How to organize OrientDB DAO in case of transactions in multithreaded environment? - orientdb

Question

I try to organize architecture of my DAO with OrientDB.
Below - example of my:
Connection manager:
public class DB {
private static final OPartitionedDatabasePoolFactory poolFactory = new OPartitionedDatabasePoolFactory();
public static ODatabaseDocumentTx fromPool() {
return poolFactory.get(sDbUrl, sDbUser, sDbPassword).acquire();
}
}
Dao (it uses in multithreaded environment):
public class Dao {
public static void addGold(String rid, long gold) {
try (ODatabaseDocumentTx db = DB.fromPool()) {
final String updateQuery = "UPDATE " + rid + " INCREMENT gold = " + gold + " LOCK RECORD";
db.command(new OCommandSQL(updateQuery)).execute();
}
}
public static void removeGold(String rid, long gold) {
try (ODatabaseDocumentTx db = DB.fromPool()) {
final String updateQuery = "UPDATE " + rid + " INCREMENT gold = " + -gold + " LOCK RECORD";
db.command(new OCommandSQL(updateQuery)).execute();
}
}
public static String transferGold(String fromRid, String toRid, long gold) {
try (ODatabaseDocumentTx db = DB.fromPool()) {
int numTries = 100;
while (true) {
try {
db.begin(OTransaction.TXTYPE.OPTIMISTIC);
removeGold(fromRid, gold);
addGold(toRid, gold);
db.commit();
return "ok";
} catch (OConcurrentModificationException e) {
db.rollback();
if (--numTries == 0) {
return "error";
}
}
}
}
}
}
It's valid to get connection from pool in case of transaction? So same database instance will be returns in same thread?
Any other advice are welcome

Answer 1

Using the OPartitionedDatabasePool should be thread safe and provide a way to get your connections. I think the OPartitionedDatabasePoolFactory is only used if you want to create multiple OPartitionedDatabasePool instances.
A static instance of OPartitionedDatabasePool:
OPartitionedDatabasePool myPool = new OPartitionedDatabasePool(dbUrl, user, password);
And then anytime a thread needs a connection:
ODatabaseDocumentTx dbConnection = MyClass.myPool.acquire();
(As in your code with OPartitionedDatabasePoolFactory).
The pool should automatically handle getting a database connection that will function on your thread.