Example #1
0
// Returns the (ordered) union of all of the changes made to multiple channels.
func (db *Database) VectorMultiChangesFeed(chans base.Set, options ChangesOptions) (<-chan *ChangeEntry, error) {
	to := ""
	var userVbNo uint16
	if db.user != nil && db.user.Name() != "" {
		to = fmt.Sprintf("  (to %s)", db.user.Name())
		userVbNo = uint16(db.Bucket.VBHash(db.user.DocID()))
	}

	base.LogTo("Changes+", "Vector MultiChangesFeed(%s, %+v) ... %s", chans, options, to)
	output := make(chan *ChangeEntry, 50)

	go func() {
		var cumulativeClock *base.SyncSequenceClock
		var lastHashedValue string
		hashedEntryCount := 0
		defer func() {
			base.LogTo("Changes+", "MultiChangesFeed done %s", to)
			close(output)
		}()

		var changeWaiter *changeWaiter
		var userCounter uint64     // Wait counter used to identify changes to the user document
		var addedChannels base.Set // Tracks channels added to the user during changes processing.
		var userChanged bool       // Whether the user document has changed

		// Restrict to available channels, expand wild-card, and find since when these channels
		// have been available to the user:
		var channelsSince channels.TimedSet
		if db.user != nil {
			channelsSince = db.user.FilterToAvailableChannels(chans)
		} else {
			channelsSince = channels.AtSequence(chans, 0)
		}

		if options.Wait {
			changeWaiter = db.startChangeWaiter(channelsSince.AsSet())
			userCounter = changeWaiter.CurrentUserCount()
			db.initializePrincipalPolling(changeWaiter.GetUserKeys())
		}

		cumulativeClock = base.NewSyncSequenceClock()
		cumulativeClock.SetTo(getChangesClock(options.Since))

		// This loop is used to re-run the fetch after every database change, in Wait mode
	outer:
		for {
			// Get the last polled stable sequence.  We don't return anything later than stable sequence in each iteration
			stableClock, err := db.changeCache.GetStableClock(true)
			if err != nil {
				base.Warn("MultiChangesFeed got error reading stable sequence: %v", err)
				return
			}

			// Updates the changeWaiter to the current set of available channels.
			if changeWaiter != nil {
				changeWaiter.UpdateChannels(channelsSince)
			}
			base.LogTo("Changes+", "MultiChangesFeed: channels expand to %#v ... %s", channelsSince.String(), to)

			// Build the channel feeds.
			feeds, err := db.initializeChannelFeeds(channelsSince, options, addedChannels, userVbNo)
			if err != nil {
				return
			}

			// This loop reads the available entries from all the feeds in parallel, merges them,
			// and writes them to the output channel:
			current := make([]*ChangeEntry, len(feeds))
			var sentSomething bool
			nextEntry := getNextSequenceFromFeeds(current, feeds)
			for {
				minEntry := nextEntry

				if minEntry == nil {
					break // Exit the loop when there are no more entries
				}

				// Calculate next entry here, to help identify whether minEntry is the last entry we're sending,
				// to guarantee hashing
				nextEntry = getNextSequenceFromFeeds(current, feeds)

				if options.ActiveOnly {
					if minEntry.Deleted || minEntry.allRemoved {
						continue
					}
				}

				// Don't send any entries later than the stable sequence
				if stableClock.GetSequence(minEntry.Seq.vbNo) < minEntry.Seq.Seq {
					continue
				}

				// Add the doc body or the conflicting rev IDs, if those options are set:
				if options.IncludeDocs || options.Conflicts {
					db.addDocToChangeEntry(minEntry, options)
				}

				// Clock handling
				if minEntry.Seq.TriggeredBy == 0 {
					// Update the cumulative clock, and stick it on the entry.
					cumulativeClock.SetMaxSequence(minEntry.Seq.vbNo, minEntry.Seq.Seq)
					// Force new hash generation for non-continuous changes feeds if this is the last entry to be sent - either
					// because there are no more entries in the channel feeds, or we're going to hit the limit.
					forceHash := false
					if options.Continuous == false && (nextEntry == nil || options.Limit == 1) {
						forceHash = true
					}
					lastHashedValue = db.calculateHashWhenNeeded(
						options,
						minEntry,
						cumulativeClock,
						&hashedEntryCount,
						lastHashedValue,
						forceHash,
					)

