Rename all zip and httprange metrics

Renames all metrics to make them easier to understand.
Adds a missing metric for number of open requests made by httprange.

6 files changed, 82 insertions, 59 deletions

diff --git a/acceptance_test.go b/acceptance_test.go
index 5b7788ce..c946167e 100644
--- a/acceptance_test.go
+++ b/acceptance_test.go
@@ -487,14 +487,17 @@ func TestPrometheusMetricsCanBeScraped(t *testing.T) {
 	require.Contains(t, string(body), "gitlab_pages_serving_time_seconds_sum")
 	require.Contains(t, string(body), `gitlab_pages_domains_source_api_requests_total{status_code="200"}`)
 	require.Contains(t, string(body), `gitlab_pages_domains_source_api_call_duration_bucket`)
-	// object storage
-	require.Contains(t, string(body), `gitlab_pages_object_storage_backend_requests_total{status_code="206"}`)
-	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_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`)
+	// httprange
+	require.Contains(t, string(body), `gitlab_pages_httprange_requests_total{status_code="206"}`)
+	require.Contains(t, string(body), "gitlab_pages_httprange_requests_duration_bucket")
+	require.Contains(t, string(body), "gitlab_pages_httprange_trace_duration")
+	require.Contains(t, string(body), "gitlab_pages_httprange_open_requests")
+	// zip archives
+	require.Contains(t, string(body), "gitlab_pages_zip_opened")
+	require.Contains(t, string(body), "gitlab_pages_zip_cache_requests")
+	require.Contains(t, string(body), "gitlab_pages_zip_cached_archives")
+	require.Contains(t, string(body), "gitlab_pages_zip_archive_entries_cached")
+	require.Contains(t, string(body), "gitlab_pages_zip_opened_entries_count")
 }
 
 func TestDisabledRedirects(t *testing.T) {
diff --git a/internal/httprange/http_reader.go b/internal/httprange/http_reader.go
index 82c3189c..efb3b981 100644
--- a/internal/httprange/http_reader.go
+++ b/internal/httprange/http_reader.go
@@ -57,8 +57,8 @@ var httpClient = &http.Client{
 	Transport: &tracedTransport{
 		next: httptransport.NewTransportWithMetrics(
 			"object_storage_client",
-			metrics.ObjectStorageBackendReqDuration,
-			metrics.ObjectStorageBackendReqTotal,
+			metrics.HTTPRangeRequestDuration,
+			metrics.HTTPRangeRequestsTotal,
 		),
 	},
 }
@@ -75,14 +75,18 @@ func (r *Reader) ensureResponse() error {
 		return err
 	}
 
-	// TODO: add Traceln info for HTTP calls with headers and response https://gitlab.com/gitlab-org/gitlab-pages/-/issues/448
+	metrics.HTTPRangeOpenRequests.Inc()
+
 	res, err := httpClient.Do(req)
 	if err != nil {
+		metrics.HTTPRangeOpenRequests.Dec()
 		return err
 	}
 
 	err = r.setResponse(res)
 	if err != nil {
+		metrics.HTTPRangeOpenRequests.Dec()
+
 		// cleanup body on failure from r.setResponse to avoid memory leak
 		res.Body.Close()
 	}
@@ -200,6 +204,9 @@ func (r *Reader) Close() error {
 		// no need to read until the end
 		err := r.res.Body.Close()
 		r.res = nil
+
+		metrics.HTTPRangeOpenRequests.Dec()
+
 		return err
 	}
 
diff --git a/internal/httprange/transport.go b/internal/httprange/transport.go
index 1432acf9..9bb6e805 100644
--- a/internal/httprange/transport.go
+++ b/internal/httprange/transport.go
@@ -86,6 +86,6 @@ func newTracer(start time.Time) *httptrace.ClientTrace {
 }
 
 func httpTraceObserve(label string, start time.Time) {
-	metrics.ObjectStorageTraceDuration.WithLabelValues(label).
+	metrics.HTTPRangeTraceDuration.WithLabelValues(label).
 		Observe(time.Since(start).Seconds())
 }
diff --git a/internal/vfs/zip/archive.go b/internal/vfs/zip/archive.go
index 85c84a9f..1fec3903 100644
--- a/internal/vfs/zip/archive.go
+++ b/internal/vfs/zip/archive.go
@@ -63,9 +63,9 @@ func (a *zipArchive) openArchive(parentCtx context.Context) (err error) {
 	defer func() {
 		// checking named return err value
 		if err != nil {
-			metrics.ZipServingOpenArchivesTotal.WithLabelValues("error").Inc()
+			metrics.ZipOpened.WithLabelValues("error").Inc()
 		} else {
-			metrics.ZipServingOpenArchivesTotal.WithLabelValues("ok").Inc()
+			metrics.ZipOpened.WithLabelValues("ok").Inc()
 		}
 	}()
 
