Analytics/SFAnalytics.m

   1 /*
   2  * Copyright (c) 2017 Apple Inc. All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24 #if __OBJC2__
  25
  26 #import "SFAnalytics+Internal.h"
  27 #import "SFAnalyticsDefines.h"
  28 #import "SFAnalyticsActivityTracker+Internal.h"
  29 #import "SFAnalyticsSampler+Internal.h"
  30 #import "SFAnalyticsMultiSampler+Internal.h"
  31 #import "SFAnalyticsSQLiteStore.h"
  32 #import "utilities/debugging.h"
  33 #import <utilities/SecFileLocations.h>
  34 #import <objc/runtime.h>
  35 #import <sys/stat.h>
  36 #import <CoreFoundation/CFPriv.h>
  37
  38 // SFAnalyticsDefines constants
  39 NSString* const SFAnalyticsTableSuccessCount = @"success_count";
  40 NSString* const SFAnalyticsTableHardFailures = @"hard_failures";
  41 NSString* const SFAnalyticsTableSoftFailures = @"soft_failures";
  42 NSString* const SFAnalyticsTableSamples = @"samples";
  43 NSString* const SFAnalyticsTableAllEvents = @"all_events";
  44
  45 NSString* const SFAnalyticsColumnSuccessCount = @"success_count";
  46 NSString* const SFAnalyticsColumnHardFailureCount = @"hard_failure_count";
  47 NSString* const SFAnalyticsColumnSoftFailureCount = @"soft_failure_count";
  48 NSString* const SFAnalyticsColumnSampleValue = @"value";
  49 NSString* const SFAnalyticsColumnSampleName = @"name";
  50
  51 NSString* const SFAnalyticsEventTime = @"eventTime";
  52 NSString* const SFAnalyticsEventType = @"eventType";
  53 NSString* const SFAnalyticsEventClassKey = @"eventClass";
  54
  55 NSString* const SFAnalyticsAttributeErrorUnderlyingChain = @"errorChain";
  56 NSString* const SFAnalyticsAttributeErrorDomain = @"errorDomain";
  57 NSString* const SFAnalyticsAttributeErrorCode = @"errorCode";
  58
  59 NSString* const SFAnalyticsUserDefaultsSuite = @"com.apple.security.analytics";
  60
  61 char* const SFAnalyticsFireSamplersNotification = "com.apple.security.sfanalytics.samplers";
  62
  63 NSString* const SFAnalyticsTopicKeySync = @"KeySyncTopic";
  64 NSString* const SFAnaltyicsTopicTrust = @"TrustTopic";
  65
  66 NSString* const SFAnalyticsTableSchema =    @"CREATE TABLE IF NOT EXISTS hard_failures (\n"
  67                                                 @"id INTEGER PRIMARY KEY AUTOINCREMENT,\n"
  68                                                 @"timestamp REAL,"
  69                                                 @"data BLOB\n"
  70                                             @");\n"
  71                                             @"CREATE TRIGGER IF NOT EXISTS maintain_ring_buffer_hard_failures AFTER INSERT ON hard_failures\n"
  72                                             @"BEGIN\n"
  73                                                 @"DELETE FROM hard_failures WHERE id != NEW.id AND id % 1000 = NEW.id % 1000;\n"
  74                                             @"END;\n"
  75                                             @"CREATE TABLE IF NOT EXISTS soft_failures (\n"
  76                                                 @"id INTEGER PRIMARY KEY AUTOINCREMENT,\n"
  77                                                 @"timestamp REAL,"
  78                                                 @"data BLOB\n"
  79                                             @");\n"
  80                                             @"CREATE TRIGGER IF NOT EXISTS maintain_ring_buffer_soft_failures AFTER INSERT ON soft_failures\n"
  81                                             @"BEGIN\n"
  82                                                 @"DELETE FROM soft_failures WHERE id != NEW.id AND id % 1000 = NEW.id % 1000;\n"
  83                                             @"END;\n"
  84                                             @"CREATE TABLE IF NOT EXISTS all_events (\n"
  85                                                 @"id INTEGER PRIMARY KEY AUTOINCREMENT,\n"
  86                                                 @"timestamp REAL,"
  87                                                 @"data BLOB\n"
  88                                             @");\n"
  89                                             @"CREATE TRIGGER IF NOT EXISTS maintain_ring_buffer_all_events AFTER INSERT ON all_events\n"
  90                                             @"BEGIN\n"
