⛓️🪝 Chainhook

Introduction

Blockchains serve as foundational infrastructure that unblocks new use cases and introduces a new generation of decentralized applications by relying on a public ledger. chainhook is a reorg-aware transaction indexing engine that helps developers get reliable blockchain data, regardless of forks and reorgs. By focusing only on the data devs care about, Chainhook helps developers work with much lighter datasets and build IFTTT logic into their applications. Chainhook can be used as a tool in your local development environment and as a service in the cloud environment.

Key Features:

• Faster, More Efficient Indexing: Instead of working with a generic blockchain indexer, taking hours to process every single transaction of every single block, developers can create their own indexes, build, iterate, and refine them in minutes. Chainhook can help developers avoid massive storage management and storage scaling issues by avoiding full chain indexation. Lighter indexes imply faster query results, which helps minimize end-user response time. This leads to an enhanced Developer Experience and an improved End-User Experience.
• Re-org and Fork Aware: Chainhook keeps a store of possible chain forks and checks each new chain event against the forks to maintain the current valid fork. All triggers, also known as predicates, are evaluated against the current valid fork. In the event of a reorg, Chainhook computes a list of new blocks to apply and old blocks to rollback and evaluates the registered predicates against those blocks.
• IFTTT Logic, powering your applications: Chainhook helps developers create elegant event-based architectures using triggers, also known as predicates. Developers can write “if_this / then_that” predicatesthat when triggered, are packaged as events and forwarded to the configured destination. By using cloud functions as destinations, developers can also cut costs on processing by only paying for processing when a block that contains some data relevant to the developer's application is being mined.

Benefits are plurals:

• Improved Developer + End User Experience
• Cost Optimization for data storage management and scaling.

---

Install chainhook

Install from the source

$ git clone https://github.com/hirosystems/chainhook.git
$ cd chainhook
$ cargo chainhook-install

---

Development workflow for Bitcoin chainhooks

Guide to if_this / then_that predicate design

To get started with Bitcoin predicates, we can use the chainhook to generate a template:

$ chainhook predicates new hello-ordinals.json --bitcoin

We will focus on the if_this and then_that parts of the specifications.

The current bitcoin predicates support the following if_this constructs:

// Get any transaction matching a given txid
// `txid` mandatory argument admits:
//  - 32 bytes hex encoded type. example: 
{
    "if_this": {
        "scope": "txid",
        "equals": "0xfaaac1833dc4883e7ec28f61e35b41f896c395f8d288b1a177155de2abd6052f"
    }
}

// Get any transaction, including an OP_RETURN output starting with a set of characters.
// `starts_with` mandatory argument admits:
//  - hex encoded bytes. example: `0x589403`
{
    "if_this": {
        "scope": "outputs",
        "op_return": {
            "starts_with": "X2["
        }
    }
}

// Get any transaction, including an OP_RETURN output matching the sequence of bytes specified 
// `equals` mandatory argument admits:
//  - hex encoded bytes. example: `0x589403`
{
    "if_this": {
        "scope": "outputs",
        "op_return": {
            "equals": "0x69bd04208265aca9424d0337dac7d9e84371a2c91ece1891d67d3554bd9fdbe60afc6924d4b0773d90000006700010000006600012"
        }
    }
}

// Get any transaction including an OP_RETURN output ending with a set of characters 
// `ends_with` mandatory argument admits:
//  - hex encoded bytes. example: `0x589403`
{
    "if_this": {
        "scope": "outputs",
        "op_return": {
            "ends_with": "0x76a914000000000000000000000000000000000000000088ac"
        }
    }
}

// Get any transaction including a p2pkh output paying a given recipient
// `p2pkh` construct admits:
//  - string type. example: "mr1iPkD9N3RJZZxXRk7xF9d36gffa6exNC"
{
    "if_this": {
        "scope": "outputs",
        "p2pkh": {
            "equals": "mr1iPkD9N3RJZZxXRk7xF9d36gffa6exNC"
        }
    }
}

// Get any transaction including a p2sh output paying a given recipient
// `p2sh` construct admits:
//  - string type. example: "2MxDJ723HBJtEMa2a9vcsns4qztxBuC8Zb2"
{
    "if_this": {
        "scope": "outputs",
        "p2sh": {
          "equals": "2MxDJ723HBJtEMa2a9vcsns4qztxBuC8Zb2"
        }
    }
}

