The use of metadataRpc and possible reduction of size

[will-yjn]

Hello there,

Our signing device is isolated and stateless. So currently we pass metadataRpc to it every time we sign a transaction. The metadataRpc is approximately 300k in size and it is inconvenient. Can you point out where in your library you utilize metadataRpc for signing transactions?

We would like to reduce the size of metadataRpc passed into the signing device, possibly eliminate it.

[emostov]

@TarikGul we should explore just using the call metadata. We can have a function the pulls out the call metadata and just returns a hex string which can then be passed to the offline device

[TarikGul]

@emostov Sounds good. What do you mean by call metadata?

[emostov]

Just the calls for each pallet; no errors, events, or storage items.

[will-yjn]

With txwrapper-core, I signed a transaction using metadataRpc at blockhash "0x11eb8502ff2369538b4bf3ef9a6fe2732db93ff8a83ba7134553f185824596f2" where specVersion is '11' and transactionVersion '0'. I have successfully broadcasted it. Does this mean that the calls or the parts relevant to transaction signature in the "Balances" module have not changed?

[TarikGul]

@will-yijinin Yup exactly!

[anhcao142]

I have problems with big metadataRpc too, hope we can have a solution

[TarikGul]

@anhcao142 Hey! Yea currently looking into ways to improve the metadata calls.

[codemaster101]

Hi @TarikGul is there any update on this. With the metadata, the file supplied to our offline device exceeds 0.5 MB, which is extremely large. The amount of data we store on the QR code, with respect to the QR codes size generates over 200 QR codes!
Unsure how much the size is reduced, (we estimate around 25%) after adding asCallsOnly, as we feel that the data being sent might not be that relevant to creating the transaction as is?

Would be great if any other solution can be found or suggested in this regard?

-rw-rw-r--  1 515118 Apr 20 15:52 polk2.json

reduced to

-rw-rw-r--  1 437415 May  5 13:56 11488_hex_string_dot.json

[TarikGul]

Yea this has been something on my mind for a bit, but not necessarily a priority (More than happy to make it one for txwrapper-core and get the ball rolling on this for a more optimal solution though). You are absolutely correct most of the data included in the metadata is not absolutely necessary to construct the transaction. More or less its just the implementation that we currently use for whats available.

I will put some emphasis on moving forward with this though. My idea was to potential contribute to polkadot-js and add a asSingleCall getter attached to the Metadata type.

[TarikGul]

@codemaster101 The following PR above, drastically reduces the size of the metadata. Once it goes in I will give you a ping.

[codemaster101]

Thanks a lot @TarikGul

[TarikGul]

@codemaster101 PR is in, checkout this example, on how to generate the stripped metadata, and registry. The release should be out sometime today - tomorrow.

[codemaster101]

Thanks @TarikGul btw we must use both balances and system as the params for metadata generator right?

[TarikGul]

Yea, you can technically get away without using system but it's recommended to use it as some calls will not decode without it.