Class: queue

queue(server, chanDB, channel)

Object represneting a single channel's media queue

Constructor

new queue(server, chanDB, channel)

Instantiates a new media queue for a given channel
Parameters:
Name Type Description
server channelManager Parent server object
chanDB Document Related Channel Document from DB
channel activeChannel Parent Channel object for desired channel queue
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Members

channel

Parent Chennel Object for desired channel queue
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liveMode

Current live-stream schedule mode
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liveRemainder

Media interrupted by current live-stream
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locked

Locks schedule upon admin request
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nextTimer

Next Media Timer
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nowPlaying

Currently Playing Media Item
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preSwitchDelta

Time before media switch to run pre-switch method call against next media
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preSwitchTimer

Next Media Pre-Switch Timer
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schedule

Map containing current schedule
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server

Parent Server Object
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streamLock

Locks scheduling functionality during livestreams
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syncDelta

Sync Delta in MS
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syncTimer

Syncronization Timer
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timestamp

Current Timestamp in Media
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Methods

(async) broadcastQueue(chanDB)

Broadcasts channel queue
Parameters:
Name Type Description
chanDB Mongoose.Document Pass through Channel Document to save on DB Transactions
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defineListeners(socket)

Defines server-side socket.io listeners for newly connected sockets
Parameters:
Name Type Description
socket Socket Newly connected socket to define listeners against
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(async) deleteMedia(socket, data)

Processes client requests to delete queued media
Parameters:
Name Type Description
socket Socket Requesting socket
data Object Event payload
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(async) deleteRange(socket, data)

Processes request to delete a range of media items from the queue
Parameters:
Name Type Description
socket Socket Requesting socket
data Object Event payload
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(async) end(quiet, noArchive, volatile, chanDB)

End currently playing media
Parameters:
Name Type Default Description
quiet Boolean false Enable to prevent ending the media client-side
noArchive Boolean false Enable to prevent ended media from being written to channel archive. Deletes media if Volatile is false
volatile Boolean false Enable to prevent DB Transactions
chanDB Mongoose.Document Pass through Channel Document to save on DB Transactions
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(async) endLivestream(wasPlaying, chanDB)

Ends running Livestream
Parameters:
Name Type Description
wasPlaying queuedMedia Media object that was playing while we started the Livestream
chanDB Mongoose.Document Pass through Channel Document to save on DB Transactions
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getItemAtEpoch(epoch) → {queuedMedia}

Gets a media item by epoch
Parameters:
Name Type Description
epoch Number Date to check by JS Epoch (Millis)
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Returns:
found media item
Type
queuedMedia

getItemByUUID(uuid) → {queuedMedia}

Get Scheduled Item by UUID
Parameters:
Name Type Description
uuid String UUID of item to reschedule
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Returns:
found item
Type
queuedMedia

getItemsBetweenEpochs(start, end, noUnfinished) → {queuedMedia}

Returns scheduled media between two given datetimes
Parameters:
Name Type Default Description
start Number Start date by JS Epoch (Millis)
end Number End date by JS Epoch (Millis)
noUnfinished Boolean false Enable to include currently playing media
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Returns:
Found Media Objects
Type
queuedMedia

getLastItem(epoch)

Gets last item from a given epoch
Parameters:
Name Type Description
epoch Number Date to check by JS Epoch (Millis), defaults to now
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Returns:
Last played item

getNextItem(epoch) → {queuedMedia}

Gets next item from a given epoch
Parameters:
Name Type Description
epoch Number Date to check by JS Epoch (Millis), defaults to now
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Returns:
Next item on the schedule
Type
queuedMedia

getStart(start)

Validates start times, and replaces bad ones with 5ms in the future
Parameters:
Name Type Description
start Number Start time to validate by JS Epoch (millis)
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Returns:
Start time as JS Epoch (millis)

(async) goLive(socket, data)

Handle client request to start an HLS live stream
Parameters:
Name Type Description
socket Socket Requesting socket
data Object Event payload
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(async) handleRawRefresh(mediaObj) → {queuedMedia}

Refreshes expired raw links before media plays
Parameters:
Name Type Description
mediaObj queuedMedia Media object that's about to play
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Returns:
passes through Media object with updated link upon success
Type
queuedMedia

(async) livestreamOverwriteSchedule(wasPlaying, chanDB)

Overwrites livestream over scheduled media content after it has ended
Parameters:
Name Type Description
wasPlaying queuedMedia Media object that was playing while we started the Livestream
chanDB Mongoose.Document Pass through Channel Document to save on DB Transactions
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(async) livestreamPushbackSchedule(wasPlaying, chanDB)

Pushes back any missed content scheduled during Livestream after Livestream has ended.
Parameters:
Name Type Description
wasPlaying queuedMedia Media object that was playing while we started the Livestream
chanDB Mongoose.Document Pass through Channel Document to save on DB Transactions
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(async) moveMedia(socket, data)

Processes request to move queued media item
Parameters:
Name Type Description
socket Socket Requesting socket
data Object Event payload
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(async) preSwitch(mediaObj)

Called 10 seconds before media begins to play
Parameters:
Name Type Description
mediaObj queuedMedia Media object that's about to play
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(async) prepQueue(chanDB)

Prepares channel queue for network transmission
Parameters:
Name Type Description
chanDB Mongoose.Document Pass through Channel Document to save on DB Transactions
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Returns:
de-hydrated scehdule information

