Rework the “disappearing messages” logic.

// FREEBIE

src/Devices/OWSReadReceiptsProcessor.m

@@ -17,7 +17,6 @@ NSString *const OWSReadReceiptsProcessorMarkedMessageAsReadNotification =
 @interface OWSReadReceiptsProcessor ()
 
 @property (nonatomic, readonly) NSArray<OWSReadReceipt *> *readReceipts;
-@property (nonatomic, readonly) OWSDisappearingMessagesJob *disappearingMessagesJob;
 @property (nonatomic, readonly) TSStorageManager *storageManager;
 
 @end
@@ -34,7 +33,6 @@ NSString *const OWSReadReceiptsProcessorMarkedMessageAsReadNotification =
 
     _readReceipts = [readReceipts copy];
     _storageManager = storageManager;
-    _disappearingMessagesJob = [[OWSDisappearingMessagesJob alloc] initWithStorageManager:storageManager];
 
     return self;
 }
@@ -85,7 +83,7 @@ NSString *const OWSReadReceiptsProcessorMarkedMessageAsReadNotification =
             [TSIncomingMessage findMessageWithAuthorId:readReceipt.senderId timestamp:readReceipt.timestamp];
         if (message) {
             [message markAsReadFromReadReceipt];
-            [self.disappearingMessagesJob setExpirationForMessage:message expirationStartedAt:readReceipt.timestamp];
+            [OWSDisappearingMessagesJob setExpirationForMessage:message expirationStartedAt:readReceipt.timestamp];
             // If it was previously saved, no need to keep it around any longer.
             [readReceipt remove];
             [[NSNotificationCenter defaultCenter]

src/Devices/OWSRecordTranscriptJob.m

@@ -4,7 +4,6 @@
 
 #import "OWSRecordTranscriptJob.h"
 #import "OWSAttachmentsProcessor.h"
-#import "OWSDisappearingMessagesJob.h"
 #import "OWSIncomingSentMessageTranscript.h"
 #import "OWSMessageSender.h"
 #import "TSInfoMessage.h"

src/Messages/Interactions/TSMessage.m

@@ -4,7 +4,6 @@
 
 #import "TSMessage.h"
 #import "NSDate+millisecondTimeStamp.h"
-#import "OWSDisappearingMessagesJob.h"
 #import "TSAttachment.h"
 #import "TSAttachmentPointer.h"
 #import "TSThread.h"

src/Messages/OWSDisappearingMessagesJob.h

@@ -1,5 +1,6 @@
-//  Created by Michael Kirk on 9/23/16.
-//  Copyright © 2016 Open Whisper Systems. All rights reserved.
+//
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -10,15 +11,13 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface OWSDisappearingMessagesJob : NSObject
 
++ (instancetype)sharedJob;
+
 - (instancetype)init NS_UNAVAILABLE;
-- (instancetype)initWithStorageManager:(TSStorageManager *)storageManager NS_DESIGNATED_INITIALIZER;
-
-- (void)run;
-- (void)setExpirationsForThread:(TSThread *)thread;
-- (void)setExpirationForMessage:(TSMessage *)message;
-- (void)setExpirationForMessage:(TSMessage *)message expirationStartedAt:(uint64_t)expirationStartedAt;
-- (void)runBy:(uint64_t)millisecondTimestamp;
 
++ (void)setExpirationsForThread:(TSThread *)thread;
++ (void)setExpirationForMessage:(TSMessage *)message;
++ (void)setExpirationForMessage:(TSMessage *)message expirationStartedAt:(uint64_t)expirationStartedAt;
 
 /**
  * Synchronize our disappearing messages settings with that of the given message. Useful so we can
@@ -31,9 +30,13 @@ NS_ASSUME_NONNULL_BEGIN
  * @param contactsManager
  *   Provides the contact name responsible for any configuration changes in an info message.
  */
-- (void)becomeConsistentWithConfigurationForMessage:(TSMessage *)message
++ (void)becomeConsistentWithConfigurationForMessage:(TSMessage *)message
                                     contactsManager:(id<ContactsManagerProtocol>)contactsManager;
 
