Run Chainhook as a Service using Stacks

You can run Chainhook as a service to evaluate Stacks blocks against your predicates. You can also dynamically register new predicates by enabling predicates registration API.

Start with the prerequisite section and configure your files to start the chainhook service.

Prerequisite

Configure Stacks Node

• Configure your stacks node using the Stacks node configuration documentation.
• Recommend the latest version of Stacks. You can check the latest version by following this link.
• Set up the bitcoin node by following this article, then get the rpcuser, rpcpassword, and rpc_port values defined in the bitcoin.conf file.

A Stacks.toml file is generated when configuring the stacks node. Below is the sample Stacks.toml file.

[node]
working_dir = "/stacks-blockchain"
rpc_bind = "0.0.0.0:20443"          # Make a note of this port to use in the `Chainhook.toml`
p2p_bind = "0.0.0.0:20444"
bootstrap_node = "02da7a464ac770ae8337a343670778b93410f2f3fef6bea98dd1c3e9224459d36b@seed-0.mainnet.stacks.co:20444,02afeae522aab5f8c99a00ddf75fbcb4a641e052dd48836408d9cf437344b63516@seed-1.mainnet.stacks.co:20444,03652212ea76be0ed4cd83a25c06e57819993029a7b9999f7d63c36340b34a4e62@seed-2.mainnet.stacks.co:20444"

[burnchain]
chain = "bitcoin"
mode = "mainnet"
peer_host = "localhost"
username = "bitcoind_username"       # Must match the rpcuser in the bitcoin.conf
password = "bitcoind_password"       # Must match the rpcpassword in the bitcoin.conf
rpc_port = 8332                      # Must match the rpcport in the bitcoin.conf
peer_port = 8333

[[events_observer]]
endpoint = "localhost:20455"
retry_count = 255
events_keys = ["*"]

NOTE:

Ensure that the username, password, and rpc_port values in the Stacks.toml file match the values in the bitcoin.conf file. Also, note the rpc_bind port to use in the Chainhook.toml configuration in the next section of this article.

Configure Chainhook

In this section, you will configure a chainhook to communicate with the network. Run the following command in your terminal and generate the Chainhook.toml file.

chainhook config generate --testnet

Ensure that the bitcoind_rpc_url, bitcoind_rpc_username, bitcoind_rpc_password match with the rpcport, rpcuser and rpcpassword in the bitcoin.conf file and the port of the stacks_node_rpc_url matches the rpc_bind in the Stacks.toml file.

The following Chainhook.toml file is generated:

[storage]
working_dir = "cache"

# The HTTP API allows you to register/deregister
# dynamically predicates
# Disable by default
#
# [http_api]
# http_port = 20456
# database_uri = "redis://localhost:6379/"

[network]
mode = "mainnet"
bitcoind_rpc_url = "http://localhost:8332"                # Must match with the rpcport in the bitcoin.conf
bitcoind_rpc_username = "<bitcoind_username>"             # Must match with the rpcuser in the bitcoin.conf
bitcoind_rpc_password = "<bitcoind_password>"             # Must match with the rpcpassword in the bitcoin.conf
stacks_node_rpc_url = "http://localhost:20443"            # Must match with the rpc_bind in the Stacks.toml file

[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

[[event_source]]
tsv_file_url = "https://archive.hiro.so/mainnet/stacks-blockchain-api/mainnet-stacks-blockchain-api-latest"

Ensure the following configurations are matched to allow chainhook to communicate with the Stacks and Bitcoin layers.

bitcoin.conf	Stacks.toml	Chainhook.toml
rpcuser	username	bitcoind_rpc_username
rpcpassword	password	bitcoind_rpc_password
rpcport	rpc_port	bitcoind_rpc_url
zmqpubhashblock		bitcoind_zmq_url
	rpc_bind	stacks_node_rpc_url
	endpoint	stacks_events_ingestion_port

NOTE:

The bitcoind_zmq_url is optional when running chainhook as a service using stacks because stacks will pull the blocks from Stacks and the Bitcoin chain.

Scan blockchain based on predicates

Now that the stacks and chainhook configurations are done, you can scan your blocks by defining your predicates. This section helps you with sample JSON files to scan the blocks in the blockchain and render the results. To understand the supported predicates for Stacks, refer to how to use chainhook with stacks.

The following are the two examples to walk you through file_append and http_post then-that predicate designs.

