fix(defrag): handle no space left error

Signed-off-by: Thomas Gosteli <[email protected]>

server/mvcc/backend/backend.go

@@ -477,22 +477,21 @@ func (b *backend) defrag() error {
 	b.readTx.Lock()
 	defer b.readTx.Unlock()
 
-	b.batchTx.unsafeCommit(true)
-
-	b.batchTx.tx = nil
-
 	// Create a temporary file to ensure we start with a clean slate.
 	// Snapshotter.cleanupSnapdir cleans up any of these that are found during startup.
 	dir := filepath.Dir(b.db.Path())
 	temp, err := ioutil.TempFile(dir, "db.tmp.*")
 	if err != nil {
 		return err
 	}
+
 	options := bolt.Options{}
 	if boltOpenOptions != nil {
 		options = *boltOpenOptions
 	}
 	options.OpenFile = func(_ string, _ int, _ os.FileMode) (file *os.File, err error) {
+		// gofail: var defragNoSpace string
+		// return nil, fmt.Errorf(defragNoSpace)
 		return temp, nil
 	}
 	// Don't load tmp db into memory regardless of opening options
@@ -515,6 +514,11 @@ func (b *backend) defrag() error {
 			zap.String("current-db-size-in-use", humanize.Bytes(uint64(sizeInUse1))),
 		)
 	}
+
+	// Commit/stop and then reset current transactions (including the readTx)
+	b.batchTx.unsafeCommit(true)
+	b.batchTx.tx = nil
+
 	// gofail: var defragBeforeCopy struct{}
 	err = defragdb(b.db, tmpdb, defragLimit)
 	if err != nil {

tests/e2e/defrag_no_space_test.go

@@ -0,0 +1,49 @@
+// Copyright 2024 The etcd Authors
+//
+// 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 e2e
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"go.etcd.io/etcd/tests/v3/framework/config"
+	"go.etcd.io/etcd/tests/v3/framework/e2e"
+)
+
+func TestDefragNoSpace(t *testing.T) {
+	e2e.BeforeTest(t)
+
+	clus, err := e2e.NewEtcdProcessCluster(context.TODO(), t,
+		e2e.WithClusterSize(1),
+		e2e.WithGoFailEnabled(true),
+	)
+	require.NoError(t, err)
+	t.Cleanup(func() { clus.Stop() })
+
+	member := clus.Procs[0]
+
+	require.NoError(t, member.Failpoints().SetupHTTP(context.Background(), "defragNoSpace", `return("no space")`))
+	require.ErrorContains(t, member.Etcdctl().Defragment(context.Background(), config.DefragOption{Timeout: time.Minute}), "no space")
+
+	// Make sure etcd continues to run even after the failed defrag attempt
+	require.NoError(t, member.Etcdctl().Put(context.Background(), "foo", "bar", config.PutOptions{}))
+	value, err := member.Etcdctl().Get(context.Background(), "foo", config.GetOptions{})
+	require.NoError(t, err)
+	require.Len(t, value.Kvs, 1)
+	require.Equal(t, "bar", string(value.Kvs[0].Value))
+}