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| -rw-r--r-- | design-notes.html | 25 |
1 files changed, 22 insertions, 3 deletions
diff --git a/design-notes.html b/design-notes.html index d0c8549e..1d3f478d 100644 --- a/design-notes.html +++ b/design-notes.html @@ -10,7 +10,7 @@ <table width="100%" cellpadding=0><tr> <td width="30%">Back to <a href="index.html">Fetchmail Home Page</a> <td width="30%" align=center>To <a href="/~esr/sitemap.html">Site Map</a> -<td width="30%" align=right>$Date: 1997/08/05 04:14:49 $ +<td width="30%" align=right>$Date: 1997/09/29 15:36:26 $ </table> <HR> <H1 ALIGN=CENTER>Design Notes On Fetchmail</H1> @@ -171,7 +171,7 @@ necessary decoder out of the fetchmail code itself to get it.<P> All .fetchmailrc encryption would do is give a false sense of security to people who don't think very hard.<P> -<H2>2. Truly concurrent queries to multiple hosts</H2> +<H2>Truly concurrent queries to multiple hosts</H2> Occasionally I get a request for this on "efficiency" grounds. These people aren't thinking either. True concurrency would do nothing to lessen @@ -188,6 +188,25 @@ Fortunately, I've only seldom seen a server that incurred significant wait time on an individual response. I judge the gain from this not worth the hideous complexity increase it would require in the code.<P> +<H2>Multiple concurrent instances of fetchmail</H1> + +What would be required for this is a per-host semaphore asserted +during each poll.<P> + +The fundamental problem here is how an instance of fetchmail polling +host foo can assert that it's doing so in a way visible to all other +fetchmails. System V semaphores would be ideal for this purpose, but +they're not portable.<P> + +I've thought about this a lot and roughed up several designs. All are +complicated and fragile, with a bunch of the standard problems (what +happens if a fetchmail aborts before clearing its semaphore, and how +do we recover reliably?)<P>. + +I'm not satisfied that there's enough functional gain here to pay +for the large increase in complexity that adding these semaphores +would entail.<P> + <H1>Multidrop and alias handling</H1> I decided to add the multidrop support partly because some users were @@ -383,7 +402,7 @@ all shaped the design in one way or another.<P> <table width="100%" cellpadding=0><tr> <td width="30%">Back to <a href="index.html">Fetchmail Home Page</a> <td width="30%" align=center>To <a href="/~esr/sitemap.html">Site Map</a> -<td width="30%" align=right>$Date: 1997/08/05 04:14:49 $ +<td width="30%" align=right>$Date: 1997/09/29 15:36:26 $ </table> <P><ADDRESS>Eric S. Raymond <A HREF="mailto:esr@thyrsus.com"><esr@snark.thyrsus.com></A></ADDRESS> |