// Get any transaction including a p2wpkh output paying a given recipient
// `p2wpkh` construct admits:
//  - string type. example: "bcrt1qnxknq3wqtphv7sfwy07m7e4sr6ut9yt6ed99jg"
{
    "if_this": {
        "scope": "outputs",
        "p2wpkh": {
          "equals": "bcrt1qnxknq3wqtphv7sfwy07m7e4sr6ut9yt6ed99jg"
        }
    }
}

// Get any transaction including a p2wsh output paying a given recipient
// `p2wsh` construct admits:
//  - string type. example: "bc1qklpmx03a8qkv263gy8te36w0z9yafxplc5kwzc"
{
    "if_this": {
        "scope": "outputs",
        "p2wsh": {
          "equals": "bc1qklpmx03a8qkv263gy8te36w0z9yafxplc5kwzc"
        }
    }
}

// Get any Bitcoin transaction including a Block commitment.
// Broadcasted payloads include Proof of Transfer reward information.
{
    "if_this": {
        "scope": "stacks_protocol",
        "operation": "block_committed"
    }
}

// Get any transaction, including a key registration operation 
{
    "if_this": {
        "scope": "stacks_protocol",
        "operation": "leader_registered"
    }
}

// Get any transaction, including an STX transfer operation 
// Coming soon
{
    "if_this": {
        "scope": "stacks_protocol",
        "operation": "stx_transferred"
    }
}

// Get any transaction, including an STX lock operation
// Coming soon
{
    "if_this": {
        "scope": "stacks_protocol",
        "operation": "stx_locked"
    }
}

// Get any transaction including a new Ordinal inscription (inscription revealed and transferred)
{
    "if_this": {
        "scope": "ordinals_protocol",
        "operation": "inscription_feed"
    }
}

In terms of actions available, the following then_that constructs are supported:

// HTTP Post block / transaction payload to a given endpoint.
// `http_post` construct admits:
//  - url (string type). Example: http://localhost:3000/api/v1/wrapBtc
//  - authorization_header (string type). Secret to add to the request `authorization` header when posting payloads
{
    "then_that": {
        "http_post": {
            "url": "http://localhost:3000/api/v1/wrapBtc",
            "authorization_header": "Bearer cn389ncoiwuencr"
        }
    }
}

// Append events to a file through the filesystem. Convenient for local tests.
// `file_append` construct admits:
//  - path (string type). Path to file on disk.
{
    "then_that": {
        "file_append": {
            "path": "/tmp/events.json",
        }
    }
}

Additional configuration knobs available:

// Ignore any block prior to given block:
"start_block": 101

// Ignore any block after given block:
"end_block": 201

// Stop evaluating chainhook after a given number of occurrences found:
"expire_after_occurrence": 1

// Include proof:
"include_proof": false

// Include Bitcoin transaction inputs in payload:
"include_inputs": false

// Include Bitcoin transaction outputs in payload:
"include_outputs": false

// Include Bitcoin transaction witness in payload:
"include_witness": false

Putting all the pieces together:

// Retrieve and HTTP Post to `http://localhost:3000/api/v1/wrapBtc` 
// the 5 first transfers to the p2wpkh `bcrt1qnxk...yt6ed99jg` address,
// of any amount, occurring after block height 10200. 
{
  "chain": "bitcoin",
  "uuid": "1",
  "name": "Wrap BTC",
  "version": 1,
  "networks": {
    "testnet": {
      "if_this": {
        "scope": "outputs",
        "p2wpkh": {
          "equals": "bcrt1qnxknq3wqtphv7sfwy07m7e4sr6ut9yt6ed99jg"
        }
      },
      "then_that": {
        "http_post": {
          "url": "http://localhost:3000/api/v1/transfers",
          "authorization_header": "Bearer cn389ncoiwuencr"
        }
      },
      "start_block": 10200,
      "expire_after_occurrence": 5,
    }
  }
}

// A specification file can also include different networks.
// In this case, the chainhook will select the predicate
// corresponding to the network it was launched against.
{
  "chain": "bitcoin",
  "uuid": "1",
  "name": "Wrap BTC",
  "version": 1,
  "networks": {
    "testnet": {
      "if_this": {
        "protocol": "ordinals",
        "operation": "inscription_feed"
      },
      "then_that": {
        "http_post": {
          "url": "http://localhost:3000/api/v1/ordinals",
          "authorization_header": "Bearer cn389ncoiwuencr"
        }
      },
      "start_block": 10200,
    },
    "mainnet": {
      "if_this": {
        "protocol": "ordinals",
        "operation": "inscription_feed"
      },
      "then_that": {
        "http_post": {
          "url": "http://my-protocol.xyz/api/v1/ordinals",
          "authorization_header": "Bearer cn389ncoiwuencr"
        }
      },
      "start_block": 90232,
    }

