summaryrefslogtreecommitdiffstats
path: root/database/engine/metric.c
blob: 2e132612e7ee89f26adf054e3135e955cfab63cf (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
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
// SPDX-License-Identifier: GPL-3.0-or-later
#include "metric.h"

typedef int32_t REFCOUNT;
#define REFCOUNT_DELETING (-100)

struct metric {
    uuid_t uuid;                    // never changes
    Word_t section;                 // never changes

    time_t first_time_s;            // the timestamp of the oldest point in the database
    time_t latest_time_s_clean;     // the timestamp of the newest point in the database
    time_t latest_time_s_hot;       // the timestamp of the latest point that has been collected (not yet stored)
    uint32_t latest_update_every_s; // the latest data collection frequency
    pid_t writer;
    uint8_t partition;
    REFCOUNT refcount;

    // THIS IS allocated with malloc()
    // YOU HAVE TO INITIALIZE IT YOURSELF !
};

#define set_metric_field_with_condition(field, value, condition) ({ \
    typeof(field) _current = __atomic_load_n(&(field), __ATOMIC_RELAXED);   \
    typeof(field) _wanted = value;                                          \
    bool did_it = true;                                                     \
                                                                            \
    do {                                                                    \
        if((condition) && (_current != _wanted)) {                          \
            ;                                                               \
        }                                                                   \
        else {                                                              \
            did_it = false;                                                 \
            break;                                                          \
        }                                                                   \
    } while(!__atomic_compare_exchange_n(&(field), &_current, _wanted,      \
            false, __ATOMIC_RELAXED, __ATOMIC_RELAXED));                    \
                                                                            \
    did_it;                                                                 \
})

static struct aral_statistics mrg_aral_statistics;

struct mrg {
    size_t partitions;

    struct mrg_partition {
        ARAL *aral;                 // not protected by our spinlock - it has its own

        RW_SPINLOCK rw_spinlock;
        Pvoid_t uuid_judy;          // JudyHS: each UUID has a JudyL of sections (tiers)

        struct mrg_statistics stats;
    } index[];
};

static inline void MRG_STATS_DUPLICATE_ADD(MRG *mrg, size_t partition) {
    mrg->index[partition].stats.additions_duplicate++;
}

static inline void MRG_STATS_ADDED_METRIC(MRG *mrg, size_t partition) {
    mrg->index[partition].stats.entries++;
    mrg->index[partition].stats.additions++;
    mrg->index[partition].stats.size += sizeof(METRIC);
}

static inline void MRG_STATS_DELETED_METRIC(MRG *mrg, size_t partition) {
    mrg->index[partition].stats.entries--;
    mrg->index[partition].stats.size -= sizeof(METRIC);
    mrg->index[partition].stats.deletions++;
}

static inline void MRG_STATS_SEARCH_HIT(MRG *mrg, size_t partition) {
    __atomic_add_fetch(&mrg->index[partition].stats.search_hits, 1, __ATOMIC_RELAXED);
}

static inline void MRG_STATS_SEARCH_MISS(MRG *mrg, size_t partition) {
    __atomic_add_fetch(&mrg->index[partition].stats.search_misses, 1, __ATOMIC_RELAXED);
}

static inline void MRG_STATS_DELETE_MISS(MRG *mrg, size_t partition) {
    mrg->index[partition].stats.delete_misses++;
}

#define mrg_index_read_lock(mrg, partition) rw_spinlock_read_lock(&(mrg)->index[partition].rw_spinlock)
#define mrg_index_read_unlock(mrg, partition) rw_spinlock_read_unlock(&(mrg)->index[partition].rw_spinlock)
#define mrg_index_write_lock(mrg, partition) rw_spinlock_write_lock(&(mrg)->index[partition].rw_spinlock)
#define mrg_index_write_unlock(mrg, partition) rw_spinlock_write_unlock(&(mrg)->index[partition].rw_spinlock)

static inline void mrg_stats_size_judyl_change(MRG *mrg, size_t mem_before_judyl, size_t mem_after_judyl, size_t partition) {
    if(mem_after_judyl > mem_before_judyl)
        __atomic_add_fetch(&mrg->index[partition].stats.size, mem_after_judyl - mem_before_judyl, __ATOMIC_RELAXED);
    else if(mem_after_judyl < mem_before_judyl)
        __atomic_sub_fetch(&mrg->index[partition].stats.size, mem_before_judyl - mem_after_judyl, __ATOMIC_RELAXED);
}

static inline void mrg_stats_size_judyhs_added_uuid(MRG *mrg, size_t partition) {
    __atomic_add_fetch(&mrg->index[partition].stats.size, JUDYHS_INDEX_SIZE_ESTIMATE(sizeof(uuid_t)), __ATOMIC_RELAXED);
}