@@ -139,8 +139,8 @@ func (a *zipArchive) readArchive() {
 	a.archive.File = nil
 
 	fileCount := float64(len(a.files))
-	metrics.ZipServingFilesPerArchiveTotalCount.Add(fileCount)
-	metrics.ZipServingFilesPerZipArchiveCurrentlyCached.Add(fileCount)
+	metrics.ZipOpenedEntriesCount.Add(fileCount)
+	metrics.ZipArchiveEntriesCached.Add(fileCount)
 }
 
 func (a *zipArchive) findFile(name string) *zip.File {
@@ -230,6 +230,6 @@ func (a *zipArchive) Readlink(ctx context.Context, name string) (string, error)
 
 // onEvicted called by the zipVFS.cache when an archive is removed from the cache
 func (a *zipArchive) onEvicted(){
-    metrics.ZipServingArchivesCurrentlyCached.Dec()
-    metrics.ZipServingFilesPerZipArchiveCurrentlyCached.Sub(float64(len(a.files)))
+    metrics.ZipCachedArchives.Dec()
+    metrics.ZipArchiveEntriesCached.Sub(float64(len(a.files)))
 }
diff --git a/internal/vfs/zip/vfs.go b/internal/vfs/zip/vfs.go
index 9ba6f859..a84b07ec 100644
--- a/internal/vfs/zip/vfs.go
+++ b/internal/vfs/zip/vfs.go
@@ -92,7 +92,7 @@ func (fs *zipVFS) findOrOpenArchive(ctx context.Context, path string) (*zipArchi
 			return nil, errAlreadyCached
 		}
 		metrics.ZipServingArchiveCache.WithLabelValues("miss").Inc()
-		metrics.ZipServingArchivesCurrentlyCached.Inc()
+		metrics.ZipCachedArchives.Inc()
 	}
 
 	zipArchive := archive.(*zipArchive)
diff --git a/metrics/metrics.go b/metrics/metrics.go
index 982112f1..b37d04d6 100644
--- a/metrics/metrics.go
+++ b/metrics/metrics.go
@@ -99,31 +99,36 @@ var (
 		Help: "The number of VFS operations",
 	}, []string{"vfs_name", "operation", "success"})
 
-	// ObjectStorageBackendReqTotal is the number of requests made to Object Storage by zip file serving
+    // HTTPRangeRequestsTotal is the number of requests made to a
+    // httprange.Resource by opening and/or reading from it. Mostly used by the
+    // internal/vfs/zip package to load archives from Object Storage.
 	// Could be bigger than the number of pages served.
-	ObjectStorageBackendReqTotal = prometheus.NewCounterVec(prometheus.CounterOpts{
-		Name: "gitlab_pages_object_storage_backend_requests_total",
-		Help: "The number of requests made to Object Storage by zip file serving with different status codes." +
+	HTTPRangeRequestsTotal = prometheus.NewCounterVec(prometheus.CounterOpts{
+		Name: "gitlab_pages_httprange_requests_total",
+		Help: "The number of requests made by the zip VFS to a Resource with " +
+		    "different status codes." +
 			"Could be bigger than the number of requests served",
 	}, []string{"status_code"})
 
-	// ObjectStorageBackendReqDuration is the time it takes to get a response
-	// from Object Storage in seconds for zip file servings
-	ObjectStorageBackendReqDuration = prometheus.NewHistogramVec(
+    // HTTPRangeRequestDuration is the time it takes to get a response
+    // from an httprange.Resource hosted in object storage for a request made by
+    // the zip VFS
+	HTTPRangeRequestDuration = prometheus.NewHistogramVec(
 		prometheus.HistogramOpts{
-			Name: "gitlab_pages_object_storage_backend_requests_duration",
-			Help: "The time (in seconds) it takes to get a response from the " +
-				"Object Storage provider for zip file serving",
+			Name: "gitlab_pages_httprange_requests_duration",
+			Help: "The time (in seconds) it takes to get a response from " +
+				"a httprange.Resource hosted in object storage for a request " +
+			    "made by the zip VFS",
 		},
 		[]string{"status_code"},
 	)
 
