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Re: JavaClient offline storage / replication
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Re: JavaClient offline storage / replication


  • Subject: Re: JavaClient offline storage / replication
  • From: Anjo Krank <email@hidden>
  • Date: Fri, 17 Apr 2009 16:20:00 +0200


Am 17.04.2009 um 15:59 schrieb Jean-Francois Veillette:

My original task was to sync 2 sites using - get this - email (No, I couldn't use anything else, it HAD to be email). I ended up with using JMS to halfway maintain queue integrity. It actually worked and because each site only had their own change sets with their own PKs (this is what the host flag in ERXLongPKFactory is for), conflicts were minimal and easy to sort out. But it was still a nightmare and I'm glad they now listened to reason :)

Very interesting ! Nice to see someone actually build a solution for this kind of problem !
I'm currious, do you have an automated mail reader that automatically 'import' change set ? does it need manual intervention ?
Can you elaborate a little bit, just enough so I get the big picture.

A bit, as I don't care to remember this in too much detail :) Actually, it looked like I pulled out the JMS as openJMS wasn't too stable to begin with and used my own tiny queue implementation.


I had what you had: SyncQueue (name, messages) + SyncMessage (queue, payload, reponse, sequence no)

Also as I had images and changes to sync, I had 6 queues:

Master:
- create one Sender for the images
- create one Sender for the master queue
- create one Receiver for the client queue

Client:
- create one Sender for the client queue
- create one Receiver for the master queue
- create one Receiver for the images

EC changes get sent into the outbound queue, then sent as mail. Client reads items (IMAP), if it's out of order, waits until he gets the correct number. There was an interface to resend. Client gets payload, execs items. Last write wins, changes are merged, conflicts are reported. Deleted are ignored. Client write receipt, master reads it and marks the item as done ("result" as text).

The rest I can't remember (except telling them that when push comes to shove, they have to start fresh and the whole thing is a terrible idea to begin with)

Cheers, Anjo
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References: 
 >JavaClient offline storage / replication (From: John Huss <email@hidden>)
 >Re: JavaClient offline storage / replication (From: Stamenkovic Florijan <email@hidden>)
 >Re: JavaClient offline storage / replication (From: Lachlan Deck <email@hidden>)
 >Re: JavaClient offline storage / replication (From: Stamenkovic Florijan <email@hidden>)
 >Re: JavaClient offline storage / replication (From: John Ours <email@hidden>)
 >Re: JavaClient offline storage / replication (From: Anjo Krank <email@hidden>)
 >Re: JavaClient offline storage / replication (From: Jean-Francois Veillette <email@hidden>)
 >Re: JavaClient offline storage / replication (From: Anjo Krank <email@hidden>)
 >Re: JavaClient offline storage / replication (From: Jean-Francois Veillette <email@hidden>)

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