From 8e337cf6a7c12e56b1fd0008dc6869abc99a2d9c Mon Sep 17 00:00:00 2001
From: Valentin Knabel <dev@vknabel.com>
Date: Wed, 14 Aug 2024 11:29:23 +0200
Subject: [PATCH] fix(cache): retry period (#50)

closes metal-stack/metal-api#259
---
 issuercache.go      | 39 ++++++++++++++++++++++++------
 issuercache_test.go | 59 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 91 insertions(+), 7 deletions(-)

diff --git a/issuercache.go b/issuercache.go
index 27465cb..57a0e95 100644
--- a/issuercache.go
+++ b/issuercache.go
@@ -19,6 +19,7 @@ type MultiIssuerCache struct {
 	cache          map[string]*Issuer
 	cacheLock      sync.RWMutex
 	reloadInterval time.Duration
+	retryInterval  time.Duration
 	log            *slog.Logger
 }
 
@@ -41,6 +42,7 @@ func NewMultiIssuerCache(log *slog.Logger, ilp IssuerListProvider, ugp UserGette
 		userGetterProvider: ugp,
 		cache:              make(map[string]*Issuer),
 		reloadInterval:     30 * time.Minute,
+		retryInterval:      30 * time.Second,
 		log:                log,
 	}
 
@@ -48,27 +50,42 @@ func NewMultiIssuerCache(log *slog.Logger, ilp IssuerListProvider, ugp UserGette
 		opt(issuerCache)
 	}
 
+	var (
+		// flush cache periodically
+		done         = make(chan bool)
+		isRetrying   bool
+		reloadTicker *time.Ticker
+	)
 	// initial update
 	err := issuerCache.updateCache()
 	if err != nil {
 		issuerCache.log.Error("error updating issuer cache", "error", err)
+		isRetrying = true
+		reloadTicker = time.NewTicker(issuerCache.retryInterval)
+	} else {
+		isRetrying = false
+		reloadTicker = time.NewTicker(issuerCache.reloadInterval)
 	}
 
-	// flush cache periodically
-	done := make(chan bool)
-	ticker := time.NewTicker(issuerCache.reloadInterval)
-
 	go func() {
 		for {
 			select {
 			case <-done:
-				ticker.Stop()
+				reloadTicker.Stop()
 				return
-			case <-ticker.C:
+
+			case <-reloadTicker.C:
 				issuerCache.log.Info("updating issuer cache")
 				err := issuerCache.updateCache()
 				if err != nil {
-					issuerCache.log.Error("error updating issuer cache", "error", err)
+					issuerCache.log.Error("error updating issuer cache, retrying...", "error", err)
+					isRetrying = true
+					reloadTicker.Reset(issuerCache.retryInterval)
+					continue
+				}
+				if isRetrying {
+					isRetrying = false
+					reloadTicker.Reset(issuerCache.reloadInterval)
 				}
 			}
 		}
@@ -88,6 +105,14 @@ func IssuerReloadInterval(duration time.Duration) MultiIssuerUserGetterOption {
 	}
 }
 
+// IssuerRetryInterval lets the client set the issuer cache retry sleep period
+func IssuerRetryInterval(duration time.Duration) MultiIssuerUserGetterOption {
+	return func(o *MultiIssuerCache) *MultiIssuerCache {
+		o.retryInterval = duration
+		return o
+	}
+}
+
 func (i *MultiIssuerCache) User(rq *http.Request) (*User, error) {
 
 	claims, err := ParseTokenClaimsUnvalidated(rq)
diff --git a/issuercache_test.go b/issuercache_test.go
index f0493aa..ee90cd3 100644
--- a/issuercache_test.go
+++ b/issuercache_test.go
@@ -276,6 +276,65 @@ func TestMultiIssuerCache_reload(t *testing.T) {
 	assert.Len(t, ic.cache, 1)
 }
 
+func TestMultiIssuerCache_retryFailing(t *testing.T) {
+	ugp := func(ic *IssuerConfig) (UserGetter, error) {
+		return nil, nil
+	}
+
+	calls := 0
+
+	ilp := func() ([]*IssuerConfig, error) {
+		calls++
+		return nil, errors.New("expected error")
+	}
+	ic, err := NewMultiIssuerCache(slog.New(slog.NewJSONHandler(os.Stdout, nil)), ilp, ugp, IssuerReloadInterval(5*time.Second), IssuerRetryInterval(500*time.Millisecond))
+	require.NoError(t, err)
+	assert.Equal(t, 1, calls)
+	assert.Empty(t, ic.cache)
+
+	// wait for reload
+	time.Sleep(2 * time.Second)
+
+	assert.Equal(t, 4, calls)
+	assert.Empty(t, ic.cache)
+}
+
+func TestMultiIssuerCache_retrySecondReload(t *testing.T) {
+	ugp := func(ic *IssuerConfig) (UserGetter, error) {
+		return nil, nil
+	}
+
+	calls := 0
+	issuerList := []*IssuerConfig{}
+
+	ilp := func() ([]*IssuerConfig, error) {
+		calls++
+		if calls > 1 {
+			return issuerList, nil
+		}
+		return nil, errors.New("expected error")
+	}
+	ic, err := NewMultiIssuerCache(slog.New(slog.NewJSONHandler(os.Stdout, nil)), ilp, ugp, IssuerReloadInterval(1*time.Second), IssuerRetryInterval(500*time.Millisecond))
+	require.NoError(t, err)
+	assert.Equal(t, 1, calls)
+	assert.Empty(t, ic.cache)
+
+	// prepare list
+	issuerList = []*IssuerConfig{
+		{
+			Annotations: nil,
+			Tenant:      "t1",
+			Issuer:      "http://issuer/t1",
+			ClientID:    "cli-t1",
+		},
+	}
+	// wait for reload
+	time.Sleep(2 * time.Second)
+
+	assert.Equal(t, 3, calls)
+	assert.Len(t, ic.cache, 1)
+}
+
 func TestMultiIssuerCache_syncCache(t *testing.T) {
 	type fields struct {
 		ilp  IssuerListProvider