				} else {
					// For backfill (triggered by), we don't want to update the cumulative clock.  All entries triggered by the
					// same sequence reference the same triggered by clock, so it should only need to get hashed once.
					// If this is the first entry for this triggered by, initialize the triggered by clock's
					// hash value.
					if minEntry.Seq.TriggeredByClock.GetHashedValue() == "" {
						cumulativeClock.SetMaxSequence(minEntry.Seq.TriggeredByVbNo, minEntry.Seq.TriggeredBy)
						clockHash, err := db.SequenceHasher.GetHash(cumulativeClock)
						if err != nil {
							base.Warn("Error calculating hash for triggered by clock:%v", base.PrintClock(cumulativeClock))
						} else {
							minEntry.Seq.TriggeredByClock.SetHashedValue(clockHash)
						}
					}
				}

				// Send the entry, and repeat the loop:

				base.LogTo("Changes+", "MultiChangesFeed sending %+v %s", minEntry, to)
				select {
				case <-options.Terminator:
					return
				case output <- minEntry:
				}
				sentSomething = true

				// Stop when we hit the limit (if any):
				if options.Limit > 0 {
					options.Limit--
					if options.Limit == 0 {
						break outer
					}
				}
			}

			if !options.Continuous && (sentSomething || changeWaiter == nil) {
				break
			}

			// Update options.Since for use in the next outer loop iteration.
			options.Since.Clock = cumulativeClock

			// If nothing found, and in wait mode: wait for the db to change, then run again.
			// First notify the reader that we're waiting by sending a nil.
			base.LogTo("Changes+", "MultiChangesFeed waiting... %s", to)
			output <- nil

		waitForChanges:
			for {
				waitResponse := changeWaiter.Wait()
				if waitResponse == WaiterClosed {
					break outer
				} else if waitResponse == WaiterHasChanges {
					select {
					case <-options.Terminator:
						return
					default:
						break waitForChanges
					}
				} else if waitResponse == WaiterCheckTerminated {
					// Check whether I was terminated while waiting for a change.  If not, resume wait.
					select {
					case <-options.Terminator:
						return
					default:
					}
				}
			}

			// Before checking again, update the User object in case its channel access has
			// changed while waiting:
			userChanged, userCounter, addedChannels, err = db.checkForUserUpdates(userCounter, changeWaiter)
			if userChanged && db.user != nil {
				channelsSince = db.user.FilterToAvailableChannels(chans)
			}
			if err != nil {
				change := makeErrorEntry("User not found during reload - terminating changes feed")
				base.LogTo("Changes+", "User not found during reload - terminating changes feed with entry %+v", change)
				output <- &change
				return
			}
		}
	}()

	return output, nil
}
Example #2
0
// Returns the (ordered) union of all of the changes made to multiple channels.
func (db *Database) SimpleMultiChangesFeed(chans base.Set, options ChangesOptions) (<-chan *ChangeEntry, error) {
	to := ""
	if db.user != nil && db.user.Name() != "" {
		to = fmt.Sprintf("  (to %s)", db.user.Name())
	}

	base.LogTo("Changes", "MultiChangesFeed(%s, %+v) ... %s", chans, options, to)
	output := make(chan *ChangeEntry, 50)

	go func() {
		defer func() {
			base.LogTo("Changes", "MultiChangesFeed done %s", to)
			close(output)
		}()

		var changeWaiter *changeWaiter
		var lowSequence uint64
		var lateSequenceFeeds map[string]*lateSequenceFeed
		var userCounter uint64     // Wait counter used to identify changes to the user document
		var addedChannels base.Set // Tracks channels added to the user during changes processing.
		var userChanged bool       // Whether the user document has changed in a given iteration loop

		// lowSequence is used to send composite keys to clients, so that they can obtain any currently
		// skipped sequences in a future iteration or request.
		oldestSkipped := db.changeCache.getOldestSkippedSequence()
		if oldestSkipped > 0 {
			lowSequence = oldestSkipped - 1
		} else {
			lowSequence = 0
		}

		// Restrict to available channels, expand wild-card, and find since when these channels
		// have been available to the user:
		var channelsSince channels.TimedSet
		if db.user != nil {
			channelsSince = db.user.FilterToAvailableChannels(chans)
		} else {
			channelsSince = channels.AtSequence(chans, 0)
		}

		if options.Wait {
			options.Wait = false
			changeWaiter = db.startChangeWaiter(channelsSince.AsSet())
			userCounter = changeWaiter.CurrentUserCount()

