[Zope-dev] Re: [Warning] Zope/ZEO clients: subprocesses can lead tonon-deterministic message loss: ONLY IF YOUR APP CODE FORKS

[sathya]

tim thanks for confirming it. Wont loose sleep over it now. I did not 
mean to sound like questioning anybodys track record. Since we have ZEO 
clusters in production it raised alarm bells thats all. Its good to know
the problem MAY occur only if u fork in your own app code and the core 
zeo/zope code by itself is not contributing to it. I guess as a general 
rule of thumb its not a good idea to use forks in zope application or 
product code anyway (unless you know what you are doing.)
Regards
sathya

> [sathya]
> 
>>...
>>The zeoclient causes threads to be created but there are no "forks" or
>>"system" calls as far as I can tell (or strace for that matter)
>>Can you please point out where in the zeo code does forking occur ? I
>>will try and duplicate this condition.
> 
[tim]
> ZEO and ZEO never fork -- they wouldn't be portable if they did (only
> Unixish systems have fork()).  The only forking you'll find here is in
> startup scripts specific to Unixish systems.
> 
> Dieter is talking about forks (whether direct or indirect) in
> *application* code, not in the Zope/ZEO cores.  If application code
> running in a Zope/ZEO process forks, and Zope/ZEO are running asyncore
> in a thread, and the fork() implementation does clone all threads
> (which does not happen under Windows or POSIX), then of course the
> fork() the application code does is going to create a clone of the
> asyncore thread too.
> 
> That said, it would indeed be helpful if Dieter revealed enough
> details about what his app did, and on which kind of system, so it
> would be possible for others to try to duplicate his results.  I have
> no doubt that he is seeing problems, BTW -- Dieter has an excellent
> track record.
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