summaryrefslogtreecommitdiff
path: root/ctdb/server/ctdb_traverse.c
blob: 4865dcc94f016f5d8f8ffaf6b7359e7a5125127d (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
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
/* 
   efficient async ctdb traverse

   Copyright (C) Andrew Tridgell  2007

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, see <http://www.gnu.org/licenses/>.
*/

#include "replace.h"
#include "system/filesys.h"
#include "system/network.h"
#include "system/wait.h"
#include "system/time.h"

#include <talloc.h>
#include <tevent.h>

#include "lib/tdb_wrap/tdb_wrap.h"
#include "lib/util/dlinklist.h"
#include "lib/util/debug.h"
#include "lib/util/samba_util.h"
#include "lib/util/sys_rw.h"
#include "lib/util/util_process.h"

#include "ctdb_private.h"
#include "ctdb_client.h"

#include "common/reqid.h"
#include "common/system.h"
#include "common/common.h"
#include "common/logging.h"

typedef void (*ctdb_traverse_fn_t)(void *private_data, TDB_DATA key, TDB_DATA data);

/*
  handle returned to caller - freeing this handler will kill the child and 
  terminate the traverse
 */
struct ctdb_traverse_local_handle {
	struct ctdb_traverse_local_handle *next, *prev;
	struct ctdb_db_context *ctdb_db;
	int fd[2];
	pid_t child;
	uint64_t srvid;
	uint32_t client_reqid;
	uint32_t reqid;
	int srcnode;
	void *private_data;
	ctdb_traverse_fn_t callback;
	bool withemptyrecords;
	struct tevent_fd *fde;
	int records_failed;
	int records_sent;
};

/*
 * called when traverse is completed by child or on error
 */
static void ctdb_traverse_child_handler(struct tevent_context *ev, struct tevent_fd *fde,
					uint16_t flags, void *private_data)
{
	struct ctdb_traverse_local_handle *h = talloc_get_type(private_data,
							struct ctdb_traverse_local_handle);
	ctdb_traverse_fn_t callback = h->callback;
	void *p = h->private_data;
	int res;
	ssize_t n;

	/* Read the number of records sent by traverse child */
	n = sys_read(h->fd[0], &res, sizeof(res));
	if (n < 0 || n != sizeof(res)) {
		/* Traverse child failed */
		DEBUG(DEBUG_ERR, ("Local traverse failed db:%s reqid:%d\n",
				  h->ctdb_db->db_name, h->reqid));
	} else if (res < 0) {
		/* Traverse failed */
		res = -res;
		DEBUG(DEBUG_ERR, ("Local traverse failed db:%s reqid:%d records:%d\n",
				  h->ctdb_db->db_name, h->reqid, res));
	} else {
		DEBUG(DEBUG_INFO, ("Local traverse end db:%s reqid:%d records:%d\n",
				   h->ctdb_db->db_name, h->reqid, res));
	}

	callback(p, tdb_null, tdb_null);
}

/*
  destroy a in-flight traverse operation
 */
static int traverse_local_destructor(struct ctdb_traverse_local_handle *h)
{
	DLIST_REMOVE(h->ctdb_db->traverse, h);
	ctdb_kill(h->ctdb_db->ctdb, h->child, SIGKILL);
	return 0;
}

/*
  callback from tdb_traverse_read()
 */
static int ctdb_traverse_local_fn(struct tdb_context *tdb, TDB_DATA key, TDB_DATA data, void *p)
{
	struct ctdb_traverse_local_handle *h = talloc_get_type(p,
							       struct ctdb_traverse_local_handle);
	struct ctdb_rec_data_old *d;
	struct ctdb_ltdb_header *hdr;
	int res, status;
	TDB_DATA outdata;

	hdr = (struct ctdb_ltdb_header *)data.dptr;

	if (ctdb_db_volatile(h->ctdb_db)) {
		/* filter out zero-length records */
		if (!h->withemptyrecords &&
		    data.dsize <= sizeof(struct ctdb_ltdb_header))
		{
			return 0;
		}

