summaryrefslogtreecommitdiffstats
path: root/src/qmgr/qmgr_entry.c
blob: 61b3434876ddff59e4e204f94d9a28f86fedd035 (plain)
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
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
/*++
/* NAME
/*	qmgr_entry 3
/* SUMMARY
/*	per-site queue entries
/* SYNOPSIS
/*	#include "qmgr.h"
/*
/*	QMGR_ENTRY *qmgr_entry_create(peer, message)
/*	QMGR_PEER *peer;
/*	QMGR_MESSAGE *message;
/*
/*	void	qmgr_entry_done(entry, which)
/*	QMGR_ENTRY *entry;
/*	int	which;
/*
/*	QMGR_ENTRY *qmgr_entry_select(queue)
/*	QMGR_QUEUE *queue;
/*
/*	void	qmgr_entry_unselect(queue, entry)
/*	QMGR_QUEUE *queue;
/*	QMGR_ENTRY *entry;
/*
/*	void	qmgr_entry_move_todo(dst, entry)
/*	QMGR_QUEUE *dst;
/*	QMGR_ENTRY *entry;
/* DESCRIPTION
/*	These routines add/delete/manipulate per-site message
/*	delivery requests.
/*
/*	qmgr_entry_create() creates an entry for the named peer and message,
/*	and appends the entry to the peer's list and its queue's todo list.
/*	Filling in and cleaning up the recipients is the responsibility
/*	of the caller.
/*
/*	qmgr_entry_done() discards a per-site queue entry.  The
/*	\fIwhich\fR argument is either QMGR_QUEUE_BUSY for an entry
/*	of the site's `busy' list (i.e. queue entries that have been
/*	selected for actual delivery), or QMGR_QUEUE_TODO for an entry
/*	of the site's `todo' list (i.e. queue entries awaiting selection
/*	for actual delivery).
/*
/*	qmgr_entry_done() discards its peer structure when the peer
/*	is not referenced anymore.
/*
/*	qmgr_entry_done() triggers cleanup of the per-site queue when
/*	the site has no pending deliveries, and the site is either
/*	alive, or the site is dead and the number of in-core queues
/*	exceeds a configurable limit (see qmgr_queue_done()).
/*
/*	qmgr_entry_done() triggers special action when the last in-core
/*	queue entry for a message is done with: either read more
/*	recipients from the queue file, delete the queue file, or move
/*	the queue file to the deferred queue; send bounce reports to the
/*	message originator (see qmgr_active_done()).
/*
/*	qmgr_entry_select() selects first entry from the named
/*	per-site queue's `todo' list for actual delivery. The entry is
/*	moved to the queue's `busy' list: the list of messages being
/*	delivered. The entry is also removed from its peer list.
/*
/*	qmgr_entry_unselect() takes the named entry off the named
/*	per-site queue's `busy' list and moves it to the queue's
/*	`todo' list. The entry is also prepended to its peer list again.
/*
/*	qmgr_entry_move_todo() moves the specified "todo" queue entry
/*	to the specified "todo" queue.
/* DIAGNOSTICS
/*	Panic: interface violations, internal inconsistencies.
/* LICENSE
/* .ad
/* .fi
/*	The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*	Wietse Venema
/*	IBM T.J. Watson Research
/*	P.O. Box 704
/*	Yorktown Heights, NY 10598, USA
/*
/*	Preemptive scheduler enhancements:
/*	Patrik Rak
/*	Modra 6
/*	155 00, Prague, Czech Republic
/*--*/

/* System library. */

#include <sys_defs.h>
#include <stdlib.h>
#include <time.h>

/* Utility library. */

#include <msg.h>
#include <mymalloc.h>
#include <events.h>
#include <vstream.h>

/* Global library. */

#include <mail_params.h>
#include <deliver_request.h>		/* opportunistic session caching */

/* Application-specific. */

#include "qmgr.h"

/* qmgr_entry_select - select queue entry for delivery */

QMGR_ENTRY *qmgr_entry_select(QMGR_PEER *peer)
{
    const char *myname = "qmgr_entry_select";
    QMGR_ENTRY *entry;
    QMGR_QUEUE *queue;

    if ((entry = peer->entry_list.next) != 0) {
	queue = entry->queue;
	QMGR_LIST_UNLINK(queue->todo, QMGR_ENTRY *, entry, queue_peers);
	queue->todo_refcount--;
	QMGR_LIST_APPEND(queue->busy, entry, queue_peers);
	queue->busy_refcount++;
	QMGR_LIST_UNLINK(peer->entry_list, QMGR_ENTRY *, entry, peer_peers);
	peer->job->selected_entries++;

