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.
Cheers,
xinxin