async-loading.puml

@startuml async loading
participant IPLD
participant "Intercepted Loader" as ILoader
participant RequestManager
participant AsyncLoader
participant LoadAttemptQueue
participant ResponseCache
participant Loader
participant Storer
IPLD -> ILoader: Load Link
activate ILoader
ILoader -> AsyncLoader: Load Link Asynchronously
activate AsyncLoader
ILoader <-- AsyncLoader: Channel For future response
... transfer to internal process ...
AsyncLoader -> LoadAttemptQueue: Try Loading This Link
deactivate AsyncLoader

LoadAttemptQueue -> ResponseCache: Try Loading This Link
alt response cache has block
ResponseCache -> Storer: Store the block for later
ResponseCache -> ResponseCache: Remove the block from cache
LoadAttemptQueue <-- ResponseCache: "Here's the block"
note over LoadAttemptQueue: Response = Block
else response cache told block is missing by remote peer
LoadAttemptQueue <-- ResponseCache: "We're missing this link"
note over LoadAttemptQueue: Response = Error Missing Link
else local store has block
LoadAttemptQueue <-- ResponseCache: "I Don't Have it!"
LoadAttemptQueue -> Loader: Try Loading This Link From Local Cache
LoadAttemptQueue <-- Loader: "Here's the block"
note over LoadAttemptQueue: Response = Block
else no block or known missing link yet
LoadAttemptQueue <-- ResponseCache: "I Don't Have it!"
LoadAttemptQueue -> Loader: Try Loading This Link From Local Cache
LoadAttemptQueue <-- Loader: "I Don't Have it!"
LoadAttemptQueue -> LoadAttemptQueue: Store load request to try later
end
loop 0 or more times till I have a response for the link
...
opt new responses comes in
RequestManager -> AsyncLoader: New Responses Present
activate AsyncLoader
AsyncLoader -> ResponseCache: New Responses Present
... transfer to internal process ...
AsyncLoader -> LoadAttemptQueue: Try Loading Again
deactivate AsyncLoader
LoadAttemptQueue -> ResponseCache: Try Loading Stored Links
alt response cache now has block
ResponseCache -> Storer: Store the block for later
ResponseCache -> ResponseCache: Remove the block from cache
LoadAttemptQueue <-- ResponseCache: "Here's the block"
note over LoadAttemptQueue: Response = Block
else response cache now knows link is missing by remote peer
LoadAttemptQueue <-- ResponseCache: "We're missing this link"
note over LoadAttemptQueue: Response = Error Missing Link
else still no response
LoadAttemptQueue <-- ResponseCache: "I don't have it"
LoadAttemptQueue -> LoadAttemptQueue: Store load request to try later
end
end
opt no more responses
RequestManager -> AsyncLoader: No more responses
activate AsyncLoader
... transfer to internal process ...
AsyncLoader -> LoadAttemptQueue: Cancel attempts to load
note over LoadAttemptQueue: Response = Error Request Finished
deactivate AsyncLoader
end
end
ILoader <-- LoadAttemptQueue: Response Sent Over Channel
IPLD <-- ILoader : "Here's the stream of block\n data or an error"
deactivate ILoader

@enduml