File: crawler.c

package info (click to toggle)
memcached 1.5.6-1.1
  • links: PTS, VCS
  • area: main
  • in suites: buster
  • size: 2,696 kB
  • sloc: ansic: 16,931; perl: 5,523; sh: 4,302; xml: 1,638; python: 393; makefile: 170
file content (694 lines) | stat: -rw-r--r-- 22,714 bytes parent folder | download
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
/*  Copyright 2016 Netflix.
 *
 *  Use and distribution licensed under the BSD license.  See
 *  the LICENSE file for full text.
 */

/* -*- Mode: C; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
#include "memcached.h"
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/resource.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <signal.h>
#include <string.h>
#include <time.h>
#include <assert.h>
#include <unistd.h>
#include <poll.h>

#define LARGEST_ID POWER_LARGEST

typedef struct {
    void *c; /* original connection structure. still with source thread attached. */
    int sfd; /* client fd. */
    bipbuf_t *buf; /* output buffer */
    char *cbuf; /* current buffer */
} crawler_client_t;

typedef struct _crawler_module_t crawler_module_t;

typedef void (*crawler_eval_func)(crawler_module_t *cm, item *it, uint32_t hv, int slab_cls);
typedef int (*crawler_init_func)(crawler_module_t *cm, void *data); // TODO: init args?
typedef void (*crawler_deinit_func)(crawler_module_t *cm); // TODO: extra args?
typedef void (*crawler_doneclass_func)(crawler_module_t *cm, int slab_cls);
typedef void (*crawler_finalize_func)(crawler_module_t *cm);

typedef struct {
    crawler_init_func init; /* run before crawl starts */
    crawler_eval_func eval; /* runs on an item. */
    crawler_doneclass_func doneclass; /* runs once per sub-crawler completion. */
    crawler_finalize_func finalize; /* runs once when all sub-crawlers are done. */
    bool needs_lock; /* whether or not we need the LRU lock held when eval is called */
    bool needs_client; /* whether or not to grab onto the remote client */
} crawler_module_reg_t;

struct _crawler_module_t {
    void *data; /* opaque data pointer */
    crawler_client_t c;
    crawler_module_reg_t *mod;
};

static int crawler_expired_init(crawler_module_t *cm, void *data);
static void crawler_expired_doneclass(crawler_module_t *cm, int slab_cls);
static void crawler_expired_finalize(crawler_module_t *cm);
static void crawler_expired_eval(crawler_module_t *cm, item *search, uint32_t hv, int i);

crawler_module_reg_t crawler_expired_mod = {
    .init = crawler_expired_init,
    .eval = crawler_expired_eval,
    .doneclass = crawler_expired_doneclass,
    .finalize = crawler_expired_finalize,
    .needs_lock = true,
    .needs_client = false
};

static void crawler_metadump_eval(crawler_module_t *cm, item *search, uint32_t hv, int i);
static void crawler_metadump_finalize(crawler_module_t *cm);

crawler_module_reg_t crawler_metadump_mod = {
    .init = NULL,
    .eval = crawler_metadump_eval,
    .doneclass = NULL,
    .finalize = crawler_metadump_finalize,
    .needs_lock = false,
    .needs_client = true
};

crawler_module_reg_t *crawler_mod_regs[3] = {
    &crawler_expired_mod,
    &crawler_expired_mod,
    &crawler_metadump_mod
};

static int lru_crawler_client_getbuf(crawler_client_t *c);
crawler_module_t active_crawler_mod;
enum crawler_run_type active_crawler_type;

static crawler crawlers[LARGEST_ID];

static int crawler_count = 0;
static volatile int do_run_lru_crawler_thread = 0;
static int lru_crawler_initialized = 0;
static pthread_mutex_t lru_crawler_lock = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t  lru_crawler_cond = PTHREAD_COND_INITIALIZER;
#ifdef EXTSTORE
/* TODO: pass this around */
static void *storage;
#endif

/* Will crawl all slab classes a minimum of once per hour */
#define MAX_MAINTCRAWL_WAIT 60 * 60