+// Clean up any messages that expired since last launch immediately
+// and continue cleaning in the background.
+- (void)startIfNecessary;
+
 @end
 
 NS_ASSUME_NONNULL_END

src/Messages/OWSDisappearingMessagesJob.m

@@ -1,26 +1,46 @@
-//  Created by Michael Kirk on 9/23/16.
-//  Copyright © 2016 Open Whisper Systems. All rights reserved.
+//
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//
 
 #import "OWSDisappearingMessagesJob.h"
 #import "ContactsManagerProtocol.h"
 #import "NSDate+millisecondTimeStamp.h"
+#import "NSTimer+OWS.h"
 #import "OWSDisappearingConfigurationUpdateInfoMessage.h"
 #import "OWSDisappearingMessagesConfiguration.h"
 #import "OWSDisappearingMessagesFinder.h"
 #import "TSIncomingMessage.h"
 #import "TSMessage.h"
+#import "TSStorageManager.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
 @interface OWSDisappearingMessagesJob ()
 
+// This property should only be accessed on the serialQueue.
 @property (nonatomic, readonly) OWSDisappearingMessagesFinder *disappearingMessagesFinder;
-@property (atomic) uint64_t scheduledAt;
+
+// 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;
 
 @end
 
+#pragma mark -
+
 @implementation OWSDisappearingMessagesJob
 
++ (instancetype)sharedJob
+{
+    static OWSDisappearingMessagesJob *sharedJob = nil;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        sharedJob = [[self alloc] initWithStorageManager:[TSStorageManager sharedManager]];
+    });
+    return sharedJob;
+}
+
 - (instancetype)initWithStorageManager:(TSStorageManager *)storageManager
 {
     self = [super init];
@@ -28,12 +48,23 @@ NS_ASSUME_NONNULL_BEGIN
         return self;
     }
 
-    _scheduledAt = ULLONG_MAX;
     _disappearingMessagesFinder = [[OWSDisappearingMessagesFinder alloc] initWithStorageManager:storageManager];
 
+    OWSSingletonAssert();
+
     return self;
 }
 
++ (dispatch_queue_t)serialQueue
+{
+    static dispatch_queue_t queue = nil;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        queue = dispatch_queue_create("org.whispersystems.disappearing.messages", DISPATCH_QUEUE_SERIAL);
+    });
+    return queue;
+}
+
 - (void)run
 {
     uint64_t now = [NSDate ows_millisecondTimeStamp];
@@ -46,18 +77,17 @@ NS_ASSUME_NONNULL_BEGIN
             return;
         }
 
-        DDLogDebug(@"%@ removing message which expired at: %lld", self.tag, message.expiresAt);
+        DDLogDebug(@"%@ Removing message which expired at: %lld", self.tag, message.expiresAt);
         [message remove];
         expirationCount++;
     }];
 
-    DDLogDebug(@"%@ removed %u expired messages", self.tag, expirationCount);
+    DDLogDebug(@"%@ Removed %u expired messages", self.tag, expirationCount);
 }
 
 - (void)runLoop
 {
-    // allow next runAt to schedule.
-    self.scheduledAt = ULLONG_MAX;
+    DDLogVerbose(@"%@ Run", self.tag);
 
     [self run];
 
@@ -69,23 +99,19 @@ NS_ASSUME_NONNULL_BEGIN
         unsigned int delaySeconds = (10 * 60); // 10 minutes.
         DDLogDebug(
             @"%@ No more expiring messages. Setting next check %u seconds into the future", self.tag, delaySeconds);
-        [self runBy:now + delaySeconds * 1000];
+        [self runByDate:[NSDate ows_dateWithMillisecondsSince1970:now + delaySeconds * 1000]];
         return;
     }
 
     uint64_t nextExpirationAt = [nextExpirationTimestampNumber unsignedLongLongValue];
-    uint64_t runByMilliseconds;
-    if (nextExpirationAt < now + 1000) {
-        DDLogWarn(@"%@ Next run requested at %llu, which is too soon. Delaying by 1 sec to prevent churn",
-            self.tag,
-            nextExpirationAt);
-        runByMilliseconds = now + 1000;
-    } else {
-        runByMilliseconds = nextExpirationAt;
-    }
+    [self runByDate:[NSDate ows_dateWithMillisecondsSince1970:MAX(nextExpirationAt, now)]];
+}
 