static inline void mrg_stats_size_judyhs_removed_uuid(MRG *mrg, size_t partition) {
    __atomic_sub_fetch(&mrg->index[partition].stats.size, JUDYHS_INDEX_SIZE_ESTIMATE(sizeof(uuid_t)), __ATOMIC_RELAXED);
}

static inline size_t uuid_partition(MRG *mrg __maybe_unused, uuid_t *uuid) {
    uint8_t *u = (uint8_t *)uuid;
    size_t *n = (size_t *)&u[UUID_SZ - sizeof(size_t)];
    return *n % mrg->partitions;
}

static inline time_t mrg_metric_get_first_time_s_smart(MRG *mrg __maybe_unused, METRIC *metric) {
    time_t first_time_s = __atomic_load_n(&metric->first_time_s, __ATOMIC_RELAXED);

    if(first_time_s <= 0) {
        first_time_s = __atomic_load_n(&metric->latest_time_s_clean, __ATOMIC_RELAXED);
        if(first_time_s <= 0)
            first_time_s = __atomic_load_n(&metric->latest_time_s_hot, __ATOMIC_RELAXED);

        if(first_time_s <= 0)
            first_time_s = 0;
        else
            __atomic_store_n(&metric->first_time_s, first_time_s, __ATOMIC_RELAXED);
    }

    return first_time_s;
}

static inline REFCOUNT metric_acquire(MRG *mrg __maybe_unused, METRIC *metric) {
    size_t partition = metric->partition;
    REFCOUNT expected = __atomic_load_n(&metric->refcount, __ATOMIC_RELAXED);
    REFCOUNT refcount;

    do {
        if(expected < 0)
            fatal("METRIC: refcount is %d (negative) during acquire", metric->refcount);

        refcount = expected + 1;
    } while(!__atomic_compare_exchange_n(&metric->refcount, &expected, refcount, false, __ATOMIC_RELAXED, __ATOMIC_RELAXED));

    if(refcount == 1)
        __atomic_add_fetch(&mrg->index[partition].stats.entries_referenced, 1, __ATOMIC_RELAXED);

    __atomic_add_fetch(&mrg->index[partition].stats.current_references, 1, __ATOMIC_RELAXED);

    return refcount;
}

static inline bool metric_release_and_can_be_deleted(MRG *mrg __maybe_unused, METRIC *metric) {
    size_t partition = metric->partition;
    REFCOUNT expected = __atomic_load_n(&metric->refcount, __ATOMIC_RELAXED);
    REFCOUNT refcount;

    do {
        if(expected <= 0)
            fatal("METRIC: refcount is %d (zero or negative) during release", metric->refcount);

        refcount = expected - 1;
    } while(!__atomic_compare_exchange_n(&metric->refcount, &expected, refcount, false, __ATOMIC_RELAXED, __ATOMIC_RELAXED));

    if(unlikely(!refcount))
        __atomic_sub_fetch(&mrg->index[partition].stats.entries_referenced, 1, __ATOMIC_RELAXED);

    __atomic_sub_fetch(&mrg->index[partition].stats.current_references, 1, __ATOMIC_RELAXED);

    time_t first, last, ue;
    mrg_metric_get_retention(mrg, metric, &first, &last, &ue);
    return (!first || !last || first > last);
}

static inline METRIC *metric_add_and_acquire(MRG *mrg, MRG_ENTRY *entry, bool *ret) {
    size_t partition = uuid_partition(mrg, entry->uuid);

    METRIC *allocation = aral_mallocz(mrg->index[partition].aral);

    mrg_index_write_lock(mrg, partition);

    size_t mem_before_judyl, mem_after_judyl;

    Pvoid_t *sections_judy_pptr = JudyHSIns(&mrg->index[partition].uuid_judy, entry->uuid, sizeof(uuid_t), PJE0);
    if(unlikely(!sections_judy_pptr || sections_judy_pptr == PJERR))
        fatal("DBENGINE METRIC: corrupted UUIDs JudyHS array");

    if(unlikely(!*sections_judy_pptr))
        mrg_stats_size_judyhs_added_uuid(mrg, partition);

    mem_before_judyl = JudyLMemUsed(*sections_judy_pptr);
    Pvoid_t *PValue = JudyLIns(sections_judy_pptr, entry->section, PJE0);
    mem_after_judyl = JudyLMemUsed(*sections_judy_pptr);
    mrg_stats_size_judyl_change(mrg, mem_before_judyl, mem_after_judyl, partition);

    if(unlikely(!PValue || PValue == PJERR))
        fatal("DBENGINE METRIC: corrupted section JudyL array");

    if(unlikely(*PValue != NULL)) {
        METRIC *metric = *PValue;

        metric_acquire(mrg, metric);

