Add validator bolt db metric collector (#7982)

* Validator db: add metrics collector

* Use the right library

* Go fmt

* Fix tests

validator/db/kv/BUILD.bazel

@@ -19,6 +19,8 @@ go_library(
         "//shared/fileutil:go_default_library",
         "//shared/params:go_default_library",
         "@com_github_pkg_errors//:go_default_library",
+        "@com_github_prometheus_client_golang//prometheus:go_default_library",
+        "@com_github_prysmaticlabs_prombbolt//:go_default_library",
         "@com_github_sirupsen_logrus//:go_default_library",
         "@io_etcd_go_bbolt//:go_default_library",
         "@io_opencensus_go//trace:go_default_library",

validator/db/kv/db.go

@@ -6,6 +6,8 @@ import (
 	"path/filepath"
 
 	"github.com/pkg/errors"
+	"github.com/prometheus/client_golang/prometheus"
+	prombolt "github.com/prysmaticlabs/prombbolt"
 	"github.com/prysmaticlabs/prysm/shared/fileutil"
 	"github.com/prysmaticlabs/prysm/shared/params"
 	bolt "go.etcd.io/bbolt"
@@ -23,6 +25,7 @@ type Store struct {
 
 // Close closes the underlying boltdb database.
 func (store *Store) Close() error {
+	prometheus.Unregister(createBoltCollector(store.db))
 	return store.db.Close()
 }
 
@@ -38,6 +41,7 @@ func (store *Store) ClearDB() error {
 	if _, err := os.Stat(store.databasePath); os.IsNotExist(err) {
 		return nil
 	}
+	prometheus.Unregister(createBoltCollector(store.db))
 	return os.Remove(filepath.Join(store.databasePath, ProtectionDbFileName))
 }
 
@@ -103,6 +107,8 @@ func NewKVStore(dirPath string, pubKeys [][48]byte) (*Store, error) {
 		}
 	}
 
+	err = prometheus.Register(createBoltCollector(kv.db))
+
 	return kv, err
 }
 
@@ -128,3 +134,8 @@ func (store *Store) Size() (int64, error) {
 	})
 	return size, err
 }
+
+// createBoltCollector returns a prometheus collector specifically configured for boltdb.
+func createBoltCollector(db *bolt.DB) prometheus.Collector {
+	return prombolt.New("boltDB", db)
+}

validator/db/kv/proposal_history_v2_test.go

@@ -89,6 +89,7 @@ func TestSaveProposalHistoryForSlot_Overwrites(t *testing.T) {
 
 		require.NotNil(t, signingRoot)
 		require.DeepEqual(t, tt.signingRoot, signingRoot[:], "Expected DB to keep object the same")
+		require.NoError(t, db.Close(), "Failed to close database")
 	}
 }
 
@@ -151,6 +152,7 @@ func TestPruneProposalHistoryBySlot_OK(t *testing.T) {
 			require.NoError(t, err, "Failed to get proposal history")
 			require.DeepEqual(t, signedRoot, sr[:], "Unexpected difference in bytes for epoch %d", slot)
 		}
+		require.NoError(t, db.Close(), "Failed to close database")
 	}
 }