Example 1 uses a print_event.json file to scan the predicates and render results using file_append. Example 2 uses print_event.json to scan the predicates and render results using http_post.

You can choose between the following examples to scan the predicates.

Example 1

Run the following command to generate a sample JSON file with predicates in your terminal.

chainhook predicates new print_event_1.json --stacks

A JSON file print_event_1.json is generated.

{
  "chain": "stacks",
  "uuid": "1da35032-e399-430c-bfbc-eca94709ad11",
  "name": "Hello world",
  "version": 1,
  "networks": {
    "testnet": {
      "start_block": 0,
      "end_block": 100,
      "if_this": {
        "scope": "print_event_1",
        "contract_identifier": "ST1SVA0SST0EDT4MFYGWGP6GNSXMMQJDVP1G8QTTC.arkadiko-freddie-v1-1",
        "contains": "vault"
      },
      "then_that": {
        "file_append": {
          "path": "arkadiko.txt"
        }
      }
    },
    "mainnet": {
      "start_block": 0,
      "end_block": 100,
      "if_this": {
        "scope": "print_event_1",
        "contract_identifier": "SP2C2YFP12AJZB4MABJBAJ55XECVS7E4PMMZ89YZR.arkadiko-freddie-v1-1",
        "contains": "vault"
      },
      "then_that": {
        "file_append": {
          "path": "arkadiko.txt"
        }
      }
    }
  }
}

NOTE:

You can get blockchain height and current block in the Explorer.

The sample arkadiko.txt should look like this:

{"apply":[{"block_identifier":{"hash":"0xf048102fee15dda049e6781c8e9aec1b39b1b9dc68d06fd9b84dced1b80ddd62","index":34307},"metadata":{"bitcoin_anchor_block_identifier":{"hash":"0x000000000000000000098e9ebc30e7c8e32b30ffecbd7dc5c715b5f07e1de25c","index":705648},"confirm_microblock_identifier":{"hash":"0xa65642590e98f54183a0be747a1c01e41d3ba211f6599eff2574d78ed2578468","index":2},"pox_cycle_index":18,"pox_cycle_length":2100,"pox_cycle_position":1797,"stacks_block_hash":"0x77a1aed86e895cb4b7b969986aa6a28eb2465e7227f351dd4e23d28448b222e9"},"parent_block_identifier":{"hash":"0x3117663ee5c5690d76e3f6c97597cbcc95085e7cecb0791d3edc4f95a4ce6f23","index":34306},"timestamp":1634625398,"transactions":[{"metadata":{"description":"invoked: SP2C2YFP12AJZB4MABJBAJ55XECVS7E4PMMZ89YZR.arkadiko-freddie-v1-1::collateralize-and-mint(u300000000, u130000000, (tuple (auto-payoff true) (stack-pox true)), \"STX-A\", SP2C2YFP12AJZB4MABJBAJ55XECVS7E4PMMZ89YZR.arkadiko-stx-reserve-v1-1, SP2C2YFP12AJZB4MABJBAJ55XECVS7E4PMMZ89YZR.arkadiko-token, SP2C2YFP12AJZB4MABJBAJ55XECVS7E4PMMZ89YZR.arkadiko-collateral-types-v1-1, SP2C2YFP12AJZB4MABJBAJ55XECVS7E4PMMZ89YZR.arkadiko-oracle-v1-1)","execution_cost":{"read_count":155,"read_length":318312,"runtime":349859000,"write_count":10,"write_length":3621},"fee":188800,"kind":{"data":{"args":["u300000000","u130000000","(tuple (auto-payoff true) (stack-pox true))","\"STX-A\"","SP2C2YFP12AJZB4MABJBAJ55XECVS7E4PMMZ89YZR.arkadiko-stx-reserve-v1-1","SP2C2YFP12AJZB4MABJBAJ55XECVS7E4PMMZ89YZR.arkadiko-token","SP2C2YFP12AJZB4MABJBAJ55XECVS7E4PMMZ89YZR.arkadiko-collateral-types-v1-1","SP2C2YFP12AJZB4MABJBAJ55XECVS7E4PMMZ89YZR.arkadiko-oracle-v1-1"],"contract_identifier":"SP2C2YFP12AJZB4MABJBAJ55XECVS7E4PMMZ89YZR.arkadiko-freddie-v1-1","method":"collateralize-and-mint"},"type":"ContractCall"},"nonce":15,"position":{"index":16},"proof":null,...

