[Dev] Preventing user from running multiple instances

[Andi Vajda]

> Excellent, Andi.  Does anyone have an objection to me making exclusive-access 
> the default for Chandler?

It would be nice, if that became the default, that when a second Chandler is 
started, the first one popped to the front instead. The repository reports an 
ExclusiveOpenDeniedError on the second open.

Andi..

>
> On Mar 2, 2005, at 11:26 AM, Andi Vajda wrote:
>
>> 
>>> For various reasons we don't want the user to be able to run multiple 
>>> instances of Chandler against the same repository.  For example, if you 
>>> fire up two instances at the same time, one of them will complain that 
>>> //Schema already exists, and there are other places where things don't 
>>> quite work.  So I was wondering if anyone had an idea for a cross-platform 
>>> way to prevent multiple concurrent instances accessing a repository. 
>>> Chandler could look for and create a lock file next to the repository 
>>> directory, and place its process ID in there, thereby allowing it to 
>>> detect whether an existing lock file is obsolete because a previous 
>>> instance died without removing it.  (Does Windows have the notion of PID?) 
>>> This method leaves the repository itself out of it -- purely an 
>>> application level function.  Or we could get the repository involved and 
>>> have it keep track of which process has it open, and the application layer 
>>> asks the repository.  I guess I would lean toward the former method.
>>> 
>>> I'm sure there must be some python module that does this already, in a 
>>> cross-platform way...
>> 
>> This is an old problem that I fixed a few months ago. If you don't want 
>> multiple Chandlers to run concurrently, start the first one with -x or 
>> --exclusive.
>> 
>> Andi..
>> 
>>> 
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