1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
|
.TH s/qmail: qmail-todo 8
.SH NAME
qmail-todo \- schedule state change of message for delivery
.SH SYNOPSIS
.B qmail-todo
.SH DESCRIPTION
.B s/qmail
with a high local and remote concurrency number
is able to deliver a tremendous amount of messages (throughput).
Depending on the provided resources however,
often this can not be achieved since
.B qmail-send
becomes a bottleneck on delivery.
.B qmail-send
preprocesses all new messages before deploying them for
.I local
or for
.I remote
delivering. In a particulur run,
.B qmail-send
does one 'todo' processing, but has the ability to close multiple jobs.
Due to this layout, potentially
.B qmail-send
can not feed all the new available (local/remote) delivery slots
and therefore, it is not possible to achieve the maximum throughput.
This is a minor problem, given
.B qmail-send
is able to complete this in short time; but due to
many file system calls (fsync and (un)link) a 'todo'
run is expensive and throttles the throughput.
.B qmail-todo
solves this 'silly qmail (queue) problem'
which is apparent only on system with high injection rates,
delegating the scheduling of 'todo' runs to a dedicated process.
.SH "COMMUNICATION"
.B qmail-todo
interfaces with
.B qmail-send
on file descriptors \fI[1,8]\fR on sending
and \fI[7,0]\fR for receiving.
.B qmail-todo
communicates with
.B qmail-clean
on file descriptors \fI[2,0]\fR for sending
and \fI[3,1]\fR for receiving.
.B qmail-todo
and
.B qmail-send
share an extended and peristent message exchange format:
.EX
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.
.EE
.EX
L<string>\0
Dump string to the logger without adding additional
'\\n' or similar.
.EE
.B qmail-todo
sends "\\0" terminated messages, whereas
.B qmail-send
just sends one character to
.BR qmail-todo .
.SH "BIG PICTURE"
.EX
+-------+ +-------+
| 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|
+-------+
.EE
.SH "EXIT CODES"
.B qmail-todo
exits
.I 0
if the messages have been processed successfully.
It exits
.I 1
in case there is a communication problem with
.BR qmail-send .
The exit code
.I 111
together with a diagnostic message is facilitated by
.B qmail-todo
in case it failes reading the required control files.
.SH "DIAGNOSTICS"
.B qmail-todo
provides additional diagnostic messages to
.B qmail-send
to be displayed in the logs. In particular, in
case of problems creating and (un)linking files.
.SH "CREDITS"
.B qmail-todo
included in
.B s/qmail
has been created by Andre Oppermann (http://www.nrg4u.com)
as part of this LDAP patch for
.BR qmail .
This man-page uses parts of his EXTERNAL discription.
.SH "SEE ALSO"
qmail-send(8),
qmail-queue(8).
|
