Add extra metric for currently cached files per archive

4 files changed, 44 insertions, 18 deletions

diff --git a/acceptance_test.go b/acceptance_test.go
index be47c2ab..5b7788ce 100644
--- a/acceptance_test.go
+++ b/acceptance_test.go
@@ -492,8 +492,9 @@ func TestPrometheusMetricsCanBeScraped(t *testing.T) {
 	require.Contains(t, string(body), `gitlab_pages_object_storage_backend_requests_duration_bucket`)
 	require.Contains(t, string(body), `gitlab_pages_object_storage_backend_httptrace_duration`)
 	require.Contains(t, string(body), `gitlab_pages_zip_archives_total`)
-	require.Contains(t, string(body), `gitlab_pages_object_storage_files_per_zip_archive`)
-	require.Contains(t, string(body), `gitlab_pages_object_storage_zip_archive_cache`)
+	require.Contains(t, string(body), `gitlab_pages_zip_archives_currently_cached`)
+	require.Contains(t, string(body), `gitlab_pages_files_per_zip_archive_currently_cached`)
+	require.Contains(t, string(body), `gitlab_pages_files_per_zip_archive_total`)
 }
 
 func TestDisabledRedirects(t *testing.T) {
diff --git a/internal/vfs/zip/archive.go b/internal/vfs/zip/archive.go
index 7a9bcc3d..94c5a545 100644
--- a/internal/vfs/zip/archive.go
+++ b/internal/vfs/zip/archive.go
@@ -138,7 +138,9 @@ func (a *zipArchive) readArchive() {
 	// recycle memory
 	a.archive.File = nil
 
-	metrics.ZipServingFilesPerArchiveCount.Observe(float64(len(a.files)))
+	fileCount := float64(len(a.files))
+	metrics.ZipServingFilesPerArchiveTotalCount.Add(fileCount)
+	metrics.ZipServingFilesPerZipArchiveCurrentlyCached.Set(fileCount)
 }
 
 func (a *zipArchive) findFile(name string) *zip.File {
diff --git a/internal/vfs/zip/vfs.go b/internal/vfs/zip/vfs.go
index 985ec3bb..5261802c 100644
--- a/internal/vfs/zip/vfs.go
+++ b/internal/vfs/zip/vfs.go
@@ -30,10 +30,16 @@ type zipVFS struct {
 
 // New creates a zipVFS instance that can be used by a serving request
 func New() vfs.VFS {
-	return &zipVFS{
+	zipVFS := &zipVFS{
 		// TODO: add cache operation callbacks https://gitlab.com/gitlab-org/gitlab-pages/-/issues/465
 		cache: cache.New(defaultCacheExpirationInterval, defaultCacheCleanupInterval),
 	}
+
+	zipVFS.cache.OnEvicted(func(s string, i interface{}) {
+		metrics.ZipServingArchivesCurrentlyCached.Dec()
+	})
+
+	return zipVFS
 }
 
 // Root opens an archive given a URL path and returns an instance of zipArchive
@@ -85,8 +91,8 @@ func (fs *zipVFS) findOrOpenArchive(ctx context.Context, path string) (*zipArchi
 		if fs.cache.Add(path, archive, cache.DefaultExpiration) != nil {
 			return nil, errAlreadyCached
 		}
-
 		metrics.ZipServingArchiveCache.WithLabelValues("miss").Inc()
+		metrics.ZipServingArchivesCurrentlyCached.Inc()
 	}
 
 	zipArchive := archive.(*zipArchive)
diff --git a/metrics/metrics.go b/metrics/metrics.go
index effb717b..982112f1 100644
--- a/metrics/metrics.go
+++ b/metrics/metrics.go
@@ -141,24 +141,39 @@ var (
 		[]string{"state"},
 	)
 
-	// ZipServingFilesPerArchiveCount
-	ZipServingFilesPerArchiveCount = prometheus.NewHistogram(
-		prometheus.HistogramOpts{
-			Name: "gitlab_pages_object_storage_files_per_zip_archive",
-			Help: "The number of files per zip archive",
-			// squared buckets up to 2^13
-			Buckets: prometheus.ExponentialBuckets(1, 2, 14),
-		},
-	)
-
 	// ZipServingArchiveCache is the number of zip archive cache hits/misses
 	ZipServingArchiveCache = prometheus.NewCounterVec(
 		prometheus.CounterOpts{
-			Name: "gitlab_pages_object_storage_zip_archive_cache",
-			Help: "The number of object storage zip archives cache hits",
+			Name: "gitlab_pages_zip_archives_cache",
+			Help: "The number of zip archives cache hits",
 		},
 		[]string{"cache"},
 	)
+
+	// ZipServingArchivesCurrentlyCached is the number of zip archives currently
+	// in the cache
+	ZipServingArchivesCurrentlyCached = prometheus.NewGauge(
+		prometheus.GaugeOpts{
+			Name: "gitlab_pages_zip_archives_currently_cached",
+			Help: "The number of zip archives currently in the cache",
+		},
+	)
+
+	// ZipServingFilesPerZipArchiveCurrentlyCached ...
+	ZipServingFilesPerZipArchiveCurrentlyCached = prometheus.NewGauge(
+		prometheus.GaugeOpts{
+			Name: "gitlab_pages_files_per_zip_archive_currently_cached",
+			Help: "The number of object storage zip archives currently in the cache",
+		},
+	)
+
+	// ZipServingFilesPerArchiveTotalCount over time
+	ZipServingFilesPerArchiveTotalCount = prometheus.NewCounter(
+		prometheus.CounterOpts{
+			Name: "gitlab_pages_files_per_zip_archive_total",
+			Help: "The number of files per zip archive total count",
+		},
+	)
 )
 
 // MustRegister collectors with the Prometheus client
@@ -183,7 +198,9 @@ func MustRegister() {
 		ObjectStorageBackendReqDuration,
 		ObjectStorageTraceDuration,
 		ZipServingOpenArchivesTotal,
-		ZipServingFilesPerArchiveCount,
+		ZipServingFilesPerArchiveTotalCount,
 		ZipServingArchiveCache,
+		ZipServingFilesPerZipArchiveCurrentlyCached,
+		ZipServingArchivesCurrentlyCached,
 	)
 }