# Failed Assert when testing conflict detection in managed mode

**URL:** <https://discuss.dgraph.io/t/failed-assert-when-testing-conflict-detection-in-managed-mode/14733>\
**Category:** Badger\
**Tags:** kind:bug\
**Created:** [June 25, 2021, 12:46pm UTC](https://discuss.dgraph.io/t/failed-assert-when-testing-conflict-detection-in-managed-mode/14733 "2021-06-25T12:46:14Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![roysc](https://yyz1.discourse-cdn.com/flex007/user_avatar/discuss.dgraph.io/roysc/32/8491_2.png) [@roysc](https://discuss.dgraph.io/u/roysc)\
**Post date:** [June 25, 2021, 12:46pm UTC](https://discuss.dgraph.io/t/failed-assert-when-testing-conflict-detection-in-managed-mode/14733/1 "2021-06-25T12:46:14Z")

</div>

### What version of Go are you using (`go version`)?

```
go version go1.16.3 linux/amd64
```

### What operating system are you using?

Ubuntu 20.04.2 LTS

### What version of Badger are you using?

v3.2103.0

### Does this issue reproduce with the latest master?

Yes

### Steps to Reproduce the issue

```go
package main

import (
	badger "github.com/dgraph-io/badger/v3"
)

var (
	key = []byte("0")
	val1 = []byte("x")
	val2 = []byte("y")
)

func main() {
	db, err := badger.OpenManaged(badger.DefaultOptions("/tmp/badger"))
	if err != nil {
		panic(err)
	}
	defer db.Close()

	txn := db.NewTransactionAt(10, true)
	txnb := db.NewTransactionAt(10, true)
	txnb.Get(key)
	txn.Set(key, val1)
	txnb.Set(key, val2)
	txn.CommitAt(11, nil)
	err = txnb.CommitAt(11, nil)
	if err != badger.ErrConflict {
		panic("should conflict")
	}
}

```

### What Badger options were set?

Default options

### What did you do?

Set the same key from separate managed transactions, when a conflicting read was performed.

### What did you expect to see?

A conflict err when attempting to commit.

### What did you see instead?

A failed assert:

```plaintext
badger 2021/06/25 20:16:44 INFO: All 0 tables opened in 0s
badger 2021/06/25 20:16:44 INFO: Discard stats nextEmptySlot: 0
badger 2021/06/25 20:16:44 INFO: Set nextTxnTs to 11
badger 2021/06/25 20:16:44 INFO: Deleting empty file: /tmp/badger/000001.vlog
2021/06/25 20:16:44 Assert failed
github.com/dgraph-io/badger/v3/y.AssertTrue
	/home/roy/golang/pkg/mod/github.com/dgraph-io/badger/v3@v3.2011.1/y/error.go:55
github.com/dgraph-io/badger/v3.(*Txn).commitAndSend
	/home/roy/golang/pkg/mod/github.com/dgraph-io/badger/v3@v3.2011.1/txn.go:588
github.com/dgraph-io/badger/v3.(*Txn).Commit
	/home/roy/golang/pkg/mod/github.com/dgraph-io/badger/v3@v3.2011.1/txn.go:665
github.com/dgraph-io/badger/v3.(*Txn).CommitAt
	/home/roy/golang/pkg/mod/github.com/dgraph-io/badger/v3@v3.2011.1/managed_db.go:75

```

When a write conflict exists for a managed DB, an internal assert fails.

This occurs because a detected conflict is indicated with `commitTs` of 0, but handling the error is skipped for managed DB instances: [badger/txn.go at aaab25305b94b57e461b09d5dc9c399b1bd6635f · dgraph-io/badger · GitHub](https://github.com/dgraph-io/badger/blob/aaab25305b94b57e461b09d5dc9c399b1bd6635f/txn.go#L563).

I propose a fix: [Fix conflict detection for managed DB by roysc · Pull Request #1716 · dgraph-io/badger · GitHub](https://github.com/dgraph-io/badger/pull/1716). This is currently a draft because while I suspect this is a bug, I’m not entirely sure what the expected behavior is here.

---

<div class="post-metadata">

**Author:** ![roysc](https://yyz1.discourse-cdn.com/flex007/user_avatar/discuss.dgraph.io/roysc/32/8491_2.png) [@roysc](https://discuss.dgraph.io/u/roysc)\
**Post date:** [July 1, 2021, 10:05am UTC](https://discuss.dgraph.io/t/failed-assert-when-testing-conflict-detection-in-managed-mode/14733/2 "2021-07-01T10:05:53Z")

</div>

The title of this topic didn’t properly reflect its meaning. Since it can’t be edited, the new topic is at [Fatal error when writing conflicting keys in managed mode](http://discuss.hypermode.com/t/fatal-error-when-writing-conflicting-keys-in-managed-mode/14784)

---

<div class="post-metadata">

**Author:** ![Naman](https://yyz1.discourse-cdn.com/flex007/user_avatar/discuss.dgraph.io/naman/32/3498_2.png) [@Naman](https://discuss.dgraph.io/u/Naman)\
**Post date:** [September 25, 2021, 6:03pm UTC](https://discuss.dgraph.io/t/failed-assert-when-testing-conflict-detection-in-managed-mode/14733/3 "2021-09-25T18:03:09Z")

</div>

Closed on September 25, 2021, 6:03pm UTC