12. Architectural Paradigms Flashcards
Various approaches to interprocess communication and event synchronisation
If interaction is by means of message passing, what must each component be aware of?
The mechanisms for IPC and the rules for making use of the mechanisms (protocols)
What must a message send follow and coincide with?
Follow readiness to send.
Coincide with readiness to recieve
Why do different DC architectures arise?
Different ways and levels of abstraction at which IPC and event synchronisation are handled.
What DC paradigms are there?
DME- Direct Message Exchange
MME- Mediated Message Exchange
RPC- Remote Procedure Call
E-B/L-B RMI- Early Binding/ Late Binding Remote Method Invocation
Describe the Simple Pattern of IPC in DME architectures
A process must be in a position to receive a message.
A process may send a message to another process.
A process that receives a message may then process it and send a response message
What does it mean that in DME event synchronisation is unmediated?
the interacting processes themselves must take care of it. Message exchange is direct
Describe Asymmetric DME. What are two examples?
The server process takes heavier loads.
Requires load balancing and could prevent scaling.
E.g. Web and Email
Describe Symmetric DME
No special role is assigned to any process. Processes are peers hence it is a peer to peer architecture.
No process simply waits for requests to respond nor simply makes requests and waits for a response. Event synchronisation is less simple than asymmetric DME
Describe IPC in MME architectures.
IPC is not a direct event between sender and receiver.
Processes communicate directly with MOM (message oriented middleware)
Messages are sent to MOM, MOM sends them to the receiving processes.
What is the role of the MOM in IPC in MME architectures
MOM is interposed between processes. It mediates the IPC. It allows even synchronisation to be decoupled in time without threading or forking.
What is a point to point MME architecture? What’s an example alternative?
Any messages going from one source process to one destination process is point to point.
messages can go to more than one destination process. An example is publish-subscribe systems.
A process subscribes with the MOM expressing interest in certain events from other processes. When a process publishes an event with the MOM, MOM notifies the subscribing processes
Describe a RPC. What is the alternative?
Remote Procedure Call
Views both IPC and event synchronisation as implicit.
Alternative: consider even synchronisation explicitly and submit to an explicit IPC discipline by means of protocols
