Re: Parallel delivery of a single message - possible?

[Matti Aarnio <mea@utu.fi>]

> Folks,
> 
> I am considering installing Zmailer, and before I put effort on it,
> I'd like to know if it helps in the following circumstances:
> 
> Imagine that I have a big mailing list, and it it critical to deliver
> the postings _fast_.  When a message appears with many envelope recipient
> addresses, all addresses are resolved and the message is scheduled for
> delivery to multiple hosts.  Before this moment, processing cannot be
> parallel.  But after the destination hosts are known, it is theoretically
> possible to start multiple delivery processes, to transfer message to
> many hosts at the same time.  I want to know if Zmailer will perform
> delivery of a single message in parallel.  All MTA's that I tried before
> (Sendmail 5.6+IDA, Sendmail 6.8, Smail) perform delivery from a single
> process, one host at a time, which is unacceptable.

	It does exactly that -- run as many parallel delivery channels
	as you configure -- parametrization is a bit fuzzy, but can be
	done in massive scales, if your operating system allows it.

	The limiting factors are the number of open files any process
	can have, and what storage STDIO uses for the file-descriptor.
	An example is Sun Solaris where processes can have up to 1024
	fds, however if STDIO is used (fopen() and friends), it allows
	only 256 files (storage is on "unsigned char").

	The limiting location is Scheduler, which keeps one fd open
	for each child process (transport channel process) for reading
	back the status information.  This limits (on Solaris) the
	number of running childs to circa 240-250.  Your system may
	vary...

> Thanks in advance.
> 
> Eugene

	/Matti Aarnio	<mea@utu.fi> <mea@nic.funet.fi>