  }
}

Guide to local Bitcoin testnet / mainnet predicate scanning

In order to scan the Bitcoin chain with a given predicate, a bitcoind instance with access to the RPC methods getblockhash and getblock must be accessible. The RPC calls latency will directly impact the speed of the scans.

Note: the configuration of a bitcoind instance is out of scope for this guide.

Assuming a bitcoind node correctly configured, scans can be performed using the following command:

$ chainhook predicates scan ./path/to/predicate.json --testnet

When using the flag --testnet, the scan operation will generate a configuration file in memory using the following settings:

[storage]
working_dir = "cache" # Directory used by chainhook node for caching data

[network]
mode = "testnet"
bitcoind_rpc_url = "http://0.0.0.0:18332"
bitcoind_rpc_username = "bitcoind_username"
bitcoind_rpc_password = "bitcoind_password"
# bitcoind_zmq_url = "tcp://0.0.0.0:18543"

[limits]
max_number_of_bitcoin_predicates = 100
max_number_of_concurrent_bitcoin_scans = 100
max_number_of_stacks_predicates = 10
max_number_of_concurrent_stacks_scans = 10
max_number_of_processing_threads = 16
max_number_of_networking_threads = 16
max_caching_memory_size_mb = 32000

When using the flag --mainnet, the scan operation will generate a configuration file in memory using the following settings:

[storage]
working_dir = "cache"

[network]
mode = "testnet"
bitcoind_rpc_url = "http://0.0.0.0:8332"
bitcoind_rpc_username = "bitcoind_username"
bitcoind_rpc_password = "bitcoind_password"
# bitcoind_zmq_url = "tcp://0.0.0.0:18543"

[limits]
max_number_of_bitcoin_predicates = 100
max_number_of_concurrent_bitcoin_scans = 100
max_number_of_stacks_predicates = 10
max_number_of_concurrent_stacks_scans = 10
max_number_of_processing_threads = 16
max_number_of_networking_threads = 16
max_caching_memory_size_mb = 32000

By passing the flag --config=/path/to/config.toml, developers can customize the credentials and network address of their Bitcoin node.

$ chainhook config new --testnet
✔ Generated config file Chainhook.toml

$ chainhook predicates scan ./path/predicate.json --config-path=./Testnet.toml

Tips and tricks

To optimize their experience with scanning, developers have a few knobs they can play with:

• Use of adequate values for start_block and end_block in predicates will drastically improve the speed.
• Networking: reducing the number of network hops between the chainhook process and the bitcoind process can also help a lot.

---

Development workflow for Stacks chainhooks

Guide to if_this / then_that predicate design

To get started with stacks predicates, we can use the chainhook to generate a template:

$ chainhook predicates new hello-arkadiko.json --stacks

We will focus on the if_this and then_that parts of the specifications.

The current stacks predicates support the following if_this constructs:

// Get any transaction matching a given txid
// `txid` mandatory argument admits:
//  - 32 bytes hex encoded type. example: "0xfaaac1833dc4883e7ec28f61e35b41f896c395f8d288b1a177155de2abd6052f" 
{
    "if_this": {
        "scope": "txid",
        "equals": "0xfaaac1833dc4883e7ec28f61e35b41f896c395f8d288b1a177155de2abd6052f"
    }
}

// Get any stacks block matching constraints
// `block_height` mandatory argument admits:
//  - `equals`, `higher_than`, `lower_than`, `between`: integer type.
{
    "if_this": {
        "scope": "block_height",
        "higher_than": 10000
    }
}

// Get any transaction related to a given fungible token asset identifier
// `asset-identifier` mandatory argument admits:
//  - string type, fully qualifying the asset identifier to observe. example: `ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM.cbtc-sip10::cbtc`
// `actions` mandatory argument admits:
//  - array of string type constrained to `mint`, `transfer` and `burn` values. example: ["mint", "burn"]
{
    "if_this": {
        "scope": "ft_event",
        "asset_identifier": "ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM.cbtc-token::cbtc",
        "actions": ["burn"]
    },
}

