Behind Live Mesh: The Pub-Sub System

infoblog » Behind Live Mesh: The Pub-Sub System

infoblog » Behind Live Mesh: The Pub-Sub System — Thu, 09 Oct 2008 06:42:08 GMT

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re: Behind Live Mesh: The Pub-Sub System

idhsu — Thu, 09 Oct 2008 14:16:24 GMT

what if a client is interested in a particular live folder(subscribed), goes down and up after a long time.whe n it send a subscription request again to folder,does it receive the updates happened while the client was down? if yes who manages it. does client send pubsub service with some more info like file already synced....

re: Behind Live Mesh: The Pub-Sub System

John West — Thu, 09 Oct 2008 17:23:59 GMT

"...In cases where one or several Queue and/or PubSub Servers go down, the system is able to detect exactly what happened and take remedial action to restore state in the cloud in cooperation with clients".

Isn't this what you would have to do for a client that goes offline? If I shut down my laptop for a day, then boot it back up, is the process in the quote above what you use to determine what files and other changes have been made so that I can get back up to sync? Or is this PubSub system complimented by another system for this scenario?

John

re: Behind Live Mesh: The Pub-Sub System

Viraj Mody — Thu, 09 Oct 2008 18:40:33 GMT

@John West:

A client going offline for long periods of time is no different than it's Queue and Subscriptions in the cloud being deleted, so yes - the same recovery protocol kicks in.

@idhsu:

When the client re-subscribes, it gets back an E-Tag representing the latest state of the resource in the cloud which it can then use to compare with its own E-Tag to determine whether things changed while it was offline.

re: Behind Live Mesh: The Pub-Sub System

Cobus — Tue, 04 Nov 2008 05:13:05 GMT

I am a bit worried about the following design decision:

"once a client is offline or doesn’t care about receiving Notifications, its Queue is of no use"

Similar to the other questions here, I have a use case where I have my Pictures folder synchronized (peer to peer) between my home PC and my laptop on the road. I have 6,000+ files in this folder, and I was wondering what would happen after a flight, when I connected back to the cloud, if my wife had been making modifications to some pictures at home. Would my queue persist until I log in (>5 hours...) or would my laptop client and home PC need to go through a massive resource intensive re-sync process?

re: Behind Live Mesh: The Pub-Sub System

Viraj Mody — Fri, 07 Nov 2008 21:39:21 GMT

@Cobus

When your makes reconnects to the cloud after a long time, its Queue might be gone but upon re-creation of the queue no massive re-sync is needed. As part of re-creating subscriptions, the client is told about any changes to resources it subscribes to (see my comment about E-Tags previously) any only those changes are sync'd down (either via the cloud or P2P - whichever is available and more efficient).