        MRG_STATS_DUPLICATE_ADD(mrg, partition);

        mrg_index_write_unlock(mrg, partition);

        if(ret)
            *ret = false;

        aral_freez(mrg->index[partition].aral, allocation);

        return metric;
    }

    METRIC *metric = allocation;
    uuid_copy(metric->uuid, *entry->uuid);
    metric->section = entry->section;
    metric->first_time_s = MAX(0, entry->first_time_s);
    metric->latest_time_s_clean = MAX(0, entry->last_time_s);
    metric->latest_time_s_hot = 0;
    metric->latest_update_every_s = entry->latest_update_every_s;
    metric->writer = 0;
    metric->refcount = 0;
    metric->partition = partition;
    metric_acquire(mrg, metric);
    *PValue = metric;

    MRG_STATS_ADDED_METRIC(mrg, partition);

    mrg_index_write_unlock(mrg, partition);

    if(ret)
        *ret = true;

    return metric;
}

static inline METRIC *metric_get_and_acquire(MRG *mrg, uuid_t *uuid, Word_t section) {
    size_t partition = uuid_partition(mrg, uuid);

    mrg_index_read_lock(mrg, partition);

    Pvoid_t *sections_judy_pptr = JudyHSGet(mrg->index[partition].uuid_judy, uuid, sizeof(uuid_t));
    if(unlikely(!sections_judy_pptr)) {
        mrg_index_read_unlock(mrg, partition);
        MRG_STATS_SEARCH_MISS(mrg, partition);
        return NULL;
    }

    Pvoid_t *PValue = JudyLGet(*sections_judy_pptr, section, PJE0);
    if(unlikely(!PValue)) {
        mrg_index_read_unlock(mrg, partition);
        MRG_STATS_SEARCH_MISS(mrg, partition);
        return NULL;
    }

    METRIC *metric = *PValue;

    metric_acquire(mrg, metric);

    mrg_index_read_unlock(mrg, partition);

    MRG_STATS_SEARCH_HIT(mrg, partition);
    return metric;
}

static inline bool acquired_metric_del(MRG *mrg, METRIC *metric) {
    size_t partition = metric->partition;

    size_t mem_before_judyl, mem_after_judyl;

    mrg_index_write_lock(mrg, partition);

    if(!metric_release_and_can_be_deleted(mrg, metric)) {
        mrg->index[partition].stats.delete_having_retention_or_referenced++;
        mrg_index_write_unlock(mrg, partition);
        return false;
    }

    Pvoid_t *sections_judy_pptr = JudyHSGet(mrg->index[partition].uuid_judy, &metric->uuid, sizeof(uuid_t));
    if(unlikely(!sections_judy_pptr || !*sections_judy_pptr)) {
        MRG_STATS_DELETE_MISS(mrg, partition);
        mrg_index_write_unlock(mrg, partition);
        return false;
    }

    mem_before_judyl = JudyLMemUsed(*sections_judy_pptr);
    int rc = JudyLDel(sections_judy_pptr, metric->section, PJE0);
    mem_after_judyl = JudyLMemUsed(*sections_judy_pptr);
    mrg_stats_size_judyl_change(mrg, mem_before_judyl, mem_after_judyl, partition);

    if(unlikely(!rc)) {
        MRG_STATS_DELETE_MISS(mrg, partition);
        mrg_index_write_unlock(mrg, partition);
        return false;
    }

    if(!*sections_judy_pptr) {
        rc = JudyHSDel(&mrg->index[partition].uuid_judy, &metric->uuid, sizeof(uuid_t), PJE0);
        if(unlikely(!rc))
            fatal("DBENGINE METRIC: cannot delete UUID from JudyHS");
        mrg_stats_size_judyhs_removed_uuid(mrg, partition);
    }

    MRG_STATS_DELETED_METRIC(mrg, partition);

    mrg_index_write_unlock(mrg, partition);

    aral_freez(mrg->index[partition].aral, metric);

    return true;
}

// ----------------------------------------------------------------------------
// public API

inline MRG *mrg_create(ssize_t partitions) {
    if(partitions < 1)
        partitions = get_netdata_cpus();

