> On Mar 28, 2016, at 10:15 AM, Pedro David Marco <pedrod_ma...@yahoo.com>
> wrote:
>
> It seems to me that when qmgr wants to deliver an email via smtp, qmgr
> "assigns" it to a smtp process. As long as there are no concurrency
> needs, the same smtp process is used repeatedly.... even for diferent
> domain destinations.
This impression is incorrect. Deliveries are handled by the first
idle smtp(8) delivery agent, or if none are idle, a new one is spawned,
up to the process limit specified in master.cf or the default process
limit.
There is no prior "assignment". Each smtp(8) delivery agent handles
one request at a time, and goes back for more when it is done.
The main complication is there are also per-nexthop destination
concurrency limits, so messages for a busy destination may need
to wait for delivery of other messages for the same destination
when the concurrency limit is reached. Similarly, once the process
limit is reached, and all delivery agents are busy, new mail waits
for other deliveries to complete.
> NOW, if one smtp process delivery takes long, long long... until
> it dies for the watchdog timeout,
Watchdog timeouts are not normal Postfix behaviour. They are a
last-resort safety measure in the face of kernel bugs or execution
on platforms that are not sufficiently compatible with Postfix.
If you're seeing watchdog timeouts, there's something wrong with
your system.
> all smtp deliveries assigned to that smtp process fail! and
> qmgr send them back to deferred queue....
Exactly one delivery is "assigned" to a busy smtp(8) delivery
agent. No other deliveries wait for that agent specifically.
However, if you restart the queue manager (via Postfix reload
or similar) it will not be able to obtain an exclusive lock
on a queue file that is open by a running delivery agent.
In that case, other recipients from the same queue file may
be blocked until the pending delivery completes. This does
not affect the delivery of new mail.
DO NOT make a habit of restarting the queue manager. In
particular, avoid routine use of "postfix reload" from cron.
> Is there any way to force postfix to use one smtp process
> for each delivery so if one fail the others get delivered?
The premise if flawed, so the question is moot. Postfix
uses multiple processes in parallel by default.
--
Viktor.
