Add prometheus endpoint to support total Used storageInfo (#5988)

Since we deprecated Total/Free we don't need to update
prometheus with those metrics. This PR also adds support
for caching implementation.

cmd/disk-cache.go

@@ -77,6 +77,13 @@ type cacheObjects struct {
 	DeleteBucketFn            func(ctx context.Context, bucket string) error
 }
 
+// CacheStorageInfo - represents total, free capacity of
+// underlying cache storage.
+type CacheStorageInfo struct {
+	Total uint64 // Total cache disk space.
+	Free  uint64 // Free cache available space.
+}
+
 // CacheObjectLayer implements primitives for cache object API layer.
 type CacheObjectLayer interface {
 	// Bucket operations.
@@ -98,7 +105,7 @@ type CacheObjectLayer interface {
 	CompleteMultipartUpload(ctx context.Context, bucket, object, uploadID string, uploadedParts []CompletePart) (objInfo ObjectInfo, err error)
 
 	// Storage operations.
-	StorageInfo(ctx context.Context) StorageInfo
+	StorageInfo(ctx context.Context) CacheStorageInfo
 }
 
 // backendDownError returns true if err is due to backend failure or faulty disk if in server mode
@@ -771,7 +778,7 @@ func (c cacheObjects) CompleteMultipartUpload(ctx context.Context, bucket, objec
 }
 
 // StorageInfo - returns underlying storage statistics.
-func (c cacheObjects) StorageInfo(ctx context.Context) (storageInfo StorageInfo) {
+func (c cacheObjects) StorageInfo(ctx context.Context) (cInfo CacheStorageInfo) {
 	var total, free uint64
 	for _, cfs := range c.cache.cfs {
 		if cfs == nil {
@@ -783,12 +790,10 @@ func (c cacheObjects) StorageInfo(ctx context.Context) (storageInfo StorageInfo)
 		total += info.Total
 		free += info.Free
 	}
-	storageInfo = StorageInfo{
+	return CacheStorageInfo{
 		Total: total,
 		Free:  free,
 	}
-	storageInfo.Backend.Type = FS
-	return storageInfo
 }
 
 // DeleteBucket - marks bucket to be deleted from cache if bucket is deleted from backend.

cmd/metrics.go

@@ -84,6 +84,28 @@ func (c *minioCollector) Collect(ch chan<- prometheus.Metric) {
 		float64(globalConnStats.getTotalInputBytes()),
 	)
 
+	// Expose cache stats only if available
+	cacheObjLayer := newCacheObjectsFn()
+	if cacheObjLayer != nil {
+		cs := cacheObjLayer.StorageInfo(context.Background())
+		ch <- prometheus.MustNewConstMetric(
+			prometheus.NewDesc(
+				prometheus.BuildFQName("minio", "disk", "cache_storage_bytes"),
+				"Total cache capacity on current Minio server instance",
+				nil, nil),
+			prometheus.GaugeValue,
+			float64(cs.Total),
+		)
+		ch <- prometheus.MustNewConstMetric(
+			prometheus.NewDesc(
+				prometheus.BuildFQName("minio", "disk", "cache_storage_free_bytes"),
+				"Total cache available on current Minio server instance",
+				nil, nil),
+			prometheus.GaugeValue,
+			float64(cs.Free),
+		)
+	}
+
 	// Expose disk stats only if applicable
 
 	// Fetch disk space info
@@ -92,7 +114,9 @@ func (c *minioCollector) Collect(ch chan<- prometheus.Metric) {
 	if objLayer == nil {
 		return
 	}
+
 	s := objLayer.StorageInfo(context.Background())
+
 	// Gateways don't provide disk info
 	if s.Backend.Type == Unknown {
 		return
@@ -108,22 +132,14 @@ func (c *minioCollector) Collect(ch chan<- prometheus.Metric) {
 		totalDisks = s.Backend.OfflineDisks + s.Backend.OnlineDisks
 	}
 
-	// Total/Free Storage Bytes
+	// Total disk usage by current Minio server instance
 	ch <- prometheus.MustNewConstMetric(
 		prometheus.NewDesc(
-			prometheus.BuildFQName("minio", "disk", "storage_bytes"),
-			"Total disk storage available to current Minio server instance",
+			prometheus.BuildFQName("minio", "disk", "storage_used_bytes"),
+			"Total disk storage used by current Minio server instance",
 			nil, nil),
 		prometheus.GaugeValue,
-		float64(s.Total),
-	)
-	ch <- prometheus.MustNewConstMetric(
-		prometheus.NewDesc(
-			prometheus.BuildFQName("minio", "disk", "storage_free_bytes"),
-			"Total free disk storage available to current Minio server instance",
-			nil, nil),
-		prometheus.GaugeValue,
-		float64(s.Free),
+		float64(s.Used),
 	)
 
 	// Minio Total Disk/Offline Disk

cmd/object-api-datatypes.go

@@ -39,9 +39,7 @@ const (
 
 // StorageInfo - represents total capacity of underlying storage.
 type StorageInfo struct {
-	Total uint64 // Total disk space.
-	Free  uint64 // Free available space.
-	Used  uint64 // Used total used per tenant.
+	Used uint64 // Used total used per tenant.
 
 	// Backend type.
 	Backend struct {

cmd/server-startup-msg.go

@@ -188,7 +188,7 @@ func printStorageInfo(storageInfo StorageInfo) {
 	}
 }
 
-func printCacheStorageInfo(storageInfo StorageInfo) {
+func printCacheStorageInfo(storageInfo CacheStorageInfo) {
 	msg := fmt.Sprintf("%s %s Free, %s Total", colorBlue("Cache Capacity:"),
 		humanize.IBytes(uint64(storageInfo.Free)),
 		humanize.IBytes(uint64(storageInfo.Total)))

cmd/web-handlers_test.go

@@ -1786,10 +1786,6 @@ func TestWebObjectLayerFaultyDisks(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Failed %v", err)
 	}
-	// if Total size is 0 it indicates faulty disk.
-	if storageInfoReply.StorageInfo.Total != 0 {
-		t.Fatalf("Should get zero Total size since disks are faulty ")
-	}
 
 	// Test authorization of Web.Download
 	req, err = http.NewRequest("GET", "/minio/download/bucket/object?token="+authorization, nil)