<br><br><div class="gmail_quote">On Mon, Jan 16, 2012 at 1:54 PM, <span dir="ltr"><<a href="mailto:exarkun@twistedmatrix.com">exarkun@twistedmatrix.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im">On 14 Jan, 09:30 am, <a href="mailto:johnaherne@rocs.co.uk">johnaherne@rocs.co.uk</a> wrote:<br>
>I have been looking at JPCalderones example of using web.request with<br>
>JSON<br>
>which seems much like what I want.<br>
><br>
>One thing I am not clear about is if I get a lot of queries coming in<br>
>more<br>
>or less simultaneously and I am using cooperate to allow other<br>
>functions to<br>
>run, will I need to guard against my data in a list being overwritten<br>
>by<br>
>subsequent requests.<br>
><br>
>The way I see it the functions to read data and and store it in my list<br>
>are<br>
>in danger of impacting each other.<br>
><br>
>The response is being built cooperatively bit by bit to permit other<br>
>functions to run so it could happen that the next request overwrites my<br>
>list where the database query is being stored.<br>
<br>
</div>Any time you have shared mutable state, you have this possibility. You<br>
do need to take measures to avoid making one request destroy the state<br>
associated with another request.<br>
<div class="im">>If this is a danger, then I need to prevent this, which seems to imply<br>
>that<br>
>I will need to block each request and not service another request until<br>
>the<br>
>previous one has completed.<br>
<br>
</div>Serializing (ie, not processing a second request until the first is<br>
completed) processing is one way to accomplish this.<br>
<br>
However, another way to accomplish it is to not have shared mutable<br>
state. A quick skim of your code suggests you don't actually have much,<br>
if any, shared mutable state.<br>
<br>
The list holding your database results is a local variable, and each<br>
request builds its own (as far as I can tell). There is no danger of<br>
different requests interfering with each other in this case.<br>
<br>
Jean-Paul<br>
<br>
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</blockquote></div>Thanks for the reply.<div><br></div><div>I think I must have been asleep when I asked this.</div><div><br></div><div>Someone else pointed this out to me earlier on but I did not have time to get to a computer before you replied.</div>
<div><br></div><div>Thanks anyway. I shall glue this to me screen for the next week or so.</div><div><br></div><div>John Aherne</div><div><br></div>