Event Monitoring with Infura

Making use of Infura improved eth_getLogs to observe token transactions.

Etherscan API is used to retrieve contract ABI.

Setup

Create file config.json and enter your Infura project ID, and Etherscan API key.
Can also enter a default contract address.

{
  "contract_address": "0x10dB9941E65DA3B7FDB0Cd05B1fd434Cb8B18158",
  "infura_project_id": "(your Infura project id)",
  "etherscan_api_key": "(your Etherscan API key)"
}

Example usage - RPC interface

Example using Tether stablecoin. We get the ABI, find the topic for Transfer event and get these events. This could be used as the ETL step for a data science application e.g. get all Transfers over a given time period and do some graph analysis.

from infmon.io import (get_contract_abi, get_event_interface, 
    get_current_block, get_contract_events, subscribe)
token_address = '0xdAC17F958D2ee523a2206206994597C13D831ec7' # Tether
token_abi = get_contract_abi(token_address)
token_interface = get_event_interface(token_abi)
# RPC interface - get token transfers in last 10 blocks
transfers = get_contract_events(
    token_address, 
    from_block=get_current_block() - 10,  
    topics=[token_interface['Transfer']['topic']])

# Display 
[token_interface['Transfer']['decode'](t) for t in transfers]

Example usage - websocket subscription

To drive a user interface in realtime we woudl like to get events streamed from a websocket. These events can then be stored in a backend cache database to service frontend clients with the state of the system.

A complication arises due to chain reorganization events which will cause already seen transactions to be reverted. Fortunately the Infura eth_subscribe websockets endpoint resends previously sent logs on the old chain with the removed attribute set to true so these can be handled.

The example below is a work in progress with a simple message handler that prints counts of Transfer events in each block if there are not removed transactions, and prints any removed transactions otherwise.

# Subscription interface 
await subscribe(token_address, topics=[token_interface['Transfer']['topic']])

# Results below:
# Initial response with subscription ID
{"jsonrpc":"2.0","id":1,"result":"0x1feed340b2f854185bd4cfcee65748d"}
# Normal blocks with count of Transfer events in block 
0x1754f43ba29f72b487889ed1dc58df214f13bcdb014a06b04aaad8e0344e27af: 9
0x0da94fb67c84ee22d9bb6e6ba806e533e90fa7e8e5704bf6d74aaeb210c791d7: 16
# Block reorganization produces transactions with removed set to True
REMOVED
{'removed': True, 'logIndex': '0x7', 'transactionIndex': '0x32', 
 'transactionHash': '0xc0b35d02011026f6dee695c40b69a972949bddb40ffe0d21391f2c23572b2a2f', 
  'blockHash': '0xc4dc057c1fa6742128befb189d82ef727b0555fd3066f974e23864c3c4f09416', 
  'blockNumber': '0x84a7fb', 'address': '0xdAC17F958D2ee523a2206206994597C13D831ec7', 
  'data': '0x0000000000000000000000000000000000000000000000000000000103d10fc0', 
  'topics': ['0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef', 
  '0x0000000000000000000000000a98fb70939162725ae66e626fe4b52cff62c2e5', 
  '0x000000000000000000000000adba6097a5c63c586aa7c9ee5665ffa746f7f255']}
REMOVED
{'removed': True, 'logIndex': '0x8', 'transactionIndex': '0x33', 
 'transactionHash': '0x925555803b5e083237deb13bb1be2a0ff12a7cc3e680553faa7fe76b83627f73', 
 'blockHash': '0xc4dc057c1fa6742128befb189d82ef727b0555fd3066f974e23864c3c4f09416', 
 'blockNumber': '0x84a7fb', 'address': '0xdAC17F958D2ee523a2206206994597C13D831ec7', 
 'data': '0x000000000000000000000000000000000000000000000000000000002878b7c0', 
 'topics': ['0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef', 
 '0x0000000000000000000000000a98fb70939162725ae66e626fe4b52cff62c2e5', 
 '0x000000000000000000000000cca1bbbc2c907afd731c2158e80172531e74cd72']}
... # More removed transactions
# Next block    
0xc4dc057c1fa6742128befb189d82ef727b0555fd3066f974e23864c3c4f09416: 74
0xf65a34ff8c131c3508f52a432b45e7a5d2c34bf2a4d8996c4e18d55d045a47dc: 36
0x16a18d1351190a69f7df34b7b5336deb3e257b9fb7b4b347b2e7962911aa6215: 15
0xb88fba7fba0b343335e2c1f5816e741a07631b86909ac106db91e45d4bbbfc59: 15

Interesting contracts

Tokens

Use EthPlorer API to retrieve list of top traded tokens as json

 curl https://api.ethplorer.io/getTopTokens?apiKey=freekey -o cache/ethplorer_top20200523.json

dYdX DEX

Contract Addresses

from infmon.eth import read_credentials, connect, get_contract
read_credentials('/home/mattmcd/.mattmcd')  # Populates environment variables
w3 = connect()   # Connects to mainnet via Infura and sets defaultAccount 

# Populate cache if needed - commented out 
# c = get_contract('dYdX_SoloMargin', '0x1E0447b19BB6EcFdAe1e4AE1694b0C3659614e4e')

# Connect to contract
solo = w3.eth.contract(**get_contract('dYdX_SoloMargin'))

solo.all_functions()
Out[7]: 
[<Function ownerSetSpreadPremium(uint256,tuple)>,
 <Function getIsGlobalOperator(address)>,
 <Function getMarketTokenAddress(uint256)>,
 ...
 <Function getAdjustedAccountValues(tuple)>,
 <Function getMarketMarginPremium(uint256)>,
 <Function getMarketInterestRate(uint256)>]

me = w3.eth.defaultAccount

solo.functions.getMarket(0).call({'from': me.address})
Out[10]: 
('0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2',
 (17223105496066458626271, 101489418110876542971309),
 (1010406097301649461, 1001404702877850791, 1590241097),
 '0xf61AE328463CD997C7b58e7045CdC613e1cFdb69',
 '0x7538651D874b7578CF52152c9ABD8f6617a38403',
 (0,),
 (0,),
 False)