-    DDLogVerbose(@"%@ Requesting next expiration to run by: %llu", self.tag, nextExpirationAt);
-    [self runBy:runByMilliseconds];
++ (void)setExpirationForMessage:(TSMessage *)message
+{
+    dispatch_async(self.serialQueue, ^{
+        [[self sharedJob] setExpirationForMessage:message];
+    });
 }
 
 - (void)setExpirationForMessage:(TSMessage *)message
@@ -104,6 +130,13 @@ NS_ASSUME_NONNULL_BEGIN
     [self setExpirationForMessage:message expirationStartedAt:[NSDate ows_millisecondTimeStamp]];
 }
 
++ (void)setExpirationForMessage:(TSMessage *)message expirationStartedAt:(uint64_t)expirationStartedAt
+{
+    dispatch_async(self.serialQueue, ^{
+        [[self sharedJob] setExpirationForMessage:message expirationStartedAt:expirationStartedAt];
+    });
+}
+
 - (void)setExpirationForMessage:(TSMessage *)message expirationStartedAt:(uint64_t)expirationStartedAt
 {
     if (!message.isExpiringMessage) {
@@ -120,7 +153,14 @@ NS_ASSUME_NONNULL_BEGIN
     }
 
     // Necessary that the async expiration run happens *after* the message is saved with expiration configuration.
-    [self runBy:message.expiresAt];
+    [self runByDate:[NSDate ows_dateWithMillisecondsSince1970:message.expiresAt]];
+}
+
++ (void)setExpirationsForThread:(TSThread *)thread
+{
+    dispatch_async(self.serialQueue, ^{
+        [[self sharedJob] setExpirationsForThread:thread];
+    });
 }
 
 - (void)setExpirationsForThread:(TSThread *)thread
@@ -138,26 +178,14 @@ NS_ASSUME_NONNULL_BEGIN
                                              }];
 }
 
-- (void)runBy:(uint64_t)timestamp
++ (void)becomeConsistentWithConfigurationForMessage:(TSMessage *)message
+                                    contactsManager:(id<ContactsManagerProtocol>)contactsManager
 {
-    // Prevent amplification.
-    if (timestamp >= self.scheduledAt) {
-        DDLogVerbose(@"%@ expiration already scheduled before %llu", self.tag, timestamp);
-        return;
-    }
-
-    // Update Schedule
-    DDLogVerbose(@"%@ Scheduled expiration run at %llu", self.tag, timestamp);
-    self.scheduledAt = timestamp;
-    uint64_t millisecondsDelay = timestamp - [NSDate ows_millisecondTimeStamp];
-    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, NSEC_PER_MSEC * millisecondsDelay),
-        dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),
-        ^{
-            [self runLoop];
-        });
+    dispatch_async(self.serialQueue, ^{
+        [[self sharedJob] becomeConsistentWithConfigurationForMessage:message contactsManager:contactsManager];
+    });
 }
 
-
 - (void)becomeConsistentWithConfigurationForMessage:(TSMessage *)message
                                     contactsManager:(id<ContactsManagerProtocol>)contactsManager
 {
@@ -206,6 +234,83 @@ NS_ASSUME_NONNULL_BEGIN
     }
 }
 