-	// ObjectStorageTraceDuration Object Storage request responsiveness in
-	// seconds for different stages of an http request see httptrace.ClientTrace
-	ObjectStorageTraceDuration = prometheus.NewHistogramVec(
+    // HTTPRangeTraceDuration httprange requests duration in seconds for
+    // different stages of an http request (see httptrace.ClientTrace)
+	HTTPRangeTraceDuration = prometheus.NewHistogramVec(
 		prometheus.HistogramOpts{
-			Name: "gitlab_pages_object_storage_backend_httptrace_duration",
-			Help: "Object Storage request tracing duration in seconds for " +
+			Name: "gitlab_pages_httprange_trace_duration",
+			Help: "httprange request tracing duration in seconds for " +
 				"different connection stages (see Go's httptrace.ClientTrace)",
 			Buckets: []float64{0.001, 0.005, 0.01, 0.02, 0.05, 0.100, 0.250,
 				0.500, 1, 2, 5, 10, 20, 50},
@@ -131,11 +136,17 @@ var (
 		[]string{"request_stage"},
 	)
 
-	// ZipServingOpenArchivesTotal is the number of zip archives that have been
-	// opened
-	ZipServingOpenArchivesTotal = prometheus.NewCounterVec(
+	// HTTPRangeOpenRequests is the number of open requests made by httprange.Reader
+    HTTPRangeOpenRequests = prometheus.NewGauge(prometheus.GaugeOpts{
+        Name: "gitlab_pages_httprange_open_requests",
+        Help: "The number of open requests made by httprange.Reader",
+
+    })
+
+    // ZipOpened is the number of zip archives that have been opened
+	ZipOpened = prometheus.NewCounterVec(
 		prometheus.CounterOpts{
-			Name: "gitlab_pages_zip_archives_total",
+			Name: "gitlab_pages_zip_opened",
 			Help: "The total number of zip archives that have been opened",
 		},
 		[]string{"state"},
@@ -144,34 +155,35 @@ var (
 	// ZipServingArchiveCache is the number of zip archive cache hits/misses
 	ZipServingArchiveCache = prometheus.NewCounterVec(
 		prometheus.CounterOpts{
-			Name: "gitlab_pages_zip_archives_cache",
-			Help: "The number of zip archives cache hits",
+			Name: "gitlab_pages_zip_cache_requests",
+			Help: "The number of zip archives cache hits/misses",
 		},
 		[]string{"cache"},
 	)
 
-	// ZipServingArchivesCurrentlyCached is the number of zip archives currently
-	// in the cache
-	ZipServingArchivesCurrentlyCached = prometheus.NewGauge(
+    // ZipCachedArchives is the number of zip archives currently in the cache
+    ZipCachedArchives = prometheus.NewGauge(
 		prometheus.GaugeOpts{
-			Name: "gitlab_pages_zip_archives_currently_cached",
+			Name: "gitlab_pages_zip_cached_archives",
 			Help: "The number of zip archives currently in the cache",
 		},
 	)
 
-	// ZipServingFilesPerZipArchiveCurrentlyCached ...
-	ZipServingFilesPerZipArchiveCurrentlyCached = prometheus.NewGauge(
+    // ZipArchiveEntriesCached is the number of files per zip archive currently
+    // in the cache
+    ZipArchiveEntriesCached = 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",
+			Name: "gitlab_pages_zip_archive_entries_cached",
+			Help: "The number of files per zip archive currently in the cache",
 		},
 	)
 
-	// ZipServingFilesPerArchiveTotalCount over time
-	ZipServingFilesPerArchiveTotalCount = prometheus.NewCounter(
+    // ZipOpenedEntriesCount is the number of files per archive total count
+    // over time
+    ZipOpenedEntriesCount = prometheus.NewCounter(
 		prometheus.CounterOpts{
-			Name: "gitlab_pages_files_per_zip_archive_total",
-			Help: "The number of files per zip archive total count",
+			Name: "gitlab_pages_zip_opened_entries_count",
+			Help: "The number of files per zip archive total count over time",
 		},
 	)
 )
@@ -194,13 +206,14 @@ func MustRegister() {
 		DiskServingFileSize,
 		ServingTime,
 		VFSOperations,
-		ObjectStorageBackendReqTotal,
-		ObjectStorageBackendReqDuration,
-		ObjectStorageTraceDuration,
-		ZipServingOpenArchivesTotal,
-		ZipServingFilesPerArchiveTotalCount,
+        HTTPRangeRequestsTotal,
+        HTTPRangeRequestDuration,
+        HTTPRangeTraceDuration,
+        HTTPRangeOpenRequests,
+        ZipOpened,
+        ZipOpenedEntriesCount,
 		ZipServingArchiveCache,
-		ZipServingFilesPerZipArchiveCurrentlyCached,
-		ZipServingArchivesCurrentlyCached,
+        ZipArchiveEntriesCached,
+        ZipCachedArchives,
 	)
 }