Application Programming Interface for Future Pub/Sub Networks Dr. Dmitrij Lagutin Helsinki Institute for Information Technology (HIIT)

Contents Requirements for a pub/sub API Examples of APIs in PSIRP and PURSUIT prototypes Ideas for a future pub/sub API Conclusions

Requirements for a pub/sub API Current TCP/IP-based API (socket) is quite old, and does not take into account many requirements of current applications Applications are dealing with information, which is structured and linked API should not depend on the location or used network API should offer a way to access various services and large amounts of data in an efficient way Future pub/sub network can also give much higher degree of control to the user or developer, which also should be taken into account in API –Used transit path, security policy, quality-of-service

Examples: PSIRP Prototype API High-level API resembles standard memory and socket operations: malloc, mmap, socket, send, recv, select –Scopes are created implicitly handle = create (size) –Creates a pointer to data and metadata of a specific size, of a memory object to be published publish (sid, rid, handle) –Publishes a read-only version of the object handle = subscribe (sid, rid) –Subscribes to the object events = listen (handle) –Listens to publication events, i.e., new versions

Examples: PSIRP Prototype API Publications are also accessible through file system /pubsub/sid/rid/data and /pubsub/sid/rid/metadata Legacy applications (text editor, web browser, file utilities) can access the data –Writing or deleting through file system is not supported

Examples: PURSUIT Prototype API Most functions takes following arguments: id, prefix_id, strategy, lid publish_scope, publish_info –Creates a scope or advertises information items (publications) publish_data (id, strategy, FID, data, data_len) –Publishes data for a specific information ID subscribe_scope, subscribe_info –Subscribes to scope or to information items unpublish_scope, unpublish_info –Unpublishes scope or information items unsubscribe_scope/unsubscribe_info –Unsubscribes from scope or information item

Examples: PURSUIT Prototype API Publication strategy –Determines how the information is disseminated, where it will be visible, etc. –DOMAIN_LOCAL (visible only in local domain) –PUBLISH_NOW (sends the data immediately, even if there are no subscribers)

Other ideas A simple way to publish, subscribe and manage publications, which similar to full-featured file system or Dropbox Natural support for streams Dividing API into two levels –High-level simple API with few basic functions such as publish or subscribe –More fine-grained API for controlling rendezvous and other pub/sub-related functionality (transit paths, security policies, quality-of-service, etc.) Any other ideas?

Conclusions Efficient API for future pub/sub networks is still an open problem Additional reading –P. Pietzuch, D. Eyers, S. Kounev, and B. Shand. Towards a Common API for Publish/Subscribe, DEBS –M. Demmer, K. Fall, T. Koponen, and S. Shenker. Towards a Modern Communications API, HotNets-VI