+- (void)startIfNecessary
+{
+    dispatch_async(dispatch_get_main_queue(), ^{
+        if (self.hasStarted) {
+            return;
+        }
+        self.hasStarted = YES;
+
+        [self runNow];
+    });
+}
+
+- (void)runNow
+{
+    [self runByDate:[NSDate new] ignoreMinDelay:YES];
+}
+
+- (void)runByDate:(NSDate *)date
+{
+    [self runByDate:date ignoreMinDelay:NO];
+}
+
+- (void)runByDate:(NSDate *)date ignoreMinDelay:(BOOL)ignoreMinDelay
+{
+    OWSAssert(date);
+
+    NSDateFormatter *dateFormatter = [NSDateFormatter new];
+    dateFormatter.dateStyle = NSDateFormatterShortStyle;
+    dateFormatter.timeStyle = kCFDateFormatterMediumStyle;
+
+    dispatch_async(dispatch_get_main_queue(), ^{
+        // Don't run more often than once per second.
+        const NSTimeInterval kMinDelaySeconds = ignoreMinDelay ? 0.f : 1.f;
+        // Don't run less often than once per N minutes.
+        const NSTimeInterval kMaxDelaySeconds = 5 * 60.f;
+        NSTimeInterval delaySeconds
+            = MAX(kMinDelaySeconds, MIN(kMaxDelaySeconds, [date timeIntervalSinceDate:[NSDate new]]));
+        NSDate *timerScheduleDate = [NSDate dateWithTimeIntervalSinceNow:delaySeconds];
+        if (self.timerScheduleDate && [timerScheduleDate timeIntervalSinceDate:self.timerScheduleDate] > 0) {
+            DDLogVerbose(@"%@ Request to run at %@ (%d sec.) ignored due to scheduled run at %@ (%d sec.)",
+                self.tag,
+                [dateFormatter stringFromDate:date],
+                (int)round(MAX(0, [date timeIntervalSinceDate:[NSDate new]])),
+                [dateFormatter stringFromDate:self.timerScheduleDate],
+                (int)round(MAX(0, [self.timerScheduleDate timeIntervalSinceDate:[NSDate new]])));
+            return;
+        }
+
+        // Update Schedule
+        NSDateFormatter *dateFormatter = [NSDateFormatter new];
+        dateFormatter.dateStyle = NSDateFormatterShortStyle;
+        dateFormatter.timeStyle = kCFDateFormatterMediumStyle;
+        DDLogVerbose(@"%@ Scheduled run at %@ (%d sec.)",
+            self.tag,
+            [dateFormatter stringFromDate:timerScheduleDate],
+            (int)round(MAX(0, [timerScheduleDate timeIntervalSinceDate:[NSDate new]])));
+        self.timerScheduleDate = timerScheduleDate;
+        [self.timer invalidate];
+        self.timer = [NSTimer weakScheduledTimerWithTimeInterval:delaySeconds
+                                                          target:self
+                                                        selector:@selector(timerDidFire)
+                                                        userInfo:nil
+                                                         repeats:NO];
+    });
+}
+
+- (void)timerDidFire
+{
+    [self.timer invalidate];
+    self.timer = nil;
+    self.timerScheduleDate = nil;
+
+    dispatch_async(OWSDisappearingMessagesJob.serialQueue, ^{
+        [self runLoop];
+    });
+}
+
 #pragma mark - Logging
 
 + (NSString *)tag

src/Messages/OWSIncomingMessageReadObserver.m

@@ -1,5 +1,6 @@
-//  Created by Michael Kirk on 9/24/16.
-//  Copyright © 2016 Open Whisper Systems. All rights reserved.
+//
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//
 
 #import "OWSIncomingMessageReadObserver.h"
 #import "NSDate+millisecondTimeStamp.h"
@@ -13,7 +14,6 @@ NS_ASSUME_NONNULL_BEGIN
 @interface OWSIncomingMessageReadObserver ()
 
 @property BOOL isObserving;
-@property (nonatomic, readonly) OWSDisappearingMessagesJob *disappearingMessagesJob;
 @property (nonatomic, readonly) OWSSendReadReceiptsJob *sendReadReceiptsJob;
 