    MRG *mrg = callocz(1, sizeof(MRG) + sizeof(struct mrg_partition) * partitions);
    mrg->partitions = partitions;

    for(size_t i = 0; i < mrg->partitions ; i++) {
        rw_spinlock_init(&mrg->index[i].rw_spinlock);

        char buf[ARAL_MAX_NAME + 1];
        snprintfz(buf, ARAL_MAX_NAME, "mrg[%zu]", i);

        mrg->index[i].aral = aral_create(buf, sizeof(METRIC), 0, 16384, &mrg_aral_statistics, NULL, NULL, false, false);
    }

    return mrg;
}

inline size_t mrg_aral_structures(void) {
    return aral_structures_from_stats(&mrg_aral_statistics);
}

inline size_t mrg_aral_overhead(void) {
    return aral_overhead_from_stats(&mrg_aral_statistics);
}

inline void mrg_destroy(MRG *mrg __maybe_unused) {
    // no destruction possible
    // we can't traverse the metrics list

    // to delete entries, the caller needs to keep pointers to them
    // and delete them one by one

    ;
}

inline METRIC *mrg_metric_add_and_acquire(MRG *mrg, MRG_ENTRY entry, bool *ret) {
//    internal_fatal(entry.latest_time_s > max_acceptable_collected_time(),
//        "DBENGINE METRIC: metric latest time is in the future");

    return metric_add_and_acquire(mrg, &entry, ret);
}

inline METRIC *mrg_metric_get_and_acquire(MRG *mrg, uuid_t *uuid, Word_t section) {
    return metric_get_and_acquire(mrg, uuid, section);
}

inline bool mrg_metric_release_and_delete(MRG *mrg, METRIC *metric) {
    return acquired_metric_del(mrg, metric);
}

inline METRIC *mrg_metric_dup(MRG *mrg, METRIC *metric) {
    metric_acquire(mrg, metric);
    return metric;
}

inline bool mrg_metric_release(MRG *mrg, METRIC *metric) {
    return metric_release_and_can_be_deleted(mrg, metric);
}

inline Word_t mrg_metric_id(MRG *mrg __maybe_unused, METRIC *metric) {
    return (Word_t)metric;
}

inline uuid_t *mrg_metric_uuid(MRG *mrg __maybe_unused, METRIC *metric) {
    return &metric->uuid;
}

inline Word_t mrg_metric_section(MRG *mrg __maybe_unused, METRIC *metric) {
    return metric->section;
}

inline bool mrg_metric_set_first_time_s(MRG *mrg __maybe_unused, METRIC *metric, time_t first_time_s) {
    internal_fatal(first_time_s < 0, "DBENGINE METRIC: timestamp is negative");

    if(unlikely(first_time_s < 0))
        return false;

    __atomic_store_n(&metric->first_time_s, first_time_s, __ATOMIC_RELAXED);

    return true;
}

inline void mrg_metric_expand_retention(MRG *mrg __maybe_unused, METRIC *metric, time_t first_time_s, time_t last_time_s, time_t update_every_s) {
    internal_fatal(first_time_s < 0 || last_time_s < 0 || update_every_s < 0,
                   "DBENGINE METRIC: timestamp is negative");
    internal_fatal(first_time_s > max_acceptable_collected_time(),
                   "DBENGINE METRIC: metric first time is in the future");
    internal_fatal(last_time_s > max_acceptable_collected_time(),
                   "DBENGINE METRIC: metric last time is in the future");

    if(first_time_s > 0)
        set_metric_field_with_condition(metric->first_time_s, first_time_s, _current <= 0 || _wanted < _current);

    if(last_time_s > 0) {
        if(set_metric_field_with_condition(metric->latest_time_s_clean, last_time_s, _current <= 0 || _wanted > _current) &&
            update_every_s > 0)
            // set the latest update every too
            set_metric_field_with_condition(metric->latest_update_every_s, update_every_s, true);
    }
    else if(update_every_s > 0)
        // set it only if it is invalid
        set_metric_field_with_condition(metric->latest_update_every_s, update_every_s, _current <= 0);
}

inline bool mrg_metric_set_first_time_s_if_bigger(MRG *mrg __maybe_unused, METRIC *metric, time_t first_time_s) {
    internal_fatal(first_time_s < 0, "DBENGINE METRIC: timestamp is negative");
    return set_metric_field_with_condition(metric->first_time_s, first_time_s, _wanted > _current);
}

inline time_t mrg_metric_get_first_time_s(MRG *mrg __maybe_unused, METRIC *metric) {
    return mrg_metric_get_first_time_s_smart(mrg, metric);
}

inline void mrg_metric_get_retention(MRG *mrg __maybe_unused, METRIC *metric, time_t *first_time_s, time_t *last_time_s, time_t *update_every_s) {
    time_t clean = __atomic_load_n(&metric->latest_time_s_clean, __ATOMIC_RELAXED);
    time_t hot = __atomic_load_n(&metric->latest_time_s_hot, __ATOMIC_RELAXED);