	/*
	 * With opportunistic session caching, the delivery agent must not
	 * only 1) save a session upon completion, but also 2) reuse a cached
	 * session upon the next delivery request. In order to not miss out
	 * on 2), we have to make caching sticky or else we get silly
	 * behavior when the in-memory queue drains. Specifically, new
	 * connections must not be made as long as cached connections exist.
	 * 
	 * Safety: don't enable opportunistic session caching unless the queue
	 * manager is able to schedule concurrent or back-to-back deliveries
	 * (we need to recognize back-to-back deliveries for transports with
	 * concurrency 1).
	 * 
	 * If caching has previously been enabled, but is not now, fetch any
	 * existing entries from the cache, but don't add new ones.
	 */
#define CONCURRENT_OR_BACK_TO_BACK_DELIVERY() \
	    (queue->busy_refcount > 1 || BACK_TO_BACK_DELIVERY())

#define BACK_TO_BACK_DELIVERY() \
		(queue->last_done + 1 >= event_time())

	/*
	 * Turn on session caching after we get up to speed. Don't enable
	 * session caching just because we have concurrent deliveries. This
	 * prevents unnecessary session caching when we have a burst of mail
	 * <= the initial concurrency limit.
	 */
	if ((queue->dflags & DEL_REQ_FLAG_CONN_STORE) == 0) {
	    if (BACK_TO_BACK_DELIVERY()) {
		if (msg_verbose)
		    msg_info("%s: allowing on-demand session caching for %s",
			     myname, queue->name);
		queue->dflags |= DEL_REQ_FLAG_CONN_MASK;
	    }
	}

	/*
	 * Turn off session caching when concurrency drops and we're running
	 * out of steam. This is what prevents from turning off session
	 * caching too early, and from making new connections while old ones
	 * are still cached.
	 */
	else {
	    if (!CONCURRENT_OR_BACK_TO_BACK_DELIVERY()) {
		if (msg_verbose)
		    msg_info("%s: disallowing on-demand session caching for %s",
			     myname, queue->name);
		queue->dflags &= ~DEL_REQ_FLAG_CONN_STORE;
	    }
	}
    }
    return (entry);
}

/* qmgr_entry_unselect - unselect queue entry for delivery */

void    qmgr_entry_unselect(QMGR_ENTRY *entry)
{
    QMGR_PEER *peer = entry->peer;
    QMGR_QUEUE *queue = entry->queue;

    /*
     * Move the entry back to the todo lists. In case of the peer list, put
     * it back to the beginning, so the select()/unselect() does not reorder
     * entries. We use this in qmgr_message_assign() to put recipients into
     * existing entries when possible.
     */
    QMGR_LIST_UNLINK(queue->busy, QMGR_ENTRY *, entry, queue_peers);
    queue->busy_refcount--;
    QMGR_LIST_APPEND(queue->todo, entry, queue_peers);
    queue->todo_refcount++;
    QMGR_LIST_PREPEND(peer->entry_list, entry, peer_peers);
    peer->job->selected_entries--;
}

/* qmgr_entry_move_todo - move entry between todo queues */

void    qmgr_entry_move_todo(QMGR_QUEUE *dst_queue, QMGR_ENTRY *entry)
{
    const char *myname = "qmgr_entry_move_todo";
    QMGR_TRANSPORT *dst_transport = dst_queue->transport;
    QMGR_MESSAGE *message = entry->message;
    QMGR_QUEUE *src_queue = entry->queue;
    QMGR_PEER *dst_peer, *src_peer = entry->peer;
    QMGR_JOB *dst_job, *src_job = src_peer->job;
    QMGR_ENTRY *new_entry;
    int     rcpt_count = entry->rcpt_list.len;

    if (entry->stream != 0)
	msg_panic("%s: queue %s entry is busy", myname, src_queue->name);
    if (QMGR_QUEUE_THROTTLED(dst_queue))
	msg_panic("%s: destination queue %s is throttled", myname, dst_queue->name);
    if (QMGR_TRANSPORT_THROTTLED(dst_transport))
	msg_panic("%s: destination transport %s is throttled",
		  myname, dst_transport->name);