  91                                                 @"DELETE FROM all_events WHERE id != NEW.id AND id % 10000 = NEW.id % 10000;\n"
  92                                             @"END;\n"
  93                                             @"CREATE TABLE IF NOT EXISTS samples (\n"
  94                                                 @"id INTEGER PRIMARY KEY AUTOINCREMENT,\n"
  95                                                 @"timestamp REAL,\n"
  96                                                 @"name STRING,\n"
  97                                                 @"value REAL\n"
  98                                             @");\n"
  99                                             @"CREATE TRIGGER IF NOT EXISTS maintain_ring_buffer_samples AFTER INSERT ON samples\n"
 100                                             @"BEGIN\n"
 101                                             @"DELETE FROM samples WHERE id != NEW.id AND id % 1000 = NEW.id % 1000;\n"
 102                                             @"END;\n"
 103                                             @"CREATE TABLE IF NOT EXISTS success_count (\n"
 104                                                 @"event_type STRING PRIMARY KEY,\n"
 105                                                 @"success_count INTEGER,\n"
 106                                                 @"hard_failure_count INTEGER,\n"
 107                                                 @"soft_failure_count INTEGER\n"
 108                                             @");\n";
 109
 110 NSUInteger const SFAnalyticsMaxEventsToReport = 1000;
 111
 112 NSString* const SFAnalyticsErrorDomain = @"com.apple.security.sfanalytics";
 113
 114 // Local constants
 115 NSString* const SFAnalyticsEventBuild = @"build";
 116 NSString* const SFAnalyticsEventProduct = @"product";
 117 const NSTimeInterval SFAnalyticsSamplerIntervalOncePerReport = -1.0;
 118
 119 @interface SFAnalytics ()
 120 @property (nonatomic) SFAnalyticsSQLiteStore* database;
 121 @property (nonatomic) dispatch_queue_t queue;
 122 @end
 123
 124 @implementation SFAnalytics {
 125     SFAnalyticsSQLiteStore* _database;
 126     dispatch_queue_t _queue;
 127     NSMutableDictionary<NSString*, SFAnalyticsSampler*>* _samplers;
 128     NSMutableDictionary<NSString*, SFAnalyticsMultiSampler*>* _multisamplers;
 129     unsigned int _disableLogging:1;
 130 }
 131
 132 + (instancetype)logger
 133 {
 134 #if TARGET_OS_SIMULATOR
 135     return nil;
 136 #else
 137
 138     if (self == [SFAnalytics class]) {
 139         secerror("attempt to instatiate abstract class SFAnalytics");
 140         return nil;
 141     }
 142
 143     SFAnalytics* logger = nil;
 144     @synchronized(self) {
 145         logger = objc_getAssociatedObject(self, "SFAnalyticsInstance");
 146         if (!logger) {
 147             logger = [[self alloc] init];
 148             objc_setAssociatedObject(self, "SFAnalyticsInstance", logger, OBJC_ASSOCIATION_RETAIN);
 149         }
 150     }
 151
 152     [logger database];  // For unit testing so there's always a database. DB shouldn't be nilled in production though
 153     return logger;
 154 #endif
 155 }
 156
 157 + (NSString*)databasePath
 158 {
 159     return nil;
 160 }
 161
 162 + (NSString *)defaultAnalyticsDatabasePath:(NSString *)basename
 163 {
 164     WithPathInKeychainDirectory(CFSTR("Analytics"), ^(const char *path) {
 165 #if TARGET_OS_IPHONE
 166         mode_t permissions = 0775;
 167 #else
 168         mode_t permissions = 0700;
 169 #endif // TARGET_OS_IPHONE
 170         int ret = mkpath_np(path, permissions);
 171         if (!(ret == 0 || ret ==  EEXIST)) {
 172             secerror("could not create path: %s (%s)", path, strerror(ret));
 173         }
 174         chmod(path, permissions);
 175     });
 176     NSString *path = [NSString stringWithFormat:@"Analytics/%@.db", basename];
 177     return [(__bridge_transfer NSURL*)SecCopyURLForFileInKeychainDirectory((__bridge CFStringRef)path) path];
 178 }
 179
 180 + (NSInteger)fuzzyDaysSinceDate:(NSDate*)date
 181 {
 182     // Sentinel: it didn't happen at all
 183     if (!date) {
 184         return -1;
 185     }
 186
 187     // Sentinel: it happened but we don't know when because the date doesn't make sense
 188     // Magic number represents January 1, 2017.
