summaryrefslogtreecommitdiffstats
path: root/libnetdata/log/log.c
blob: 90581269d5d7dff6125d7f871b1af1c9524337df (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
874
875
876
877
878
879
// SPDX-License-Identifier: GPL-3.0-or-later

#include <daemon/main.h>
#include "../libnetdata.h"

int web_server_is_multithreaded = 1;

const char *program_name = "";
uint64_t debug_flags = DEBUG;

int access_log_syslog = 1;
int error_log_syslog = 1;
int output_log_syslog = 1;  // debug log

int stdaccess_fd = -1;
FILE *stdaccess = NULL;

const char *stdaccess_filename = NULL;
const char *stderr_filename = NULL;
const char *stdout_filename = NULL;
const char *facility_log = NULL;

// ----------------------------------------------------------------------------
// Log facility(https://tools.ietf.org/html/rfc5424)
//
// The facilities accepted in the Netdata are in according with the following
// header files for their respective operating system:
// sys/syslog.h (Linux )
// sys/sys/syslog.h (FreeBSD)
// bsd/sys/syslog.h (darwin-xnu)

#define LOG_AUTH_KEY "auth"
#define LOG_AUTHPRIV_KEY "authpriv"
#ifdef __FreeBSD__
# define LOG_CONSOLE_KEY "console"
#endif
#define LOG_CRON_KEY "cron"
#define LOG_DAEMON_KEY "daemon"
#define LOG_FTP_KEY "ftp"
#ifdef __APPLE__
# define LOG_INSTALL_KEY "install"
#endif
#define LOG_KERN_KEY "kern"
#define LOG_LPR_KEY "lpr"
#define LOG_MAIL_KEY "mail"
//#define LOG_INTERNAL_MARK_KEY "mark"
#ifdef __APPLE__
# define LOG_NETINFO_KEY "netinfo"
# define LOG_RAS_KEY "ras"
# define LOG_REMOTEAUTH_KEY "remoteauth"
#endif
#define LOG_NEWS_KEY "news"
#ifdef __FreeBSD__
# define LOG_NTP_KEY "ntp"
#endif
#define LOG_SECURITY_KEY "security"
#define LOG_SYSLOG_KEY "syslog"
#define LOG_USER_KEY "user"
#define LOG_UUCP_KEY "uucp"
#ifdef __APPLE__
# define LOG_LAUNCHD_KEY "launchd"
#endif
#define LOG_LOCAL0_KEY "local0"
#define LOG_LOCAL1_KEY "local1"
#define LOG_LOCAL2_KEY "local2"
#define LOG_LOCAL3_KEY "local3"
#define LOG_LOCAL4_KEY "local4"
#define LOG_LOCAL5_KEY "local5"
#define LOG_LOCAL6_KEY "local6"
#define LOG_LOCAL7_KEY "local7"

static int log_facility_id(const char *facility_name)
{
    static int
        hash_auth = 0,
        hash_authpriv = 0,
#ifdef __FreeBSD__
        hash_console = 0,
#endif
        hash_cron = 0,
        hash_daemon = 0,
        hash_ftp = 0,
#ifdef __APPLE__
        hash_install = 0,
#endif
        hash_kern = 0,
        hash_lpr = 0,
        hash_mail = 0,
//      hash_mark = 0,
#ifdef __APPLE__
        hash_netinfo = 0,
        hash_ras = 0,
        hash_remoteauth = 0,
#endif
        hash_news = 0,
#ifdef __FreeBSD__
        hash_ntp = 0,
#endif
        hash_security = 0,
        hash_syslog = 0,
        hash_user = 0,
        hash_uucp = 0,
#ifdef __APPLE__
        hash_launchd = 0,
#endif
        hash_local0 = 0,
        hash_local1 = 0,
        hash_local2 = 0,
        hash_local3 = 0,
        hash_local4 = 0,
        hash_local5 = 0,
        hash_local6 = 0,
        hash_local7 = 0;

