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Importing Contracts

NOTE: Contract Import functionality is in experimental state 👷‍♀️👷

This page explains how to initialize an indexer using a contract that is already deployed on a blockchain. This process allows users to quickly and easily start up an indexer with basic logic using Envio given a deployed contract.

Import the project configuration using contract address​

Initialize envio​

envio init

Name your indexer​

? Name your indexer:

Choose the project directory (default is the current directory)​

? Set the directory:  (.) .

Select ContractImport initialization option​

? Choose an initialization option
  Template
  SubgraphMigration
> ContractImport
[↑↓ to move, enter to select, type to filter]

Select the blockchain that the contract is deployed on​

? Which blockchain would you like to import a contract from?
> Mainnet
  Goerli
  Optimism
  Bsc
  Matic
  OptimismGoerli
  ArbitrumOne
[↑↓ to move, enter to select, type to filter]

List of supported networks:

  • Mainnet
  • Goerli
  • Optimism
  • Bsc
  • Matic
  • OptimismGoerli
  • ArbitrumOne
  • ArbitrumGoerli
  • Avalanche
  • Mumbai
  • Sepolia

In the experimental state, this feature supports importing a single contract from a single blockchain.

Enter in the address of the contract to import​

? [BETA VERSION] What is the address of the contract?

Choose a language of your choice for the event handlers​

? Which language would you like to use?
> "Javascript"
  "Typescript"
  "Rescript"
[↑↓ to move, enter to select, type to filter]

Configuration file​

The contract-specific details that will be automatically populated in the config.yaml file are:

  • Network ID
  • Start Block
  • Contract Name
  • Contract Address
  • Event Signature (for all events) with requiredEntities

Users can remove the events from the configuration file which do not need to be indexed. By default the contract import process populates the configuration file for all events.

For more information on how to write the configuration file, go here.

However, users are not required to do make any changes to the config.yaml file for the indexer to run.

Schema​

By default, the contract import process will create an entity for each event in the contract. The fields in these entities will correspond to the parameters that are emitted inside the event.

Additionally, EventsSummary entity will be created that:

  • Stores a count of how many entities of each type have been created
  • Links to a vector of entities of each type that have been created

For more information on how to write the schema file, go here.

Event Handlers​

Loaders and handlers for each event will be automatically generated.

For all events, the loader function will load EventsSummary entity using a fixed key to be updated in the handler.

For all events, the handler function will perform two operations:

  • Create an instance of the event-specific entity with all the parameters that have been emitted
  • Update the event-specific entity counter in the loaded EventsSummary entity

For more information on how to write the event handlers file, go here.

Start the indexer​

Dev note: 📢 make sure you have docker open

The following command will start the docker and create databases for indexed data.

Run

envio dev

The indexer will then start indexing the contract specified in the config.yaml file from the start_block specified.

Troubleshooting​

Should the request for the contract details fail, the process will backoff and retry in duration that increases exponentially with each retry. If the backoff duration exceeds 32 seconds, the process will fail - please contact the team on Discord for more help.