XRPL: How to get the history of the balance of an account?

Question

I would like to query the history of the balance of an XRPL account with the new WebSocket API.

For example, how do I check the balance of an account on a particular day?

I know with the v2 api, there was a possibility to query balance_changes. But this doesn't seem to be part of the new version.

For example:

https://data.ripple.com/v2/accounts/rf1BiGeXwwQoi8Z2ueFYTEXSwuJYfV2Jpn/balance_changes?start=2018-01-01T00:00:00Z

How is this done with the new Websocket API's?

Answer 1

There's no convenient API call that the WebSocket API can do to get this. I assume you want the XRP balance, not token/issued currency balances, which are in a different place.

One way to go about it is to make an account_tx call and then iterate through the metadata. Many, but not all, transactions will have a ModifiedNode entry of type AccountRoot —if that transaction changed the account's XRP balance, you can see the difference in the PreviousFields vs. FinalFields for that entry. The Look Up Transaction Results tutorial has some details on how to parse out metadata this way. There are some kind of tricky edge cases here: for example, if you send a transaction that buys 10 drops of XRP in the exchange but burns 10 drops of XRP as a transaction cost, then the metadata won't show a balance change because the net change was zero (+10, -10).

Another approach could be to estimate what ledger_index was most recently closed at a given time, then use account_info to look up the account's balance as of that time. The hard part there is figuring out what the latest ledger index was at a given time. This is one of the places where the Data API was just more convenient than the WebSocket API—there's no way to look up by date in WebSocket so you have to try a ledger index, see what the close time of the ledger was, try another ledger index, see what the date is, etc.