    if(unlikely(!hash_auth))
    {
        hash_auth = simple_hash(LOG_AUTH_KEY);
        hash_authpriv = simple_hash(LOG_AUTHPRIV_KEY);
#ifdef __FreeBSD__
        hash_console = simple_hash(LOG_CONSOLE_KEY);
#endif
        hash_cron = simple_hash(LOG_CRON_KEY);
        hash_daemon = simple_hash(LOG_DAEMON_KEY);
        hash_ftp = simple_hash(LOG_FTP_KEY);
#ifdef __APPLE__
        hash_install = simple_hash(LOG_INSTALL_KEY);
#endif
        hash_kern = simple_hash(LOG_KERN_KEY);
        hash_lpr = simple_hash(LOG_LPR_KEY);
        hash_mail = simple_hash(LOG_MAIL_KEY);
//        hash_mark = simple_uhash();
#ifdef __APPLE__
        hash_netinfo = simple_hash(LOG_NETINFO_KEY);
        hash_ras = simple_hash(LOG_RAS_KEY);
        hash_remoteauth = simple_hash(LOG_REMOTEAUTH_KEY);
#endif
        hash_news = simple_hash(LOG_NEWS_KEY);
#ifdef __FreeBSD__
        hash_ntp = simple_hash(LOG_NTP_KEY);
#endif
        hash_security = simple_hash(LOG_SECURITY_KEY);
        hash_syslog = simple_hash(LOG_SYSLOG_KEY);
        hash_user = simple_hash(LOG_USER_KEY);
        hash_uucp = simple_hash(LOG_UUCP_KEY);
#ifdef __APPLE__
        hash_launchd = simple_hash(LOG_LAUNCHD_KEY);
#endif
        hash_local0 = simple_hash(LOG_LOCAL0_KEY);
        hash_local1 = simple_hash(LOG_LOCAL1_KEY);
        hash_local2 = simple_hash(LOG_LOCAL2_KEY);
        hash_local3 = simple_hash(LOG_LOCAL3_KEY);
        hash_local4 = simple_hash(LOG_LOCAL4_KEY);
        hash_local5 = simple_hash(LOG_LOCAL5_KEY);
        hash_local6 = simple_hash(LOG_LOCAL6_KEY);
        hash_local7 = simple_hash(LOG_LOCAL7_KEY);
    }

    int hash = simple_hash(facility_name);
    if ( hash == hash_auth )
    {
        return LOG_AUTH;
    }
    else if  ( hash == hash_authpriv )
    {
        return LOG_AUTHPRIV;
    }
#ifdef __FreeBSD__
    else if ( hash == hash_console )
    {
        return LOG_CONSOLE;
    }
#endif
    else if ( hash == hash_cron )
    {
        return LOG_CRON;
    }
    else if ( hash == hash_daemon )
    {
        return LOG_DAEMON;
    }
    else if ( hash == hash_ftp )
    {
        return LOG_FTP;
    }
#ifdef __APPLE__
    else if ( hash == hash_install )
    {
        return LOG_INSTALL;
    }
#endif
    else if ( hash == hash_kern )
    {
        return LOG_KERN;
    }
    else if ( hash == hash_lpr )
    {
        return LOG_LPR;
    }
    else if ( hash == hash_mail )
    {
        return LOG_MAIL;
    }
    /*
    else if ( hash == hash_mark )
    {
        //this is internal for all OS
        return INTERNAL_MARK;
    }
    */
#ifdef __APPLE__
    else if ( hash == hash_netinfo )
    {
        return LOG_NETINFO;
    }
    else if ( hash == hash_ras )
    {
        return LOG_RAS;
    }
    else if ( hash == hash_remoteauth )
    {
        return LOG_REMOTEAUTH;
    }
#endif
    else if ( hash == hash_news )
    {
        return LOG_NEWS;
    }
#ifdef __FreeBSD__
    else if ( hash == hash_ntp )
    {
        return LOG_NTP;
    }
#endif
    else if ( hash == hash_security )
    {
        //FreeBSD is the unique that does not consider
        //this facility deprecated. We are keeping
        //it for other OS while they are kept in their headers.
#ifdef __FreeBSD__
        return LOG_SECURITY;
#else
        return LOG_AUTH;
#endif
    }
    else if ( hash == hash_syslog )
    {
        return LOG_SYSLOG;
    }
    else if ( hash == hash_user )
    {
        return LOG_USER;
    }
    else if ( hash == hash_uucp )
    {
        return LOG_UUCP;
    }
    else if ( hash == hash_local0 )
    {
        return LOG_LOCAL0;
    }
    else if ( hash == hash_local1 )
    {
        return LOG_LOCAL1;
    }
    else if ( hash == hash_local2 )
    {
        return LOG_LOCAL2;
    }
    else if ( hash == hash_local3 )
    {
        return LOG_LOCAL3;
    }
    else if ( hash == hash_local4 )
    {
        return LOG_LOCAL4;
    }
    else if ( hash == hash_local5 )
    {
        return LOG_LOCAL5;
    }
    else if ( hash == hash_local6 )
    {
        return LOG_LOCAL6;
    }
    else if ( hash == hash_local7 )
    {
        return LOG_LOCAL7;
    }
#ifdef __APPLE__
    else if ( hash == hash_launchd )
    {
        return LOG_LAUNCHD;
    }
#endif