		/* filter out non-authoritative records */
		if (hdr->dmaster != h->ctdb_db->ctdb->pnn) {
			return 0;
		}
	}

	d = ctdb_marshall_record(h, h->reqid, key, NULL, data);
	if (d == NULL) {
		/* error handling is tricky in this child code .... */
		h->records_failed++;
		return -1;
	}

	outdata.dptr = (uint8_t *)d;
	outdata.dsize = d->length;

	res = ctdb_control(h->ctdb_db->ctdb, h->srcnode, 0, CTDB_CONTROL_TRAVERSE_DATA,
			   CTDB_CTRL_FLAG_NOREPLY, outdata, NULL, NULL, &status, NULL, NULL);
	if (res != 0 || status != 0) {
		h->records_failed++;
		return -1;
	}

	h->records_sent++;
	return 0;
}

struct traverse_all_state {
	struct ctdb_context *ctdb;
	struct ctdb_traverse_local_handle *h;
	uint32_t reqid;
	uint32_t srcnode;
	uint32_t client_reqid;
	uint64_t srvid;
	bool withemptyrecords;
};

/*
  setup a non-blocking traverse of a local ltdb. The callback function
  will be called on every record in the local ltdb. To stop the
  traverse, talloc_free() the traverse_handle.

  The traverse is finished when the callback is called with tdb_null for key and data
 */
static struct ctdb_traverse_local_handle *ctdb_traverse_local(struct ctdb_db_context *ctdb_db,
							      ctdb_traverse_fn_t callback,
							      struct traverse_all_state *all_state)
{
	struct ctdb_traverse_local_handle *h;
	int ret;

	h = talloc_zero(all_state, struct ctdb_traverse_local_handle);
	if (h == NULL) {
		return NULL;
	}

	ret = pipe(h->fd);

	if (ret != 0) {
		talloc_free(h);
		return NULL;
	}

	h->child = ctdb_fork(ctdb_db->ctdb);

	if (h->child == (pid_t)-1) {
		close(h->fd[0]);
		close(h->fd[1]);
		talloc_free(h);
		return NULL;
	}

	h->callback = callback;
	h->private_data = all_state;
	h->ctdb_db = ctdb_db;
	h->client_reqid = all_state->client_reqid;
	h->reqid = all_state->reqid;
	h->srvid = all_state->srvid;
	h->srcnode = all_state->srcnode;
	h->withemptyrecords = all_state->withemptyrecords;

	if (h->child == 0) {
		/* start the traverse in the child */
		int res, status;
		pid_t parent = getpid();
		struct ctdb_context *ctdb = ctdb_db->ctdb;
		struct ctdb_rec_data_old *d;
		TDB_DATA outdata;

		close(h->fd[0]);

		prctl_set_comment("ctdb_traverse");
		if (switch_from_server_to_client(ctdb) != 0) {
			DEBUG(DEBUG_CRIT, ("Failed to switch traverse child into client mode\n"));
			_exit(0);
		}

		d = ctdb_marshall_record(h, h->reqid, tdb_null, NULL, tdb_null);
		if (d == NULL) {
			res = 0;
			sys_write(h->fd[1], &res, sizeof(int));
			_exit(0);
		}

		res = tdb_traverse_read(ctdb_db->ltdb->tdb, ctdb_traverse_local_fn, h);
		if (res == -1 || h->records_failed > 0) {
			/* traverse failed */
			res = -(h->records_sent);
		} else {
			res = h->records_sent;
		}

		/* Wait till all the data is flushed from output queue */
		while (ctdb_queue_length(ctdb->daemon.queue) > 0) {
			tevent_loop_once(ctdb->ev);
		}

		/* End traverse by sending empty record */
		outdata.dptr = (uint8_t *)d;
		outdata.dsize = d->length;
		ret = ctdb_control(ctdb, h->srcnode, 0,
				   CTDB_CONTROL_TRAVERSE_DATA,
				   CTDB_CTRL_FLAG_NOREPLY, outdata,
				   NULL, NULL, &status, NULL, NULL);
		if (ret == -1 || status == -1) {
			if (res > 0) {
				res = -res;
			}
		}

		sys_write(h->fd[1], &res, sizeof(res));

		ctdb_wait_for_process_to_exit(parent);
		_exit(0);
	}

	close(h->fd[1]);
	set_close_on_exec(h->fd[0]);

	talloc_set_destructor(h, traverse_local_destructor);

