snek

snek

snek is a tool for tailing the Cardano blockchain and emitting events for each block and transaction that it sees.

How it works

Input can be a local or remote Cardano full node, using either NtC (local UNIX socket, TCP over socat) or NtN to remote nodes.

Events are created with a simple schema.

{
    "type": "event type",
    "timestamp": "wall clock timestamp of event",
    "context": "metadata about the event",
    "payload": "the full event specific payload"
}

The chainsync input produces three event types: block, rollback, and transaction. Each type has a unique payload.

block:

{
    "context": {
        "blockNumber": 123,
        "slotNumber": 1234567,
    },
    "payload": {
        "blockBodySize": 123,
        "issuerVkey": "a712f81ab2eac...",
        "blockHash": "abcd123...",
        "blockCbor": "85828a1a000995c21..."
    }
}

rollback:

{
    "payload": {
        "blockHash": "abcd123...",
        "slotNumber": 1234567
    }
}

transaction:

{
    "context": {
        "blockNumber": 123,
        "slotNumber": 1234567,
        "transactionHash": "0deadbeef123...",
        "transactionIdx": 0,
    },
    "payload": {
        "blockHash": "abcd123...",
        "transactionCbor": "a500828258200a1ad..."
        "inputs": [
          "abcdef123...#0",
          "abcdef123...#1",
        ],
        "outputs": [
            {
                "address": "addr1qwerty123...",
                "amount":  12345687,
                "assets": [
                    {
                        "name": "Foo",
                        "nameHex": "abcd123...",
                        "amount": 123,
                        "fingerprint": "asset1abcd...",
                        "policyId": "54321..."
                    }
                ]
            }
        ],
        "metadata": {
            674: {
                "msg": [
                    "Test message"
                ]
            }
        },
        "fee": 1234567,
        "ttl": 123
    }
}

Each event is output individually. The log output prints each event to stdout using Uber's Zap logging library.

Configuration

snek supports multiple configuration methods for versatility: commandline arguments, YAML config file, and environment variables (in that order).

You can get a list of all available commandline arguments by using the -h/-help flag.

$ ./snek -h
Usage of snek:
  -config string
        path to config file to load
  -input string
        input plugin to use, 'list' to show available (default "chainsync")
  -input-chainsync-address string
        specifies the TCP address of the node to connect to
...
  -output string
        output plugin to use, 'list' to show available (default "log")
  -output-log-level string
        specifies the log level to use (default "info")

Each commandline argument (other than -config) has a corresponding environment variable. For example, the -input option has the INPUT environment variable, the -input-chainsync-address option has the INPUT_CHAINSYNC_ADDRESS environment variable, and -output has OUTPUT.

You can also specify each option in the config file.

input: chainsync

output: log

Plugin arguments can be specified under a special top-level key in the config file.

plugins:
  input:
    chainsync:
      network: preview

  output:
    log:
      level: info

Filtering

snek supports filtering events before they are output using multiple criteria. An event must match all configured filters to be emitted. Each filter supports specifying multiple possible values separated by commas. When specifying multiple values for a filter, only one of the values specified must match an event.

You can get a list of all available filter options by using the -h/-help flag.

$ ./snek -h
Usage of snek:
...
  -filter-address string
        specifies address to filter on
  -filter-asset string
        specifies the asset fingerprint (asset1xxx) to filter on
  -filter-policy string
        specifies asset policy ID to filter on
  -filter-type string
        specifies event type to filter on
...

Multiple filter options can be used together, and only events matching all filters will be output.

Example usage

Native using remote node

export INPUT_CHAINSYNC_NETWORK=preview
./snek 

Alternatively using equivalent commandline options:

./snek \
  -input-chainsync-network preview

In Docker using local node

First, follow the instructions for Running a Cardano Node in Docker.

docker run --rm -ti \
  -v node-ipc:/node-ipc \
  ghcr.io/blinklabs-io/snek:main

Filtering

Filtering on event type

Only output chainsync.transaction event types

$ snek -filter-type chainsync.transaction

Only output chainsync.rollback and chainsync.block event types

$ snek -filter-type chainsync.transaction,chainsync.block

Filtering on asset policy

Only output transactions involving an asset with a particular policy ID

$ snek -filter-type chainsync.transaction -filter-policy 13aa2accf2e1561723aa26871e071fdf32c867cff7e7d50ad470d62f

Filtering on asset fingerprint

Only output transactions involving a particular asset

$ snek -filter-type chainsync.transaction -filter-asset asset108xu02ckwrfc8qs9d97mgyh4kn8gdu9w8f5sxk

Filtering on a policy ID and asset fingerprint

Only output transactions involving both a particular policy ID and a particular asset (which do not need to be related)

$ snek -filter-type chainsync.transaction -filter-asset asset108xu02ckwrfc8qs9d97mgyh4kn8gdu9w8f5sxk -filter-policy 13aa2accf2e1561723aa26871e071fdf32c867cff7e7d50ad470d62f

Filtering on an address

Only output transactions with outputs matching a particular address

$ snek -filter-type chainsync.transaction -filter-address addr1qyht4ja0zcn45qvyx477qlyp6j5ftu5ng0prt9608dxp6l2j2c79gy9l76sdg0xwhd7r0c0kna0tycz4y5s6mlenh8pq4jxtdy

Filtering on a stake address

Only output transactions with outputs matching a particular stake address

$ snek -filter-type chainsync.transaction -filter-address stake1u9f9v0z5zzlldgx58n8tklphu8mf7h4jvp2j2gddluemnssjfnkzz

Push notifications

The example shows how push notification output can be used with filtering options. In this example, push notifications will be sent to the block events. Push notifications will be sent to the specified project_id in the serviceAccount.json file. Please refer to https://github.com/blinklabs-io/snek-mobile for more details on how to send push notifications to snek-mobile.

$ snek -filter-type chainsync.block -output push -output-push-serviceAccountFilePath /path/to/serviceAccount.json