// Get any transaction related to a given non-fungible token asset identifier
// `asset-identifier` mandatory argument admits:
//  - string type, fully qualifying the asset identifier to observe. example: `ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM.monkey-sip09::monkeys`
// `actions` mandatory argument admits:
//  - array of string type constrained to `mint`, `transfer` and `burn` values. example: ["mint", "burn"]
{
    "if_this": {
        "scope": "nft_event",
        "asset_identifier": "ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM.monkey-sip09::monkeys",
        "actions": ["mint", "transfer", "burn"]
    },
}

// Get any transaction moving STX tokens
// `actions` mandatory argument admits:
//  - array of string type constrained to `mint`, `transfer`, `burn`, and `lock` values. example: ["mint", "lock"]
{
    "if_this": {
        "scope": "stx_event",
        "actions": ["transfer", "lock"]
    },
}

// Get any transaction emitting given print events predicate
// `contract-identifier` mandatory argument admits:
//  - string type, fully qualifying the contract to observe. example: `ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM.monkey-sip09`
// `contains` or `matches_regex` argument admits:
//  - `contains` string type, used for matching event containing the specific string.
//  - `matches_regex` string type that should be a valid regex, used for matching event that regex matches with specific string.
{
    "if_this": {
        "scope": "print_event",
        "contract_identifier": "ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM.monkey-sip09",
        "contains": "vault"
    },
}

{
  "if_this": {
        "scope": "print_event",
        "contract_identifier": "ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM.monkey-sip09",
        "matches_regex": "(?:^|\\W)vault(?:$|\\W)"
  }
}

// Get any transaction calling a specific method for a given contract **directly**.
// Warning: if the watched method is being called by another contract, this predicate won't detect it.
// `contract-identifier` mandatory argument admits:
//  - string type, fully qualifying the contract to observe. example: `SP000000000000000000002Q6VF78.pox`
// `method` mandatory argument admits:
//  - string type, used for specifying the method to observe. example: `stack-stx`
{
    "if_this": {
        "scope": "contract_call",
        "contract_identifier": "SP000000000000000000002Q6VF78.pox",
        "method": "stack-stx"
    },
}

// Get any transaction, including a contract deployment
// `deployer` mandatory argument admits:
//  - string "*"
//  - string encoding a valid STX address. example: "ST2CY5V39NHDPWSXMW9QDT3HC3GD6Q6XX4CFRK9AG"
{
    "if_this": {
        "scope": "contract_deployment",
        "deployer": "ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM"
    },
}

// Get any transaction, including a contract deployment implementing a given trait (coming soon)
// `implement-trait` mandatory argument admits:
//  - string type, fully qualifying the trait's shape to observe. example: `ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM.sip09-protocol`
{
    "if_this": {
        "scope": "contract_deployment",
        "implement_trait": "ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM.sip09-protocol"
    },
}

In terms of actions available, the following then_that constructs are supported:

// HTTP Post block / transaction payload to a given endpoint.
// `http_post` construct admits:
//  - url (string type). Example: http://localhost:3000/api/v1/wrapBtc
//  - authorization_header (string type). Secret to add to the request `authorization` header when posting payloads
{
    "then_that": {
        "http_post": {
            "url": "http://localhost:3000/api/v1/wrapBtc",
            "authorization_header": "Bearer cn389ncoiwuencr"
        }
    }
}

// Append events to a file through the filesystem. Convenient for local tests.
// `file_append` construct admits:
//  - path (string type). Path to file on disk.
{
    "then_that": {
        "file_append": {
            "path": "/tmp/events.json",
        }
    }
}

Additional configuration knobs available:

// Ignore any block prior to given block:
"start_block": 101

// Ignore any block after given block:
"end_block": 201

// Stop evaluating chainhook after a given number of occurrences found:
"expire_after_occurrence": 1

// Include decoded clarity values in payload
"decode_clarity_values": true

// Include the contract ABI for transactions that deploy contracts:
"include_contract_abi": true

Putting all the pieces together:

// Retrieve and HTTP Post to `http://localhost:3000/api/v1/wrapBtc` 
// the 5 first transactions interacting with ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM.monkey-sip09,
// emitting print events containing the word 'vault'. 
{
  "chain": "stacks",
  "uuid": "1",
  "name": "Lorem ipsum",
  "version": 1,
  "networks": {
    "testnet": {
        "if_this": {
            "scope": "print_event",
            "contract_identifier": "ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM.monkey-sip09",
            "contains": "vault"
        },
        "then_that": {
            "http_post": {
            "url": "http://localhost:3000/api/v1/vaults",
            "authorization_header": "Bearer cn389ncoiwuencr"
            }
        },
        "start_block": 10200,
        "expire_after_occurrence": 5,
    }
  }
}

// A specification file can also include different networks.
// In this case, the chainhook will select the predicate
// corresponding to the network it was launched against.
{
  "chain": "stacks",
  "uuid": "1",
  "name": "Lorem ipsum",
  "version": 1,
  "networks": {
    "testnet": {
        "if_this": {
            "scope": "print_event",
            "contract_identifier": "ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM.monkey-sip09",
            "contains": "vault"
        },
        "then_that": {
            "http_post": {
                "url": "http://localhost:3000/api/v1/vaults",
                "authorization_header": "Bearer cn389ncoiwuencr"
            }
        },
        "start_block": 10200,
        "expire_after_occurrence": 5,
    },
    "mainnet": {
        "if_this": {
            "scope": "print_event",
            "contract_identifier": "SP456HQKV0RJXZFY1DGX8MNSNYVE3VGZJSRT459863.monkey-sip09",
            "contains": "vault"
        },
      "then_that": {
            "http_post": {
                "url": "http://my-protocol.xyz/api/v1/vaults",
                "authorization_header": "Bearer cn389ncoiwuencr"
            }
      },
      "start_block": 90232,
      "expire_after_occurrence": 5,
    }
  }
}

Guide to local Stacks testnet / mainnet predicate scanning

Developers can test their Stacks predicates without spinning up a Stacks node. To date, the Stacks blockchain has just over 2 years of activity, and the chainhook utility is able to work with both testnet and mainnet chainstates, in memory.

To test a Stacks if_this / then_that predicate, the following command can by used:

$ chainhook predicates scan ./path/to/predicate.json  --testnet

The first time this command run, a chainstate archive will be downloaded, uncompressed, and written to disk (around 3GB required for the testnet, 10GB for the mainnet).

The subsequent scans will use the cached chainstate if already present, speeding up iterations and the overall feedback loop.

---

Run chainhook as a service for streaming new blocks

chainhook can be run as a background service for streaming and processing new canonical blocks appended to the Bitcoin and Stacks blockchains.

When running chainhook as a service, if_this / then_that predicates can be registered by passing the path of the json file in the command line:

$ chainhook service start --predicate-path=./path/to/predicate-1.json --predicate-path=./path/to/predicate-2.json --config-path=./path/to/config.toml

Predicates can also be added dynamically. When the --predicate-path option is not passed or when the --start-http-api option is passed, chainhook will instantiate a REST API allowing developers to list, add, and removes predicates at runtime:

$ chainhook service start --config-path=./path/to/config.toml

$ chainhook service start --predicate-path=./path/to/predicate-1.json --start-http-api --config-path=./path/to/config.toml

A comprehensive OpenAPI specification explaining how to interact with the Chainhook REST API can be found here.

Bugs and feature requests

If you encounter a bug or have a feature request, we encourage you to follow the steps below:

1. Search for existing issues: Before submitting a new issue, please search existing and closed issues to check if a similar problem or feature request has already been reported.
2. Open a new issue: If it hasn't been addressed, please open a new issue. Choose the appropriate issue template and provide as much detail as possible, including steps to reproduce the bug or a clear description of the requested feature.
3. Evaluation SLA: Our team reads and evaluates all the issues and pull requests. We are avaliable Monday to Friday and we make a best effort to respond within 7 business days.

Please do not use the issue tracker for personal support requests or to ask for the status of a transaction. You'll find help at the #support Discord channel.

Contribute

Development of this product happens in the open on GitHub, and we are grateful to the community for contributing bugfixes and improvements. Read below to learn how you can take part in improving the product.

Code of Conduct

Please read our Code of conduct since we expect project participants to adhere to it.

Contributing Guide

Read our contributing guide to learn about our development process, how to propose bugfixes and improvements, and how to build and test your changes.

Community

Join our community and stay connected with the latest updates and discussions:

• Join our Discord community chat to engage with other users, ask questions, and participate in discussions.

• Visit hiro.so for updates and subcribing to the mailing list.

• Follow Hiro on Twitter.