Snapper Design Proposal (Draft)

snapper.md

snapper design proposal (draft)

purpose

• provide efficient map and color change history access for the space clients.

design goals/considerations

• reliable
• no read bottleneck for clients
• easy to implement
• easy to run as server-less tasks
• low cost, but some gas fee seems OK

design key points

• all components are stateless
• use events for state management
• use ipfs for data storage
• NOT use ipfs dynamic name resolution facilities (for efficiency and reliability)

components

1. snapper (run as aws lambda or in server)
2. snapper-contract (run as smart contract)

snapper

• generate map snapshots and color change deltas
• store snapshot/delta into ipfs
• call snapper-contract to emit events about cache states

process

map snapshot

1. get latest map snapshot from event/ipfs
2. get color changes after latest snapshot
3. apply changes to latest snapshot to generate new snapshot
4. store snapshot to ipfs
5. ask snapper-contract to emit snapshot info event

color delta

1. get latest delta from event
2. get color changes after latest delta
3. generate new delta
4. store new delta to ipfs
5. ask snapper-contract to emit delta info event

note: color delta can be generated along with map snapshot if using the same interval.

snapper-contract

• receive meta info from snapper and emit events

data structures

snapshot

• png, 1000 x 1000, 8-bit/color rgb, no-filter, highest compression, non-interlaced

cons

• not the smallest in size

pros

• just a image (eg. people can simply open it in browser)
• support any color
• small enough (with random image at around 700k for theoretical upper limit, normally should be smaller than 350k)

examples

316k    fractal16.png
240k    moutain16.png
104k    panda16.png
688k    random16.png

delta

{
    delta: [
        {
            bk_num: int,                // block number for this delta
            time: ISO8601 string,       // real world time for this block
            cs: [
                {
                    i: int              // pixel id
                    c: int              // pixel color
                },
                ...
            ]
        },
        ...
    ],
    prev_cid: string?                   // ipfs cid of previous delta, null for first delta
}

snapshot info (event)

{
    bk_num: int,        // block number for this snapshot
    cid: string         // ipfs cid for this snapshot
}

delta info (event)

{
    bk_num: int,        // block number for this delta
    cid: string         // ipfs cid for this delta
}