Support batched JSONRPC requests

[romanz]

Following #228

[vlad20012]

What do you think about using https://github.com/paritytech/jsonrpc/tree/master/tcp ?

[romanz]

Thanks for the suggestion, will take a look :)

[vesparny]

Hi, is this feature being considered for future implementation?
Batched requests would definitely give a performance boost, especially for wallets containing multiple transactions

[Kixunil]

@vesparny if you're asking because you're experiencing performance issues it could be actually caused by inefficiency in some electrs code. We were brainstorming about it in #308

If you have the time, you could check the next branch (and accompanied bitcoind fork) to see if your issue is fixed there. The branch still has to be changed but at least we would have more data.

[craigraw]

I believe that when Electrs is used over Tor (which is increasingly becoming the default), there is no improvement that will have a bigger impact on perceived performance. To illustrate this I created a custom build of Sparrow, loaded the same wallet twice and configured a connection to an ElectrumX server over Tor. One of the wallets used batched JSONRPC, the other did not. The difference was stark - the batched load completed in 7 secs while the non-batched in 68 seconds. Here are the loading logs - same wallet, same server:

[Kixunil]

@craigraw I believe you're performing requests one-by-one, each issued only after previous completes, right? In that case it should be possible to send several requests in parallel to achieve better performance.

Of course I do agree that batching is just better. If parallel requests are easy to implement for you it might be a useful temporary solution.

[romanz]

Please take a look at #405 :)

[craigraw]

For the purposes of detecting and switching to batched JSON-RPC, can the 0.9.0 version be used (from the client_name of the server.version request)?

[romanz]

It's possible, but I would suggest sending a simple "batched" request to see if the server actually supports that :)
For example (note the [...] brackets):

$ echo '[{"jsonrpc": "2.0", "method": "server.ping", "id": 0}]' | netcat 127.0.0.1 50001
[{"id":0,"jsonrpc":"2.0","result":null}]

[Overtorment]

to my experience, you might accidentally crash an electrum server if you send unsupported request 😂

[romanz]

It was the case, but it should be resolved by #398 - i.e. electrs 0.8.10 shouldn't crash when getting an unsupported request :)

$ echo '[{"jsonrpc": "2.0", "method": "server.ping", "id": 0}]' | netcat 127.0.0.1 50001 
{"error":{"code":-32700,"message":"parse error"},"id":null,"jsonrpc":"2.0"}

[romanz]

Tested on latest https://github.com/sparrowwallet/sparrow version - seems to be working as expected :)

[craigraw]

This is embarrassing to say, but adding the -rc* to the end of the Electrs version broke the batching detection in Sparrow. My bad!

I'll fix this going forward of course, but I'd greatly appreciate it if the 0.9.0 final release had no suffix so the current Sparrow release works. I'm sure this will be the case anyway. Thanks!

[romanz]

No worries, and thanks for letting me know :)