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