 @end
@@ -34,7 +34,6 @@ NS_ASSUME_NONNULL_BEGIN
     }
 
     _isObserving = NO;
-    _disappearingMessagesJob = [[OWSDisappearingMessagesJob alloc] initWithStorageManager:storageManager];
     _sendReadReceiptsJob = [[OWSSendReadReceiptsJob alloc] initWithMessageSender:messageSender];
 
     return self;
@@ -61,7 +60,7 @@ NS_ASSUME_NONNULL_BEGIN
     }
 
     TSIncomingMessage *message = (TSIncomingMessage *)notification.object;
-    [self.disappearingMessagesJob setExpirationForMessage:message];
+    [OWSDisappearingMessagesJob setExpirationForMessage:message];
     [self.sendReadReceiptsJob runWith:message];
 }
 

src/Messages/OWSMessageSender.m

@@ -341,7 +341,6 @@ NSString *const OWSMessageSenderRateLimitedException = @"RateLimitedException";
 @property (nonatomic, readonly) YapDatabaseConnection *dbConnection;
 @property (nonatomic, readonly) id<ContactsManagerProtocol> contactsManager;
 @property (nonatomic, readonly) ContactsUpdater *contactsUpdater;
-@property (nonatomic, readonly) OWSDisappearingMessagesJob *disappearingMessagesJob;
 @property (atomic, readonly) NSMutableDictionary<NSString *, NSOperationQueue *> *sendingQueueMap;
 
 @end
@@ -366,7 +365,6 @@ NSString *const OWSMessageSenderRateLimitedException = @"RateLimitedException";
 
     _uploadingService = [[OWSUploadingService alloc] initWithNetworkManager:networkManager];
     _dbConnection = storageManager.newDatabaseConnection;
-    _disappearingMessagesJob = [[OWSDisappearingMessagesJob alloc] initWithStorageManager:storageManager];
 
     OWSSingletonAssert();
 
@@ -1060,20 +1058,20 @@ NSString *const OWSMessageSenderRateLimitedException = @"RateLimitedException";
         [self sendSyncTranscriptForMessage:message];
     }
 
-    [self.disappearingMessagesJob setExpirationForMessage:message];
+    [OWSDisappearingMessagesJob setExpirationForMessage:message];
 }
 
 - (void)handleMessageSentRemotely:(TSOutgoingMessage *)message sentAt:(uint64_t)sentAt
 {
     [message updateWithWasSentAndDelivered];
     [self becomeConsistentWithDisappearingConfigurationForMessage:message];
-    [self.disappearingMessagesJob setExpirationForMessage:message expirationStartedAt:sentAt];
+    [OWSDisappearingMessagesJob setExpirationForMessage:message expirationStartedAt:sentAt];
 }
 
 - (void)becomeConsistentWithDisappearingConfigurationForMessage:(TSOutgoingMessage *)outgoingMessage
 {
-    [self.disappearingMessagesJob becomeConsistentWithConfigurationForMessage:outgoingMessage
-                                                              contactsManager:self.contactsManager];
+    [OWSDisappearingMessagesJob becomeConsistentWithConfigurationForMessage:outgoingMessage
+                                                            contactsManager:self.contactsManager];
 }
 
 - (void)handleSendToMyself:(TSOutgoingMessage *)outgoingMessage

src/Messages/TSMessagesManager.h

@@ -13,7 +13,6 @@ NS_ASSUME_NONNULL_BEGIN
 @class OWSSignalServiceProtosEnvelope;
 @class OWSSignalServiceProtosDataMessage;
 @class ContactsUpdater;
-@class OWSDisappearingMessagesJob;
 @class OWSMessageSender;
 @protocol ContactsManagerProtocol;
 @protocol OWSCallMessageHandler;

src/Messages/TSMessagesManager.m

@@ -48,12 +48,13 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, readonly) id<ContactsManagerProtocol> contactsManager;
 @property (nonatomic, readonly) TSStorageManager *storageManager;
 @property (nonatomic, readonly) OWSMessageSender *messageSender;
-@property (nonatomic, readonly) OWSDisappearingMessagesJob *disappearingMessagesJob;
 @property (nonatomic, readonly) OWSIncomingMessageFinder *incomingMessageFinder;
 @property (nonatomic, readonly) OWSBlockingManager *blockingManager;
 