    return LOG_DAEMON;
}

//we do not need to use this now, but I already created this function to be
//used case necessary.
/*
char *log_facility_name(int code)
{
    char *defvalue = { "daemon" };
    switch(code)
    {
        case LOG_AUTH:
            {
                return "auth";
            }
        case LOG_AUTHPRIV:
            {
                return "authpriv";
            }
#ifdef __FreeBSD__
        case LOG_CONSOLE:
            {
                return "console";
            }
#endif
        case LOG_CRON:
            {
                return "cron";
            }
        case LOG_DAEMON:
            {
                return defvalue;
            }
        case LOG_FTP:
            {
                return "ftp";
            }
#ifdef __APPLE__
        case LOG_INSTALL:
            {
                return "install";
            }
#endif
        case LOG_KERN:
            {
                return "kern";
            }
        case LOG_LPR:
            {
                return "lpr";
            }
        case LOG_MAIL:
            {
                return "mail";
            }
#ifdef __APPLE__
        case LOG_NETINFO:
            {
                return "netinfo" ;
            }
        case LOG_RAS:
            {
                return "ras";
            }
        case LOG_REMOTEAUTH:
            {
                return "remoteauth";
            }
#endif
        case LOG_NEWS:
            {
                return "news";
            }
#ifdef __FreeBSD__
        case LOG_NTP:
            {
                return "ntp" ;
            }
        case LOG_SECURITY:
            {
                return "security";
            }
#endif
        case LOG_SYSLOG:
            {
                return "syslog";
            }
        case LOG_USER:
            {
                return "user";
            }
        case LOG_UUCP:
            {
                return "uucp";
            }
        case LOG_LOCAL0:
            {
                return "local0";
            }
        case LOG_LOCAL1:
            {
                return "local1";
            }
        case LOG_LOCAL2:
            {
                return "local2";
            }
        case LOG_LOCAL3:
            {
                return "local3";
            }
        case LOG_LOCAL4:
            {
                return "local4" ;
            }
        case LOG_LOCAL5:
            {
                return "local5";
            }
        case LOG_LOCAL6:
            {
                return "local6";
            }
        case LOG_LOCAL7:
            {
                return "local7" ;
            }
#ifdef __APPLE__
        case LOG_LAUNCHD:
            {
                return "launchd";
            }
#endif
    }

    return defvalue;
}
*/

// ----------------------------------------------------------------------------

void syslog_init() {
    static int i = 0;

    if(!i) {
        openlog(program_name, LOG_PID,log_facility_id(facility_log));
        i = 1;
    }
}

#define LOG_DATE_LENGTH 26

static inline void log_date(char *buffer, size_t len) {
    if(unlikely(!buffer || !len))
        return;

    time_t t;
    struct tm *tmp, tmbuf;

    t = now_realtime_sec();
    tmp = localtime_r(&t, &tmbuf);

    if (tmp == NULL) {
        buffer[0] = '\0';
        return;
    }

    if (unlikely(strftime(buffer, len, "%Y-%m-%d %H:%M:%S", tmp) == 0))
        buffer[0] = '\0';

    buffer[len - 1] = '\0';
}

static netdata_mutex_t log_mutex = NETDATA_MUTEX_INITIALIZER;
static inline void log_lock() {
    netdata_mutex_lock(&log_mutex);
}
static inline void log_unlock() {
    netdata_mutex_unlock(&log_mutex);
}

static FILE *open_log_file(int fd, FILE *fp, const char *filename, int *enabled_syslog, int is_stdaccess, int *fd_ptr) {
    int f, devnull = 0;

    if(!filename || !*filename || !strcmp(filename, "none") ||  !strcmp(filename, "/dev/null")) {
        filename = "/dev/null";
        devnull = 1;
    }

    if(!strcmp(filename, "syslog")) {
        filename = "/dev/null";
        devnull = 1;

    syslog_init();
        if(enabled_syslog) *enabled_syslog = 1;
    }
    else if(enabled_syslog) *enabled_syslog = 0;