    *last_time_s = MAX(clean, hot);
    *first_time_s = mrg_metric_get_first_time_s_smart(mrg, metric);
    *update_every_s = __atomic_load_n(&metric->latest_update_every_s, __ATOMIC_RELAXED);
}

inline bool mrg_metric_set_clean_latest_time_s(MRG *mrg __maybe_unused, METRIC *metric, time_t latest_time_s) {
    internal_fatal(latest_time_s < 0, "DBENGINE METRIC: timestamp is negative");

//    internal_fatal(latest_time_s > max_acceptable_collected_time(),
//                   "DBENGINE METRIC: metric latest time is in the future");

//    internal_fatal(metric->latest_time_s_clean > latest_time_s,
//                   "DBENGINE METRIC: metric new clean latest time is older than the previous one");

    if(latest_time_s > 0) {
        if(set_metric_field_with_condition(metric->latest_time_s_clean, latest_time_s, true)) {
            set_metric_field_with_condition(metric->first_time_s, latest_time_s, _current <= 0 || _wanted < _current);

            return true;
        }
    }

    return false;
}

// returns true when metric still has retention
inline bool mrg_metric_zero_disk_retention(MRG *mrg __maybe_unused, METRIC *metric) {
    Word_t section = mrg_metric_section(mrg, metric);
    bool do_again = false;
    size_t countdown = 5;

    do {
        time_t min_first_time_s = LONG_MAX;
        time_t max_end_time_s = 0;
        PGC_PAGE *page;
        PGC_SEARCH method = PGC_SEARCH_FIRST;
        time_t page_first_time_s = 0;
        time_t page_end_time_s = 0;
        while ((page = pgc_page_get_and_acquire(main_cache, section, (Word_t)metric, page_first_time_s, method))) {
            method = PGC_SEARCH_NEXT;

            bool is_hot = pgc_is_page_hot(page);
            bool is_dirty = pgc_is_page_dirty(page);
            page_first_time_s = pgc_page_start_time_s(page);
            page_end_time_s = pgc_page_end_time_s(page);

            if ((is_hot || is_dirty) && page_first_time_s > 0 && page_first_time_s < min_first_time_s)
                min_first_time_s = page_first_time_s;

            if (is_dirty && page_end_time_s > max_end_time_s)
                max_end_time_s = page_end_time_s;

            pgc_page_release(main_cache, page);
        }

        if (min_first_time_s == LONG_MAX)
            min_first_time_s = 0;

        if (--countdown && !min_first_time_s && __atomic_load_n(&metric->latest_time_s_hot, __ATOMIC_RELAXED))
            do_again = true;
        else {
            internal_error(!countdown, "METRIC: giving up on updating the retention of metric without disk retention");

            do_again = false;
            set_metric_field_with_condition(metric->first_time_s, min_first_time_s, true);
            set_metric_field_with_condition(metric->latest_time_s_clean, max_end_time_s, true);
        }
    } while(do_again);

    time_t first, last, ue;
    mrg_metric_get_retention(mrg, metric, &first, &last, &ue);
    return (first && last && first < last);
}

inline bool mrg_metric_set_hot_latest_time_s(MRG *mrg __maybe_unused, METRIC *metric, time_t latest_time_s) {
    internal_fatal(latest_time_s < 0, "DBENGINE METRIC: timestamp is negative");

//    internal_fatal(latest_time_s > max_acceptable_collected_time(),
//                   "DBENGINE METRIC: metric latest time is in the future");

    if(likely(latest_time_s > 0)) {
        __atomic_store_n(&metric->latest_time_s_hot, latest_time_s, __ATOMIC_RELAXED);
        return true;
    }

    return false;
}

inline time_t mrg_metric_get_latest_time_s(MRG *mrg __maybe_unused, METRIC *metric) {
    time_t clean = __atomic_load_n(&metric->latest_time_s_clean, __ATOMIC_RELAXED);
    time_t hot = __atomic_load_n(&metric->latest_time_s_hot, __ATOMIC_RELAXED);

    return MAX(clean, hot);
}

inline bool mrg_metric_set_update_every(MRG *mrg __maybe_unused, METRIC *metric, time_t update_every_s) {
    internal_fatal(update_every_s < 0, "DBENGINE METRIC: timestamp is negative");

    if(update_every_s > 0)
        return set_metric_field_with_condition(metric->latest_update_every_s, update_every_s, true);

    return false;
}

inline bool mrg_metric_set_update_every_s_if_zero(MRG *mrg __maybe_unused, METRIC *metric, time_t update_every_s) {
    internal_fatal(update_every_s < 0, "DBENGINE METRIC: timestamp is negative");

    if(update_every_s > 0)
        return set_metric_field_with_condition(metric->latest_update_every_s, update_every_s, _current <= 0);