		}

		// If a request has a low sequence that matches the current lowSequence,
		// ignore the low sequence.  This avoids infinite looping of the records between
		// low::high.  It also means any additional skipped sequences between low::high won't
		// be sent until low arrives or is abandoned.
		if options.Since.LowSeq != 0 && options.Since.LowSeq == lowSequence {
			options.Since.LowSeq = 0
		}

		// For a continuous feed, initialise the lateSequenceFeeds that track late-arriving sequences
		// to the channel caches.
		if options.Continuous {
			lateSequenceFeeds = make(map[string]*lateSequenceFeed)
		}

		// This loop is used to re-run the fetch after every database change, in Wait mode
	outer:
		for {

			// Updates the changeWaiter to the current set of available channels
			if changeWaiter != nil {
				changeWaiter.UpdateChannels(channelsSince)
			}
			base.LogTo("Changes+", "MultiChangesFeed: channels expand to %#v ... %s", channelsSince, to)

			// lowSequence is used to send composite keys to clients, so that they can obtain any currently
			// skipped sequences in a future iteration or request.
			oldestSkipped = db.changeCache.getOldestSkippedSequence()
			if oldestSkipped > 0 {
				lowSequence = oldestSkipped - 1
			} else {
				lowSequence = 0
			}

			// Populate the parallel arrays of channels and names:
			feeds := make([]<-chan *ChangeEntry, 0, len(channelsSince))
			names := make([]string, 0, len(channelsSince))

			// Get read lock for late-arriving sequences, to avoid sending the same late arrival in
			// two different changes iterations.  e.g. without the RLock, a late-arriving sequence
			// could be written to channel X during one iteration, and channel Y during another.  Users
			// with access to both channels would see two versions on the feed.
			for name, vbSeqAddedAt := range channelsSince {
				chanOpts := options
				seqAddedAt := vbSeqAddedAt.Sequence

				// Check whether requires backfill based on addedChannels in this _changes feed
				isNewChannel := false
				if addedChannels != nil {
					_, isNewChannel = addedChannels[name]
				}

				// Check whether requires backfill based on current sequence, seqAddedAt
				// Triggered by handling:
				//   1. options.Since.TriggeredBy == seqAddedAt : We're in the middle of backfill for this channel, based
				//    on the access grant in sequence options.Since.TriggeredBy.  Normally the entire backfill would be done in one
				//    changes feed iteration, but this can be split over multiple iterations when 'limit' is used.
				//   2. options.Since.TriggeredBy == 0 : Not currently doing a backfill
				//   3. options.Since.TriggeredBy != 0 and <= seqAddedAt: We're in the middle of a backfill for another channel, but the backfill for
				//     this channel is still pending.  Initiate the backfill for this channel - will be ordered below in the usual way (iterating over all channels)

				// Backfill required when seqAddedAt is before current sequence
				backfillRequired := seqAddedAt > 1 && options.Since.Before(SequenceID{Seq: seqAddedAt})

				// Ensure backfill isn't already in progress for this seqAddedAt
				backfillPending := options.Since.TriggeredBy == 0 || options.Since.TriggeredBy < seqAddedAt

				if isNewChannel || (backfillRequired && backfillPending) {
					// Newly added channel so initiate backfill:
					chanOpts.Since = SequenceID{Seq: 0, TriggeredBy: seqAddedAt}
				}
				feed, err := db.changesFeed(name, chanOpts)
				if err != nil {
					base.Warn("MultiChangesFeed got error reading changes feed %q: %v", name, err)
					return
				}
				feeds = append(feeds, feed)
				names = append(names, name)

				// Late sequence handling - for out-of-order sequences prior to options.Since that
				// have arrived in the channel cache since this changes request started.  Only need for
				// continuous feeds - one-off changes requests only need the standard channel cache.
				if options.Continuous {
					lateSequenceFeedHandler := lateSequenceFeeds[name]
					if lateSequenceFeedHandler != nil {
						latefeed, err := db.getLateFeed(lateSequenceFeedHandler)
						if err != nil {
							base.Warn("MultiChangesFeed got error reading late sequence feed %q: %v", name, err)
						} else {
							// Mark feed as actively used in this iteration.  Used to remove lateSequenceFeeds
							// when the user loses channel access
							lateSequenceFeedHandler.active = true
							feeds = append(feeds, latefeed)
							names = append(names, fmt.Sprintf("late_%s", name))
						}