    // don't do anything if the user is willing
    // to have the standard one
    if(!strcmp(filename, "system")) {
        if(fd != -1 && !is_stdaccess) {
            if(fd_ptr) *fd_ptr = fd;
            return fp;
        }

        filename = "stderr";
    }

    if(!strcmp(filename, "stdout"))
        f = STDOUT_FILENO;

    else if(!strcmp(filename, "stderr"))
        f = STDERR_FILENO;

    else {
        f = open(filename, O_WRONLY | O_APPEND | O_CREAT, 0664);
        if(f == -1) {
            error("Cannot open file '%s'. Leaving %d to its default.", filename, fd);
            if(fd_ptr) *fd_ptr = fd;
            return fp;
        }
    }

    // if there is a level-2 file pointer
    // flush it before switching the level-1 fds
    if(fp)
        fflush(fp);

    if(devnull && is_stdaccess) {
        fd = -1;
        fp = NULL;
    }

    if(fd != f && fd != -1) {
        // it automatically closes
        int t = dup2(f, fd);
        if (t == -1) {
            error("Cannot dup2() new fd %d to old fd %d for '%s'", f, fd, filename);
            close(f);
            if(fd_ptr) *fd_ptr = fd;
            return fp;
        }
        // info("dup2() new fd %d to old fd %d for '%s'", f, fd, filename);
        close(f);
    }
    else fd = f;

    if(!fp) {
        fp = fdopen(fd, "a");
        if (!fp)
            error("Cannot fdopen() fd %d ('%s')", fd, filename);
        else {
            if (setvbuf(fp, NULL, _IOLBF, 0) != 0)
                error("Cannot set line buffering on fd %d ('%s')", fd, filename);
        }
    }

    if(fd_ptr) *fd_ptr = fd;
    return fp;
}

void reopen_all_log_files() {
    if(stdout_filename)
        open_log_file(STDOUT_FILENO, stdout, stdout_filename, &output_log_syslog, 0, NULL);

    if(stderr_filename)
        open_log_file(STDERR_FILENO, stderr, stderr_filename, &error_log_syslog, 0, NULL);

    if(stdaccess_filename)
         stdaccess = open_log_file(stdaccess_fd, stdaccess, stdaccess_filename, &access_log_syslog, 1, &stdaccess_fd);
}

void open_all_log_files() {
    // disable stdin
    open_log_file(STDIN_FILENO, stdin, "/dev/null", NULL, 0, NULL);

    open_log_file(STDOUT_FILENO, stdout, stdout_filename, &output_log_syslog, 0, NULL);
    open_log_file(STDERR_FILENO, stderr, stderr_filename, &error_log_syslog, 0, NULL);
    stdaccess = open_log_file(stdaccess_fd, stdaccess, stdaccess_filename, &access_log_syslog, 1, &stdaccess_fd);
}

// ----------------------------------------------------------------------------
// error log throttling

time_t error_log_throttle_period = 1200;
unsigned long error_log_errors_per_period = 200;
unsigned long error_log_errors_per_period_backup = 0;

int error_log_limit(int reset) {
    static time_t start = 0;
    static unsigned long counter = 0, prevented = 0;

    // fprintf(stderr, "FLOOD: counter=%lu, allowed=%lu, backup=%lu, period=%llu\n", counter, error_log_errors_per_period, error_log_errors_per_period_backup, (unsigned long long)error_log_throttle_period);

    // do not throttle if the period is 0
    if(error_log_throttle_period == 0)
        return 0;

