From 50381055ad427790b5761426604be1f5a16f5d29 Mon Sep 17 00:00:00 2001
From: Wolfgang Welz <welzwo@gmail.com>
Date: Fri, 2 Aug 2019 14:01:22 +0200
Subject: [PATCH] Improve error handling in BadgerDB singleton
---
packages/database/badger_instance.go | 77 +++++++++++++++++-----------
packages/database/database.go | 48 ++++++++---------
2 files changed, 70 insertions(+), 55 deletions(-)
diff --git a/packages/database/badger_instance.go b/packages/database/badger_instance.go
index 50b5d8ba..6cf834f7 100644
--- a/packages/database/badger_instance.go
+++ b/packages/database/badger_instance.go
@@ -6,48 +6,63 @@ import (
"github.com/dgraph-io/badger"
"github.com/dgraph-io/badger/options"
+ "github.com/pkg/errors"
)
var instance *badger.DB
+var once sync.Once
-var openLock sync.Mutex
-
-func GetBadgerInstance() (result *badger.DB, err error) {
- openLock.Lock()
+// Returns whether the given file or directory exists.
+func exists(path string) (bool, error) {
+ _, err := os.Stat(path)
+ if err == nil {
+ return true, nil
+ }
+ if os.IsNotExist(err) {
+ return false, nil
+ }
+ return false, err
+}
- if instance == nil {
- directory := *DIRECTORY.Value
+func checkDir(dir string) error {
+ exists, err := exists(dir)
+ if err != nil {
+ return err
+ }
- if _, osErr := os.Stat(directory); os.IsNotExist(osErr) {
- if osErr := os.Mkdir(directory, 0700); osErr != nil {
- err = osErr
+ if !exists {
+ return os.Mkdir(dir, 0700)
+ }
+ return nil
+}
- return
- }
- } else if osErr != nil {
- err = osErr
+func createDB() (*badger.DB, error) {
+ directory := *DIRECTORY.Value
+ if err := checkDir(directory); err != nil {
+ return nil, errors.Wrap(err, "Could not check directory")
+ }
- return
- }
+ opts := badger.DefaultOptions(directory)
+ opts.Logger = &logger{}
+ opts.Truncate = true
+ opts.TableLoadingMode = options.MemoryMap
- opts := badger.DefaultOptions(directory)
- opts.Logger = &logger{}
- opts.Truncate = true
- opts.TableLoadingMode = options.MemoryMap
+ db, err := badger.Open(opts)
+ if err != nil {
+ return nil, errors.Wrap(err, "Could not open new DB")
+ }
- db, badgerErr := badger.Open(opts)
- if badgerErr != nil {
- err = badgerErr
+ return db, nil
+}
- return
+func GetBadgerInstance() *badger.DB {
+ once.Do(func() {
+ db, err := createDB()
+ if err != nil {
+ // errors should cause a panic to avoid singleton deadlocks
+ panic(err)
}
-
instance = db
- }
-
- openLock.Unlock()
-
- result = instance
-
- return
+ })
+ return instance
}
diff --git a/packages/database/database.go b/packages/database/database.go
index 4a0e9657..573d0dd4 100644
--- a/packages/database/database.go
+++ b/packages/database/database.go
@@ -6,12 +6,10 @@ import (
"github.com/dgraph-io/badger"
)
-var databasesByName = make(map[string]*databaseImpl)
-var getLock sync.Mutex
+var dbMap = make(map[string]*prefixDb)
+var mu sync.Mutex
-var ErrKeyNotFound = badger.ErrKeyNotFound
-
-type databaseImpl struct {
+type prefixDb struct {
db *badger.DB
name string
prefix []byte
@@ -19,30 +17,32 @@ type databaseImpl struct {
}
func Get(name string) (Database, error) {
- getLock.Lock()
- defer getLock.Unlock()
-
- if database, exists := databasesByName[name]; exists {
- return database, nil
+ // avoid locking if it's a clean hit
+ if db, exists := dbMap[name]; exists {
+ return db, nil
}
- badgerInstance, err := GetBadgerInstance()
- if err != nil {
- return nil, err
+ mu.Lock()
+ defer mu.Unlock()
+
+ // needs to be re-checked after locking
+ if db, exists := dbMap[name]; exists {
+ return db, nil
}
- database := &databaseImpl{
- db: badgerInstance,
+ badger := GetBadgerInstance()
+ db := &prefixDb{
+ db: badger,
name: name,
prefix: []byte(name + "_"),
}
- databasesByName[name] = database
+ dbMap[name] = db
- return databasesByName[name], nil
+ return db, nil
}
-func (this *databaseImpl) Set(key []byte, value []byte) error {
+func (this *prefixDb) Set(key []byte, value []byte) error {
if err := this.db.Update(func(txn *badger.Txn) error { return txn.Set(append(this.prefix, key...), value) }); err != nil {
return err
}
@@ -50,7 +50,7 @@ func (this *databaseImpl) Set(key []byte, value []byte) error {
return nil
}
-func (this *databaseImpl) Contains(key []byte) (bool, error) {
+func (this *prefixDb) Contains(key []byte) (bool, error) {
err := this.db.View(func(txn *badger.Txn) error {
_, err := txn.Get(append(this.prefix, key...))
if err != nil {
@@ -60,14 +60,14 @@ func (this *databaseImpl) Contains(key []byte) (bool, error) {
return nil
})
- if err == ErrKeyNotFound {
+ if err == badger.ErrKeyNotFound {
return false, nil
} else {
return err == nil, err
}
}
-func (this *databaseImpl) Get(key []byte) ([]byte, error) {
+func (this *prefixDb) Get(key []byte) ([]byte, error) {
var result []byte = nil
err := this.db.View(func(txn *badger.Txn) error {
@@ -86,7 +86,7 @@ func (this *databaseImpl) Get(key []byte) ([]byte, error) {
return result, err
}
-func (this *databaseImpl) Delete(key []byte) error {
+func (this *prefixDb) Delete(key []byte) error {
err := this.db.Update(func(txn *badger.Txn) error {
err := txn.Delete(append(this.prefix, key...))
return err
@@ -94,10 +94,10 @@ func (this *databaseImpl) Delete(key []byte) error {
return err
}
-func (this *databaseImpl) ForEach(consumer func([]byte, []byte)) error {
+func (this *prefixDb) ForEach(consumer func([]byte, []byte)) error {
err := this.db.View(func(txn *badger.Txn) error {
iteratorOptions := badger.DefaultIteratorOptions
- iteratorOptions.Prefix = this.prefix
+ iteratorOptions.Prefix = this.prefix // filter by prefix
// create an iterator the default options
it := txn.NewIterator(iteratorOptions)
--
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