mongodb protocol_error ai_generated true

MongoServerError: Transaction number 1 on session 0x1234 is not the expected transaction number (expected 2)

ID: mongodb/transaction-number-mismatch

Also available as: JSON · Markdown · 中文

88%Fix Rate

84%Confidence

1Evidence

2024-02-28First Seen

Version Compatibility

Version	Status	Introduced	Deprecated	Notes
MongoDB 4.2	active	—	—	—
MongoDB 5.0	active	—	—	—
MongoDB 6.0	active	—	—	—
MongoDB 7.0	active	—	—	—

Root Cause

A client attempted to commit or abort a transaction with a stale transaction number, likely due to a retry logic bug where the same session is reused without incrementing the transaction number, or a session is accidentally shared across concurrent transactions.

generic

中文

客户端尝试使用过时的事务编号提交或中止事务，可能是由于重试逻辑错误，同一会话被重用而未递增事务编号，或会话被意外地在并发事务间共享。

Official Documentation

https://www.mongodb.com/docs/manual/core/transactions/

Workarounds

90% success Ensure each transaction uses a new session or explicitly increments the transaction number. In Node.js driver: use `session.startTransaction()` and `session.commitTransaction()` within a loop that creates a new session for each attempt. Example: `const session = client.startSession(); session.startTransaction(); try { ... await session.commitTransaction(); } catch { await session.abortTransaction(); } finally { session.endSession(); }`
```
Ensure each transaction uses a new session or explicitly increments the transaction number. In Node.js driver: use `session.startTransaction()` and `session.commitTransaction()` within a loop that creates a new session for each attempt. Example: `const session = client.startSession(); session.startTransaction(); try { ... await session.commitTransaction(); } catch { await session.abortTransaction(); } finally { session.endSession(); }`
```
88% success For retry logic, use a fresh session for each retry attempt instead of reusing the same session. In Python: `with client.start_session() as session: session.start_transaction(); ...` inside the retry loop.
```
For retry logic, use a fresh session for each retry attempt instead of reusing the same session. In Python: `with client.start_session() as session: session.start_transaction(); ...` inside the retry loop.
```
85% success Check for accidental session sharing in async code (e.g., passing the same session object to multiple concurrent coroutines). Use `session.advanceTransactionNumber()` if driver supports it, or enforce sequential transaction processing per session.
```
Check for accidental session sharing in async code (e.g., passing the same session object to multiple concurrent coroutines). Use `session.advanceTransactionNumber()` if driver supports it, or enforce sequential transaction processing per session.
```

中文步骤

确保每个事务使用新会话或显式递增事务编号。在 Node.js 驱动中：在每次尝试的循环中使用 `session.startTransaction()` 和 `session.commitTransaction()` 创建新会话。示例：`const session = client.startSession(); session.startTransaction(); try { ... await session.commitTransaction(); } catch { await session.abortTransaction(); } finally { session.endSession(); }`

对于重试逻辑，每次重试尝试使用新会话，而不是重用同一会话。在 Python 中：在重试循环内使用 `with client.start_session() as session: session.start_transaction(); ...`。

检查异步代码中的意外会话共享（例如，将同一会话对象传递给多个并发协程）。如果驱动程序支持，使用 `session.advanceTransactionNumber()`，或强制每个会话按顺序处理事务。

Dead Ends

Common approaches that don't work:

90% fail
The underlying session management bug in the code remains; the error will recur on the next transaction.
85% fail
Killing the session only frees server resources; the client code still holds a stale session reference and will create a new session with the same problem.
95% fail
The error is about transaction number sequencing, not timeout; changing timeouts has no effect.