# Assumptions

- Each service assumes at the outset that it's the only one in
  existence.
- Each service periodicially probes for the existence of other services.
- If two services of the same type find one another, they'll link up and
  synchronize.
- If three services of the same type exist, but A knows about B and B
  knows about A and C, B and C will synch, and then A and B will synch
  the content of B and C.

# Problems

- Service foo wants to search for services of the same type on other
  nodes that may or may not exist.
- Service foo wants to use another piece of software running on the same
  node to search for other instances.
- The datastore backing service foo isn't capable of synchronizing on
  its own with others of its type.
- The datastore backing service foo cannot grow without bound.
- Service foo isn't designed to have a web front end, but needs one.
  - Service foo needs a plug-in that exposes the service over HTTP.
- Each instance of service foo needs a unique identifier.

# Nonspecific solutions

- Designate a service on the node that maintains a catalogue of other
  services running on the node and make them available on the local
  network.
- Designate a service on the node that listens for announcements of
  other services on neighboring nodes.
- Designate a service on the node that watches for new instances of the
  same service to appear.
  - The monitoring daemon checks to see if the service announcement has
    already been picked up.
  - The monitoring daemon contacts the service's administrative
    interface and executes the necessary commands to inform it of a new
    instance to contact.
  - Service foo contacts the new instance and initiates synchronization.

I guess I'm talking about ejabberd and avahi here. Maybe with some glue
code and the odd exposed administrative interface.

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