 @end
 
+#pragma mark -
+
 @implementation TSMessagesManager
 
 + (instancetype)sharedManager {
@@ -103,7 +104,6 @@ NS_ASSUME_NONNULL_BEGIN
     _messageSender = messageSender;
 
     _dbConnection = storageManager.newDatabaseConnection;
-    _disappearingMessagesJob = [[OWSDisappearingMessagesJob alloc] initWithStorageManager:storageManager];
     _incomingMessageFinder = [[OWSIncomingMessageFinder alloc] initWithDatabase:storageManager.database];
     _blockingManager = [OWSBlockingManager sharedManager];
 
@@ -940,8 +940,8 @@ NS_ASSUME_NONNULL_BEGIN
                                                        storageManager:self.storageManager];
         [readReceiptsProcessor process];
 
-        [self.disappearingMessagesJob becomeConsistentWithConfigurationForMessage:incomingMessage
-                                                                  contactsManager:self.contactsManager];
+        [OWSDisappearingMessagesJob becomeConsistentWithConfigurationForMessage:incomingMessage
+                                                                contactsManager:self.contactsManager];
 
         // Update thread preview in inbox
         [thread touch];

src/Util/NSTimer+OWS.h

@@ -0,0 +1,19 @@
+//
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface NSTimer (OWS)
+
+// This method avoids the classic NSTimer retain cycle bug
+// by using a weak reference to the target.
++ (NSTimer *)weakScheduledTimerWithTimeInterval:(NSTimeInterval)timeInterval
+                                         target:(id)target
+                                       selector:(SEL)selector
+                                       userInfo:(nullable id)userInfo
+                                        repeats:(BOOL)repeats;
+
+@end
+
+NS_ASSUME_NONNULL_END

src/Util/NSTimer+OWS.m

@@ -0,0 +1,69 @@
+//
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//
+
+#import "NSTimer+OWS.h"
+#import <objc/runtime.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface NSTimerProxy : NSObject
+
+@property (nonatomic, weak) id target;
+@property (nonatomic) SEL selector;
+
+@end
+
+#pragma mark -
+
+@implementation NSTimerProxy
+
+- (void)timerFired:(NSDictionary *)userInfo
+{
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
+    [self.target performSelector:self.selector withObject:userInfo];
+#pragma clang diagnostic pop
+}
+
+@end
+
+#pragma mark -
+
+static void *kNSTimer_OWS_Proxy = &kNSTimer_OWS_Proxy;
+
+@implementation NSTimer (OWS)
+
+- (NSTimerProxy *)ows_proxy
+{
+    return objc_getAssociatedObject(self, kNSTimer_OWS_Proxy);
+}
+
+- (void)ows_setProxy:(NSTimerProxy *)proxy
+{
+    OWSAssert(proxy);
+
+    objc_setAssociatedObject(self, kNSTimer_OWS_Proxy, proxy, OBJC_ASSOCIATION_RETAIN);
+}
+
++ (NSTimer *)weakScheduledTimerWithTimeInterval:(NSTimeInterval)timeInterval
+                                         target:(id)target
+                                       selector:(SEL)selector
+                                       userInfo:(nullable id)userInfo
+                                        repeats:(BOOL)repeats
+{
+    NSTimerProxy *proxy = [NSTimerProxy new];
+    proxy.target = target;
+    proxy.selector = selector;
+    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:timeInterval
+                                                      target:proxy
+                                                    selector:@selector(timerFired:)
+                                                    userInfo:userInfo
+                                                     repeats:repeats];
+    [timer ows_setProxy:proxy];
+    return timer;
+}
+
+@end
+
+NS_ASSUME_NONNULL_END