	DLIST_ADD(ctdb_db->traverse, h);

	h->fde = tevent_add_fd(ctdb_db->ctdb->ev, h, h->fd[0], TEVENT_FD_READ,
			       ctdb_traverse_child_handler, h);
	if (h->fde == NULL) {
		close(h->fd[0]);
		talloc_free(h);
		return NULL;
	}
	tevent_fd_set_auto_close(h->fde);

	return h;
}


struct ctdb_traverse_all_handle {
	struct ctdb_context *ctdb;
	struct ctdb_db_context *ctdb_db;
	uint32_t reqid;
	ctdb_traverse_fn_t callback;
	void *private_data;
	uint32_t null_count;
	bool timedout;
};

/*
  destroy a traverse_all op
 */
static int ctdb_traverse_all_destructor(struct ctdb_traverse_all_handle *state)
{
	reqid_remove(state->ctdb->idr, state->reqid);
	return 0;
}

/* called when a traverse times out */
static void ctdb_traverse_all_timeout(struct tevent_context *ev,
				      struct tevent_timer *te,
				      struct timeval t, void *private_data)
{
	struct ctdb_traverse_all_handle *state = talloc_get_type(private_data, struct ctdb_traverse_all_handle);

	DEBUG(DEBUG_ERR,(__location__ " Traverse all timeout on database:%s\n", state->ctdb_db->db_name));
	CTDB_INCREMENT_STAT(state->ctdb, timeouts.traverse);

	state->timedout = true;
	state->callback(state->private_data, tdb_null, tdb_null);
}


struct traverse_start_state {
	struct ctdb_context *ctdb;
	struct ctdb_traverse_all_handle *h;
	uint32_t srcnode;
	uint32_t reqid;
	uint32_t db_id;
	uint64_t srvid;
	bool withemptyrecords;
	int num_records;
};


/*
  setup a cluster-wide non-blocking traverse of a ctdb. The
  callback function will be called on every record in the local
  ltdb. To stop the traverse, talloc_free() the traverse_handle.

  The traverse is finished when the callback is called with tdb_null
  for key and data
 */
static struct ctdb_traverse_all_handle *ctdb_daemon_traverse_all(struct ctdb_db_context *ctdb_db,
								 ctdb_traverse_fn_t callback,
								 struct traverse_start_state *start_state)
{
	struct ctdb_traverse_all_handle *state;
	struct ctdb_context *ctdb = ctdb_db->ctdb;
	int ret;
	TDB_DATA data;
	struct ctdb_traverse_all r;
	struct ctdb_traverse_all_ext r_ext;
	uint32_t destination;

	state = talloc(start_state, struct ctdb_traverse_all_handle);
	if (state == NULL) {
		return NULL;
	}

	state->ctdb         = ctdb;
	state->ctdb_db      = ctdb_db;
	state->reqid        = reqid_new(ctdb_db->ctdb->idr, state);
	state->callback     = callback;
	state->private_data = start_state;
	state->null_count   = 0;
	state->timedout     = false;
	
	talloc_set_destructor(state, ctdb_traverse_all_destructor);

	if (start_state->withemptyrecords) {
		r_ext.db_id = ctdb_db->db_id;
		r_ext.reqid = state->reqid;
		r_ext.pnn   = ctdb->pnn;
		r_ext.client_reqid = start_state->reqid;
		r_ext.srvid = start_state->srvid;
		r_ext.withemptyrecords = start_state->withemptyrecords;

		data.dptr = (uint8_t *)&r_ext;
		data.dsize = sizeof(r_ext);
	} else {
		r.db_id = ctdb_db->db_id;
		r.reqid = state->reqid;
		r.pnn   = ctdb->pnn;
		r.client_reqid = start_state->reqid;
		r.srvid = start_state->srvid;

		data.dptr = (uint8_t *)&r;
		data.dsize = sizeof(r);
	}

	if (ctdb_db_volatile(ctdb_db)) {
		/* volatile database, traverse all active nodes */
		destination = CTDB_BROADCAST_ACTIVE;
	} else {
		unsigned int i;
		/* persistent database, traverse one node, preferably
		 * the local one
		 */
		destination = ctdb->pnn;
		/* check we are in the vnnmap */
		for (i=0; i < ctdb->vnn_map->size; i++) {
			if (ctdb->vnn_map->map[i] == ctdb->pnn) {
				break;
			}
		}
		/* if we are not in the vnn map we just pick the first
		 * node instead
		 */
		if (i == ctdb->vnn_map->size) {
			destination = ctdb->vnn_map->map[0];
		}
	}

