokenExpirationDuration = 100 // in epochs
 	defaultErrorThreshold                 = 100
 
 	defaultRebalanceInterval  = 15 * time.Second
@@ -1969,7 +1969,7 @@ func NewPool(options InitParameters) (*Pool, error) {
 		return nil, err
 	}
 
-	cache, err := newCache()
+	cache, err := newCache(options.sessionExpirationDuration)
 	if err != nil {
 		return nil, fmt.Errorf("couldn't create cache: %w", err)
 	}
@@ -2087,6 +2087,10 @@ func fillDefaultInitParams(params *InitParameters, cache *sessionCache) {
 		params.nodeStreamTimeout = defaultStreamTimeout
 	}
 
+	if cache.tokenDuration == 0 {
+		cache.tokenDuration = defaultSessionTokenExpirationDuration
+	}
+
 	if params.isMissingClientBuilder() {
 		params.setClientBuilder(func(addr string) client {
 			var prm wrapperPrm

pool/sampler_test.go

@@ -47,7 +47,7 @@ func TestHealthyReweight(t *testing.T) {
 		buffer  = make([]float64, len(weights))
 	)
 
-	cache, err := newCache()
+	cache, err := newCache(0)
 	require.NoError(t, err)
 
 	client1 := newMockClient(names[0], *newPrivateKey(t))