69 lines
2.1 KiB
Markdown
69 lines
2.1 KiB
Markdown
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# Download Flow
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Sequence of interactions that result in dat blocks being transferred across the network.
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## Local Store
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When data is available in the local blockstore,
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```mermaid
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sequenceDiagram
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actor Alice
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participant API
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Alice->>API: Download(CID)
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API->>+Node/StoreStream: Retrieve(CID)
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loop Get manifest block, then data blocks
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Node/StoreStream->>NetworkStore: GetBlock(CID)
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NetworkStore->>LocalStore: GetBlock(CID)
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LocalStore->>NetworkStore: Block
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NetworkStore->>Node/StoreStream: Block
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end
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Node/StoreStream->>Node/StoreStream: Handle erasure coding
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Node/StoreStream->>-API: Data stream
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API->>Alice: Stream download of block
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```
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## Network Store
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When data is not found ih the local blockstore, the block-exchange engine is used to discover the location of the block within the network. Connection will be established to the node(s) that have the block, and exchange can take place.
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```mermaid
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sequenceDiagram
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box
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actor Alice
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participant API
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participant Node/StoreStream
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participant NetworkStore
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participant Discovery
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participant Engine
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end
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box
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participant OtherNode
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end
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Alice->>API: Download(CID)
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API->>+Node/StoreStream: Retrieve(CID)
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Node/StoreStream->>-API: Data stream
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API->>Alice: Download stream begins
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loop Get manifest block, then data blocks
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Node/StoreStream->>NetworkStore: GetBlock(CID)
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NetworkStore->>Engine: RequestBlock(CID)
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opt CID not known
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Engine->>Discovery: Discovery Block
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Discovery->>Discovery: Locates peers who provide block
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Discovery->>Engine: Peers
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Engine->>Engine: Update peers admin
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end
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Engine->>Engine: Select optimal peer
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Engine->>OtherNode: Send WantHave list
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OtherNode->>Engine: Send BlockPresence
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Engine->>Engine: Update peers admin
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Engine->>Engine: Decide to buy block
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Engine->>OtherNode: Send WantBlock list
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OtherNode->>Engine: Send Block
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Engine->>NetworkStore: Block
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NetworkStore->>NetworkStore: Add to Local store
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NetworkStore->>Node/StoreStream: Resolve Block
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Node/StoreStream->>Node/StoreStream: Handle erasure coding
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Node/StoreStream->>API: Push data to stream
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end
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API->>Alice: Download stream finishes
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```
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