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Simplify reasoning around disappearing messages

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1. Max duration between runs is now a separate timer we set up once and
   don't touch, so we can separate any potential bugs in scheduling logic.
2. When we want to "run now" we just run now, rather than going through
   the scheduler.
3. Detect if messages aren't being deleted in a timely way.

// FREEBIE
pull/1/head
Michael Kirk 7 years ago
parent 57ae2b173f
commit b7625689cb
1 changed files with 94 additions and 61 deletions
Show Stats Download Patch File Download Diff File

155
SignalServiceKit/src/Messages/OWSDisappearingMessagesJob.m
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@ -17,6 +17,7 @@
#import "TSMessage.h"
NS_ASSUME_NONNULL_BEGIN
// Can we move to Signal-iOS?
@interface OWSDisappearingMessagesJob ()
@ -24,13 +25,25 @@ NS_ASSUME_NONNULL_BEGIN
@property (nonatomic, readonly) OWSDisappearingMessagesFinder *disappearingMessagesFinder;
+ (dispatch_queue_t)serialQueue;
// These three properties should only be accessed on the main thread.
@property (nonatomic) BOOL hasStarted;
@property (nonatomic, nullable) NSTimer *timer;
@property (nonatomic, nullable) NSDate *timerScheduleDate;
@property (nonatomic, nullable) NSTimer *nextDisappearanceTimer;
@property (nonatomic, nullable) NSDate *nextDisappearanceDate;
@property (nonatomic, nullable) NSTimer *fallbackTimer;
@end
void AssertIsOnDisappearingMessagesQueue()
{
#ifdef DEBUG
if (@available(iOS 10.0, *)) {
dispatch_assert_queue(OWSDisappearingMessagesJob.serialQueue);
}
#endif
}
#pragma mark -
@implementation OWSDisappearingMessagesJob
@ -55,6 +68,18 @@ NS_ASSUME_NONNULL_BEGIN
_databaseConnection = primaryStorage.newDatabaseConnection;
_disappearingMessagesFinder = [OWSDisappearingMessagesFinder new];
// suspenders in case a deletion schedule is missed.
NSTimeInterval kFallBackTimerInterval = 5 * kMinuteInterval;
[AppReadiness runNowOrWhenAppIsReady:^{
if (CurrentAppContext().isMainApp) {
self->_fallbackTimer = [NSTimer weakScheduledTimerWithTimeInterval:kFallBackTimerInterval
target:self
selector:@selector(fallbackTimerDidFire)
userInfo:nil
repeats:YES];
}
}];
OWSSingletonAssert();
[[NSNotificationCenter defaultCenter] addObserver:self
@ -84,14 +109,15 @@ NS_ASSUME_NONNULL_BEGIN
return queue;
}
// This method should only be called on the serialQueue.
- (void)run
- (NSUInteger)deleteExpiredMessages
{
AssertIsOnDisappearingMessagesQueue();
uint64_t now = [NSDate ows_millisecondTimeStamp];
OWSBackgroundTask *_Nullable backgroundTask = [OWSBackgroundTask backgroundTaskWithLabelStr:__PRETTY_FUNCTION__];
__block uint expirationCount = 0;
__block NSUInteger expirationCount = 0;
[self.databaseConnection readWriteWithBlock:^(YapDatabaseReadWriteTransaction *_Nonnull transaction) {
[self.disappearingMessagesFinder enumerateExpiredMessagesWithBlock:^(TSMessage *message) {
// sanity check
@ -108,34 +134,36 @@ NS_ASSUME_NONNULL_BEGIN
transaction:transaction];
}];
DDLogDebug(@"%@ Removed %u expired messages", self.logTag, expirationCount);
DDLogDebug(@"%@ Removed %tu expired messages", self.logTag, expirationCount);
backgroundTask = nil;
return expirationCount;
}
// This method should only be called on the serialQueue.
- (void)runLoop
// deletes any expired messages and schedules the next run.