	/* tell all the nodes in the cluster to start sending records to this
	 * node, or if it is a persistent database, just tell the local
	 * node
	 */

	if (start_state->withemptyrecords) {
		ret = ctdb_daemon_send_control(ctdb, destination, 0,
				       CTDB_CONTROL_TRAVERSE_ALL_EXT,
				       0, CTDB_CTRL_FLAG_NOREPLY, data, NULL, NULL);
	} else {
		ret = ctdb_daemon_send_control(ctdb, destination, 0,
				       CTDB_CONTROL_TRAVERSE_ALL,
				       0, CTDB_CTRL_FLAG_NOREPLY, data, NULL, NULL);
	}

	if (ret != 0) {
		talloc_free(state);
		return NULL;
	}

	DEBUG(DEBUG_NOTICE,("Starting traverse on DB %s (id %d)\n",
			    ctdb_db->db_name, state->reqid));

	/* timeout the traverse */
	tevent_add_timer(ctdb->ev, state,
			 timeval_current_ofs(ctdb->tunable.traverse_timeout, 0),
			 ctdb_traverse_all_timeout, state);

	return state;
}

/*
  called when local traverse ends
 */
static void traverse_all_callback(void *p, TDB_DATA key, TDB_DATA data)
{
	struct traverse_all_state *state = talloc_get_type(p, struct traverse_all_state);

	/* we're done */
	talloc_free(state);
}

/*
 * extended version to take the "withemptyrecords" parameter"
 */
int32_t ctdb_control_traverse_all_ext(struct ctdb_context *ctdb, TDB_DATA data, TDB_DATA *outdata)
{
	struct ctdb_traverse_all_ext *c = (struct ctdb_traverse_all_ext *)data.dptr;
	struct traverse_all_state *state;
	struct ctdb_db_context *ctdb_db;

	if (data.dsize != sizeof(struct ctdb_traverse_all_ext)) {
		DEBUG(DEBUG_ERR,(__location__ " Invalid size in ctdb_control_traverse_all_ext\n"));
		return -1;
	}

	ctdb_db = find_ctdb_db(ctdb, c->db_id);
	if (ctdb_db == NULL) {
		return -1;
	}

	if (ctdb_db->unhealthy_reason) {
		if (ctdb->tunable.allow_unhealthy_db_read == 0) {
			DEBUG(DEBUG_ERR,("db(%s) unhealty in ctdb_control_traverse_all: %s\n",
					ctdb_db->db_name, ctdb_db->unhealthy_reason));
			return -1;
		}
		DEBUG(DEBUG_WARNING,("warn: db(%s) unhealty in ctdb_control_traverse_all: %s\n",
				     ctdb_db->db_name, ctdb_db->unhealthy_reason));
	}

	state = talloc(ctdb_db, struct traverse_all_state);
	if (state == NULL) {
		return -1;
	}

	state->reqid = c->reqid;
	state->srcnode = c->pnn;
	state->ctdb = ctdb;
	state->client_reqid = c->client_reqid;
	state->srvid = c->srvid;
	state->withemptyrecords = c->withemptyrecords;

	state->h = ctdb_traverse_local(ctdb_db, traverse_all_callback, state);
	if (state->h == NULL) {
		talloc_free(state);
		return -1;
	}

	return 0;
}

/*
  called when a CTDB_CONTROL_TRAVERSE_ALL control comes in. We then
  setup a traverse of our local ltdb, sending the records as
  CTDB_CONTROL_TRAVERSE_DATA records back to the originator
 */
int32_t ctdb_control_traverse_all(struct ctdb_context *ctdb, TDB_DATA data, TDB_DATA *outdata)
{
	struct ctdb_traverse_all *c = (struct ctdb_traverse_all *)data.dptr;
	struct traverse_all_state *state;
	struct ctdb_db_context *ctdb_db;

	if (data.dsize != sizeof(struct ctdb_traverse_all)) {
		DEBUG(DEBUG_ERR,(__location__ " Invalid size in ctdb_control_traverse_all\n"));
		return -1;
	}