    // prevent all logs if the errors per period is 0
    if(error_log_errors_per_period == 0)
#ifdef NETDATA_INTERNAL_CHECKS
        return 0;
#else
        return 1;
#endif

    time_t now = now_monotonic_sec();
    if(!start) start = now;

    if(reset) {
        if(prevented) {
            char date[LOG_DATE_LENGTH];
            log_date(date, LOG_DATE_LENGTH);
            fprintf(
                stderr,
                "%s: %s LOG FLOOD PROTECTION reset for process '%s' "
                "(prevented %lu logs in the last %"PRId64" seconds).\n",
                date,
                program_name,
                program_name,
                prevented,
                (int64_t)(now - start));
        }

        start = now;
        counter = 0;
        prevented = 0;
    }

    // detect if we log too much
    counter++;

    if(now - start > error_log_throttle_period) {
        if(prevented) {
            char date[LOG_DATE_LENGTH];
            log_date(date, LOG_DATE_LENGTH);
            fprintf(
                stderr,
                "%s: %s LOG FLOOD PROTECTION resuming logging from process '%s' "
                "(prevented %lu logs in the last %"PRId64" seconds).\n",
                date,
                program_name,
                program_name,
                prevented,
                (int64_t)error_log_throttle_period);
        }

        // restart the period accounting
        start = now;
        counter = 1;
        prevented = 0;

        // log this error
        return 0;
    }

    if(counter > error_log_errors_per_period) {
        if(!prevented) {
            char date[LOG_DATE_LENGTH];
            log_date(date, LOG_DATE_LENGTH);
            fprintf(
                stderr,
                "%s: %s LOG FLOOD PROTECTION too many logs (%lu logs in %"PRId64" seconds, threshold is set to %lu logs "
                "in %"PRId64" seconds). Preventing more logs from process '%s' for %"PRId64" seconds.\n",
                date,
                program_name,
                counter,
                (int64_t)(now - start),
                error_log_errors_per_period,
                (int64_t)error_log_throttle_period,
                program_name,
                (int64_t)(start + error_log_throttle_period - now));
        }

        prevented++;

        // prevent logging this error
#ifdef NETDATA_INTERNAL_CHECKS
        return 0;
#else
        return 1;
#endif
    }

    return 0;
}

// ----------------------------------------------------------------------------
// debug log

void debug_int( const char *file, const char *function, const unsigned long line, const char *fmt, ... ) {
    va_list args;

    char date[LOG_DATE_LENGTH];
    log_date(date, LOG_DATE_LENGTH);

    va_start( args, fmt );
    printf("%s: %s DEBUG : %s : (%04lu@%-10.10s:%-15.15s): ", date, program_name, netdata_thread_tag(), line, file, function);
    vprintf(fmt, args);
    va_end( args );
    putchar('\n');

    if(output_log_syslog) {
        va_start( args, fmt );
        vsyslog(LOG_ERR,  fmt, args );
        va_end( args );
    }

    fflush(stdout);
}

// ----------------------------------------------------------------------------
// info log

void info_int( const char *file, const char *function, const unsigned long line, const char *fmt, ... )
{
    va_list args;

    // prevent logging too much
    if(error_log_limit(0)) return;

    if(error_log_syslog) {
        va_start( args, fmt );
        vsyslog(LOG_INFO,  fmt, args );
        va_end( args );
    }

    char date[LOG_DATE_LENGTH];
    log_date(date, LOG_DATE_LENGTH);

    log_lock();

    va_start( args, fmt );
    if(debug_flags) fprintf(stderr, "%s: %s INFO  : %s : (%04lu@%-10.10s:%-15.15s): ", date, program_name, netdata_thread_tag(), line, file, function);
    else            fprintf(stderr, "%s: %s INFO  : %s : ", date, program_name, netdata_thread_tag());
    vfprintf( stderr, fmt, args );
    va_end( args );

    fputc('\n', stderr);

    log_unlock();
}

// ----------------------------------------------------------------------------
// error log

#if defined(STRERROR_R_CHAR_P)
// GLIBC version of strerror_r
static const char *strerror_result(const char *a, const char *b) { (void)b; return a; }
#elif defined(HAVE_STRERROR_R)
// POSIX version of strerror_r
static const char *strerror_result(int a, const char *b) { (void)a; return b; }
#elif defined(HAVE_C__GENERIC)

// what a trick!
// http://stackoverflow.com/questions/479207/function-overloading-in-c
static const char *strerror_result_int(int a, const char *b) { (void)a; return b; }
static const char *strerror_result_string(const char *a, const char *b) { (void)b; return a; }

