Is it possible to check latency of already approved transactions?

Question

I am running a BTC core node and I would like to perform some experiments and analysis on Bitcoin transaction latency. However, I see that the method getrwatransaction returns an object with:

"blocktime" : xxx, (numeric) The block time expressed in UNIX epoch time

"time" : n, (numeric) Same as "blocktime"

As I would like to get information on transaction latency, in a way that I can subtract the first appearance of such transaction in the mempool with the block creation epoch, those two parameters should not be the same, otherwise I only see it as a redundant and useless information.

Is there a way to get such piece of information? I see that mempool does not store (obviously) all the record of received transactions, so I was wondering whether such information is stored in the transaction itself, or if it is possible to get it somehow.

Answer 1

You can use either getrawmempool (for all mempool transactions) or getmempoolentry (for individual transactions) to get the exact time a transaction was accepted into your node's mempool:

"time": xxx, (numeric) local time transaction entered pool in seconds since 1 Jan 1970 GMT

You can also listen for the hashtx ZeroMQ event and store the time when that event was received. Storing timestamps is something you will need to do anyway, since when the transaction becomes confirmed, Bitcoin Core seems to immediately discard the mempool entry data.

Answer 2

As a useful info for who might be needing such data, I have found out that that using blockchain.info APIs, information about latency on newer transactions can be fetched. In fact, if we try to query BTC core node:

getrawtransaction "614095eeb59da281af6d49d85a153bfd8ec41acca272289e49bc6bd60b7ac7f6" true

we notice that "time": 1669848740, equals to "blocktime" one. However, if we query blockchain.info APIs, we obtain "time":1669848666, giving us a latency of 74 seconds.