    return false;
}

inline time_t mrg_metric_get_update_every_s(MRG *mrg __maybe_unused, METRIC *metric) {
    return __atomic_load_n(&metric->latest_update_every_s, __ATOMIC_RELAXED);
}

inline bool mrg_metric_set_writer(MRG *mrg, METRIC *metric) {
    pid_t expected = __atomic_load_n(&metric->writer, __ATOMIC_RELAXED);
    pid_t wanted = gettid();
    bool done = true;

    do {
        if(expected != 0) {
            done = false;
            break;
        }
    } while(!__atomic_compare_exchange_n(&metric->writer, &expected, wanted, false, __ATOMIC_RELAXED, __ATOMIC_RELAXED));

    if(done)
        __atomic_add_fetch(&mrg->index[metric->partition].stats.writers, 1, __ATOMIC_RELAXED);
    else
        __atomic_add_fetch(&mrg->index[metric->partition].stats.writers_conflicts, 1, __ATOMIC_RELAXED);

    return done;
}

inline bool mrg_metric_clear_writer(MRG *mrg, METRIC *metric) {
    // this function can be called from a different thread than the one than the writer

    pid_t expected = __atomic_load_n(&metric->writer, __ATOMIC_RELAXED);
    pid_t wanted = 0;
    bool done = true;

    do {
        if(!expected) {
            done = false;
            break;
        }
    } while(!__atomic_compare_exchange_n(&metric->writer, &expected, wanted, false, __ATOMIC_RELAXED, __ATOMIC_RELAXED));

    if(done)
        __atomic_sub_fetch(&mrg->index[metric->partition].stats.writers, 1, __ATOMIC_RELAXED);

    return done;
}

inline void mrg_update_metric_retention_and_granularity_by_uuid(
        MRG *mrg, Word_t section, uuid_t *uuid,
        time_t first_time_s, time_t last_time_s,
        time_t update_every_s, time_t now_s)
{
    if(unlikely(last_time_s > now_s)) {
        nd_log_limit_static_global_var(erl, 1, 0);
        nd_log_limit(&erl, NDLS_DAEMON, NDLP_WARNING,
                     "DBENGINE JV2: wrong last time on-disk (%ld - %ld, now %ld), "
                     "fixing last time to now",
                     first_time_s, last_time_s, now_s);
        last_time_s = now_s;
    }

    if (unlikely(first_time_s > last_time_s)) {
        nd_log_limit_static_global_var(erl, 1, 0);
        nd_log_limit(&erl, NDLS_DAEMON, NDLP_WARNING,
                     "DBENGINE JV2: wrong first time on-disk (%ld - %ld, now %ld), "
                     "fixing first time to last time",
                     first_time_s, last_time_s, now_s);

        first_time_s = last_time_s;
    }

    if (unlikely(first_time_s == 0 || last_time_s == 0)) {
        nd_log_limit_static_global_var(erl, 1, 0);
        nd_log_limit(&erl, NDLS_DAEMON, NDLP_WARNING,
                     "DBENGINE JV2: zero on-disk timestamps (%ld - %ld, now %ld), "
                     "using them as-is",
                     first_time_s, last_time_s, now_s);
    }

    bool added = false;
    METRIC *metric = mrg_metric_get_and_acquire(mrg, uuid, section);
    if (!metric) {
        MRG_ENTRY entry = {
                .uuid = uuid,
                .section = section,
                .first_time_s = first_time_s,
                .last_time_s = last_time_s,
                .latest_update_every_s = (uint32_t) update_every_s
        };
        metric = mrg_metric_add_and_acquire(mrg, entry, &added);
    }

    if (likely(!added))
        mrg_metric_expand_retention(mrg, metric, first_time_s, last_time_s, update_every_s);

    mrg_metric_release(mrg, metric);
}

inline void mrg_get_statistics(MRG *mrg, struct mrg_statistics *s) {
    memset(s, 0, sizeof(struct mrg_statistics));

