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Adapters.md

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Adapters

What is an Adapter

  • They are used to process work in a sub task (off-chain, within the ChainLink node)
  • They can be used to communicate with external services
  • Two categories of adapters: core and external
  • Utilize a minimal REST API

Core Adapters

  • bitcoinComparisonJSON Returns a signed Bitcoin transaction. Signs either a completion transaction or a failure transaction based on a value comparison of the input.
  • ethereumBytes32 Formats the input as Ethereum bytes32 value and writes it into the specified contract. Returns the unformatted value that was provided as input.
  • ethereumInt256 Formats the input as Ethereum int256 value and writes it into the specified contract. Returns the unformatted value that was provided as input.
  • ethereumUint256 Formats the input as Ethereum uint256 value and writes it into the specified contract. Returns the unformatted value that was provided as input.
  • ethereumFormatted Writes a preformatted Ethereum hexadecimal value into the blockchain as configured. Returns the preformatted value that was provided as input.
  • ethereumLogWatcher Returns the data field of an Ethereum event log, if one is provided. Otherwise, returns the value that was provided as the input. (Requires WeiWatchers integration.)
  • httpGetJSON Retrieves JSON and returns the specific field selected in the configuration.
  • jsonReceiver Generates a URL for the oracle to receive JSON push notifications. Parses the pushed JSON and returns the specific field selected in the configuration.

External Adapters

  • Can be written in any language as long as they return data conforming to the oracle schema
  • Expand functionality of services offered by the oracle
  • Can take input (from a separate API) and provide output (either to another adapter or to the core ChainLink software)
  • URLs can be provided to specify where to parse data from
  • Data can be passed into an adapter (including results from previous sub tasks)

Adapter Workflow

  • Perform request to an external API
  • Process response and either:
    • Return to the core (ChainLink node software), or
    • Pass value to the next adapter

Future changes planned for adapters

  • Allow for adapters to pull data from sub tasks other than the immediate predecessor
  • Allow for sub task pipeline to fan out and in to allow for sub tasks to rely on multiple processes
  • Create a DSL to make specifications simpler and more composable

Sources