- (NSUInteger)runLoop
{
DDLogVerbose(@"%@ Run", self.logTag);
DDLogVerbose(@"%@ in runLoop", self.logTag);
AssertIsOnDisappearingMessagesQueue();
[self run];
NSUInteger deletedCount = [self deleteExpiredMessages];
uint64_t now = [NSDate ows_millisecondTimeStamp];
__block NSNumber *nextExpirationTimestampNumber;
[self.databaseConnection readWithBlock:^(YapDatabaseReadTransaction *_Nonnull transaction) {
nextExpirationTimestampNumber =
[self.disappearingMessagesFinder nextExpirationTimestampWithTransaction:transaction];
}];
if (!nextExpirationTimestampNumber) {
// In theory we could kill the loop here. It should resume when the next expiring message is saved,
// But this is a safeguard for any race conditions that exist while running the job as a new message is saved.
DDLogDebug(@"%@ No more expiring messages.", self.logTag);
[self scheduleRunLater];
return;
return deletedCount;
}
uint64_t nextExpirationAt = [nextExpirationTimestampNumber unsignedLongLongValue];
[self scheduleRunByDate:[NSDate ows_dateWithMillisecondsSince1970:MAX(nextExpirationAt, now)]];
uint64_t nextExpirationAt = nextExpirationTimestampNumber.unsignedLongLongValue;
NSDate *nextEpirationDate = [NSDate ows_dateWithMillisecondsSince1970:nextExpirationAt];
[self scheduleRunByDate:nextEpirationDate];
return deletedCount;
}
+ (void)setExpirationForMessage:(TSMessage *)message
@ -304,32 +332,12 @@ NS_ASSUME_NONNULL_BEGIN
}
self.hasStarted = YES;
[self scheduleRunNow];
dispatch_async(OWSDisappearingMessagesJob.serialQueue, ^{
[self runLoop];
});
});
}
- (void)scheduleRunNow
{
[self scheduleRunByDate:[NSDate new] ignoreMinDelay:YES];
}
- (NSTimeInterval)maxDelaySeconds
{
// Don't run less often than once per N minutes.
return 5 * kMinuteInterval;
}
// Waits the maximum amount of time to run again.
- (void)scheduleRunLater
{
[self scheduleRunByDate:[NSDate dateWithTimeIntervalSinceNow:self.maxDelaySeconds] ignoreMinDelay:YES];
}
- (void)scheduleRunByDate:(NSDate *)date
{
[self scheduleRunByDate:date ignoreMinDelay:NO];
}
- (NSDateFormatter *)dateFormatter
{
static NSDateFormatter *dateFormatter;
@ -344,7 +352,7 @@ NS_ASSUME_NONNULL_BEGIN
return dateFormatter;
}
- (void)scheduleRunByDate:(NSDate *)date ignoreMinDelay:(BOOL)ignoreMinDelay
- (void)scheduleRunByDate:(NSDate *)date
{
OWSAssert(date);
@ -355,16 +363,16 @@ NS_ASSUME_NONNULL_BEGIN
}
// Don't run more often than once per second.