    /*
     * Create new entry, swap the recipients between the two entries,
     * adjusting the job counters accordingly, then dispose of the old entry.
     * 
     * Note that qmgr_entry_done() will also take care of adjusting the
     * recipient limits of all the message jobs, so we do not have to do that
     * explicitly for the new job here.
     * 
     * XXX This does not enforce the per-entry recipient limit, but that is not
     * a problem as long as qmgr_entry_move_todo() is called only to bounce
     * or defer mail.
     */
    dst_job = qmgr_job_obtain(message, dst_transport);
    dst_peer = qmgr_peer_obtain(dst_job, dst_queue);

    new_entry = qmgr_entry_create(dst_peer, message);

    recipient_list_swap(&entry->rcpt_list, &new_entry->rcpt_list);

    src_job->rcpt_count -= rcpt_count;
    dst_job->rcpt_count += rcpt_count;

    qmgr_entry_done(entry, QMGR_QUEUE_TODO);
}

/* qmgr_entry_done - dispose of queue entry */

void    qmgr_entry_done(QMGR_ENTRY *entry, int which)
{
    const char *myname = "qmgr_entry_done";
    QMGR_QUEUE *queue = entry->queue;
    QMGR_MESSAGE *message = entry->message;
    QMGR_PEER *peer = entry->peer;
    QMGR_JOB *sponsor, *job = peer->job;
    QMGR_TRANSPORT *transport = job->transport;

    /*
     * Take this entry off the in-core queue.
     */
    if (entry->stream != 0)
	msg_panic("%s: file is open", myname);
    if (which == QMGR_QUEUE_BUSY) {
	QMGR_LIST_UNLINK(queue->busy, QMGR_ENTRY *, entry, queue_peers);
	queue->busy_refcount--;
    } else if (which == QMGR_QUEUE_TODO) {
	QMGR_LIST_UNLINK(peer->entry_list, QMGR_ENTRY *, entry, peer_peers);
	job->selected_entries++;
	QMGR_LIST_UNLINK(queue->todo, QMGR_ENTRY *, entry, queue_peers);
	queue->todo_refcount--;
    } else {
	msg_panic("%s: bad queue spec: %d", myname, which);
    }

    /*
     * Decrease the in-core recipient counts and free the recipient list and
     * the structure itself.
     */
    job->rcpt_count -= entry->rcpt_list.len;
    message->rcpt_count -= entry->rcpt_list.len;
    qmgr_recipient_count -= entry->rcpt_list.len;
    recipient_list_free(&entry->rcpt_list);
    myfree((void *) entry);

    /*
     * Make sure that the transport of any retired or finishing job that
     * donated recipient slots to this message gets them back first. Then, if
     * possible, pass the remaining unused recipient slots to the next job on
     * the job list.
     */
    for (sponsor = message->job_list.next; sponsor; sponsor = sponsor->message_peers.next) {
	if (sponsor->rcpt_count >= sponsor->rcpt_limit || sponsor == job)
	    continue;
	if (sponsor->stack_level < 0 || message->rcpt_offset == 0)
	    qmgr_job_move_limits(sponsor);
    }
    if (message->rcpt_offset == 0) {
	qmgr_job_move_limits(job);
    }

    /*
     * We implement a rate-limited queue by emulating a slow delivery
     * channel. We insert the artificial delays with qmgr_queue_suspend().
     * 
     * When a queue is suspended, we must postpone any job scheduling decisions
     * until the queue is resumed. Otherwise, we make those decisions now.
     * The job scheduling decisions are made by qmgr_job_blocker_update().
     */
    if (which == QMGR_QUEUE_BUSY && transport->rate_delay > 0) {
	if (queue->window > 1)
	    msg_panic("%s: queue %s/%s: window %d > 1 on rate-limited service",
		      myname, transport->name, queue->name, queue->window);
	if (QMGR_QUEUE_THROTTLED(queue))	/* XXX */
	    qmgr_queue_unthrottle(queue);
	if (QMGR_QUEUE_READY(queue))
	    qmgr_queue_suspend(queue, transport->rate_delay);
    }
    if (!QMGR_QUEUE_SUSPENDED(queue)
	&& queue->blocker_tag == transport->blocker_tag)
	qmgr_job_blocker_update(queue);

    /*
     * When there are no more entries for this peer, discard the peer
     * structure.
     */
    peer->refcount--;
    if (peer->refcount == 0)
	qmgr_peer_free(peer);

    /*
     * Maintain back-to-back delivery status.
     */
    if (which == QMGR_QUEUE_BUSY)
	queue->last_done = event_time();

    /*
     * When the in-core queue for this site is empty and when this site is
     * not dead or suspended, discard the in-core queue. When this site is
     * dead, but the number of in-core queues exceeds some threshold, get rid
     * of this in-core queue anyway, in order to avoid running out of memory.
     */
    if (queue->todo.next == 0 && queue->busy.next == 0) {
	if (QMGR_QUEUE_THROTTLED(queue) && qmgr_queue_count > 2 * var_qmgr_rcpt_limit)
	    qmgr_queue_unthrottle(queue);
	if (QMGR_QUEUE_READY(queue))
	    qmgr_queue_done(queue);
    }

