ethOnBlock

ethOnBlock is a stream of changes in the EVM state when a new block is mined. The stream includes the results of eth_call and other RPC requests provided by users and is restricted based on the number of calls.

Service available via Gateway-API only.

Stream Endpoint

• Method: ethOnBlock

• Gateway-API Endpoint: ws://127.0.0.1:28333/ws

Parameters

Key	Description	Values
include	Fields to include in the on block event stream	name, response, blockHeight, tag [Default: all]
call-params	Fields used to build an RPC call request	method- see chart below for available methods and additional fields required for each method tag- latest, 0, or negative number. [Default: 0] name- unique string identifier for call. [Default: integer counter]

Method	Call Documentation	Additional Fields
eth_call	https://eth.wiki/json-rpc/API#eth_call	from, to, gas, value, data
eth_getBalance	https://eth.wiki/json-rpc/API#eth_getbalance	address
eth_getTransactionCount	https://eth.wiki/json-rpc/API#eth_gettransactioncount	address
eth_getCode	https://eth.wiki/json-rpc/API#eth_getcode	address
eth_getStorageAt	https://eth.wiki/json-rpc/API#eth_getstorageat	address, pos
eth_blockNumber	https://eth.wiki/json-rpc/API#eth_blocknumber	None

Example

WebSocket

Subscribing to the ethOnBlock stream via the Gateway-API in Python (Line 6 creates the subscription):

import asyncio, jason, websockets

async def main():
    async with websockets.connect(ws_uri) as websocket:
        payload = {
            "jsonrpc": "2.0",
            "id": 1,
            "method": "subscribe",
            "params": [
                "ethOnBlock",
                {
                    "include": ["name", "response", "block_height", "tag"],
                    "call-params": [
                        {
                            "name": "my_call_name",
                            "to": "0xd46e8dd67c5d32be8058bb8eb970870f07244567",
                            "gas": "0x76c0",
                            "value": "0x9184e72a",
                            "data": "0x00"
                        },
                        {
                            "name": "number",
                            "method": "eth_blockNumber"
                        }
                    ]
                }
            ]
        }
        await websocket.send(json.dumps(payload))
        subscription_id = await websocket.recv()
        while True:
            next_notification = await websocket.recv()
            print(next_notification)  # or process it generally
        await websocket.send(json.dumps({"jsonrpc": "2.0", "id": 2, "method": "unsubscribe", "params": [subscription_id]}))
        
if __name__ == '__main__':
    asyncio.get_event_loop().run_until_complete(main())

gRPC

Response

WebSocket

TaskCompletedEventis received after all calls have been executed upon receipt of a block.TaskDisabledEvent is received if there is an error response to a call, indicating that the call has been disabled.

Python Gateway:

<<< {'name': 'balance', 'response': {'result': '0x1'}, 'blockHeight': 11654331, 'tag': 11654331}
{'name': 'height', 'response': {'result': '0xb1d4bb'}, 'blockHeight': 11654331, 'tag': 11654331}
{'name': 'TaskDisabledEvent', 'response': {'commandMethod': 'eth_getBalance', 'blockOffset': 0, 'callName': 'balance', 'callPayload': {'address': '0x0000000000000000000000000000000000000000'}, 'active': False}, 'blockHeight': 11654331, 'tag': 11654331}
{'name': 'number', 'response': {'result': '0x0'}, 'blockHeight': 11654331, 'tag': 11654331}
{'name': 'TaskCompletedEvent', 'response': {}, 'blockHeight': 11654331, 'tag': 11654331}}

Go Gateway:

<<< {'name': 'balance', 'response': '0x1', 'block_height': 11654331, 'tag': 11654331}
{'name': 'height', 'response': '0xb1d4bb', 'block_height': 11654331, 'tag': 11654331}
{'name': 'TaskDisabledEvent', 'response': '{commandMethod:eth_call blockOffset:0 callName:my_call callPayload:{"data":"0x00","to":"0x0000000000000000000000000000000000000000"} active:false}', 'block_height': '13462626', 'tag': '0xcd6c62'}
{'name': 'number', 'response': '0x0', 'block_height': 11654331, 'tag': 11654331}
{'name': 'TaskCompletedEvent', 'response': '', 'block_height': 11654331, 'tag': 11654331}}

gRPC