Solidity event high-speed multithread reading


This is an example for high-speed EVM blockchain event reading in Python. The example shows How to read Solidity events, or use eth_getLogs RPC, to maximize output.

  • We use Contract class and its Event subclass

  • The example uses a thread pool reader with 16 parallel reading threads (JSON-RPC API requets)

  • The example uses optimised ujson library for decoding JSON

  • We do ABI decoding by hand to optimise speed - to avoid wasting time to decode data we do not read, or will discard

  • This example needs you to have a JSON-RPC Polygon full node. A free JSON-RPC node endpoint is not sufficient, as they do not store history. Try e.g. QuickNode or nodes from

  • For the best performance, always run local nodes at the same server or close your server where you run your application

About the code

Running the code

The script is shipped with eth_defi package. To run in UNIX shell from master checkout :

export JSON_RPC_POLYGON_FULL_NODE=https://...

# Read blocks 25,000,000 - 26,000,000 around when Enzyme was deployment on Polygon
START_BLOCK=25000000 END_BLOCK=26000000 python scripts/

After run you will see output like:

Scanning blocks 25,999,700 - 25,999,800, done 100.0%
Scanning blocks 25,999,800 - 25,999,900, done 100.0%
Scanning blocks 25,999,900 - 26,000,000, done 100.0%
Scanning blocks 26,000,000 - 26,000,100, done 100.0%
INFO:futureproof.executors:21 task(s) completed in the last 2.01 seconds
INFO:futureproof.executors:Shutting down monitor...
Found 64
   Token RAI: Chainlink aggregator is set to 0x7f45273fD7C644714825345670414Ea649b50b16
   Token amGHST: Chainlink aggregator is set to 0xe638249AF9642CdA55A92245525268482eE4C67b
   Token SUSHI: Chainlink aggregator is set to 0x17414Eb5159A082e8d41D243C1601c2944401431
We did 10,001 JSON-RPC API requests, avg 179.68 requests/second, as the run took 0:00:55.658691

Example code

"""Multithread reader example.

See :ref:`multithread-reader` for full tutorial.

import datetime
import logging
import os

from hexbytes import HexBytes
from web3 import HTTPProvider, Web3

from eth_defi.abi import get_contract
from eth_defi.chain import install_chain_middleware
from eth_defi.event_reader.conversion import decode_data, convert_uint256_bytes_to_address, convert_int256_bytes_to_int
from eth_defi.event_reader.filter import Filter
from eth_defi.event_reader.multithread import MultithreadEventReader
from eth_defi.event_reader.progress_update import PrintProgressUpdate
from eth_defi.token import fetch_erc20_details

def main():
    # Set up stdout logger
    logging.basicConfig(level=os.environ.get("LOG_LEVEL", "info").upper(), handlers=[logging.StreamHandler()])

    # Set up Web3 connection
    json_rpc_url = os.environ.get("JSON_RPC_POLYGON_FULL_NODE")
    assert json_rpc_url, f"You need to give JSON_RPC_POLYGON_FULL_NODE environment variable pointing ot your full node"

    web3 = Web3(HTTPProvider(json_rpc_url))

    start_block = os.environ.get("START_BLOCK")
    if start_block:
        start_block = int(start_block)
        start_block = 1

    end_block = os.environ.get("END_BLOCK")
    if end_block:
        end_block = int(end_block)
        end_block = web3.eth.block_number

    # Get one of the contracts prepackaged ABIs from eth_defi package
    value_interpreter_contract = get_contract(web3, "enzyme/ValueInterpreter.json")

    # Read events only for this contract
    # See
    target_contract_address = "0x66De7e286Aae66f7f3Daf693c22d16EEa48a0f45"

    # Create eth_getLogs event filtering
    filter = Filter.create_filter(

    # Set up multithreaded Polygon event reader.
    # Print progress to the console how many blocks there are left to read.
    reader = MultithreadEventReader(json_rpc_url, max_threads=16, notify=PrintProgressUpdate(), max_blocks_once=10_000)

    # Loop over the events as the multihreaded reader pool is feeding them to us.
    # Events will always arrive in the order they happened on chain.
    decoded_events = []
    start = datetime.datetime.utcnow()
    for event in reader(
        # Decode the solidity event
        # Indexed event parameters go to EVM topics, the second element is the first parameter
        # Non-indexed event parameters go to EVM arguments, first element is the first parameter
        arguments = decode_data(event["data"])
        topics = event["topics"]

        # event PrimitiveAdded(
        #     address indexed primitive,
        #     address aggregator,
        #     RateAsset rateAsset,
        #     uint256 unit
        # );
        primitive = convert_uint256_bytes_to_address(HexBytes(topics[1]))
        aggregator = convert_uint256_bytes_to_address(arguments[0])
        rate_asset = convert_int256_bytes_to_int(arguments[1])
        unit = convert_int256_bytes_to_int(arguments[2])

        # Primitive is a ERC-20 token, resolve its name and symbol while we are decoded the events
        token = fetch_erc20_details(web3, primitive)

        decoded = {
            "primitive": primitive,
            "aggregator": aggregator,
            "rate_asset": rate_asset,
            "unit": unit,
            "token": token,



    duration = datetime.datetime.utcnow() - start

    # Print out the results to the user at the end
    print(f"Found {len(decoded_events)}")
    for evt in decoded_events:
        print(f"   Token {evt['token'].symbol}: Chainlink aggregator is set to {evt['aggregator']}")

    api_counts = reader.get_total_api_call_counts()
    total = api_counts["total"]
    rate = total / duration.total_seconds()
    print(f"We did {total:,} JSON-RPC API requests, avg {rate:.2f} requests/second, as the run took {duration}")

if __name__ == "__main__":