(async) queueURL(socket, data)

Accepts new URL's to queue from the client
Parameters:
Name Type Description
socket Socket Socket we're receiving the URL from
data Object Event payload
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refreshNextTimer(volatile)

Calculates next item to play, and sets timer to play it at it's scheduled start
Parameters:
Name Type Default Description
volatile Boolean false Disables DB Transactions if true
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(async) rehydrateQueue(chanDB)

Rehydrates media schedule from DB
Parameters:
Name Type Description
chanDB Mongoose.Document Pass through Channel Document to save on DB Transactions
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(async) removeMedia(uuid, socket, chanDB, noScheduling) → {Media}

Removes a media item
Parameters:
Name Type Default Description
uuid String UUID of item to reschedule
socket Socket Requesting Socket
chanDB Mongoose.Document Channnel Document Passthrough to save on DB Access
noScheduling Boolean false Disables schedule timer refresh if true
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Returns:
Deleted Media Item
Type
Media

(async) removeRange(start, end, socket, noUnfinished)

Removes range of media items from the queue
Parameters:
Name Type Default Description
start Number Start date by JS Epoch (millis)
end Number End date by JS Epoch (millis)
socket Socket Requesting Socket
noUnfinished Boolean false Set to true to include items that may be currently playing
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(async) rescheduleMedia(uuid, start, socket, chanDB)

Reschedules a media item
Parameters:
Name Type Description
uuid String UUID of item to reschedule
start Number New start time by JS Epoch (Millis)
socket Socket Requesting Socket
chanDB Mongoose.Document Channnel Document Passthrough to save on DB Access
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(async) scheduleMedia(media, socket, chanDB, force, volatile, startVolatile, saveLate, noSave)

Schedules a Media Item This is a fun method and I think it deserves it's own little explination... Since we're working with a time based schedule, using start epochs as keys for our iterable seemed the best option I don't want to store everything in a sparse array because that *feels* icky, and would probably be a pain in the ass. Maps seem like a good choice, if it wheren't for the issue of keeping them ordered... That's where this comes in. You see if we temporarily store it in a sparse array and convert into a map, we can quickly and easily create a properly sorted schedule map that, out side of adding items, behaves normally. Also a note on preformance: While .forEach ONLY runs through populated items in sparse arrays, many JS implementations run through them in the background, simply skipping them before executing the provided function. Looping through object.keys(arr), however, avoids this entirely, since it ONLY loops through defiened items within the array. No skipped empties for your runtime to worry about. Even more preformance benefits can be had by using a real for loop on the arrays keys, skipping the overhead of forEach entirely. This might seem gross but it completely avoids the computational workload of a sorting algo, especially when you consider that, no matter what, re-ordering the schedule map would've required us to iterate through and rebuild the map anyways... Also it looks like due to implementation limitations, epochs stored as MS are too large for array elements, so we store them there as seconds. This also means that our current implementation will break exactly on unix epoch 4294967295 (Feb 7, 2106 6:28:15 AM UTC) Hopefully javascript arrays will allow for larger lengths by then. If not blame the W3C :P If for some reason they haven't and we're not dead, we could probably implement an object that wraps a 2d array and set/gets it using modulo/devision/multiplication Further Reading: https://stackoverflow.com/questions/59480871/foreach-vs-object-keys-foreach-performance-on-sparse-arrays https://community.appsmith.com/content/blog/dark-side-foreach-why-you-should-think-twice-using-it
Parameters:
Name Type Default Description
media Media Media item to schedule
socket Socket Requesting Socket
chanDB Mongoose.Document Channnel Document Passthrough to save on DB Access
force Boolean false Ignore certain conditions that would prevent scehduling and play the bitch anyways, used for internal function calls
volatile Boolean false Prevent DB Writes, used for internal function calls
startVolatile Boolean false Runs refreshNextTimer calls without DB writes, used for internal function calls
saveLate Boolean false Saves items even if they're about to, or have already started. Used for internal function calls
noSave Boolean false Allows function to edit Channel Document, but not save. Used for internal function calls in which the channel document is passed through, but will be saved immediatly after the scheduleMedia() call.
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sendMedia(socket)

Send media update to a specific socket or broadcast it to the entire channel
Parameters:
Name Type Description
socket Socket Requesting Socket
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(async) start(mediaObj, timestamp, volatile)

Kicks off a media item
Parameters:
Name Type Default Description
mediaObj queuedMedia Media object that's about to play
timestamp Number Media start timestamp in seconds
volatile Boolean false Disables DB Transactions
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stop(socket)

Stops currently playing media item
Parameters:
Name Type Description
socket Socket Requesting Socket
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Returns:
returns false if there is nothing to stop

(async) stopMedia(socket)

Processes requests to stop currently playing media from client
Parameters:
Name Type Description
socket Socket Socket we received the request from
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(async) stopScheduleTimers(noArchive)

Clears and scheduling timers
Parameters:
Name Type Default Description
noArchive Boolean true Disables Archiving
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sync()

Sends a syncronization ping out to client Sockets and increments the tracked timestamp by the Synchronization Delta Called auto-magically by the Synchronization Timer
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(async) toggleLock(socket)

Handle client request to (un)lock queue
Parameters:
Name Type Description
socket Socket Requesting socket
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