 189     if ([date compare:[NSDate dateWithTimeIntervalSince1970:1483228800]] == NSOrderedAscending) {
 190         return 1000;
 191     }
 192
 193     NSInteger secondsPerDay = 60 * 60 * 24;
 194
 195     NSTimeInterval timeIntervalSinceDate = [[NSDate date] timeIntervalSinceDate:date];
 196     if (timeIntervalSinceDate < secondsPerDay) {
 197         return 0;
 198     }
 199     else if (timeIntervalSinceDate < (secondsPerDay * 7)) {
 200         return 1;
 201     }
 202     else if (timeIntervalSinceDate < (secondsPerDay * 30)) {
 203         return 7;
 204     }
 205     else if (timeIntervalSinceDate < (secondsPerDay * 365)) {
 206         return 30;
 207     }
 208     else {
 209         return 365;
 210     }
 211 }
 212
 213 // Instantiate lazily so unit tests can have clean databases each
 214 - (SFAnalyticsSQLiteStore*)database
 215 {
 216     if (!_database) {
 217         _database = [SFAnalyticsSQLiteStore storeWithPath:self.class.databasePath schema:SFAnalyticsTableSchema];
 218         if (!_database) {
 219             seccritical("Did not get a database! (Client %@)", NSStringFromClass([self class]));
 220         }
 221     }
 222     return _database;
 223 }
 224
 225 - (void)removeState
 226 {
 227     [_samplers removeAllObjects];
 228     [_multisamplers removeAllObjects];
 229
 230     __weak __typeof(self) weakSelf = self;
 231     dispatch_sync(_queue, ^{
 232         __strong __typeof(self) strongSelf = weakSelf;
 233         if (strongSelf) {
 234             [strongSelf.database close];
 235             strongSelf->_database = nil;
 236         }
 237     });
 238 }
 239
 240 - (void)setDateProperty:(NSDate*)date forKey:(NSString*)key
 241 {
 242     __weak __typeof(self) weakSelf = self;
 243     dispatch_sync(_queue, ^{
 244         __strong __typeof(self) strongSelf = weakSelf;
 245         if (strongSelf) {
 246             [strongSelf.database setDateProperty:date forKey:key];
 247         }
 248     });
 249 }
 250
 251 - (NSDate*)datePropertyForKey:(NSString*)key
 252 {
 253     __block NSDate* result = nil;
 254     __weak __typeof(self) weakSelf = self;
 255     dispatch_sync(_queue, ^{
 256         __strong __typeof(self) strongSelf = weakSelf;
 257         if (strongSelf) {
 258             result = [strongSelf.database datePropertyForKey:key];
 259         }
 260     });
 261     return result;
 262 }
 263
 264 + (void)addOSVersionToEvent:(NSMutableDictionary*)eventDict {
 265     static dispatch_once_t onceToken;
 266     static NSString *build = NULL;
 267     static NSString *product = NULL;
 268     dispatch_once(&onceToken, ^{
 269         NSDictionary *version = CFBridgingRelease(_CFCopySystemVersionDictionary());
 270         if (version == NULL)
 271             return;
 272         build = version[(__bridge NSString *)_kCFSystemVersionBuildVersionKey];
 273         product = version[(__bridge NSString *)_kCFSystemVersionProductNameKey];
 274     });
 275     if (build) {
 276         eventDict[SFAnalyticsEventBuild] = build;
 277     }
 278     if (product) {
 279         eventDict[SFAnalyticsEventProduct] = product;
 280     }
 281 }
 282
 283 - (instancetype)init
 284 {
 285     if (self = [super init]) {
 286         _queue = dispatch_queue_create("SFAnalytics data access queue", DISPATCH_QUEUE_SERIAL_WITH_AUTORELEASE_POOL);
 287         _samplers = [NSMutableDictionary<NSString*, SFAnalyticsSampler*> new];
 288         _multisamplers = [NSMutableDictionary<NSString*, SFAnalyticsMultiSampler*> new];
 289         [self database];    // for side effect of instantiating DB object. Used for testing.
