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Setting up Configuration File

The config.yaml outlines the specifications for the indexer including details including network and contract specifications and the event information to be used in the indexing process.

Field Descriptions

  • name - Name of the project
  • description - Description of the project
  • networks - Configuration of the blockchain networks that the project is deployed on
    • id - Chain identifier of the network
    • rpc_config - RPC Config that will be used to subscribe to blockchain data on this network (TIP: This is optional and in most cases does not need to be specified if the network is supported with HyperSync. We recommend using HyperSync instead of RPC for 100x speed-up)
      • url - URL of the RPC endpoint
    • start_block - Initial block from which the indexer will start listening for events
    • end_block - An optional field to specify the last block an indexer must index to
    • contracts - Configuration for each contract deployed on the network
      • name - User-defined contract name
      • abi_file_path - File location of the contract ABI [Optional]
      • address - An array of addresses that the contract is deployed to on the network
      • handler - Location of the file that handles the events emitted by this contract
      • events - Configuration for each event emitted by this contract that the indexer will listen for
        • event - Event signature or name of the event (must match the name in the ABI)
        • required_entities - An array of entities that need to loaded and made accessible within the handler function (an empty array indicates that no entities are required)(Optional, if this is left out all entities will be available)
          • name - The name of the required entity (must match an entity defined in schema.graphql)
          • labels - This is an optional name given for loaded entities in the loaders that can be used in the event handlers (useful in differentiating entities that should be modified differently by the same event)

After you have set up your config file and the scheme, you are ready to generate the indexing code required to write the event handlers.

Run:

envio codegen

Contract Addresses

For the address field in the configuration file, the address that emits the events should be used.

If the contract uses a transparent proxy pattern, the address of the proxy contract should be used in the configuration file as this is the contract that emits the events. However, the ABI of the contract should be retrieved from the implementation contract.

If the contract does not use a proxy contract, then the same address from which ABI was obtained should be used in the configuration file.

Should there be multiple contract addresses from which events should be indexed from, they can be entered as an array in format ["0xAddress1", "0xAddress2"] for the address field - or via a simple dash denominated list as seen in this example repo.

Human readable ABI format

In the configuration you can optionally pass the file path to the abi for a contract in the abi_file_path field or you can specify the event signature in the event field.

An example is shown below of this feature from the above example

events:
- event: "NewGreeting(address user, string greeting)"
- event: "ClearGreeting(address user)"

More information on Human Readable ABI parsing is available here

Dev note: 📢 An error in the ABI or the event signature will result in the events not matching and hence may not reflect in the raw_events_table or propagate correctly into the event handler logic.

Additional guidelines

  • Contract name field (Greeter in the example above) should contain a single word, as it is used to create a namespace for functions in the indexer.
  • Address field should contain the address of the proxy contract, which emits the events on the specified blockchain.
  • Should the human readable ABI format not be used, then the ABI which is referenced in config file needs to be copied from the implementation contract into the specified abi directory.

Example config.yaml from Greeter template using ReScript language:

name: Greeter
description: Greeter indexer
networks:
- id: 137 # Polygon
start_block: 45336336
contracts:
- name: PolygonGreeter
abi_file_path: abis/greeter-abi.json
address: 0x9D02A17dE4E68545d3a58D3a20BbBE0399E05c9c
handler: ./src/EventHandlers.bs.js
events:
- event: NewGreeting
- event: ClearGreeting