/*** LRU CRAWLER THREAD ***/

#define LRU_CRAWLER_WRITEBUF 8192

static void lru_crawler_close_client(crawler_client_t *c) {
    //fprintf(stderr, "CRAWLER: Closing client\n");
    sidethread_conn_close(c->c);
    c->c = NULL;
    c->cbuf = NULL;
    bipbuf_free(c->buf);
    c->buf = NULL;
}

static void lru_crawler_release_client(crawler_client_t *c) {
    //fprintf(stderr, "CRAWLER: Closing client\n");
    redispatch_conn(c->c);
    c->c = NULL;
    c->cbuf = NULL;
    bipbuf_free(c->buf);
    c->buf = NULL;
}

static int crawler_expired_init(crawler_module_t *cm, void *data) {
    struct crawler_expired_data *d;
    if (data != NULL) {
        d = data;
        d->is_external = true;
        cm->data = data;
    } else {
        // allocate data.
        d = calloc(1, sizeof(struct crawler_expired_data));
        if (d == NULL) {
            return -1;
        }
        // init lock.
        pthread_mutex_init(&d->lock, NULL);
        d->is_external = false;
        d->start_time = current_time;

        cm->data = d;
    }
    pthread_mutex_lock(&d->lock);
    memset(&d->crawlerstats, 0, sizeof(crawlerstats_t) * POWER_LARGEST);
    for (int x = 0; x < POWER_LARGEST; x++) {
        d->crawlerstats[x].start_time = current_time;
        d->crawlerstats[x].run_complete = false;
    }
    pthread_mutex_unlock(&d->lock);
    return 0;
}

static void crawler_expired_doneclass(crawler_module_t *cm, int slab_cls) {
    struct crawler_expired_data *d = (struct crawler_expired_data *) cm->data;
    pthread_mutex_lock(&d->lock);
    d->crawlerstats[slab_cls].end_time = current_time;
    d->crawlerstats[slab_cls].run_complete = true;
    pthread_mutex_unlock(&d->lock);
}

static void crawler_expired_finalize(crawler_module_t *cm) {
    struct crawler_expired_data *d = (struct crawler_expired_data *) cm->data;
    pthread_mutex_lock(&d->lock);
    d->end_time = current_time;
    d->crawl_complete = true;
    pthread_mutex_unlock(&d->lock);

    if (!d->is_external) {
        free(d);
    }
}

/* I pulled this out to make the main thread clearer, but it reaches into the
 * main thread's values too much. Should rethink again.
 */
static void crawler_expired_eval(crawler_module_t *cm, item *search, uint32_t hv, int i) {
    struct crawler_expired_data *d = (struct crawler_expired_data *) cm->data;
    pthread_mutex_lock(&d->lock);
    crawlerstats_t *s = &d->crawlerstats[i];
    int is_flushed = item_is_flushed(search);
#ifdef EXTSTORE
    bool is_valid = true;
    if (search->it_flags & ITEM_HDR) {
        item_hdr *hdr = (item_hdr *)ITEM_data(search);
        if (extstore_check(storage, hdr->page_id, hdr->page_version) != 0)
            is_valid = false;
    }
#endif
    if ((search->exptime != 0 && search->exptime < current_time)
        || is_flushed
#ifdef EXTSTORE
        || !is_valid
#endif
        ) {
        crawlers[i].reclaimed++;
        s->reclaimed++;

        if (settings.verbose > 1) {
            int ii;
            char *key = ITEM_key(search);
            fprintf(stderr, "LRU crawler found an expired item (flags: %d, slab: %d): ",
                search->it_flags, search->slabs_clsid);
            for (ii = 0; ii < search->nkey; ++ii) {
                fprintf(stderr, "%c", key[ii]);
            }
            fprintf(stderr, "\n");
        }
        if ((search->it_flags & ITEM_FETCHED) == 0 && !is_flushed) {
            crawlers[i].unfetched++;
        }
#ifdef EXTSTORE
        STORAGE_delete(storage, search);
#endif
        do_item_unlink_nolock(search, hv);
        do_item_remove(search);
        assert(search->slabs_clsid == 0);
    } else {
        s->seen++;
        refcount_decr(search);
        if (search->exptime == 0) {
            s->noexp++;
        } else if (search->exptime - current_time > 3599) {
            s->ttl_hourplus++;
        } else {
            rel_time_t ttl_remain = search->exptime - current_time;
            int bucket = ttl_remain / 60;
            if (bucket <= 60) {
                s->histo[bucket]++;
            }
        }
    }
    pthread_mutex_unlock(&d->lock);
}

