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Middleware Protocols. RPC, Message oriented Communication, etc. 2-5. An adapted reference model for networked communication. Message oriented communication RPCs, i.e., enhance access transparency but they are not always appropriate to distributed system. Persistence and Synchronicity
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Middleware Protocols RPC, Message oriented Communication, etc. 2-5 • An adapted reference model for networked communication.
Message oriented communication RPCs, i.e., enhance access transparency but they are not always appropriate to distributed system. Persistence and Synchronicity Different types of communications
Persistent communication 2-20 • General organization of a communication system in which hosts are connected through a network • Example : E-mail system. If the target server is unreachable, the local one continue to store messages ( in contrast with a transient communication method).
Persistence and Synchronicity in Communication 2-22.1 • Persistent asynchronous communication • Persistent synchronous communication
Persistence and Synchronicity in Communication 2-22.2 • Transient asynchronous communication (one way RPC) • Receipt-based transient synchronous communication
Persistence and Synchronicity in Communication • Delivery-based transient synchronous communication at message delivery(asynchronous RPCs) • Response-based transient synchronous communication (RPCs)
The need for persistent communication services is clear in developing middleware for large-scale distributed applications. Only transient or persistent communications like only synchronous or asynchronous communications is not sufficient! Message passing communication
Berkeley Sockets With new high performance multicomputer systems standard socket primitives are insufficient. Primitives have to be at a good level of abstraction and suitable for new high speed interconnection protocols • Socket primitives for TCP/IP.
The Message-Passing Interface (MPI) MPI uses the underlying network and it assumes communication take place within a known group of processes MPI supports all the previous communication diagrams except for (d) • Some of the most intuitive message-passing primitives of MPI.
Message-Queuing Model basic idea: applications communicate by inserting messages in specific queues 2-26 • Four combinations for loosely-coupled communications using queues.
Message-Queuing Model • Basic interface to a queue in a message-queuing system.
General Architecture of a Message-Queuing System (1) The collection of queues is distributed across multiple machines queue names db • The relationship between queue-level addressing and network-level addressing.
General Architecture of a Message-Queuing System (2) 2-29 • A message-queuing system with routers can solve the problem of a large scale system queue-to-location mapping
Message Brokersit converts incoming messages to a format compatible with the destination application 2-30 • The general organization of a message broker in a message-queuing system. • It is generally not considered an integral part of the queuing system.