Shu, Xinxin wrote:

Hi list , I am working on intergrating LMDB with ceph, I met follow error "Invalid argument" when I commit transaction to LMDB, details are descripted as following. Two threads operate on LMDB, each thread is responsible for create write transaction and read transaction , the write transaction will update LMDB, and read transaction is for iterator that read values from LMDB, the two threads share same MDB_env. I check mdb_txn_commit source code , there are two places to return "EINVAL",

1. if (txn == NULL || txn->mt_env == NULL) return EINVAL;
2. if (txn != env->me_txn) { DPUTS("attempt to commit unknown transaction"); rc = EINVAL; goto fail; }

I check txn and txn->mt_env and rule out the first case , so only the second case cause "EINVAL", and variable env->me_txn is only initialized when you start a write transaction with mdb_txn_open, and there is a lock to prevent several writer from operating on LMDB. Btw , I tried to add lock to synchronize the two threads , everything seems ok. My question is in what situation can cause "txn != env-> me_txn",. I'm very new to LMDB, if there is anything wrong, please correct me.

Most likely it means you're using a write transaction that was legitimate at some point in time, but is no longer valid. E.g., you're trying to reuse a txn after it was already committed or aborted.

Cheers, xinxin