More on MOM

More! Even more!

what does a programmer need for MOM systems 1

an interface for transmitting produced events

what does a programmer need for MOM systems 2

a middleware that routes events appropriately

what does a programmer need for MOM systems 3

components that can receive events they should consume

what does an event channel “mean” 1

all events of one type

what does an event channel “mean” 2

all events relating to one service

design decisions on event channels 1

how are channels defined and discovered?

design decisions on event channels 2

how are events produced and consumed?

design decisions on event channels 3

how are events held and routed?

design decisions on event channels 4

what guarantees do we give the system about how these operations occur in detail?

defining a channel

make an interface for producing and consuming events, then we can use component services to make channels discoverable by name or property etc

issues with channel buffering 1

how many events should a channel be able to store? what happens if that limit is exceeded?

issues with channel buffering 2

are there limits to the number of producers or consumers on a single channel? how should we handle situations where we need more?

pub sub

producers publish events on chosen channels, consumers subscribe to channels of interest

consuming 1

pull mode - component requests an event and blocks until one is available

consuming 2

push mode - component provides an interface that the channel can call when an event is available

difference between pull and push 1

pull mode, control is in the components. push mode, control is in the middleware

difference between pull and push 2

pull mode, channel doesn’t know who is interested in its events. push mode, channel knows.

difference between pull and push 3

pull mode, component pulls events occasionally. push mode, component registers a long term interest