Applying Database Replication to Multi-player Online Games
Applying Database Replication to Multi-player Online Games Yi Lin Bettina Kemme Marta Patio-Martnez Ricardo Jimnez-Peris Oct 30, 2006 Outline Motivation Requirements of MOGs Benefits of database replication Introduction to database replication A proof-of-concept game Experiments
What MOGs need? Isolated game worlds Fault tolerance Scalability What Database Replication does? Read One DB
Write All DBs Most replication protocols are READONE-WRITE-ALL Providing fault tolerance Scalability Data consistency Motivation Why dont we apply database replication to MOGs? Unclear about How to apply?
What are the challenges? How is the performance? Using a small game for proof-of-concept Introduction to Database Replication Transaction A transaction contains one or more read and/or write requests Atomic. Commit: all requests successful. Abort: none of writes will take effect Consistent Isolated
Durable Challenge of database replication: How to guarantee data consistency in terms of transaction? Database Replication: challenge Replication protocols Keep copies consistent Isolate concurrent transactions w(x) w(x)
Ideally: The whole system behaves as if there is one database Replica control x x SEQ Replication Protocol T1 T2
Extract writeset commit x commit r(x) w(x) T2 apply ws, commit abort Extract writeset x
xx Other replication protocols Lazy Primary Limitation: Need to know if a transaction is read-only or not in advance JDBC JDBC Comm Mgr Comm Mgr
Txn Mgr Txn Mgr Conn Mgr Conn Mgr Symmetric Limitation: Need to know all operations in a transaction in advance SRCA-REP
Need support of group communication systems We build a middleware platform, MiddleSIR, to accommodate all these protocols. A proof-of-concept game Modeling based on transactions E.g., two players might type same string concurrently. Model: Typing a string as one transaction, while typing a
character as an operation E.g., All players see the same game interfaces Model: Periodically reading data (e.g., strings, bullets, scores) from database as one transaction. Experiments in WANs, Scalability Experiments in WANs, 4 servers, Write transactions Conclusion
Propose a new approach of system supports for MOGs Applying database replication to MOGs for fault tolerance, scalability, performance, ease of concurrency control Use a small game for proof-of-concept Data consistency is guaranteed Response time is good, even in WANs. Scalability is not good. Read-one / Write-All replication only scales if the percentage of reads is very high. Future work: use partial replication (Write only a few servers)
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