watcher-ts/packages/codegen/non-subgraph-demo.md

Subgraph watcher demo

• The following core services need to be running for the demo:

  • ipld-eth-db
    • Version: v4.2.3-alpha
  • geth
    • State diffing service should use ipld-eth-db for database.
    • Version: v1.10.26-statediff-4.2.2-alpha
    • Endpoint: http://127.0.0.1:8545
  • ipld-eth-server
    • Should use ipld-eth-db for database.
    • Version: v4.2.3-alpha
    • Endpoints:
      • GQL: http://127.0.0.1:8082/graphql
      • RPC: http://127.0.0.1:8081

• In packages/codegen, create a config.yaml file:

  # Config to generate demo-erc721-watcher using codegen.
  # Contracts to watch (required).
  contracts:
      # Contract name.
    - name: ERC721
      # Contract file path or an url.
      path: ../../node_modules/@openzeppelin/contracts/token/ERC721/ERC721.sol
      # Contract kind
      kind: ERC721
  
  # Output folder path (logs output using `stdout` if not provided).
  outputFolder: ../demo-erc721-watcher
  
  # Code generation mode [eth_call | storage | all | none] (default: none).
  mode: all
  
  # Kind of watcher [lazy | active] (default: active).
  kind: active
  
  # Watcher server port (default: 3008).
  port: 3009
  
  # Flatten the input contract file(s) [true | false] (default: true).
  flatten: true
  

• Run codegen to generate watcher:

  yarn codegen --config-file ./config.yaml
  

  The watcher should be generated in packages/demo-erc721-watcher

• Create a postgres12 database for the watcher:

  sudo su - postgres
  
  # If database already exists
  # dropdb demo-erc721-watcher
  
  createdb demo-erc721-watcher
  

• Create database for the job queue and enable the pgcrypto extension on them (https://github.com/timgit/pg-boss/blob/master/docs/usage.md#intro):

  # If database already exists
  # dropdb demo-erc721-watcher-job-queue
  
  createdb demo-erc721-watcher-job-queue
  

  postgres@tesla:~$ psql -U postgres -h localhost demo-erc721-watcher-job-queue
  Password for user postgres:
  psql (12.7 (Ubuntu 12.7-1.pgdg18.04+1))
  SSL connection (protocol: TLSv1.3, cipher: TLS_AES_256_GCM_SHA384, bits: 256, compression: off)
  Type "help" for help.
  
  demo-erc721-watcher-job-queue=# CREATE EXTENSION pgcrypto;
  CREATE EXTENSION
  demo-erc721-watcher-job-queue=# exit
  

Custom hooks:

For generating default state for ERC721 from the indexer methods, replace the handleEvent hook in demo-erc721-watcher/src/hooks.ts file with:

export async function handleEvent (indexer: Indexer, eventData: ResultEvent): Promise<void> {
  assert(indexer);
  assert(eventData);

  // Perform indexing based on the type of event.
  switch (eventData.event.__typename) {
    case 'TransferEvent': {
      // Get event fields from eventData.
      const { from, to, tokenId } = eventData.event;

      // Update balance entry for the sender in database.
      if (from !== '0x0000000000000000000000000000000000000000') {
        await indexer._balances(eventData.block.hash, eventData.contract, from, true);
      }

      // Update balance entry for the receiver in database.
      if (to !== '0x0000000000000000000000000000000000000000') {
        await indexer._balances(eventData.block.hash, eventData.contract, to, true);
      }

      // Update owner for the tokenId in database.
      await indexer._owners(eventData.block.hash, eventData.contract, tokenId, true);

      break;
    }
    case 'ApprovalEvent': {
      // Get event fields from eventData.
      const { tokenId } = eventData.event;

      // Update tokenApprovals for the tokenId in database.
      await indexer._tokenApprovals(eventData.block.hash, eventData.contract, tokenId, true);

      break;
    }
    case 'ApprovalForAllEvent': {
      // Get event fields from eventData.
      const { owner, operator } = eventData.event;

      // Update operatorApprovals for the tokenId in database.
      await indexer._operatorApprovals(eventData.block.hash, eventData.contract, owner, operator, true);

      break;
    }
  }
}

Here, the diff is passed as true to indexer methods to store default state.

• In watcher-ts repo, follow the instructions in Setup for installing and building packages.

  # After setup
  yarn && yarn build
  

• In packages/demo-erc721-watcher, run the job-runner:

  yarn job-runner
  

• Run the watcher:

  yarn server
  

Operations

Run the following in packages/erc721-watcher:

• Get the signer account address and export to a shell variable:

  yarn account
  

  export SIGNER_ADDRESS="<SIGNER_ADDRESS>"
  

• Connect MetaMask to http://localhost:8545 (with chain ID 99)

• Add a second account to Metamask and export the account address to a shell variable for later use:

  export RECIPIENT_ADDRESS="<RECIPIENT_ADDRESS>"
  

• Deploy token:

  yarn nft:deploy
  

• Set the returned address to the variable $NFT_ADDRESS:

  NFT_ADDRESS=<NFT_ADDRESS>
  

• Run the following GQL mutation in generated watcher graphql endpoint http://127.0.0.1:3009/graphql

  mutation {
    watchContract(
      address: "NFT_ADDRESS"
      kind: "ERC721"
      checkpoint: true
    )
  }
  

• Run the following GQL subscription in generated watcher graphql endpoint:

  subscription {
    onEvent {
      event {
        __typename
        ... on TransferEvent {
          from
          to
          tokenId
        },
        ... on ApprovalEvent {
          owner
          approved
          tokenId
        }
      },
      block {
        number
        hash
      }
    }
  }
  

• Mint token:

  yarn nft:mint --nft $NFT_ADDRESS --to $SIGNER_ADDRESS --token-id 1
  

  • A Transfer event to $SIGNER_ADDRESS shall be visible in the subscription at endpoint.

  • An auto-generated diff entry State should be added with parent cid pointing to the initial checkpoint State.

• Run the getState query at the endpoint to get the latest State for NFT_ADDRESS:

  query {
    getState (
      blockHash: "EVENT_BLOCK_HASH"
      contractAddress: "NFT_ADDRESS"
      # kind: "checkpoint"
      kind: "diff"
    ) {
      cid
      block {
        cid
        hash
        number
        timestamp
        parentHash
      }
      contractAddress
      data
    }
  }
  

• Transfer token:

  yarn nft:transfer --nft $NFT_ADDRESS --from $SIGNER_ADDRESS --to $RECIPIENT_ADDRESS --token-id 1
  

  • An Approval event for ZERO_ADDRESS shall be visible in the subscription at endpoint.

  • A Transfer event to $RECIPIENT_ADDRESS shall be visible in the subscription at endpoint.

  • An auto-generated diff entry State should be added with parent cid pointing to the previous State.

• Run the getState query again at the endpoint with event blockHash.

• Get the latest blockHash:

  yarn block:latest
  

• In packages/demo-erc721-watcher, create a checkpoint using CLI:

  yarn checkpoint create --address $NFT_ADDRESS
  

  • Run the getState query again with the output blockHash and kind checkpoint at the endpoint.

  • The latest checkpoint should have the aggregate of state diffs since the last checkpoint.

  • The State entries can be seen in pg-admin in table state.