Now, use the following command to scan the blocks based on the predicates defined in the print_event_1.json file.

chainhook predicates scan print_event_1.json --testnet

The output of the above command will be a text file arkadiko.txt generated based on the predicate definition.

TIP: To optimize your experience with scanning, the following are a few knobs you can play with: Use of adequate values for start_block and end_block in predicates will drastically improve the performance. Networking: reducing the number of network hops between the chainhook and the bitcoind processes can also help.

The sample output file, arkadiko.txt, looks like this:

{"apply":[{"block_identifier":{"hash":"0xf048102fee15dda049e6781c8e9aec1b39b1b9dc68d06fd9b84dced1b80ddd62","index":34307},"metadata":{"bitcoin_anchor_block_identifier":{"hash":"0x000000000000000000098e9ebc30e7c8e32b30ffecbd7dc5c715b5f07e1de25c","index":705648},"confirm_microblock_identifier":{"hash":"0xa65642590e98f54183a0be747a1c01e41d3ba211f6599eff2574d78ed2578468","index":2},"pox_cycle_index":18,"pox_cycle_length":2100,"pox_cycle_position":1797,"stacks_block_hash":"0x77a1aed86e895cb4b7b969986aa6a28eb2465e7227f351dd4e23d28448b222e9"},"parent_block_identifier":{"hash":"0x3117663ee5c5690d76e3f6c97597cbcc95085e7cecb0791d3edc4f95a4ce6f23","index":34306},"timestamp":1634625398,"transactions":[{"metadata":{"description":"invoked: SP2C2YFP12AJZB4MABJBAJ55XECVS7E4PMMZ89YZR.arkadiko-freddie-v1-1::collateralize-and-mint(u300000000, u130000000, (tuple (auto-payoff true) (stack-pox true)), \"STX-A\", SP2C2YFP12AJZB4MABJBAJ55XECVS7E4PMMZ89YZR.arkadiko-stx-reserve-v1-1, SP2C2YFP12AJZB4MABJBAJ55XECVS7E4PMMZ89YZR.arkadiko-token, SP2C2YFP12AJZB4MABJBAJ55XECVS7E4PMMZ89YZR.arkadiko-collateral-types-v1-1, SP2C2YFP12AJZB4MABJBAJ55XECVS7E4PMMZ89YZR.arkadiko-oracle-v1-1)","execution_cost":{"read_count":155,"read_length":318312,"runtime":349859000,"write_count":10,"write_length":3621},"fee":188800,"kind":{"data":{"args":["u300000000","u130000000","(tuple (auto-payoff true) (stack-pox true))","\"STX-A\"",.........

Example 2

Run the following command to generate a sample JSON file with predicates in your terminal.

chainhook predicates new print_event_2.json --stacks

A JSON file print_event_2.json is generated.

{
  "chain": "stacks",
  "uuid": "1",
  "name": "Lorem ipsum",
  "version": 1,
  "networks": {
    "testnet": {
        "if_this": {
            "scope": "print_event_2",
            "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,
    }
  }
}

NOTE:

The start_block is the required field to use the http_post then-that predicate.

Now, use the following command to scan the blocks based on the predicates defined in the print_event_2.json file.

chainhook predicates scan print_event_2.json --testnet

The above command posts events to the URL http://localhost:3000/api/v1/vaults mentioned in the Chainhook.toml file.

Initiate Chainhook Service

In this section, you'll learn how to initiate the chainhook service using the following two ways and use the REST API call to post the events onto a server.

• Initiate the chainhook service by passing the predicate path to the command as shown below.

  chainhook service start --predicate-path=print_event_1.json --config-path=Chainhook.toml

  The above command registers the predicates based on the predicate definition in the print_event_1.json file.

• You can also dynamically register predicates via the predicate registration server. To do this:

  • Uncomment the following lines of code in the Chainhook.toml file to enable the predicate registration server.

    [http_api]
    http_port = 20456
    database_uri = "redis://localhost:6379/"
  • Start the Chainhook service by running chainhook service start --config-path=Chainhook.toml.
  • Now, the predicate registration server is running at localhost:20456. To dynamically register a new predicate, send a POST request to localhost:20456/v1/chainhooks with the new predicate, in JSON format, included in the request body. For complete documentation on the API endpoints available, see the OpenAPI specification.
  • 

TIP:

You can also run chainhook service by passing multiple predicates. Example: chainhook service start --predicate-path=predicate_1.json --predicate-path=predicate_2.json --config-path=Chainhook.toml