Srinath Perera discusses multi-tenancy and why it is crucial for implementing a Platform as a Service (PaaS). He outlines four levels of multi-tenancy maturity and how WSO2's Carbon platform achieves tenant isolation through separate security domains, databases, and execution contexts while maintaining performance and scalability. Implementing multi-tenancy requires balancing tenant isolation with efficient resource sharing and introduces challenges around data security, tenant migration, and scaling to large numbers of tenants.

1. Multi-tenancy: Winning formula for a PaaS by Srinath Perera, Ph.D. Senior Software Architect WSO2 Inc.

3. What and Why Multi-tenancy?

4. Implementing Multi-tenancy

5. Data Multi-tenancy

6. Execution Multi-tenancy

7. Scaling Up

8. ConclusionPhoto by Bruno Girin on Flickr, http://www.flickr.com/photos/brunogirin/27981693/, Licensed under CC

11. Idea is a big pool of servers and share.

12. Economics of scale through Optimize large scale operations.

13. Resource Pooling.

14. No need for capacity planning, start small and grow as needed.

15. Outsource and enabling specialization. photo by LoopZilla on Flickr, http://www.flickr.com/photos/loopzilla/2328231843/sizes/m/in/photostream/, Licensed under CC

16. Cloud Offerings

18. SaaS is great when they can be used

19. They are usually very specific (e.g. email, CRM ..)

20. If they match, then great, but if they are not, not much choice for the user.

21. PaaS stays in the middle ground

22. Framework to host your apps

24. Now sharing happens in the application level as oppose to sharing at OS level for multiple processes and sharing at HW level with VMs.

25. That can bring greater savings “There is no delight in owning anything unshared.” Seneca (Roman philosopher, mid-1st century AD) photo by Ben Gray on Flickr, http://www.flickr.com/photos/ben_grey/4582294721/, Licensed under CC

27. We cannot allocate runtime resource per account (disk may be ok, as it is cheap). For example, we cannot run a VM per account.

28. By sharing the same server with many users, Multi-tenancy provides much reduced runtime cost per server. Flexibility

30. Say there are 100k accounts, but 10k active users at a time. VM based model needs 100k VMs, which means there is a cost incurred per account.

31. With Multi-tenancy one server can handle many accounts, and by mixing and matching heavy and light users, Multi-tenancy can operate with much less number of servers. photo by hans s on Flickr, http://www.flickr.com/photos/archeon/2359334908/

32. Motivating Usecases

36. Idea is to let scientists visually compose workflows and run them.

37. There are many gateways that do this. Enable multiple science gateways to share the same infrastructure thus reducing the maintenance cost and resource sharing . Same would work for most e-Gov stuff and for most organizations. photo by Image Editor on Flickr, http://www.flickr.com/photos/11304375@N07/2769519295/, Licensed under CC

38. How Good is this Multi-Tenancy implementation?

40. (F. Chong and G. Carraro, “Architecture strategies for catching the long tail,” MSDN Library, Microsoft Corporation, 2006.)

41. Provide a way to understand Multi-tenant implementations.

42. Level1: Instance per Client

43. Level 2: Configurable instance per Client

44. Level 3: Single instance can serve multiple Clients

47. It is about trading off Isolation vs. Sharing As often the case in research, implementing Multi-tenancy is a tradeoff photo by Todd Anderson on Flickr, http://www.flickr.com/photos/toddography/12034661/, Licensed under CC

48. WSO2 Carbon Platform

50. Execution: Business Processes, Workflows and Mashups

51. Security: ownership and authorization of both data, as well as executions in the framework

54. Each domain may have its own User Store and Permissions, thus have a set of users and permissions enabling users to access resources

56. Separate Schema

59. WSO2 Relational Storage Service uses this models to provide users with DBs 25

61. Some databases have ways to support this directly but many don’t

62. Failure difficult to handle

63. Scales reasonably well9/13/11 26

65. Requires all accesses to qualify with tenant

66. Failure is global

67. (Stratos uses this approach internally for all provide isolation within WSO2 Registry)9/13/11 27

69. Axis2 have stateless executions and keep all state in a Context.

72. Example

74. We currently relay on monitoring and auditing where we can kill CPU hogging processes

75. We are exploring the possibility of changing the priority of CPU hogging processes in the work queues (e.g. workflow engine, ESB etc.). photo Fortes by on Flickr, http://www.fotopedia.com/items/flickr-3193056200

76. Scaling Up

78. To reach Level 4, we have to scale.

79. To do that

80. We have to run this with many nodes, and we have to partition.

81. We have to replicate or partition. But we are talking about 1000s of tenants, likely one tenant can not hold all of them.

82. So We need to partition

84. Overhead of Multi-Tenancy

85. Service Performance

86. Workflow Performance Setup Multi-tenant and non-multi-tenant versions Run 200 workflows from each client Overhead is minimal MT supports only add few additional lookups and checks Java Security does not come in to play as we do not run user provided code.

88. AfkhamAzeez, Srinath Perera, DimuthuGamage, Ruwan Linton, PrabathSiriwardana, DimuthuLeelaratne, SanjivaWeerawarana, Paul Fremantle, "Multi-Tenant SOA Middleware for Cloud Computing" 3rd International Conference on Cloud Computing, Florida, 2010

90. We discussed details about implementing it

91. Isolation (Data, Execution) .. Isolation vs. sharing tradeoff

92. Four level’s of multi-tenancy

93. Scaling Design

94. Lot of open questions yet to be solved. Your thoughts and code both are welcome.

96. Feedback URL https://appserver.stratoslive.wso2.com/t/wso2con2011.com/webapps/feedback-sample-1.0.0/feedback