1. An Efficient Process Live Migration Mechanism for Load Balanced Distributed Virtual Environments Balazs Gerofi, Hajime Fujita, Yutaka Ishikawa Yutaka Ishikawa Laboratory The University Of Tokyo IEEE Cluster2010

2. Outline Motivation Cluster Server Architecture DVE Software Components Process Live Migration Multiple Socket Migration Optimizations Dynamic Load Balancing Evaluation Conclusion IEEE Cluster2010

3. Motivation In Distributed Virtual Environments (DVE): – Massively Multi-player Online Games (MMPOG) – Networked Virtual Environments (NVE) – Distributed Simulations such as the High-Level Architecture (HLA) 10,000 ~ 100,000 of clients may be involved Cluster of servers is used for providing services on large scale – Zoning (i.e., partitioning the virtual space among servers) Main limitations of application level load-balancing: – Client migrations are heavy, server state needs to be transferred, client(s) reconnect, etc.. – Physical machine limited to neighboring zones Is operating system level load-balancing feasible? – Server processes are highly interactive – Maintain a massive amount of network connections (clients) – Maintain connections with other in-cluster components – How to migrate such processes? IEEE Cluster2010

4. Outline Motivation Cluster Server Architecture DVE Software Components Process Live Migration Multiple Socket Migration Optimizations Dynamic Load Balancing Evaluation Conclusion IEEE Cluster2010

5. Cluster Server Architecture IEEE Cluster2010 Each DVE server is equipped with a public and a private interfaces, same IP address is assigned to the public interfaces Router broadcasts incoming packets to all DVE server nodes – Migrating zone server processes does not require any work on the router! Zone server processes are distinguished based on separate port numbers (as opposed to separate IP addresses)

6. Outline Motivation Cluster Server Architecture DVE Software Components Process Live Migration Multiple Socket Migration Optimizations Dynamic Load Balancing Evaluation Conclusion IEEE Cluster2010

7. Server Node Software Components IEEE Cluster2010 mig_mod: migration module with live migration and socket support (extension of Berkeley C/R module) cap_trans_mod: packet capturing and address translation kernel module (detailes in paper) transd: translation daemon migd: migration daemon cond: load monitor and load balancer zone_serv: zone server processes Linux kernel mig_mod cap_trans_mod zone_serv 1 zone_serv n migd transd cond …

8. Outline Motivation Cluster Server Architecture DVE Software Components Process Live Migration Multiple Socket Migration Optimizations Dynamic Load Balancing Evaluation Conclusion IEEE Cluster2010

9. source host destination host Process Image Process Live Migration network IEEE Cluster2010 network sockets

10. source host destination host Process Image Process Live Migration network IEEE Cluster2010 network sockets Transfer the whole process image in the background without stopping the execution

11. source host destination host Process Image Process Live Migration - dirty memory page network IEEE Cluster2010 network sockets Track dirty pages for a certain period, process is still being executed

12. source host destination host Process Live Migration - dirty memory page network IEEE Cluster2010 network sockets Stop process (freeze phase), transfer dirty memory, export network connections and transfer data to destination Process Image

13. source host destination host Process Live Migration network IEEE Cluster2010 network sockets Apply changes and resume execution Process Image Note: main goal is short process freeze time!

14. Outline Motivation Cluster Server Architecture DVE Software Components Process Live Migration Multiple Socket Migration Optimizations Dynamic Load Balancing Evaluation Conclusion IEEE Cluster2010

15. source host destination host Process Image Iterative socket migration (during process freeze phase) - dirty memory page network IEEE Cluster2010 network sockets Incoming packet loss prevention!

16. source host destination host Process Image Iterative socket migration (during process freeze phase) - dirty memory page network IEEE Cluster2010 network sockets Extract remote IP and port number, set up a filter at the destination node to capture incoming packets and disable socket

17. source host destination host Process Image Iterative socket migration (during process freeze phase) - dirty memory page network IEEE Cluster2010 network sockets Migrate socket data to destination node

18. source host destination host Process Image Iterative socket migration (during process freeze phase) - dirty memory page network IEEE Cluster2010 network sockets Inject any packets that were captured on the destination node and attach socket to the process

19. source host destination host Process Image Iterative socket migration (during process freeze phase) - dirty memory page network IEEE Cluster2010 network sockets

20. source host destination host Process Image Iterative socket migration (during process freeze phase) - dirty memory page network IEEE Cluster2010 network sockets

21. source host destination host Process Image Iterative socket migration (during process freeze phase) - dirty memory page network IEEE Cluster2010 network sockets Note: requires several synchronization steps with short writes following each other!

22. source host destination host Process Image Collective socket migration (during process freeze phase) - dirty memory page network IEEE Cluster2010 network sockets

23. source host destination host Process Image Collective socket migration (during process freeze phase) - dirty memory page network IEEE Cluster2010 network sockets Extract remote IP and port number for all sockets, set up filters to capture incoming packets and disable sockets

24. source host destination host Process Image Collective socket migration (during process freeze phase) - dirty memory page network IEEE Cluster2010 network sockets Extract socket data into one unified buffer and transfer everything in one go

25. source host destination host Process Image Collective socket migration (during process freeze phase) - dirty memory page network IEEE Cluster2010 network sockets Attach sockets, inject packets. Note: the amount of socket data transferred can be still large!

