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concurrent writes and deadlocks #739

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winteraz opened this issue Jan 10, 2018 · 2 comments
Open

concurrent writes and deadlocks #739

winteraz opened this issue Jan 10, 2018 · 2 comments

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@winteraz
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Only one read-write transaction is allowed at a time.

From documentation I understand that concurrent writes are not allowed. I'm not sure if this is correct thus this question to clarify: is boltdb designed only for one single writer (globally)? Am I suppose to maintain a lock on any write?
Use case:
I want to store access logs of http requests. Does this mean that I need to use a global channel to serialise the access bolt writes ?


e.g. 

var globalChan = make(chan string, 10)

func init() {
	const bucketName = "widgets"
	tx, err := db.Begin(true)
	if err != nil {
		panic(err)
	}
	_, err = tx.CreateBucketIfNotExists([]byte(bucketName))
	if err != nil {
		return err
	}
	go func() {
		for URL := range globalCHan {
			tx, err := db.Begin(true)
			if err != nil {
				panic(err)
			}
			bk := tx.Bucket([]byte(bucketName))
			// Set the value "bar" for the key "foo".
			if err := b.Put([]byte(time.Now().String()), []byte("bar")); err != nil {
				return err
			}
		}

	}()
}

func HandleFunc(w http.ResponseWriter, r *http.Request) {
    globalChan <- r.URL.String()
}

@mei-rune
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mei-rune commented Jan 18, 2018

tx.Commit() or tx.Rollback() is missing

@gigimushroom
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db uses

wlock   sync.Mutex   // Allows only one writer at a time.

You dont need a global channel, just use transaction, only one will be processing, other will block and wait

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3 participants