					} else {
						// Initialize lateSequenceFeeds[name] for next iteration
						lateSequenceFeeds[name] = db.newLateSequenceFeed(name)
					}
				}
			}
			// If the user object has changed, create a special pseudo-feed for it:
			if db.user != nil {
				feeds, names = db.appendUserFeed(feeds, names, options)
			}

			current := make([]*ChangeEntry, len(feeds))

			// This loop reads the available entries from all the feeds in parallel, merges them,
			// and writes them to the output channel:
			var sentSomething bool
			for {
				// Read more entries to fill up the current[] array:
				for i, cur := range current {
					if cur == nil && feeds[i] != nil {
						var ok bool
						current[i], ok = <-feeds[i]
						if !ok {
							feeds[i] = nil
						}
					}
				}

				// Find the current entry with the minimum sequence:
				minSeq := MaxSequenceID
				var minEntry *ChangeEntry
				for _, cur := range current {
					if cur != nil && cur.Seq.Before(minSeq) {
						minSeq = cur.Seq
						minEntry = cur
					}
				}

				if minEntry == nil {
					break // Exit the loop when there are no more entries
				}

				// Clear the current entries for the sequence just sent:
				if minEntry.Removed != nil {
					minEntry.allRemoved = true
				}
				for i, cur := range current {
					if cur != nil && cur.Seq == minSeq {
						current[i] = nil
						// Track whether this is a removal from all user's channels
						if cur.Removed == nil && minEntry.allRemoved == true {
							minEntry.allRemoved = false
						}
						// Also concatenate the matching entries' Removed arrays:
						if cur != minEntry && cur.Removed != nil {
							if minEntry.Removed == nil {
								minEntry.Removed = cur.Removed
							} else {
								minEntry.Removed = minEntry.Removed.Union(cur.Removed)
							}
						}
					}
				}

				if options.ActiveOnly {
					if minEntry.Deleted || minEntry.allRemoved {
						continue
					}
				}

				// Update options.Since for use in the next outer loop iteration.  Only update
				// when minSeq is greater than the previous options.Since value - we don't want to
				// roll back the Since value when we get an late sequence is processed.
				if options.Since.Before(minSeq) {
					options.Since = minSeq
				}

				// Add the doc body or the conflicting rev IDs, if those options are set:
				if options.IncludeDocs || options.Conflicts {
					db.addDocToChangeEntry(minEntry, options)
				}

				// Update the low sequence on the entry we're going to send
				minEntry.Seq.LowSeq = lowSequence

				// Send the entry, and repeat the loop:
				base.LogTo("Changes+", "MultiChangesFeed sending %+v %s", minEntry, to)
				select {
				case <-options.Terminator:
					return
				case output <- minEntry:
				}
				sentSomething = true

				// Stop when we hit the limit (if any):
				if options.Limit > 0 {
					options.Limit--
					if options.Limit == 0 {
						break outer
					}
				}
			}

			if !options.Continuous && (sentSomething || changeWaiter == nil) {
				break
			}

			// If nothing found, and in wait mode: wait for the db to change, then run again.
			// First notify the reader that we're waiting by sending a nil.
			base.LogTo("Changes+", "MultiChangesFeed waiting... %s", to)
			output <- nil
		waitForChanges:
			for {
				waitResponse := changeWaiter.Wait()
				if waitResponse == WaiterClosed {
					break outer
				} else if waitResponse == WaiterHasChanges {
					select {
					case <-options.Terminator:
						return
					default:
						break waitForChanges
					}
				} else if waitResponse == WaiterCheckTerminated {
					// Check whether I was terminated while waiting for a change.  If not, resume wait.
					select {
					case <-options.Terminator:
						return
					default:
					}
				}
			}

			// Check whether user channel access has changed while waiting:
			var err error
			userChanged, userCounter, addedChannels, err = db.checkForUserUpdates(userCounter, changeWaiter)
			if err != nil {
				change := makeErrorEntry("User not found during reload - terminating changes feed")
				base.LogTo("Changes+", "User not found during reload - terminating changes feed with entry %+v", change)
				output <- &change
				return
			}
			if userChanged && db.user != nil {
				channelsSince = db.user.FilterToAvailableChannels(chans)
			}

			// Clean up inactive lateSequenceFeeds (because user has lost access to the channel)
			for channel, lateFeed := range lateSequenceFeeds {
				if !lateFeed.active {
					db.closeLateFeed(lateFeed)
					delete(lateSequenceFeeds, channel)
				} else {
					lateFeed.active = false
				}
			}
		}
	}()

	return output, nil
}