I want to monitor my heat. I can raise and lower my thermostats via computer
and read the temperature in the room as well as on the hot water radiator
pipes.
I want to write a system that:
1. For a number of thermometers, send temperature readings to message
queue/topic
2. For a number of thermostats, send thermostat change events to message
queue/topic
3. Dequeue readings and events and send them to a sql database
4. Dequeue and maintain the state of all thermometers and thermostats for
analysis
5. Execute rules based on the state of the system and trigger actions as
appropriate
6. Allow the state to be queried by a browser or a web service
7. Allow the triggered actions to be queried by a browser or web service
8. Allow the devices to be set/cleared via browser or web service
A rule frozen pipe rule could be:
if [hot water temperature on the pipe going to my radiator is rising]
and
[hot water temperature on the return pipe is still cold] and [radiator's
room temperature is cold and not rising] then trigger a message to tell me
my pipe might be frozen.
A triggered message could be an email or SMS or phone call.
I think ServiceMix allows all these things to be relatively independent.
I think ServiceMix allows me to add rules, actions, inputs and queries as
time goes on without changing ones that work already.
I used to have a single Java program that did everything but rules. Most of
the code was handling exceptions and recovering from problems. Every new
exceptional condition caused a rewrite or at least a new recovery. It isn't
as stable as I wished and took too much effort to make stable.
Now I have little programs (#1 & #2 above). The temperature reader doesn't
worry if the sql insert failed. The sql logger (#3) doesn't worry if the
thermometer didn't read. Either of them can put a message on another queue
that there is a problem and I can address that as a separate concern. Camel
is the glue that makes them work together.
I wonder if keeping my state (#4) would be done well in an EJB that listens
for messages or is there a EIP for this I'm not aware of?
I wonder if rules (#5) can be easily incorporated into ServiceMix? DROOLS
and ODE come to mind. I'd have to make a rule that this thermostat, this
room temperature, these pipe temperatures must all trend together. And when
an action is to be taken (maybe by sending a message to a queue/topic),
another component that does the notification. Camel would glue them
together.
I'd like to write a web app or an Android app (#6) to see my state and maybe
turn on and off the heat (#7) from my phone or computer.
Eventually I'd like to monitor more than just my house. Maybe my neighbors
would like the same thing. This is another dimension to the problem – it
would be good if it generalizes. I'd need a hierarchy of the devices that
trend together that based on which house it is.
In summary:
Is this architecturally sound?
Is an EJB a good choice to maintain state or is there a better way?
Is ServiceMix a good choice to publish web pages or web services for
querying the state?
Eventually I'd need to sign the messages so I know they are authentic, is
this possible?
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