Eth_subscribe not returning all data for a swap{} transaction

Questions
1

I am trying to monitor contract events with the topic swap{} keccak hash: “0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef”

I can successfully connect to the websocket filter and I am getting messages whenever this event fires on a contract address.

Problem is, the [‘data’] variable I get back in the message seems to be missing part of the expected message.

Recieved log:   'data': '0x00000000000000000000000000000000000000000000005411a685c98ef94747'
Expected log (from etherscan): 0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002dcbf4840eca000000000000000000000000000000000000000000000000005411a685c98ef947470000000000000000000000000000000000000000000000000000000000000000

As you can see, there is a whole section of the data missing in the reply. The data translates to the following information:
* amount0In :0
* amount1In :3300000000000000000
* amount0Out :1550798353237114701639
* amount1Out :0

Currently, the message I get only gives me only amount0, and I need both amount0 and amount1 for my use case

Raw data from the websocket response:
{"jsonrpc":"2.0","method":"eth_subscription","params":{"subscription":"0x1feed340d52bba03e5ee349f34f56a6b","result":{"removed":false,"logIndex":"0xfb","transactionIndex":"0x37","transactionHash":"0x51ee25d2035041d5b1a3badea9d466781fbdf24cbf5c056d4d01cc202b72c6a4","blockHash":"0xce8ca6baee336d3ee59a796c61eeb0125f5a623dbb1f4c20a15f3dfd0d142825","blockNumber":"0xa48b66","address":"0x56d811088235F11C8920698a204A5010a788f4b3","data":"0x00000000000000000000000000000000000000000000005411a685c98ef94747","topics":["0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef","0x000000000000000000000000b9b752f7f4a4680eeb327ffe728f46666763a796","0x0000000000000000000000005ce1fd9e8d7aba85dd43079606fedfa4385b06b8"]}}}

I am using python to make the websocket calls, with no special web3 library.

How can I get the entire length of data? Is infura restricting/limiting the amount of bytes it sends back in the ‘data’ field?

2

Hi @ub5zNq8N_ub5zNq8N - welcome to the Infura community! Can you send over the code you’re using to get this message? That’ll help us troubleshoot.

3 
import websocket
import json
import ssl
import thread
import time
infura_wss="wss://mainnet.infura.io/ws/v3/keyhere"

def on_open(ws):
        ws.send(json.dumps({
                    "jsonrpc": "2.0",
                    "id": 2,
                    "method": "eth_subscribe",
                    "params": ["logs",
                              {"address": ["0x56d811088235F11C8920698a204A5010a788f4b3"],
                              "topics": ["0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef"]
                              }]
                }))

def on_error(ws, error):
    print(error)

def on_close(ws):
    print("### closed ###")

def on_message(ws, message):
    print(message)

ws = websocket.WebSocketApp(infura_wss_address,
                          on_message = on_message,
                          on_error = on_error,
                          on_close = on_close)
ws.on_open = on_open
ws.run_forever(sslopt={"cert_reqs": ssl.CERT_NONE})

The message response is not being processed, I am only printing the raw data sent from Infura within Python. It seems to me Infura is not sending the entire log:

Example message print:
{"jsonrpc":"2.0","method":"eth_subscription","params":{"subscription":"0x1feed340d52bba03e5ee349f34f56a6b","result":{"removed":false,"logIndex":"0xfb","transactionIndex":"0x37","transactionHash":"0x51ee25d2035041d5b1a3badea9d466781fbdf24cbf5c056d4d01cc202b72c6a4","blockHash":"0xce8ca6baee336d3ee59a796c61eeb0125f5a623dbb1f4c20a15f3dfd0d142825","blockNumber":"0xa48b66","address":"0x56d811088235F11C8920698a204A5010a788f4b3","data":"0x00000000000000000000000000000000000000000000005411a685c98ef94747","topics":["0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef","0x000000000000000000000000b9b752f7f4a4680eeb327ffe728f46666763a796","0x0000000000000000000000005ce1fd9e8d7aba85dd43079606fedfa4385b06b8"]}}}

In the message, this is the data that we received:
“data”:“0x00000000000000000000000000000000000000000000005411a685c98ef94747”

But I am expecting a larger byte string:
0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002dcbf4840eca000000000000000000000000000000000000000000000000005411a685c98ef947470000000000000000000000000000000000000000000000000000000000000000

You can see the associated data in the log on etherscan at this link (the last one, #253):
https://etherscan.io/tx/0x51ee25d2035041d5b1a3badea9d466781fbdf24cbf5c056d4d01cc202b72c6a4#eventlog

4

Hi @ub5zNq8N_ub5zNq8N,

I think the issue is that you are specifying the Transfer topic in your subscription (0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef) and not the Swap event (0xd78ad95fa46c994b6551d0da85fc275fe613ce37657fb8d5e3d130840159d822 ) so the response you got is for log number 251 (0xfb) on the same etherscan page, not for 253 (0xfd).

To correct this issue in on_open change the topics parameter to "0xd78ad95fa46c994b6551d0da85fc275fe613ce37657fb8d5e3d130840159d822"

Thanks,
Ryan

5

Thank you! Looks like my wires were crossed…I had to do 2 things, change the hash, as you stated…

and also change the address to the correct contract address.

Really appreciate the help.