    for(size_t i = 0; i < mrg->partitions ;i++) {
        s->entries += __atomic_load_n(&mrg->index[i].stats.entries, __ATOMIC_RELAXED);
        s->entries_referenced += __atomic_load_n(&mrg->index[i].stats.entries_referenced, __ATOMIC_RELAXED);
        s->size += __atomic_load_n(&mrg->index[i].stats.size, __ATOMIC_RELAXED);
        s->current_references += __atomic_load_n(&mrg->index[i].stats.current_references, __ATOMIC_RELAXED);
        s->additions += __atomic_load_n(&mrg->index[i].stats.additions, __ATOMIC_RELAXED);
        s->additions_duplicate += __atomic_load_n(&mrg->index[i].stats.additions_duplicate, __ATOMIC_RELAXED);
        s->deletions += __atomic_load_n(&mrg->index[i].stats.deletions, __ATOMIC_RELAXED);
        s->delete_having_retention_or_referenced += __atomic_load_n(&mrg->index[i].stats.delete_having_retention_or_referenced, __ATOMIC_RELAXED);
        s->delete_misses += __atomic_load_n(&mrg->index[i].stats.delete_misses, __ATOMIC_RELAXED);
        s->search_hits += __atomic_load_n(&mrg->index[i].stats.search_hits, __ATOMIC_RELAXED);
        s->search_misses += __atomic_load_n(&mrg->index[i].stats.search_misses, __ATOMIC_RELAXED);
        s->writers += __atomic_load_n(&mrg->index[i].stats.writers, __ATOMIC_RELAXED);
        s->writers_conflicts += __atomic_load_n(&mrg->index[i].stats.writers_conflicts, __ATOMIC_RELAXED);
    }

    s->size += sizeof(MRG) + sizeof(struct mrg_partition) * mrg->partitions;
}

// ----------------------------------------------------------------------------
// unit test

struct mrg_stress_entry {
    uuid_t uuid;
    time_t after;
    time_t before;
};

struct mrg_stress {
    MRG *mrg;
    bool stop;
    size_t entries;
    struct mrg_stress_entry *array;
    size_t updates;
};

static void *mrg_stress(void *ptr) {
    struct mrg_stress *t = ptr;
    MRG *mrg = t->mrg;

    ssize_t start = 0;
    ssize_t end = (ssize_t)t->entries;
    ssize_t step = 1;

    if(gettid() % 2) {
        start = (ssize_t)t->entries - 1;
        end = -1;
        step = -1;
    }

    while(!__atomic_load_n(&t->stop, __ATOMIC_RELAXED)) {
        for (ssize_t i = start; i != end; i += step) {
            struct mrg_stress_entry *e = &t->array[i];

            time_t after = __atomic_sub_fetch(&e->after, 1, __ATOMIC_RELAXED);
            time_t before = __atomic_add_fetch(&e->before, 1, __ATOMIC_RELAXED);

            mrg_update_metric_retention_and_granularity_by_uuid(
                    mrg, 0x01,
                    &e->uuid,
                    after,
                    before,
                    1,
                    before);

            __atomic_add_fetch(&t->updates, 1, __ATOMIC_RELAXED);
        }
    }

    return ptr;
}

int mrg_unittest(void) {
    MRG *mrg = mrg_create(0);
    METRIC *m1_t0, *m2_t0, *m3_t0, *m4_t0;
    METRIC *m1_t1, *m2_t1, *m3_t1, *m4_t1;
    bool ret;

    uuid_t test_uuid;
    uuid_generate(test_uuid);
    MRG_ENTRY entry = {
            .uuid = &test_uuid,
            .section = 0,
            .first_time_s = 2,
            .last_time_s = 3,
            .latest_update_every_s = 4,
    };
    m1_t0 = mrg_metric_add_and_acquire(mrg, entry, &ret);
    if(!ret)
        fatal("DBENGINE METRIC: failed to add metric");

    // add the same metric again
    m2_t0 = mrg_metric_add_and_acquire(mrg, entry, &ret);
    if(m2_t0 != m1_t0)
        fatal("DBENGINE METRIC: adding the same metric twice, does not return the same pointer");
    if(ret)
        fatal("DBENGINE METRIC: managed to add the same metric twice");

    m3_t0 = mrg_metric_get_and_acquire(mrg, entry.uuid, entry.section);
    if(m3_t0 != m1_t0)
        fatal("DBENGINE METRIC: cannot find the metric added");

    // add the same metric again
    m4_t0 = mrg_metric_add_and_acquire(mrg, entry, &ret);
    if(m4_t0 != m1_t0)
        fatal("DBENGINE METRIC: adding the same metric twice, does not return the same pointer");
    if(ret)
        fatal("DBENGINE METRIC: managed to add the same metric twice");

    // add the same metric in another section
    entry.section = 1;
    m1_t1 = mrg_metric_add_and_acquire(mrg, entry, &ret);
    if(!ret)
        fatal("DBENGINE METRIC: failed to add metric in section %zu", (size_t)entry.section);

    // add the same metric again
    m2_t1 = mrg_metric_add_and_acquire(mrg, entry, &ret);
    if(m2_t1 != m1_t1)
        fatal("DBENGINE METRIC: adding the same metric twice (section %zu), does not return the same pointer", (size_t)entry.section);
    if(ret)
        fatal("DBENGINE METRIC: managed to add the same metric twice in (section 0)");

    m3_t1 = mrg_metric_get_and_acquire(mrg, entry.uuid, entry.section);
    if(m3_t1 != m1_t1)
        fatal("DBENGINE METRIC: cannot find the metric added (section %zu)", (size_t)entry.section);

