Incoming Queuing
MTA kicks off a fml process. It reads a message from STDIN.
The fml process reads a message once and write it onto the hard disk
(write it into the incoming queue). After the queuing succeeded, the
process starts to analyze a message. For this logic, the original mail
is saved before main processing starts.
If the queuing fails, fml calls exit(EX_TEMPFAIL). In almost cases,
exit(75). If MTA receives this exit code, MTA tries to deliver again
later.
Mail::Delivery::Queue class processes the incoming queue.
The queus is removed when the process ends.
fml Sends Back A Mail Message
Mail::Delivery::Queue class inserts a message to send back into the
mail queue. Later FML::Process::QueueManager handles the real delivery
process.
Article delivery processing is a little diffferent but based on
queueing by Mail::Delivery::Queue. If someting error occurs in
delivery, another fml process tries to deliver it later.
Coding In &fml8; Sources.
Code is like this to send back a message:
$curproc->reply_message( "you are not a ML member." );
If no recipient specified, the recipient is the sender of the message
(From: address).
To send a file, like this:
$curproc->reply_message( {
type => "text/plain; charset=iso-2022-jp",
path => "/etc/fml/main.cf",
filename => "main.cf",
disposition => "main.cf example",
});
$curproc->reply_message( {
type => "image/gif",
path => "/some/where/logo001.gif",
filename => "logo.gif",
disposition => "attachment",
});
Mail Queue And Delivery System
FML::Process::QueueManager picks up one queue from the queue directory.
Mail::Message parses it.
Mail::Delivery processes the real delivery via FML::Mailer.
Mail::Delivery::Queue
|
| ---> queue directory
V
FML::Process::QueueManager
|
| <--- queue directory
V
FML::Mailer
|
V
Mail::Delivery
In manipulating queue, we should lock the target queue by flock(2).
Mail Queue Directory
The queue directory consists of the following plural directories:
new/
active/
incoming/
deferred/
info/sender/
info/recipients/
info/transport/
info/ stores envelope information.
incoming/ holds incoming queue, others hold outgoing information.
In creating a new outgoing queue file,
make a temporary file in new/ once.
When the delivery preparation is ended,
move the queue from new/ to active/.
Hence files under active/ is delivery ready.
Lock The Queue
When we need to handle the specific queue file,
use lock()/unlock() method for each $queue_id object.
The lock algorithm is based on flock(2) for the file.