	ctdb_db = find_ctdb_db(ctdb, c->db_id);
	if (ctdb_db == NULL) {
		return -1;
	}

	if (ctdb_db->unhealthy_reason) {
		if (ctdb->tunable.allow_unhealthy_db_read == 0) {
			DEBUG(DEBUG_ERR,("db(%s) unhealty in ctdb_control_traverse_all: %s\n",
					ctdb_db->db_name, ctdb_db->unhealthy_reason));
			return -1;
		}
		DEBUG(DEBUG_WARNING,("warn: db(%s) unhealty in ctdb_control_traverse_all: %s\n",
				     ctdb_db->db_name, ctdb_db->unhealthy_reason));
	}

	state = talloc(ctdb_db, struct traverse_all_state);
	if (state == NULL) {
		return -1;
	}

	state->reqid = c->reqid;
	state->srcnode = c->pnn;
	state->ctdb = ctdb;
	state->client_reqid = c->client_reqid;
	state->srvid = c->srvid;
	state->withemptyrecords = false;

	state->h = ctdb_traverse_local(ctdb_db, traverse_all_callback, state);
	if (state->h == NULL) {
		talloc_free(state);
		return -1;
	}

	return 0;
}


/*
  called when a CTDB_CONTROL_TRAVERSE_DATA control comes in. We then
  call the traverse_all callback with the record
 */
int32_t ctdb_control_traverse_data(struct ctdb_context *ctdb, TDB_DATA data, TDB_DATA *outdata)
{
	struct ctdb_rec_data_old *d = (struct ctdb_rec_data_old *)data.dptr;
	struct ctdb_traverse_all_handle *state;
	TDB_DATA key;
	ctdb_traverse_fn_t callback;
	void *private_data;

	if (data.dsize < sizeof(uint32_t) || data.dsize != d->length) {
		DEBUG(DEBUG_ERR,("Bad record size in ctdb_control_traverse_data\n"));
		return -1;
	}

	state = reqid_find(ctdb->idr, d->reqid, struct ctdb_traverse_all_handle);
	if (state == NULL || d->reqid != state->reqid) {
		/* traverse might have been terminated already */
		return -1;
	}

	key.dsize = d->keylen;
	key.dptr  = &d->data[0];
	data.dsize = d->datalen;
	data.dptr = &d->data[d->keylen];

	if (key.dsize == 0 && data.dsize == 0) {
		state->null_count++;
		/* Persistent databases are only scanned on one node (the local
		 * node)
		 */
		if (ctdb_db_volatile(state->ctdb_db)) {
			if (state->null_count != ctdb_get_num_active_nodes(ctdb)) {
				return 0;
			}
		}
	}

	callback = state->callback;
	private_data = state->private_data;

	callback(private_data, key, data);
	return 0;
}	

/*
  kill a in-progress traverse, used when a client disconnects
 */
int32_t ctdb_control_traverse_kill(struct ctdb_context *ctdb, TDB_DATA data, 
				   TDB_DATA *outdata, uint32_t srcnode)
{
	struct ctdb_traverse_start *d = (struct ctdb_traverse_start *)data.dptr;
	struct ctdb_db_context *ctdb_db;
	struct ctdb_traverse_local_handle *t;

	ctdb_db = find_ctdb_db(ctdb, d->db_id);
	if (ctdb_db == NULL) {
		return -1;
	}

	for (t=ctdb_db->traverse; t; t=t->next) {
		if (t->client_reqid == d->reqid &&
		    t->srvid == d->srvid) {
			talloc_free(t);
			break;
		}
	}

	return 0;
}


/*
  this is called when a client disconnects during a traverse
  we need to notify all the nodes taking part in the search that they
  should kill their traverse children
 */
static int ctdb_traverse_start_destructor(struct traverse_start_state *state)
{
	struct ctdb_traverse_start r;
	TDB_DATA data;

	DEBUG(DEBUG_ERR,(__location__ " Traverse cancelled by client disconnect for database:0x%08x\n", state->db_id));
	r.db_id = state->db_id;
	r.reqid = state->reqid;
	r.srvid = state->srvid;

	data.dptr = (uint8_t *)&r;
	data.dsize = sizeof(r);

	ctdb_daemon_send_control(state->ctdb, CTDB_BROADCAST_CONNECTED, 0, 
				 CTDB_CONTROL_TRAVERSE_KILL, 
				 0, CTDB_CTRL_FLAG_NOREPLY, data, NULL, NULL);
	return 0;
}