static void crawler_metadump_eval(crawler_module_t *cm, item *it, uint32_t hv, int i) {
    //int slab_id = CLEAR_LRU(i);
    char keybuf[KEY_MAX_LENGTH * 3 + 1];
    int is_flushed = item_is_flushed(it);
    /* Ignore expired content. */
    if ((it->exptime != 0 && it->exptime < current_time)
        || is_flushed) {
        refcount_decr(it);
        return;
    }
    // TODO: uriencode directly into the buffer.
    uriencode(ITEM_key(it), keybuf, it->nkey, KEY_MAX_LENGTH * 3 + 1);
    int total = snprintf(cm->c.cbuf, 4096,
            "key=%s exp=%ld la=%llu cas=%llu fetch=%s cls=%u size=%lu\n",
            keybuf,
            (it->exptime == 0) ? -1 : (long)(it->exptime + process_started),
            (unsigned long long)(it->time + process_started),
            (unsigned long long)ITEM_get_cas(it),
            (it->it_flags & ITEM_FETCHED) ? "yes" : "no",
            ITEM_clsid(it),
            (unsigned long) ITEM_ntotal(it));
    refcount_decr(it);
    // TODO: some way of tracking the errors. these are very unlikely though.
    if (total >= LRU_CRAWLER_WRITEBUF - 1 || total <= 0) {
        /* Failed to write, don't push it. */
        return;
    }
    bipbuf_push(cm->c.buf, total);
}

static void crawler_metadump_finalize(crawler_module_t *cm) {
    if (cm->c.c != NULL) {
        // Ensure space for final message.
        lru_crawler_client_getbuf(&cm->c);
        memcpy(cm->c.cbuf, "END\r\n", 5);
        bipbuf_push(cm->c.buf, 5);
    }
}

static int lru_crawler_poll(crawler_client_t *c) {
    unsigned char *data;
    unsigned int data_size = 0;
    struct pollfd to_poll[1];
    to_poll[0].fd = c->sfd;
    to_poll[0].events = POLLOUT;

    int ret = poll(to_poll, 1, 1000);

    if (ret < 0) {
        // fatal.
        return -1;
    }

    if (ret == 0) return 0;

    if (to_poll[0].revents & POLLIN) {
        char buf[1];
        int res = read(c->sfd, buf, 1);
        if (res == 0 || (res == -1 && (errno != EAGAIN && errno != EWOULDBLOCK))) {
            lru_crawler_close_client(c);
            return -1;
        }
    }
    if ((data = bipbuf_peek_all(c->buf, &data_size)) != NULL) {
        if (to_poll[0].revents & (POLLHUP|POLLERR)) {
            lru_crawler_close_client(c);
            return -1;
        } else if (to_poll[0].revents & POLLOUT) {
            int total = write(c->sfd, data, data_size);
            if (total == -1) {
                if (errno != EAGAIN && errno != EWOULDBLOCK) {
                    lru_crawler_close_client(c);
                    return -1;
                }
            } else if (total == 0) {
                lru_crawler_close_client(c);
                return -1;
            } else {
                bipbuf_poll(c->buf, total);
            }
        }
    }
    return 0;
}

/* Grab some space to work with, if none exists, run the poll() loop and wait
 * for it to clear up or close.
 * Return NULL if closed.
 */
static int lru_crawler_client_getbuf(crawler_client_t *c) {
    void *buf = NULL;
    if (c->c == NULL) return -1;
    /* not enough space. */
    while ((buf = bipbuf_request(c->buf, LRU_CRAWLER_WRITEBUF)) == NULL) {
        // TODO: max loops before closing.
        int ret = lru_crawler_poll(c);
        if (ret < 0) return ret;
    }

    c->cbuf = buf;
    return 0;
}

static void lru_crawler_class_done(int i) {
    crawlers[i].it_flags = 0;
    crawler_count--;
    do_item_unlinktail_q((item *)&crawlers[i]);
    do_item_stats_add_crawl(i, crawlers[i].reclaimed,
            crawlers[i].unfetched, crawlers[i].checked);
    pthread_mutex_unlock(&lru_locks[i]);
    if (active_crawler_mod.mod->doneclass != NULL)
        active_crawler_mod.mod->doneclass(&active_crawler_mod, i);
}

