Re: Filters with multiple copies of pine running

On Tue, 6 Feb 2007, Ross wrote:

>> Pine talks to the server by using the IMAP protocol, so there is no 
>> possibility of locking or anything like that.
>
> Then there is no possibility of operating a multiuser login secure system. It 
> will crash. That server must somehow lock files/records to allow a write or 
> crash for multiuser. A write is required to create/update any 
> message/file/record.

Sorry, I wasn't clear. Of course the server has locks and maintains 
consistency and everything. But that doesn't mean the clients can 
effectively use that locking. In the case we're talking about the client 
is copying a message to a different folder based on what it knows about 
the message. It's easy to imagine that two different clients both decide 
to do the same copy. The problem can be minimized in some ways like we've 
talked about.

>> There are definitely race conditions. For example, one client can expunge a 
>> message and the other one won't know about that for a while, or one could 
>> set the Delete flag and the other wouldn't know (for a while).
>
> No, the system will not work that way. In a multiuser system, where multiple 
> users such as this access one database of messages/files/records, one user 
> must be allowed to create/update message/file/records & other users see the 
> change before being allowed to continue with access. That is the purpose of 
> locking & updating. Pine must be able to deal with that or is not a multiuser 
> program, & a crash will occur.

Then I guess pine is not a "multiuser" program because that's the way it 
works. I use it all the time with multiple connections at the same time 
and I'm happy.

I think I'll sign off now, thanks.

Steve
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