FIspace Review meeting M12 CSB

Cloud Service Bus Bus Coordinator Bus Node Service A Service SDI VM External Services and Data Scalable communication, based on peer2peer overlay Automatic scalability Robustness Queuing Message expiration Publish/subscribe Request/response Multi-tenancy VM Service Service B Service

3 SR Overlay – The Virtual Ring SR is based on the Chord overlay Each process has a logical id of m bits, e.g., the output of hashing the process’s name or IP address and port number (e.g., using SHA-1) Each process p maintains links to its neighbors in the ring – successor (p) – the “first” process clockwise – predecessor (p) - the “first” process counter-clockwise For example, process N8 maintains links to process N21 (its successor) and to processes N1 (its predecessor) N1 N8 N21 N42 N55 N51 N32 N8’s Predecessor N8’s Successor

4 SR Overlay – The Finger Table Each process p also maintains links to a process with id= – p+2^0 (or to successor of p+2^0) – p+2^1 (or to successor of p+2^1) –. – p+2^i (or to successor of p+2^i) –. – p+2^(m-1) (or to successor of p+2^(m-1) This list of links is called finger table and it contains O(log N) links p p+2^0 p+2^1 p+2^2 p+2^3 p+2^4 p+2^5

5 Point-to-Point Communication Routing requires only O(log N) hops (messages) – With each forwarding the distance to the target is reduced by (at least) 50% Example, assume process N8 wants to send a message to processes N55 – At N8: send(message,N55) – N8 returns next hop = N42 – N42 returns next hop = N51 – N51 returns next hop = N55 N1 N8 N21 N32 N42 N55 N51 N1, N21, N32, N42 N1, N32, N51 N8’s finger table N42’s finger table

Queuing Any client can send messages to a “queue”; any client can retrieve messages from a “queue” for applications (with multiple readers) Highly reliable (persistent) delivery of transactional data Asynchronous (receivers can run and get data any time later) Identical message order for all receivers

Request/ response Synchronous Request/Response – synchronously query one another for a value of specific attributes or for any other information – requester sends a request and waits for a response, up to a specified timeout – optimal when the response information can be retrieved quickly by the responder Asynchronous Request/Response – response with unpredictable timing – multiple responses to a single request – for example, future notifications upon attribute value change. response listener callback, – send response messages at any time, without a limit of number of responses for each request Time-limited asynchronous Request/Response – time required to produce a response is long – requester is not blocked on a synchronous request – requester sends an asynchronous query, and sets a response timer – WAIT_TIMEOUT notification