 290     }
 291
 292     return self;
 293 }
 294
 295 // MARK: Event logging
 296
 297 - (void)logSuccessForEventNamed:(NSString*)eventName
 298 {
 299     [self logEventNamed:eventName class:SFAnalyticsEventClassSuccess attributes:nil];
 300 }
 301
 302 - (void)logHardFailureForEventNamed:(NSString*)eventName withAttributes:(NSDictionary*)attributes
 303 {
 304     [self logEventNamed:eventName class:SFAnalyticsEventClassHardFailure attributes:attributes];
 305 }
 306
 307 - (void)logSoftFailureForEventNamed:(NSString*)eventName withAttributes:(NSDictionary*)attributes
 308 {
 309     [self logEventNamed:eventName class:SFAnalyticsEventClassSoftFailure attributes:attributes];
 310 }
 311
 312 - (void)logResultForEvent:(NSString*)eventName hardFailure:(bool)hardFailure result:(NSError*)eventResultError
 313 {
 314     if(!eventResultError) {
 315         [self logSuccessForEventNamed:eventName];
 316     } else {
 317         // Make an Attributes dictionary
 318         NSMutableDictionary* eventAttributes = [NSMutableDictionary dictionary];
 319
 320         /* if we have underlying errors, capture the chain below the top-most error */
 321         NSError *underlyingError = eventResultError.userInfo[NSUnderlyingErrorKey];
 322         if ([underlyingError isKindOfClass:[NSError class]]) {
 323             NSMutableString *chain = [NSMutableString string];
 324             int count = 0;
 325             do {
 326                 [chain appendFormat:@"%@-%ld:", underlyingError.domain, (long)underlyingError.code];
 327                 underlyingError = underlyingError.userInfo[NSUnderlyingErrorKey];
 328             } while (count++ < 5 && [underlyingError isKindOfClass:[NSError class]]);
 329
 330             eventAttributes[SFAnalyticsAttributeErrorUnderlyingChain] = chain;
 331         }
 332
 333         eventAttributes[SFAnalyticsAttributeErrorDomain] = eventResultError.domain;
 334         eventAttributes[SFAnalyticsAttributeErrorCode] = @(eventResultError.code);
 335
 336         if(hardFailure) {
 337             [self logHardFailureForEventNamed:eventName withAttributes:eventAttributes];
 338         } else {
 339             [self logSoftFailureForEventNamed:eventName withAttributes:eventAttributes];
 340         }
 341     }
 342 }
 343
 344 - (void)noteEventNamed:(NSString*)eventName
 345 {
 346     [self logEventNamed:eventName class:SFAnalyticsEventClassNote attributes:nil];
 347 }
 348
 349 - (void)logEventNamed:(NSString*)eventName class:(SFAnalyticsEventClass)class attributes:(NSDictionary*)attributes
 350 {
 351     if (!eventName) {
 352         secerror("SFAnalytics: attempt to log an event with no name");
 353         return;
 354     }
 355
 356     __weak __typeof(self) weakSelf = self;
 357     dispatch_sync(_queue, ^{
 358         __strong __typeof(self) strongSelf = weakSelf;
 359         if (!strongSelf || strongSelf->_disableLogging) {
 360             return;
 361         }
 362
 363         NSDictionary* eventDict = [self eventDictForEventName:eventName withAttributes:attributes eventClass:class];
 364         [strongSelf.database addEventDict:eventDict toTable:SFAnalyticsTableAllEvents];
 365
 366         if (class == SFAnalyticsEventClassHardFailure) {
 367             [strongSelf.database addEventDict:eventDict toTable:SFAnalyticsTableHardFailures];
 368             [strongSelf.database incrementHardFailureCountForEventType:eventName];
 369         }
 370         else if (class == SFAnalyticsEventClassSoftFailure) {
 371             [strongSelf.database addEventDict:eventDict toTable:SFAnalyticsTableSoftFailures];
 372             [strongSelf.database incrementSoftFailureCountForEventType:eventName];