/*
  callback which sends records as messages to the client
 */
static void traverse_start_callback(void *p, TDB_DATA key, TDB_DATA data)
{
	struct traverse_start_state *state;
	struct ctdb_rec_data_old *d;
	TDB_DATA cdata;

	state = talloc_get_type(p, struct traverse_start_state);

	d = ctdb_marshall_record(state, state->reqid, key, NULL, data);
	if (d == NULL) {
		return;
	}

	cdata.dptr = (uint8_t *)d;
	cdata.dsize = d->length;

	srvid_dispatch(state->ctdb->srv, state->srvid, 0, cdata);
	if (key.dsize == 0 && data.dsize == 0) {
		DEBUG(DEBUG_NOTICE, ("Ending traverse on DB %s (id %d), records %d\n",
				     state->h->ctdb_db->db_name, state->h->reqid,
				     state->num_records));

	    	if (state->h->timedout) {
		    	/* timed out, send TRAVERSE_KILL control */
			talloc_free(state);
		} else {
			/* end of traverse */
			talloc_set_destructor(state, NULL);
			talloc_free(state);
		}
	} else {
		state->num_records++;
	}
}


/**
 * start a traverse_all - called as a control from a client.
 * extended version to take the "withemptyrecords" parameter.
 */
int32_t ctdb_control_traverse_start_ext(struct ctdb_context *ctdb,
					TDB_DATA data,
					TDB_DATA *outdata,
					uint32_t srcnode,
					uint32_t client_id)
{
	struct ctdb_traverse_start_ext *d = (struct ctdb_traverse_start_ext *)data.dptr;
	struct traverse_start_state *state;
	struct ctdb_db_context *ctdb_db;
	struct ctdb_client *client = reqid_find(ctdb->idr, client_id, struct ctdb_client);

	if (client == NULL) {
		DEBUG(DEBUG_ERR,(__location__ " No client found\n"));
		return -1;		
	}

	if (data.dsize != sizeof(*d)) {
		DEBUG(DEBUG_ERR,("Bad record size in ctdb_control_traverse_start\n"));
		return -1;
	}

	ctdb_db = find_ctdb_db(ctdb, d->db_id);
	if (ctdb_db == NULL) {
		return -1;
	}

	if (ctdb_db->unhealthy_reason) {
		if (ctdb->tunable.allow_unhealthy_db_read == 0) {
			DEBUG(DEBUG_ERR,("db(%s) unhealty in ctdb_control_traverse_start: %s\n",
					ctdb_db->db_name, ctdb_db->unhealthy_reason));
			return -1;
		}
		DEBUG(DEBUG_WARNING,("warn: db(%s) unhealty in ctdb_control_traverse_start: %s\n",
				     ctdb_db->db_name, ctdb_db->unhealthy_reason));
	}

	state = talloc(client, struct traverse_start_state);
	if (state == NULL) {
		return -1;
	}
	
	state->srcnode = srcnode;
	state->reqid = d->reqid;
	state->srvid = d->srvid;
	state->db_id = d->db_id;
	state->ctdb = ctdb;
	state->withemptyrecords = d->withemptyrecords;
	state->num_records = 0;

	state->h = ctdb_daemon_traverse_all(ctdb_db, traverse_start_callback, state);
	if (state->h == NULL) {
		talloc_free(state);
		return -1;
	}

	talloc_set_destructor(state, ctdb_traverse_start_destructor);

	return 0;
}

/**
 * start a traverse_all - called as a control from a client.
 */
int32_t ctdb_control_traverse_start(struct ctdb_context *ctdb,
				    TDB_DATA data,
				    TDB_DATA *outdata,
				    uint32_t srcnode,
				    uint32_t client_id)
{
	struct ctdb_traverse_start *d = (struct ctdb_traverse_start *)data.dptr;
	struct ctdb_traverse_start_ext d2;
	TDB_DATA data2;

	ZERO_STRUCT(d2);
	d2.db_id = d->db_id;
	d2.reqid = d->reqid;
	d2.srvid = d->srvid;
	d2.withemptyrecords = false;

	data2.dsize = sizeof(d2);
	data2.dptr = (uint8_t *)&d2;

	return ctdb_control_traverse_start_ext(ctdb, data2, outdata, srcnode, client_id);
}