# Main Requirements

• Use Node-RED's native Context Storage feature
• Integrate with uibuilder's cache control messages
• Control (clear or replay) the cache using a control input message
• Control the cache by topic or client/user id
• Control the overall size of the cache by restricting the maximum number of messages (by topic/client/user)
• Allow replay of a specific position in the cache
• Multi-instance - use as many infocash nodes as memory allows, uses node context so all data is isolated.
• Identify clients by a specified message property (defaults to "_socketId" to work with uibuilder)
• Take any uibuilder control message. Only respond to cache control messages. No further flow logic required.
• uibuilder control messages will not be cached.
• Slight delay (250ms) on replay along with a deduplication of requests (debounce) to handle the fact that front-ends need to send a trigger on window.load AND on socket connected.
• Allow reverse replay. Default is first-in-first out (FIFO) but should be able to replay as LIFO (last in, first out).
• Allow replay of first, last or specific index position only.
• Update status on new entry, visual warning if nearly full or full.

# Caveats

• Replayed messages are NOT exact copies of the original message. Only key data is saved in the cache. The msg.payload and topic/_socketId/user-id (as needed).
  • Maybe other properties can be saved in the future but this is complex if we want to avoid costly cloning.

# Options Needed

• Cache Data by:

  • any message (no categorisation, flat record of input messages)
  • topic (a queue of input messages per topic)
  • user (a queue of input messages per client or user id)
  • both topic and user

• Number of entries

# Control Message Details

These come from the design of uibuilder but can be used by any node or created yourself.

# "Global" Control

Controls the whole cache.

• Cache Replay

  Example msg (example from a client reloading the page):

  {
      "uibuilderCtrl": "ready for content",
      "cacheControl": "REPLAY",
      "from": "client",
      "_socketId": "/nr/uib#Bxtu968meXIZhcpSAAAH",
      "_uibAuth": {},
      "topic": "uib1Topic",
      "_msgid": "70d3a693.1b7348"
  }
  

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• Cache Clear

# Topic Control

Controls a single topic in the cache.

# Client or User Control

Controls the cache for a single client or user

# Other ideas

• Record timestamp with msg?
• Allow replay in reverse order?
• Button to manually clear the cache (possibly several buttons to clear the full cache or a topic/client/user)?
• Option to auto-clear if store or variable name is changed?
• Maybe add cache-control:NEW to allow sending only of cached messages since the last cache-control:REPLAY or NEW.
• Allow the replay delay time to be changed in the admin ui
• Cache messages for a maximum time (in seconds)
• Reset after replay if desired