Canton — Push Model

In the RedStone Push model, price data is persisted on the Canton ledger. An off-chain relayer periodically calls the WritePrices choice on an adapter contract, which processes the RedStone payload, verifies the signatures and timestamps, and stores the aggregated values on the ledger. Consumers can then read the latest prices at any time without supplying a payload themselves.

Unlike the Pull Model, the Push model keeps oracle values available on the ledger between updates, at the cost of persistent contract state.

Data flow

1. An off-chain relayer fetches a signed RedStone payload from RedStone’s Data Distribution Layer.
2. The relayer submits the payload to the adapter’s WritePrices choice.
3. The Daml logic verifies signatures, checks timestamps, and aggregates the values.
4. Only values with a newer data timestamp than what is already stored are written. If nothing is newer, the call is a no-op and leaves the state unchanged.
5. Each write archives the current adapter contract and creates a new one with the updated data — its contract ID changes.
6. When a PricePillFactory is configured, the write also creates an individual PricePill contract per feed, so a consumer can read a single feed without accessing the adapter directly.

Smart contracts

Adapter

The main oracle contract, persisting the aggregated feed data. Its main choices:

Choice	Kind	Description
GetPrices	read-only	Processes a payload passed in the call and returns aggregated prices — the Pull path, also available on the adapter.
WritePrices	writing	Processes a payload and persists the aggregated values; creates PricePills when a factory is configured. Caller must be an updater.
ReadPrices	read-only	Returns the stored aggregated values for the requested feeds.
ReadPriceData	read-only	Returns the stored value, data timestamp and write timestamp per feed (None for feeds not written yet).
GetUniqueSignerThreshold	read-only	Returns the minimum number of unique signers required for data to be accepted.

All read choices verify that the caller is a viewer or an updater.

PricePill

An individual contract holding a snapshot of a single feed’s price data, created by the PricePillFactory during WritePrices. It lets consumers read one feed in isolation — ReadPrice, ReadData, ReadTimestamp, ReadFeedId, ReadDescription — and report whether its data is stale via IsDataStale.

PricePill lifecycle

1. Creation — a pill is created during WritePrices with the latest data and a staleness window (pill_staleness_ms = 1 day).
2. Active period — the pill is readable while it is not stale. It becomes stale once the ledger time passes packageTimestamp + stalenessMs (measured from the data timestamp). ReadData and ReadPrice refuse to return stale data.
3. Retention — the adapter always keeps the 2 newest pills per feed regardless of age. Older pills are “demoted” on a write and archived on a later WritePrices call once more than pill_keep_ms (1 minute) has elapsed since demotion.
4. Archival — old pills are archived by the factory; only the updater party may archive them.

Full reference

See the complete Push oracle documentation — every choice with its parameters, the PricePill lifecycle and the possible transaction failures — in the canton-connector adapter README.