 373         }
 374         else if (class == SFAnalyticsEventClassSuccess || class == SFAnalyticsEventClassNote) {
 375             [strongSelf.database incrementSuccessCountForEventType:eventName];
 376         }
 377     });
 378 }
 379
 380 - (NSDictionary*)eventDictForEventName:(NSString*)eventName withAttributes:(NSDictionary*)attributes eventClass:(SFAnalyticsEventClass)eventClass
 381 {
 382     NSMutableDictionary* eventDict = attributes ? attributes.mutableCopy : [NSMutableDictionary dictionary];
 383     eventDict[SFAnalyticsEventType] = eventName;
 384     // our backend wants timestamps in milliseconds
 385     eventDict[SFAnalyticsEventTime] = @([[NSDate date] timeIntervalSince1970] * 1000);
 386     eventDict[SFAnalyticsEventClassKey] = @(eventClass);
 387     [SFAnalytics addOSVersionToEvent:eventDict];
 388
 389     return eventDict;
 390 }
 391
 392 // MARK: Sampling
 393
 394 - (SFAnalyticsSampler*)addMetricSamplerForName:(NSString *)samplerName withTimeInterval:(NSTimeInterval)timeInterval block:(NSNumber *(^)(void))block
 395 {
 396     if (!samplerName) {
 397         secerror("SFAnalytics: cannot add sampler without name");
 398         return nil;
 399     }
 400     if (timeInterval < 1.0f && timeInterval != SFAnalyticsSamplerIntervalOncePerReport) {
 401         secerror("SFAnalytics: cannot add sampler with interval %f", timeInterval);
 402         return nil;
 403     }
 404     if (!block) {
 405         secerror("SFAnalytics: cannot add sampler without block");
 406         return nil;
 407     }
 408
 409     __block SFAnalyticsSampler* sampler = nil;
 410
 411     __weak __typeof(self) weakSelf = self;
 412     dispatch_sync(_queue, ^{
 413         __strong __typeof(self) strongSelf = weakSelf;
 414         if (strongSelf->_samplers[samplerName]) {
 415             secerror("SFAnalytics: sampler \"%@\" already exists", samplerName);
 416         } else {
 417             sampler = [[SFAnalyticsSampler alloc] initWithName:samplerName interval:timeInterval block:block clientClass:[self class]];
 418             strongSelf->_samplers[samplerName] = sampler;   // If sampler did not init because of bad data this 'removes' it from the dict, so a noop
 419         }
 420     });
 421
 422     return sampler;
 423 }
 424
 425 - (SFAnalyticsMultiSampler*)AddMultiSamplerForName:(NSString *)samplerName withTimeInterval:(NSTimeInterval)timeInterval block:(NSDictionary<NSString *,NSNumber *> *(^)(void))block
 426 {
 427     if (!samplerName) {
 428         secerror("SFAnalytics: cannot add sampler without name");
 429         return nil;
 430     }
 431     if (timeInterval < 1.0f && timeInterval != SFAnalyticsSamplerIntervalOncePerReport) {
 432         secerror("SFAnalytics: cannot add sampler with interval %f", timeInterval);
 433         return nil;
 434     }
 435     if (!block) {
 436         secerror("SFAnalytics: cannot add sampler without block");
 437         return nil;
 438     }
 439
 440     __block SFAnalyticsMultiSampler* sampler = nil;
 441     __weak __typeof(self) weakSelf = self;
 442     dispatch_sync(_queue, ^{
 443         __strong __typeof(self) strongSelf = weakSelf;
 444         if (strongSelf->_multisamplers[samplerName]) {
 445             secerror("SFAnalytics: multisampler \"%@\" already exists", samplerName);
 446         } else {
 447             sampler = [[SFAnalyticsMultiSampler alloc] initWithName:samplerName interval:timeInterval block:block clientClass:[self class]];
 448             strongSelf->_multisamplers[samplerName] = sampler;
 449         }
 450
 451     });
 452
 453     return sampler;
 454 }
 455
 456 - (SFAnalyticsSampler*)existingMetricSamplerForName:(NSString *)samplerName
 457 {