static void *item_crawler_thread(void *arg) {
    int i;
    int crawls_persleep = settings.crawls_persleep;

    pthread_mutex_lock(&lru_crawler_lock);
    pthread_cond_signal(&lru_crawler_cond);
    settings.lru_crawler = true;
    if (settings.verbose > 2)
        fprintf(stderr, "Starting LRU crawler background thread\n");
    while (do_run_lru_crawler_thread) {
    pthread_cond_wait(&lru_crawler_cond, &lru_crawler_lock);

    while (crawler_count) {
        item *search = NULL;
        void *hold_lock = NULL;

        for (i = POWER_SMALLEST; i < LARGEST_ID; i++) {
            if (crawlers[i].it_flags != 1) {
                continue;
            }

            /* Get memory from bipbuf, if client has no space, flush. */
            if (active_crawler_mod.c.c != NULL) {
                int ret = lru_crawler_client_getbuf(&active_crawler_mod.c);
                if (ret != 0) {
                    lru_crawler_class_done(i);
                    continue;
                }
            } else if (active_crawler_mod.mod->needs_client) {
                lru_crawler_class_done(i);
                continue;
            }
            pthread_mutex_lock(&lru_locks[i]);
            search = do_item_crawl_q((item *)&crawlers[i]);
            if (search == NULL ||
                (crawlers[i].remaining && --crawlers[i].remaining < 1)) {
                if (settings.verbose > 2)
                    fprintf(stderr, "Nothing left to crawl for %d\n", i);
                lru_crawler_class_done(i);
                continue;
            }
            uint32_t hv = hash(ITEM_key(search), search->nkey);
            /* Attempt to hash item lock the "search" item. If locked, no
             * other callers can incr the refcount
             */
            if ((hold_lock = item_trylock(hv)) == NULL) {
                pthread_mutex_unlock(&lru_locks[i]);
                continue;
            }
            /* Now see if the item is refcount locked */
            if (refcount_incr(search) != 2) {
                refcount_decr(search);
                if (hold_lock)
                    item_trylock_unlock(hold_lock);
                pthread_mutex_unlock(&lru_locks[i]);
                continue;
            }

            crawlers[i].checked++;
            /* Frees the item or decrements the refcount. */
            /* Interface for this could improve: do the free/decr here
             * instead? */
            if (!active_crawler_mod.mod->needs_lock) {
                pthread_mutex_unlock(&lru_locks[i]);
            }

            active_crawler_mod.mod->eval(&active_crawler_mod, search, hv, i);

            if (hold_lock)
                item_trylock_unlock(hold_lock);
            if (active_crawler_mod.mod->needs_lock) {
                pthread_mutex_unlock(&lru_locks[i]);
            }

            if (crawls_persleep-- <= 0 && settings.lru_crawler_sleep) {
                pthread_mutex_unlock(&lru_crawler_lock);
                usleep(settings.lru_crawler_sleep);
                pthread_mutex_lock(&lru_crawler_lock);
                crawls_persleep = settings.crawls_persleep;
            } else if (!settings.lru_crawler_sleep) {
                // TODO: only cycle lock every N?
                pthread_mutex_unlock(&lru_crawler_lock);
                pthread_mutex_lock(&lru_crawler_lock);
            }
        }
    }

    if (active_crawler_mod.mod != NULL) {
        if (active_crawler_mod.mod->finalize != NULL)
            active_crawler_mod.mod->finalize(&active_crawler_mod);
        while (active_crawler_mod.c.c != NULL && bipbuf_used(active_crawler_mod.c.buf)) {
            lru_crawler_poll(&active_crawler_mod.c);
        }
        // Double checking in case the client closed during the poll
        if (active_crawler_mod.c.c != NULL) {
            lru_crawler_release_client(&active_crawler_mod.c);
        }
        active_crawler_mod.mod = NULL;
    }

    if (settings.verbose > 2)
        fprintf(stderr, "LRU crawler thread sleeping\n");

