Stop background refresh of cached data for requests that result in ACL not found errors (#9738)

.changelog/9738.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+cache: Prevent spamming the logs for days when a cached request encounters an "ACL not found" error.
+```

agent/cache/cache.go

@@ -27,6 +27,7 @@ import (
 	"github.com/armon/go-metrics/prometheus"
 	"golang.org/x/time/rate"
 
+	"github.com/hashicorp/consul/acl"
 	"github.com/hashicorp/consul/lib"
 	"github.com/hashicorp/consul/lib/ttlcache"
 )
@@ -655,6 +656,8 @@ func (c *Cache) fetch(key string, r getOptions, allowNew bool, attempt uint, ign
 			newEntry.State = result.State
 		}
 
+		preventRefresh := acl.IsErrNotFound(err)
+
 		// Error handling
 		if err == nil {
 			labels := []metrics.Label{{Name: "result_not_modified", Value: strconv.FormatBool(result.NotModified)}}
@@ -688,9 +691,13 @@ func (c *Cache) fetch(key string, r getOptions, allowNew bool, attempt uint, ign
 				newEntry.RefreshLostContact = time.Time{}
 			}
 		} else {
+			// TODO (mkeeler) maybe change the name of this label to be more indicative of it just
+			// stopping the background refresh
+			labels := []metrics.Label{{Name: "fatal", Value: strconv.FormatBool(preventRefresh)}}
+
 			// TODO(kit): Add tEntry.Name to label on fetch_error and deprecate second write
-			metrics.IncrCounter([]string{"consul", "cache", "fetch_error"}, 1)
-			metrics.IncrCounter([]string{"consul", "cache", tEntry.Name, "fetch_error"}, 1)
+			metrics.IncrCounterWithLabels([]string{"consul", "cache", "fetch_error"}, 1, labels)
+			metrics.IncrCounterWithLabels([]string{"consul", "cache", tEntry.Name, "fetch_error"}, 1, labels)
 
 			// Increment attempt counter
 			attempt++
@@ -725,7 +732,13 @@ func (c *Cache) fetch(key string, r getOptions, allowNew bool, attempt uint, ign
 
 		// If refresh is enabled, run the refresh in due time. The refresh
 		// below might block, but saves us from spawning another goroutine.
-		if tEntry.Opts.Refresh {
+		//
+		// We want to have ACL not found errors stop cache refresh for the cases
+		// where the token used for the query was deleted. If the request
+		// was coming from a cache notification then it will start the
+		// request back up again shortly but in the general case this prevents
+		// spamming the logs with tons of ACL not found errors for days.
+		if tEntry.Opts.Refresh && !preventRefresh {
 			// Check if cache was stopped
 			if atomic.LoadUint32(&c.stopped) == 1 {
 				return

agent/cache/cache_test.go

@@ -15,6 +15,7 @@ import (
 	"github.com/stretchr/testify/require"
 	"golang.org/x/time/rate"
 
+	"github.com/hashicorp/consul/acl"
 	"github.com/hashicorp/consul/lib/ttlcache"
 	"github.com/hashicorp/consul/sdk/testutil"
 )
@@ -1512,6 +1513,124 @@ func TestCache_Prepopulate(t *testing.T) {
 	require.Equal(t, 17, result)
 }
 
+func TestCache_RefreshLifeCycle(t *testing.T) {
+	typ := &MockType{}
+	t.Cleanup(func() { typ.AssertExpectations(t) })
+
+	typ.On("RegisterOptions").Times(0).Return(RegisterOptions{
+		// Maintain a blocking query, retry dropped connections quickly
+		Refresh:          true,
+		SupportsBlocking: true,
+		RefreshTimer:     0 * time.Second,
+		QueryTimeout:     10 * time.Minute,
+	})
+
+	makeRequest := func(index uint64) fakeRequest {
+		return fakeRequest{
+			info: RequestInfo{
+				Key:        "v1",
+				Token:      "token",
+				Datacenter: "dc1",
+				MinIndex:   index,
+			},
+		}
+	}
+
+	typ.On("Fetch", mock.Anything, mock.Anything).Once().Return(FetchResult{
+		Value: true,
+		Index: 2,
+	}, nil)
+
+	releaseSecondReq := make(chan time.Time)
+	typ.On("Fetch", mock.Anything, mock.Anything).Once().Return(FetchResult{}, acl.PermissionDenied("forced error")).WaitUntil(releaseSecondReq)
+
+	releaseThirdReq := make(chan time.Time)
+	typ.On("Fetch", mock.Anything, mock.Anything).Once().Return(FetchResult{}, acl.ErrNotFound).WaitUntil(releaseThirdReq)
+
+	c := New(Options{})
+	c.RegisterType("t", typ)
+
+	key := makeEntryKey("t", "dc1", "token", "v1")
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	// get the background refresh going
+	result, _, err := c.Get(ctx, "t", makeRequest(1))
+	require.NoError(t, err)
+	require.Equal(t, true, result)
+
+	// ensure that the entry is fetching again
+	c.entriesLock.Lock()
+	entry, ok := c.entries[key]
+	require.True(t, ok)
+	require.True(t, entry.Fetching)
+	c.entriesLock.Unlock()
+
+	requestChan := make(chan error)
+
+	getError := func(index uint64) {
+		_, _, err := c.Get(ctx, "t", makeRequest(index))
+		if ctx.Err() != nil {
+			return
+		}
+		requestChan <- err
+	}
+
+	// background a call that will wait for a newer version
+	go getError(2)
+
+	// I really dislike the arbitrary sleep here. However we want to test out some of the
+	// branching in getWithIndex (called by Get) and that doesn't expose any way for us to
+	// know when that go routine has gotten far enough and is waiting on the latest value.
+	// Therefore the only thing we can do for now is to sleep long enough to let that
+	// go routine progress far enough.
+	time.Sleep(100 * time.Millisecond)
+
+	// release the blocking query to simulate an ACL permission denied error
+	close(releaseSecondReq)
+
+	// ensure we were woken up and see the permission denied error
+	select {
+	case err := <-requestChan:
+		require.True(t, acl.IsErrPermissionDenied(err))
+	case <-time.After(500 * time.Millisecond):
+		require.Fail(t, "blocking cache Get never returned")
+	}
+
+	// ensure that the entry is fetching again
+	c.entriesLock.Lock()
+	entry, ok = c.entries[key]
+	require.True(t, ok)
+	require.True(t, entry.Fetching)
+	c.entriesLock.Unlock()
+
+	// background a call that will wait for a newer version - will result in an acl not found error
+	go getError(5)
+
+	// Same arbitrary sleep as the one after the second request and the same reasoning.
+	time.Sleep(100 * time.Millisecond)
+
+	// release the blocking query to simulate an ACL not found error
+	close(releaseThirdReq)
+
+	// ensure we were woken up and see the ACL not found error
+	select {
+	case err := <-requestChan:
+		require.True(t, acl.IsErrNotFound(err))
+	case <-time.After(500 * time.Millisecond):
+		require.Fail(t, "blocking cache Get never returned")
+	}
+
+	// ensure that the ACL not found error killed off the background refresh
+	// but didn't remove it from the cache
+	c.entriesLock.Lock()
+	entry, ok = c.entries[key]
+	require.True(t, ok)
+	require.False(t, entry.Fetching)
+	c.entriesLock.Unlock()
+}
+
 type fakeType struct {
 	index uint64
 }