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From Peter Firmstone <j...@zeus.net.au>
Subject Re: Lookup Service Discovery using DNS?
Date Tue, 26 Jan 2010 04:34:27 GMT
Had some thoughts about a GlobalLooup Service, an alternative drop in 
replacement to Reggie that breaks with some traditions:

The GlobalLookup Service is visible from the internet and has a public 
domain name, it is discovered remotely using DNS-SD

   1. Services download a Global lookup service smart proxy during
   2. Smart proxy provides a unique service ID if required and also
      provides a single default group and domain from the Server.
   3. Smart proxy publishes via DNS-SD each implemented interface, along
      with the service ID ( utilising a txt key) and the default group.
      (These may or may not be visible outside the local domain). 
   4. The Service might register and upload it's proxy in a number of
      other domains and subgroups with GlobalLookup Services.
   5. The Local Service proxy is not registered with the local network
      Global Lookup Service, it is instead looked up as required by the
      Global Lookup smart proxy and matched at the client.
   6. Upon receiving a Lookup request, the lookup service proxy collects
      a list of currently available services from DNS-SD
   7. The lookup request includes the domains and groups to be queried
      (this could be publicly visible services anywhere in the world).
   8. A smart proxy for the Lookup service at the client downloads and
      unmarshalls proxy objects and Entries to be queried locally, any
      retrieved from other domains (only when not visible outside their
      local network) will be retrieved directly from the local
      GlobalLookup Service cache at the server.  The proxy objects in
      the Global server cache, have to be registered by the remote
      services themselves and will appear to be registered in the local
      domain and group to local clients.
   9. The Global Lookup Service cache on the server utilises existing
      marshalled entry comparisons to minimise the number of service
      proxies returned to the client.
  10. The local lookup proxy implementation queries unmarshalled Entry's
      (provided that the downloaded code is trusted, with limited
      permissions as specified in a bundle), enabling more complex
      queries utilising the hashCode() method for greater less than
      comparisons.  This is done in a pre configured number of threads,
      where only matching entry's are kept and all other instances
      garbage collected.  The bytecode and classloading is kept to a
      minimum by sharing of compatible bytecode via a codebase service
      that abstracts the bytecode from the origin of the marshalled objects.
  11. New Entry types, will need to be made publicly available for use
      and signing in a public source code staging area.  Untrusted
      Entries can only be utilised in Marshalled from.
  12. If a service moves, it keeps a copy of the domains and groups
      where it was previously registered and re-registers remotely, if
      configured to do so.  Leases are only kept for Globally remote
  13. Local services are rediscovered every time using DNS-SD
  14. If a GlobalService goes down and is replaced, it wont affect local
      services, however remote registered services will eventually
  15. If a remote service goes away, it will re-register itself with the
      local networks GlobalLooup Service.  The local GlobalLookup
      service will discard it's proxy after it's Lease expires.
  16. The remote services will have registration retry's at longer time
      intervals, if unsuccessful, to prevent a DOS packet storm, the
      retry will only occur after a Lease expires in any case.

DNS-SD enables the use of any port, by having the remote services 
register their proxy's, the packets will have the masquerading headers, 
so packets find their way back to the Service, even if private.

Feel free to point out omissions and issues or make suggestions.

Just some thoughts... Cheers,


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