26. source host destination host Process Image Incremental collective socket migration (during dirty-log phase) - dirty memory page network IEEE Cluster2010 network sockets

27. source host destination host Process Image Incremental collective socket migration (during dirty-log phase) - dirty memory page network IEEE Cluster2010 network sockets All socket data are transferred asynchronously and tracking structures are allocated for each connection network sockets

28. source host destination host Process Image Incremental collective socket migration (during dirty-log phase) - dirty memory page network IEEE Cluster2010 network sockets Some pages are dirtied and some sockets’ state change are detected network sockets

29. source host destination host Process Image Incremental collective socket migration (during dirty-log phase) - dirty memory page network IEEE Cluster2010 network sockets Dirty pages transferred and modified sockets’ state are updated, tracking loop timeout is decreased network sockets

30. source host destination host Process Image Incremental collective socket migration (during dirty-log phase) - dirty memory page network IEEE Cluster2010 network sockets When number of dirty pages or tracking timeout goes below a pre-defined limit, enter process freeze phase network sockets

31. source host destination host Process Image Incremental collective socket migration (during dirty-log phase) - dirty memory page network IEEE Cluster2010 network sockets Transfer dirty pages and set up packet capture filter network sockets

32. source host destination host Process Image Incremental collective socket migration (during dirty-log phase) - dirty memory page network IEEE Cluster2010 network sockets Update sockets that have changed in the last iteration and disable sockets on the source machine network sockets Note: transferred socket data in freeze phase is much less than the overall socket representation!

33. source host destination host Process Image Incremental collective socket migration (during dirty-log phase) - dirty memory page network IEEE Cluster2010 Inject packets and re- enable sockets on the destination machine network sockets

34. Outline Motivation Cluster Server Architecture DVE Software Components Process Live Migration Multiple Socket Migration Optimizations Dynamic Load Balancing Evaluation Conclusion IEEE Cluster2010

35. Dynamic Load Balancing Decentralized middleware Load balancing is sender initiated performing a hand-shake with the receiver Transfer policy: – Threshold driven (if load exceeds a certain value) Location policy: – Based on knowledge of load on the rest of the nodes, preferring a node that is on the opposite side of the cluster load average Selection policy: – Prefers a process that consumes as much CPU power as much the difference between the given node’s load and the cluster load average Information policy: – Periodic policy, nodes broadcast their load IEEE Cluster2010

36. Outline Motivation Cluster Server Architecture DVE Software Components Process Live Migration Multiple Socket Migration Optimizations Dynamic Load Balancing Evaluation Conclusion IEEE Cluster2010

37. Evaluation: experimental framework Dedicated single IP address cluster 5 DVE server nodes + a MySQL server 2.4GHz Dual-Core AMD Opteron 2 GB RAM Gigabit Ethernet for both in-cluster and public network IEEE Cluster2010

38. Evaluation: OpenArena server OpenArena is an open-source multi-player online game based on the Quake III engine [1] Uses UDP for client-server communication ~20 messages (updates) per second Live migrated when 24 clients were participating in a session IEEE Cluster2010 [1] http://openarena.ws/smfnews.php Based on tcpdump’s result on the client machines ~25ms service downtime due to migration

39. Evaluation: DVE simulation DVE simulation with communication characteristics resembling real- world MMOPGs using TCP connections Client state update: 20 msgs / sec, 256~512 bytes message size [2] DVE server processes maintain MySQL to local DB server CPU consumption grows proportionally with number of clients in a given zone, 10,000 clients involved Virtual space consists of 10x10 zones, each DVE server node is assigned to 20 zones initially IEEE Cluster2010 [2] Traffic characteristics of a massively multi-player online role playing game, NetGames’05 15 minutes simulation during which clients are instructed to move to the up-left and bottom-right corner of the virtual space Files are assumed to be available on each node

40. Live migration process downtime IEEE Cluster2010

41. Socket data transferred during process freeze phase IEEE Cluster2010

42. Load distribution during simulation without load balancing IEEE Cluster2010 node1, node2 and node5 becomes overloaded when clients move to zones maintained by these nodes

43. Load distribution during simulation with load balancing IEEE Cluster2010 Load stays balanced throughout the simulation

44. Number of zone server processes on each node during the simulation IEEE Cluster2010 Lighter processes are migrated over to node3 and node4 in order to balance the overall load of the system

45. Outline Motivation Cluster Server Architecture DVE Software Components Process Live Migration Multiple Socket Migration Optimizations Dynamic Load Balancing Evaluation Conclusion IEEE Cluster2010

46. Conclusion Process live migration – Optimizations for migrating a massive amount network connections – No modifications to the TCP protocol or to the client side network stack Dynamic load balancing engine exploiting process live migration DVE simulation for demonstrating load balancer and live migration Other possible scenarios: – Fault tolerance (IEEE NCA2010) – Power management IEEE Cluster2010

47. Thank you for your attention! Questions? IEEE Cluster2010

48. Related Work Connection Migration: – NEC’s distributed Web Server arch: each session has its own virtual IP address – SockMi, Tcpcp: TCP migration with IP layer forwarding, don’t decouple the process from the source machine – TCP Migrate option: extension to the TCP protocol Process migration and incremental checkpointing: – V-System, Amoeba, Mach, Sprite, MOSIX – limited connection migration support – BLCR: no support for connection and incremental checkp. – Zap’s VNAT: support required on client side as well Load balancing DVEs: – Several studies addressing application level solutions – MOSIX: home-node approach leaves residual dependencies IEEE Cluster2010