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Pull Model Oracle

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Pronunciation
[pool mod-uhl awr-uh-kl]
Analogy
A pull model oracle is like a restaurant chef calling the supplier when a specific ingredient runs low.
Definition
An oracle design where smart contracts initiate requests to fetch external data on demand from off-chain services.
Key Points Intro
Pull model oracles provide on-demand data retrieval to smart contracts.
Key Points

On-demand: contract calls oracle when data is needed

Gas cost: each request incurs transaction fees

Latency: dependent on block confirmations and response time

Asynchronous: uses callbacks to deliver data

Example
A DeFi lending protocol calls Chainlink’s ETH/USD price feed before executing a liquidation.
Technical Deep Dive
Contracts invoke an oracle’s requestData function, specifying job IDs and callback signatures. Oracle nodes listen for events, fetch data off-chain (e.g., via HTTP), and submit the result in a subsequent transaction. Contracts implement a fulfillOracleCallback to process the response, with gas stipends and failure handling.
Security Warning
If the oracle fails to respond or is compromised, contracts may act on stale or incorrect data.
Caveat
Frequent pulls can become cost-prohibitive and risk block gas limit exhaustion.
Related Terms
Oracle
Push Model Oracle
Gas Limit

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