 458     __block SFAnalyticsSampler* sampler = nil;
 459
 460     __weak __typeof(self) weakSelf = self;
 461     dispatch_sync(_queue, ^{
 462         __strong __typeof(self) strongSelf = weakSelf;
 463         if (strongSelf) {
 464             sampler = strongSelf->_samplers[samplerName];
 465         }
 466     });
 467     return sampler;
 468 }
 469
 470 - (SFAnalyticsMultiSampler*)existingMultiSamplerForName:(NSString *)samplerName
 471 {
 472     __block SFAnalyticsMultiSampler* sampler = nil;
 473
 474     __weak __typeof(self) weakSelf = self;
 475     dispatch_sync(_queue, ^{
 476         __strong __typeof(self) strongSelf = weakSelf;
 477         if (strongSelf) {
 478             sampler = strongSelf->_multisamplers[samplerName];
 479         }
 480     });
 481     return sampler;
 482 }
 483
 484 - (void)removeMetricSamplerForName:(NSString *)samplerName
 485 {
 486     if (!samplerName) {
 487         secerror("Attempt to remove sampler without specifying samplerName");
 488         return;
 489     }
 490
 491     __weak __typeof(self) weakSelf = self;
 492     dispatch_async(_queue, ^{
 493         __strong __typeof(self) strongSelf = weakSelf;
 494         if (strongSelf) {
 495             [strongSelf->_samplers[samplerName] pauseSampling];    // when dealloced it would also stop, but we're not sure when that is so let's stop it right away
 496             [strongSelf->_samplers removeObjectForKey:samplerName];
 497         }
 498     });
 499 }
 500
 501 - (void)removeMultiSamplerForName:(NSString *)samplerName
 502 {
 503     if (!samplerName) {
 504         secerror("Attempt to remove multisampler without specifying samplerName");
 505         return;
 506     }
 507
 508     __weak __typeof(self) weakSelf = self;
 509     dispatch_async(_queue, ^{
 510         __strong __typeof(self) strongSelf = weakSelf;
 511         if (strongSelf) {
 512             [strongSelf->_multisamplers[samplerName] pauseSampling];    // when dealloced it would also stop, but we're not sure when that is so let's stop it right away
 513             [strongSelf->_multisamplers removeObjectForKey:samplerName];
 514         }
 515     });
 516 }
 517
 518 - (SFAnalyticsActivityTracker*)logSystemMetricsForActivityNamed:(NSString *)eventName withAction:(void (^)(void))action
 519 {
 520     if (![eventName isKindOfClass:[NSString class]]) {
 521         secerror("Cannot log system metrics without name");
 522         return nil;
 523     }
 524     SFAnalyticsActivityTracker* tracker = [[SFAnalyticsActivityTracker alloc] initWithName:eventName clientClass:[self class]];
 525     if (action) {
 526         [tracker performAction:action];
 527     }
 528     return tracker;
 529 }
 530
 531 - (void)logMetric:(NSNumber *)metric withName:(NSString *)metricName
 532 {
 533     [self logMetric:metric withName:metricName oncePerReport:NO];
 534 }
 535
 536 - (void)logMetric:(NSNumber*)metric withName:(NSString*)metricName oncePerReport:(BOOL)once
 537 {
 538     if (![metric isKindOfClass:[NSNumber class]] || ![metricName isKindOfClass:[NSString class]]) {
 539         secerror("SFAnalytics: Need a valid result and name to log result");
 540         return;
 541     }
 542
 543     __weak __typeof(self) weakSelf = self;
 544     dispatch_async(_queue, ^{
 545         __strong __typeof(self) strongSelf = weakSelf;
 546         if (strongSelf && !strongSelf->_disableLogging) {
 547             if (once) {
 548                 [strongSelf.database removeAllSamplesForName:metricName];
 549             }
 550             [strongSelf.database addSample:metric forName:metricName];
 551         }
 552     });
 553 }
 554
 555 @end
 556
 557 #endif // __OBJC2__