    STATS_LOCK();
    stats_state.lru_crawler_running = false;
    STATS_UNLOCK();
    }
    pthread_mutex_unlock(&lru_crawler_lock);
    if (settings.verbose > 2)
        fprintf(stderr, "LRU crawler thread stopping\n");

    return NULL;
}

static pthread_t item_crawler_tid;

int stop_item_crawler_thread(void) {
    int ret;
    pthread_mutex_lock(&lru_crawler_lock);
    do_run_lru_crawler_thread = 0;
    pthread_cond_signal(&lru_crawler_cond);
    pthread_mutex_unlock(&lru_crawler_lock);
    if ((ret = pthread_join(item_crawler_tid, NULL)) != 0) {
        fprintf(stderr, "Failed to stop LRU crawler thread: %s\n", strerror(ret));
        return -1;
    }
    settings.lru_crawler = false;
    return 0;
}

/* Lock dance to "block" until thread is waiting on its condition:
 * caller locks mtx. caller spawns thread.
 * thread blocks on mutex.
 * caller waits on condition, releases lock.
 * thread gets lock, sends signal.
 * caller can't wait, as thread has lock.
 * thread waits on condition, releases lock
 * caller wakes on condition, gets lock.
 * caller immediately releases lock.
 * thread is now safely waiting on condition before the caller returns.
 */
int start_item_crawler_thread(void) {
    int ret;

    if (settings.lru_crawler)
        return -1;
    pthread_mutex_lock(&lru_crawler_lock);
    do_run_lru_crawler_thread = 1;
    if ((ret = pthread_create(&item_crawler_tid, NULL,
        item_crawler_thread, NULL)) != 0) {
        fprintf(stderr, "Can't create LRU crawler thread: %s\n",
            strerror(ret));
        pthread_mutex_unlock(&lru_crawler_lock);
        return -1;
    }
    /* Avoid returning until the crawler has actually started */
    pthread_cond_wait(&lru_crawler_cond, &lru_crawler_lock);
    pthread_mutex_unlock(&lru_crawler_lock);

    return 0;
}

/* 'remaining' is passed in so the LRU maintainer thread can scrub the whole
 * LRU every time.
 */
static int do_lru_crawler_start(uint32_t id, uint32_t remaining) {
    uint32_t sid = id;
    int starts = 0;

    pthread_mutex_lock(&lru_locks[sid]);
    if (crawlers[sid].it_flags == 0) {
        if (settings.verbose > 2)
            fprintf(stderr, "Kicking LRU crawler off for LRU %u\n", sid);
        crawlers[sid].nbytes = 0;
        crawlers[sid].nkey = 0;
        crawlers[sid].it_flags = 1; /* For a crawler, this means enabled. */
        crawlers[sid].next = 0;
        crawlers[sid].prev = 0;
        crawlers[sid].time = 0;
        if (remaining == LRU_CRAWLER_CAP_REMAINING) {
            remaining = do_get_lru_size(sid);
        }
        crawlers[sid].remaining = remaining;
        crawlers[sid].slabs_clsid = sid;
        crawlers[sid].reclaimed = 0;
        crawlers[sid].unfetched = 0;
        crawlers[sid].checked = 0;
        do_item_linktail_q((item *)&crawlers[sid]);
        crawler_count++;
        starts++;
    }
    pthread_mutex_unlock(&lru_locks[sid]);
    if (starts) {
        STATS_LOCK();
        stats_state.lru_crawler_running = true;
        stats.lru_crawler_starts++;
        STATS_UNLOCK();
    }
    return starts;
}

static int lru_crawler_set_client(crawler_module_t *cm, void *c, const int sfd) {
    crawler_client_t *crawlc = &cm->c;
    if (crawlc->c != NULL) {
        return -1;
    }
    crawlc->c = c;
    crawlc->sfd = sfd;

    crawlc->buf = bipbuf_new(1024 * 128);
    if (crawlc->buf == NULL) {
        return -2;
    }
    return 0;
}

int lru_crawler_start(uint8_t *ids, uint32_t remaining,
                             const enum crawler_run_type type, void *data,
                             void *c, const int sfd) {
    int starts = 0;
    bool is_running;
    static rel_time_t block_ae_until = 0;
    pthread_mutex_lock(&lru_crawler_lock);
    STATS_LOCK();
    is_running = stats_state.lru_crawler_running;
    STATS_UNLOCK();
    if (is_running &&
            !(type == CRAWLER_AUTOEXPIRE && active_crawler_type == CRAWLER_AUTOEXPIRE)) {
        pthread_mutex_unlock(&lru_crawler_lock);
        block_ae_until = current_time + 60;
        return -1;
    }

    if (type == CRAWLER_AUTOEXPIRE && block_ae_until > current_time) {
        pthread_mutex_unlock(&lru_crawler_lock);
        return -1;
    }

