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EXTTODO
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EXTTODO
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EXTTODO by Claudio Jeker <jeker@n-r-g.com> and
Andre Oppermann <opi@nrg4u.com>
(c) 2002-2004 Internet Business Solutions Ltd.
The EXTTODO patch is a part of the qmail-ldap patch.
This patches for qmail come with NO WARRANTY.
RELEASE: 5. Jan. 2003 ($Date: 2004/04/16 13:24:16 $)
EXTTODO:
======================
TOC:
WHAT DOES IT DO
INSTALL
CONFIG FILES
SETUP
BIG PICTURE
NEWS:
This is the first release of the EXTTODO patch.
================================================================================
WHAT DOES IT DO
The exttodo patch addresses a problem known as the silly qmail (queue)
problem. This problem is found only on system with high injection rates.
qmail with a big local and remote concurrency could deliver a tremendous
amount of messages but normally this can not be achieved because qmail-send
becomes a bottleneck on those high volumes servers.
qmail-send preprocesses all new messages before distributing them for local
or remote delivering. In one run qmail-send does one todo run but has the
ability to close multiple jobs. Because of this layout qmail-send can not
feed all the new available (local/remote) delivery slots and therefor it is
not possible to achieve the maximum throughput.
This would be a minor problem if one qmail-send run could be done in extreme
short time but because of many file system calls (fsync and (un)link) a todo
run is expensive and throttles the throughput.
The exttodo patch tries to solve the problem by moving the todo routine into
an external program. This reduces the run time in qmail-send.
exttodo adds a new program to qmail called qmail-todo. qmail-todo prepares
incoming messages for local and remote delivering (by creating info/<messid>
local/<messid> and remote/<messid> and removing todo/<messid>). See also
INTERNALS. As next qmail-todo transmits the <messid> to qmail-send which will
add this message into the priority queue which schedules the message for
delivery.
INSTALL
To enable the exttodo patch you need to define EXTERNAL_TODO while compiling
qmail(-ldap) this can be done with the -D flag of cc (e.g. cc -DEXTERNAL_TODO).
NOTE: the exttodo patch can also be used on qmail systems without the
qmail-ldap patch.
================================================================================
CONFIG FILES
No additional control files are used or needed.
================================================================================
SETUP
qmail-todo will be started by qmail-start and therefor no additional setup
is needed.
To verify that exttodo is running just check if qmail-todo is running.
================================================================================
BIG PICTURE
+-------+ +-------+
| clean | | clean |
+--0-1--+ +--0-1--+ +-----------+
trigger ^ | ^ | +->0,1 lspawn |
| | v | v / +-----------+
+-------+ v +--2-3--+ +--5-6--+ /
| | | | 0<--7 1,2<-+
| queue |--+--| todo | | send |
| | | | 1-->8 3,4<-+
+-------+ +-------+ +---0---+ \
| \ +-----------+
v +->0,1 rspwan |
+---0---+ +-----------+
| logger|
+-------+
Communication between qmail-send and qmail-todo
todo -> send:
D[LRB]<mesgid>\0
Start delivery for new message with id <messid>.
the character L, R or B defines the type
of delivery, local, remote or both respectively.
L<string>\0
Dump string to the logger without adding additional \n or similar.
send -> todo:
H Got a SIGHUP reread ~/control/locals and ~/control/virtualdomains
X Quit ASAP.
qmail-todo sends "\0" terminated messages whereas qmail-send just send one
character to qmail-todo.