const NSTimeInterval kMinDelaySeconds = ignoreMinDelay ? 0.f : 1.f;
NSTimeInterval delaySeconds = MAX(kMinDelaySeconds, MIN(self.maxDelaySeconds, date.timeIntervalSinceNow));
const NSTimeInterval kMinDelaySeconds = 1.0;
NSTimeInterval delaySeconds = MAX(kMinDelaySeconds, date.timeIntervalSinceNow);
NSDate *newTimerScheduleDate = [NSDate dateWithTimeIntervalSinceNow:delaySeconds];
if (self.timerScheduleDate && [self.timerScheduleDate isBeforeDate:newTimerScheduleDate]) {
if (self.nextDisappearanceDate && [self.nextDisappearanceDate isBeforeDate:newTimerScheduleDate]) {
DDLogVerbose(@"%@ Request to run at %@ (%d sec.) ignored due to earlier scheduled run at %@ (%d sec.)",
self.logTag,
[self.dateFormatter stringFromDate:date],
(int)round(MAX(0, [date timeIntervalSinceDate:[NSDate new]])),
[self.dateFormatter stringFromDate:self.timerScheduleDate],
(int)round(MAX(0, [self.timerScheduleDate timeIntervalSinceDate:[NSDate new]])));
[self.dateFormatter stringFromDate:self.nextDisappearanceDate],
(int)round(MAX(0, [self.nextDisappearanceDate timeIntervalSinceDate:[NSDate new]])));
return;
}
@ -373,17 +381,17 @@ NS_ASSUME_NONNULL_BEGIN
self.logTag,
[self.dateFormatter stringFromDate:newTimerScheduleDate],
(int)round(MAX(0, [newTimerScheduleDate timeIntervalSinceDate:[NSDate new]])));
[self resetTimer];
self.timerScheduleDate = newTimerScheduleDate;
self.timer = [NSTimer weakScheduledTimerWithTimeInterval:delaySeconds
target:self
selector:@selector(timerDidFire)
userInfo:nil
repeats:NO];
[self resetNextDisappearanceTimer];
self.nextDisappearanceDate = newTimerScheduleDate;
self.nextDisappearanceTimer = [NSTimer weakScheduledTimerWithTimeInterval:delaySeconds
target:self
selector:@selector(disappearanceTimerDidFire)
userInfo:nil
repeats:NO];
});
}
- (void)timerDidFire
- (void)disappearanceTimerDidFire
{
OWSAssertIsOnMainThread();
DDLogDebug(@"%@ in %s", self.logTag, __PRETTY_FUNCTION__);
@ -394,20 +402,43 @@ NS_ASSUME_NONNULL_BEGIN
return;
}
[self resetTimer];
[self resetNextDisappearanceTimer];
dispatch_async(OWSDisappearingMessagesJob.serialQueue, ^{
[self runLoop];
});
}
- (void)resetTimer
- (void)fallbackTimerDidFire
{
OWSAssertIsOnMainThread();
DDLogDebug(@"%@ in %s", self.logTag, __PRETTY_FUNCTION__);
BOOL recentlyScheduledDisappearanceTimer = NO;
if (fabs(self.nextDisappearanceDate.timeIntervalSinceNow) < 1.0) {
recentlyScheduledDisappearanceTimer = YES;
}
dispatch_async(OWSDisappearingMessagesJob.serialQueue, ^{
NSUInteger deletedCount = [self runLoop];
// Normally deletions should happen via the disappearanceTimer, to make sure that they're timely.
// So, if we're deleting something via the fallback timer, something may have gone wrong. The
// exception is if we're in close proximity to the disappearanceTimer, in which case a race condition
// is inevitable.
if (!recentlyScheduledDisappearanceTimer && deletedCount > 0) {
OWSProdLogAndFail(@"%@ unexpectedly deleted disappearing messages via fallback timer.");
}
});
}
- (void)resetNextDisappearanceTimer
{
OWSAssertIsOnMainThread();
[self.timer invalidate];
self.timer = nil;
self.timerScheduleDate = nil;
[self.nextDisappearanceTimer invalidate];
self.nextDisappearanceTimer = nil;
self.nextDisappearanceDate = nil;
}
#pragma mark - Notifications
@ -417,7 +448,9 @@ NS_ASSUME_NONNULL_BEGIN
OWSAssertIsOnMainThread();
[AppReadiness runNowOrWhenAppIsReady:^{
[self scheduleRunNow];
dispatch_async(OWSDisappearingMessagesJob.serialQueue, ^{
[self runLoop];
});
}];
}
@ -425,7 +458,7 @@ NS_ASSUME_NONNULL_BEGIN
{
OWSAssertIsOnMainThread();
[self resetTimer];
[self resetNextDisappearanceTimer];
}
@end

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