profiling a milter (dkim in particular)

15 msg	Header for message size?
3 msg	address rewriting
2 msg	address_verify_relayhost and relay_domains
5 msg	pflogsumm reports
11 msg	Changing Queue IDs
3 msg	another authentication failure( with sasl)
2 msg	Bypass Spam checks for certain destinations
11 msg	Postfix 'too nice' with content_filter

profiling a milter (dkim in particular)
\ Vivek Khera (19 Sep 2007)
. \ (Wietse Venema) (19 Sep 2007)
. . \ Vivek Khera (20 Sep 2007)
. . . \ (Wietse Venema) (20 Sep 2007)
. . . . \ Victor Duchovni (20 Sep 2007)
. \ Mark Martinec (19 Sep 2007)
. . \ Vivek Khera (20 Sep 2007)

7 msg	spammers tacking on headers how to block?
7 msg	[Fwd: Re: RFC 821]
1 msg	Re:
4 msg	(No Subject)
2 msg	RFC 821
7 msg	Suspending mail delievery to a specific user
2 msg	Re: OT - massive newsletter
12 msg	List management issue: possibly Off Topic
2 msg	bad protocol error Testing SASL configuration
2 msg	warning: smtpd_sasl_auth_enable is true, but SA...
1 msg	Quota Problem

Subject:	profiling a milter (dkim in particular)
Group:	Postfix-users
From:	Vivek Khera
Date:	19 Sep 2007

I'm looking to insert a DKIM signer into my outgoing mail chain
(mostly to appease the Yahoo!s). Before I do that, I want to see
what the impact is on my mail outgoing throughput.

What I want to know is how much time a message of a given size spends
going through the milter on average. I can measure it indirectly or
directly.

Since I don't see any options to dkim-milter's configuration to emit
timing or detailed logging information to get this information
directly, and I can't see how to make postfix emit the information on
how much time the message spent in the milter, I figure I need to do
some indirect timing by comparing time to go through postfix with and
without the milter.

I set up postfix to relay all mail to the smtp-sink, and set up smtp-
source to generate messages that will be signed by the milter.
However, timing this is tricky... I can time easily how long it takes
to generate and inject the messages into postfix by smtp-source, but
tracking when the last message leaves postfix is a bit trickier. I
can see when smtp-sink has received all of its messages, and I can
see in the log file when the last one was delivered to the sink, but
then timing becomes a manual process, and the accuracy is limited to
1 second (which I guess I can live with.)

If I could make smtp-sink exit after N messages, I could use that
event to mark the completion of each test run and it could then be
automated.

Any ideas on how to automate detecting when all test messages have
gone completely through the system? Basically I want to know how
long it took from the time smtp-source starts to the time smtp-sink
has received all the messages generated.

Also, is the milter single-threaded or does it handle multiple
simultaneous connections from postfix? I'm pretty sure it is
handling multiple messages at the same time but I just wanted to
confirm. The docs for dkim-milter are pretty thin.

Thanks!