    /*
     * Update the in-core message reference count. When the in-core message
     * structure has no more references, dispose of the message.
     */
    message->refcount--;
    if (message->refcount == 0)
	qmgr_active_done(message);
}

/* qmgr_entry_create - create queue todo entry */

QMGR_ENTRY *qmgr_entry_create(QMGR_PEER *peer, QMGR_MESSAGE *message)
{
    QMGR_ENTRY *entry;
    QMGR_QUEUE *queue = peer->queue;

    /*
     * Sanity check.
     */
    if (QMGR_QUEUE_THROTTLED(queue))
	msg_panic("qmgr_entry_create: dead queue: %s", queue->name);

    /*
     * Create the delivery request.
     */
    entry = (QMGR_ENTRY *) mymalloc(sizeof(QMGR_ENTRY));
    entry->stream = 0;
    entry->message = message;
    recipient_list_init(&entry->rcpt_list, RCPT_LIST_INIT_QUEUE);
    message->refcount++;
    entry->peer = peer;
    QMGR_LIST_APPEND(peer->entry_list, entry, peer_peers);
    peer->refcount++;
    entry->queue = queue;
    QMGR_LIST_APPEND(queue->todo, entry, queue_peers);
    queue->todo_refcount++;
    peer->job->read_entries++;

    /*
     * Warn if a destination is falling behind while the active queue
     * contains a non-trivial amount of single-recipient email. When a
     * destination takes up more and more space in the active queue, then
     * other mail will not get through and delivery performance will suffer.
     * 
     * XXX At this point in the code, the busy reference count is still less
     * than the concurrency limit (otherwise this code would not be invoked
     * in the first place) so we have to make make some awkward adjustments
     * below.
     * 
     * XXX The queue length test below looks at the active queue share of an
     * individual destination. This catches the case where mail for one
     * destination is falling behind because it has to round-robin compete
     * with many other destinations. However, Postfix will also perform
     * poorly when most of the active queue is tied up by a small number of
     * concurrency limited destinations. The queue length test below detects
     * such conditions only indirectly.
     * 
     * XXX This code does not detect the case that the active queue is being
     * starved because incoming mail is pounding the disk.
     */
    if (var_helpful_warnings && var_qmgr_clog_warn_time > 0) {
	int     queue_length = queue->todo_refcount + queue->busy_refcount;
	time_t  now;
	QMGR_TRANSPORT *transport;
	double  active_share;

	if (queue_length > var_qmgr_active_limit / 5
	    && (now = event_time()) >= queue->clog_time_to_warn) {
	    active_share = queue_length / (double) qmgr_message_count;
	    msg_warn("mail for %s is using up %d of %d active queue entries",
		     queue->nexthop, queue_length, qmgr_message_count);
	    if (active_share < 0.9)
		msg_warn("this may slow down other mail deliveries");
	    transport = queue->transport;
	    if (transport->dest_concurrency_limit > 0
	    && transport->dest_concurrency_limit <= queue->busy_refcount + 1)
		msg_warn("you may need to increase the main.cf %s%s from %d",
			 transport->name, _DEST_CON_LIMIT,
			 transport->dest_concurrency_limit);
	    else if (queue->window > var_qmgr_active_limit * active_share)
		msg_warn("you may need to increase the main.cf %s from %d",
			 VAR_QMGR_ACT_LIMIT, var_qmgr_active_limit);
	    else if (queue->peers.next != queue->peers.prev)
		msg_warn("you may need a separate master.cf transport for %s",
			 queue->nexthop);
	    else {
		msg_warn("you may need to reduce %s connect and helo timeouts",
			 transport->name);
		msg_warn("so that Postfix quickly skips unavailable hosts");
		msg_warn("you may need to increase the main.cf %s and %s",
			 VAR_MIN_BACKOFF_TIME, VAR_MAX_BACKOFF_TIME);
		msg_warn("so that Postfix wastes less time on undeliverable mail");
		msg_warn("you may need to increase the master.cf %s process limit",
			 transport->name);
	    }
	    msg_warn("please avoid flushing the whole queue when you have");
	    msg_warn("lots of deferred mail, that is bad for performance");
	    msg_warn("to turn off these warnings specify: %s = 0",
		     VAR_QMGR_CLOG_WARN_TIME);
	    queue->clog_time_to_warn = now + var_qmgr_clog_warn_time;
	}
    }
    return (entry);
}