    // delete the first metric
    mrg_metric_release(mrg, m2_t0);
    mrg_metric_release(mrg, m3_t0);
    mrg_metric_release(mrg, m4_t0);
    mrg_metric_set_first_time_s(mrg, m1_t0, 0);
    mrg_metric_set_clean_latest_time_s(mrg, m1_t0, 0);
    mrg_metric_set_hot_latest_time_s(mrg, m1_t0, 0);
    if(!mrg_metric_release_and_delete(mrg, m1_t0))
        fatal("DBENGINE METRIC: cannot delete the first metric");

    m4_t1 = mrg_metric_get_and_acquire(mrg, entry.uuid, entry.section);
    if(m4_t1 != m1_t1)
        fatal("DBENGINE METRIC: cannot find the metric added (section %zu), after deleting the first one", (size_t)entry.section);

    // delete the second metric
    mrg_metric_release(mrg, m2_t1);
    mrg_metric_release(mrg, m3_t1);
    mrg_metric_release(mrg, m4_t1);
    mrg_metric_set_first_time_s(mrg, m1_t1, 0);
    mrg_metric_set_clean_latest_time_s(mrg, m1_t1, 0);
    mrg_metric_set_hot_latest_time_s(mrg, m1_t1, 0);
    if(!mrg_metric_release_and_delete(mrg, m1_t1))
        fatal("DBENGINE METRIC: cannot delete the second metric");

    struct mrg_statistics s;
    mrg_get_statistics(mrg, &s);
    if(s.entries != 0)
        fatal("DBENGINE METRIC: invalid entries counter");

    size_t entries = 1000000;
    size_t threads = mrg->partitions / 3 + 1;
    size_t tiers = 3;
    size_t run_for_secs = 5;
    netdata_log_info("preparing stress test of %zu entries...", entries);
    struct mrg_stress t = {
            .mrg = mrg,
            .entries = entries,
            .array = callocz(entries, sizeof(struct mrg_stress_entry)),
    };

    time_t now = max_acceptable_collected_time();
    for(size_t i = 0; i < entries ;i++) {
        uuid_generate_random(t.array[i].uuid);
        t.array[i].after = now / 3;
        t.array[i].before = now / 2;
    }
    netdata_log_info("stress test is populating MRG with 3 tiers...");
    for(size_t i = 0; i < entries ;i++) {
        struct mrg_stress_entry *e = &t.array[i];
        for(size_t tier = 1; tier <= tiers ;tier++) {
            mrg_update_metric_retention_and_granularity_by_uuid(
                    mrg, tier,
                    &e->uuid,
                    e->after,
                    e->before,
                    1,
                    e->before);
        }
    }
    netdata_log_info("stress test ready to run...");

    usec_t started_ut = now_monotonic_usec();

    pthread_t th[threads];
    for(size_t i = 0; i < threads ; i++) {
        char buf[15 + 1];
        snprintfz(buf, sizeof(buf) - 1, "TH[%zu]", i);
        netdata_thread_create(&th[i], buf,
                              NETDATA_THREAD_OPTION_JOINABLE | NETDATA_THREAD_OPTION_DONT_LOG,
                              mrg_stress, &t);
    }

    sleep_usec(run_for_secs * USEC_PER_SEC);
    __atomic_store_n(&t.stop, true, __ATOMIC_RELAXED);

    for(size_t i = 0; i < threads ; i++)
        netdata_thread_cancel(th[i]);

    for(size_t i = 0; i < threads ; i++)
        netdata_thread_join(th[i], NULL);

    usec_t ended_ut = now_monotonic_usec();

    struct mrg_statistics stats;
    mrg_get_statistics(mrg, &stats);

    netdata_log_info("DBENGINE METRIC: did %zu additions, %zu duplicate additions, "
         "%zu deletions, %zu wrong deletions, "
         "%zu successful searches, %zu wrong searches, "
         "in %"PRIu64" usecs",
        stats.additions, stats.additions_duplicate,
        stats.deletions, stats.delete_misses,
        stats.search_hits, stats.search_misses,
        ended_ut - started_ut);

    netdata_log_info("DBENGINE METRIC: updates performance: %0.2fk/sec total, %0.2fk/sec/thread",
         (double)t.updates / (double)((ended_ut - started_ut) / USEC_PER_SEC) / 1000.0,
         (double)t.updates / (double)((ended_ut - started_ut) / USEC_PER_SEC) / 1000.0 / threads);

    mrg_destroy(mrg);

    netdata_log_info("DBENGINE METRIC: all tests passed!");

    return 0;
}