MB-20590 - mossStore.Stats() API

Of note, num_bytes_used_disk and total_compactions are returned.

The current implementation rescans the directory every time to compute
the num_bytes_used_disk, and while simple, could likely be improved
for higher performance.

Change-Id: Ia81e1ef9d150a7087735bbd39dbbec13fda8c06a
Reviewed-on: http://review.couchbase.org/67524
Reviewed-by: Marty Schoch <marty.schoch@gmail.com>
Tested-by: Steve Yen <steve.yen@gmail.com>

store.go

@@ -59,6 +59,9 @@ type Store struct {
 	refs         int
 	footer       *Footer
 	nextFNameSeq int64
+
+	totPersists    uint64
+	totCompactions uint64
 }
 
 // StoreOptions are provided to OpenStore().
@@ -377,6 +380,7 @@ func (s *Store) Persist(higher Snapshot, persistOptions StorePersistOptions) (
 	footer.prevFooter = s.footer
 	prevFooter := s.footer
 	s.footer = footer
+	s.totPersists++
 	s.m.Unlock()
 
 	if prevFooter != nil {

store_compact.go

@@ -206,6 +206,7 @@ func (s *Store) compact(footer *Footer, higher Snapshot,
 	s.m.Lock()
 	footerPrev := s.footer
 	s.footer = footerReady // Owns the frefCompact ref-count.
+	s.totCompactions++
 	s.m.Unlock()
 
 	if footerPrev != nil {

store_stats.go

@@ -0,0 +1,42 @@
+//  Copyright (c) 2016 Couchbase, Inc.
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the
+//  License. You may obtain a copy of the License at
+//    http://www.apache.org/licenses/LICENSE-2.0
+//  Unless required by applicable law or agreed to in writing,
+//  software distributed under the License is distributed on an "AS
+//  IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+//  express or implied. See the License for the specific language
+//  governing permissions and limitations under the License.
+
+package moss
+
+import (
+	"io/ioutil"
+)
+
+// Stats returns a map of stats.
+func (s *Store) Stats() (map[string]interface{}, error) {
+	finfos, err := ioutil.ReadDir(s.dir)
+	if err != nil {
+		return nil, err
+	}
+
+	var numBytesUsedDisk uint64
+	for _, finfo := range finfos {
+		if !finfo.IsDir() {
+			numBytesUsedDisk += uint64(finfo.Size())
+		}
+	}
+
+	s.m.Lock()
+	totPersists := s.totPersists
+	totCompactions := s.totCompactions
+	s.m.Unlock()
+
+	return map[string]interface{}{
+		"num_bytes_used_disk": numBytesUsedDisk,
+		"total_persists":      totPersists,
+		"total_compactions":   totCompactions,
+	}, nil
+}

store_test.go

@@ -80,6 +80,23 @@ func TestOpenEmptyStore(t *testing.T) {
 
 	s.Options() // It should not panic.
 
+	sstats, err := s.Stats()
+	if err != nil {
+		t.Errorf("expected no stats err")
+	}
+	if sstats == nil {
+		t.Errorf("expected non-nil stats")
+	}
+	if sstats["num_bytes_used_disk"].(uint64) != 0 {
+		t.Errorf("expected 0 stats to start")
+	}
+	if sstats["total_persists"].(uint64) != 0 {
+		t.Errorf("expected 0 stats to start")
+	}
+	if sstats["total_compactions"].(uint64) != 0 {
+		t.Errorf("expected 0 stats to start")
+	}
+
 	ss, err := s.Snapshot()
 	if err != nil || ss == nil {
 		t.Errorf("expected snapshot, no err")
@@ -242,6 +259,20 @@ func testSimpleStore(t *testing.T, sync bool) {
 		t.Errorf("expected llss close to work")
 	}
 
+	sstats, err := store.Stats()
+	if err != nil {
+		t.Errorf("expected no stats err")
+	}
+	if sstats == nil {
+		t.Errorf("expected non-nil stats")
+	}
+	if sstats["num_bytes_used_disk"].(uint64) <= 0 {
+		t.Errorf("expected >0 num_bytes_used_disk")
+	}
+	if sstats["total_persists"].(uint64) <= 0 {
+		t.Errorf("expected >0 total_persists")
+	}
+
 	if store.Close() != nil {
 		t.Errorf("expected store close to work")
 	}