    /* Configure the module */
    if (!is_running) {
        assert(crawler_mod_regs[type] != NULL);
        active_crawler_mod.mod = crawler_mod_regs[type];
        active_crawler_type = type;
        if (active_crawler_mod.mod->init != NULL) {
            active_crawler_mod.mod->init(&active_crawler_mod, data);
        }
        if (active_crawler_mod.mod->needs_client) {
            if (c == NULL || sfd == 0) {
                pthread_mutex_unlock(&lru_crawler_lock);
                return -2;
            }
            if (lru_crawler_set_client(&active_crawler_mod, c, sfd) != 0) {
                pthread_mutex_unlock(&lru_crawler_lock);
                return -2;
            }
        }
    }

    /* we allow the autocrawler to restart sub-LRU's before completion */
    for (int sid = POWER_SMALLEST; sid < POWER_LARGEST; sid++) {
        if (ids[sid])
            starts += do_lru_crawler_start(sid, remaining);
    }
    if (starts) {
        pthread_cond_signal(&lru_crawler_cond);
    }
    pthread_mutex_unlock(&lru_crawler_lock);
    return starts;
}

/*
 * Also only clear the crawlerstats once per sid.
 */
enum crawler_result_type lru_crawler_crawl(char *slabs, const enum crawler_run_type type,
        void *c, const int sfd, unsigned int remaining) {
    char *b = NULL;
    uint32_t sid = 0;
    int starts = 0;
    uint8_t tocrawl[POWER_LARGEST];

    /* FIXME: I added this while debugging. Don't think it's needed? */
    memset(tocrawl, 0, sizeof(uint8_t) * POWER_LARGEST);
    if (strcmp(slabs, "all") == 0) {
        for (sid = 0; sid < POWER_LARGEST; sid++) {
            tocrawl[sid] = 1;
        }
    } else {
        for (char *p = strtok_r(slabs, ",", &b);
             p != NULL;
             p = strtok_r(NULL, ",", &b)) {

            if (!safe_strtoul(p, &sid) || sid < POWER_SMALLEST
                    || sid >= MAX_NUMBER_OF_SLAB_CLASSES) {
                pthread_mutex_unlock(&lru_crawler_lock);
                return CRAWLER_BADCLASS;
            }
            tocrawl[sid | TEMP_LRU] = 1;
            tocrawl[sid | HOT_LRU] = 1;
            tocrawl[sid | WARM_LRU] = 1;
            tocrawl[sid | COLD_LRU] = 1;
        }
    }

    starts = lru_crawler_start(tocrawl, remaining, type, NULL, c, sfd);
    if (starts == -1) {
        return CRAWLER_RUNNING;
    } else if (starts == -2) {
        return CRAWLER_ERROR; /* FIXME: not very helpful. */
    } else if (starts) {
        return CRAWLER_OK;
    } else {
        return CRAWLER_NOTSTARTED;
    }
}

/* If we hold this lock, crawler can't wake up or move */
void lru_crawler_pause(void) {
    pthread_mutex_lock(&lru_crawler_lock);
}

void lru_crawler_resume(void) {
    pthread_mutex_unlock(&lru_crawler_lock);
}

int init_lru_crawler(void *arg) {
    if (lru_crawler_initialized == 0) {
#ifdef EXTSTORE
        storage = arg;
#endif
        if (pthread_cond_init(&lru_crawler_cond, NULL) != 0) {
            fprintf(stderr, "Can't initialize lru crawler condition\n");
            return -1;
        }
        pthread_mutex_init(&lru_crawler_lock, NULL);
        active_crawler_mod.c.c = NULL;
        active_crawler_mod.mod = NULL;
        active_crawler_mod.data = NULL;
        lru_crawler_initialized = 1;
    }
    return 0;
}