#define strerror_result(a, b) _Generic((a), \
    int: strerror_result_int, \
    char *: strerror_result_string \
    )(a, b)

#else
#error "cannot detect the format of function strerror_r()"
#endif

void error_int( const char *prefix, const char *file, const char *function, const unsigned long line, const char *fmt, ... ) {
    // save a copy of errno - just in case this function generates a new error
    int __errno = errno;

    va_list args;

    // prevent logging too much
    if(error_log_limit(0)) return;

    if(error_log_syslog) {
        va_start( args, fmt );
        vsyslog(LOG_ERR,  fmt, args );
        va_end( args );
    }

    char date[LOG_DATE_LENGTH];
    log_date(date, LOG_DATE_LENGTH);

    log_lock();

    va_start( args, fmt );
    if(debug_flags) fprintf(stderr, "%s: %s %-5.5s : %s : (%04lu@%-10.10s:%-15.15s): ", date, program_name, prefix, netdata_thread_tag(), line, file, function);
    else            fprintf(stderr, "%s: %s %-5.5s : %s : ", date, program_name, prefix, netdata_thread_tag());
    vfprintf( stderr, fmt, args );
    va_end( args );

    if(__errno) {
        char buf[1024];
        fprintf(stderr, " (errno %d, %s)\n", __errno, strerror_result(strerror_r(__errno, buf, 1023), buf));
        errno = 0;
    }
    else
        fputc('\n', stderr);

    log_unlock();
}

void fatal_int( const char *file, const char *function, const unsigned long line, const char *fmt, ... ) {
    // save a copy of errno - just in case this function generates a new error
    int __errno = errno;
    va_list args;
    const char *thread_tag;
    char os_threadname[NETDATA_THREAD_NAME_MAX + 1];

    if(error_log_syslog) {
        va_start( args, fmt );
        vsyslog(LOG_CRIT,  fmt, args );
        va_end( args );
    }

    thread_tag = netdata_thread_tag();
    if (!netdata_thread_tag_exists()) {
        os_thread_get_current_name_np(os_threadname);
        if ('\0' != os_threadname[0]) { /* If it is not an empty string replace "MAIN" thread_tag */
            thread_tag = os_threadname;
        }
    }

    char date[LOG_DATE_LENGTH];
    log_date(date, LOG_DATE_LENGTH);

    log_lock();

    va_start( args, fmt );
    if(debug_flags) fprintf(stderr, "%s: %s FATAL : %s : (%04lu@%-10.10s:%-15.15s): ", date, program_name, thread_tag, line, file, function);
    else            fprintf(stderr, "%s: %s FATAL : %s : ", date, program_name, thread_tag);
    vfprintf( stderr, fmt, args );
    va_end( args );

    perror(" # ");
    fputc('\n', stderr);

    log_unlock();

    char action_data[70+1];
    snprintfz(action_data, 70, "%04lu@%-10.10s:%-15.15s/%d", line, file, function, __errno);
    char action_result[60+1];

    snprintfz(action_result, 60, "%s:%s", program_name, strncmp(thread_tag, "STREAM_RECEIVER", strlen("STREAM_RECEIVER")) ? thread_tag : "[x]");
    send_statistics("FATAL", action_result, action_data);

    netdata_cleanup_and_exit(1);
}

// ----------------------------------------------------------------------------
// access log

void log_access( const char *fmt, ... ) {
    va_list args;

    if(access_log_syslog) {
        va_start( args, fmt );
        vsyslog(LOG_INFO,  fmt, args );
        va_end( args );
    }

    if(stdaccess) {
        static netdata_mutex_t access_mutex = NETDATA_MUTEX_INITIALIZER;

        if(web_server_is_multithreaded)
            netdata_mutex_lock(&access_mutex);

        char date[LOG_DATE_LENGTH];
        log_date(date, LOG_DATE_LENGTH);
        fprintf(stdaccess, "%s: ", date);

        va_start( args, fmt );
        vfprintf( stdaccess, fmt, args );
        va_end( args );
        fputc('\n', stdaccess);

        if(web_server_is_multithreaded)
            netdata_mutex_unlock(&access_mutex);
    }
}