getinfo JSON-RPC method

[mpguerra]

Motivation

lightwalletd uses the getinfo JSON-RPC method.

Required Fields

The method is documented here: https://zcash.github.io/rpc/getinfo.html

But only the following fields are used by lightwalletd: https://github.com/zcash/lightwalletd/blob/master/common/common.go#L91

Field list:

{
  "build": xxxxx,           (string) `zcashd`'s CLIENT_BUILD
  "subversion": xxxxx,   (string) Subversion as sent to the P2P network in `version` messages - `zcashd`'s CLIENT_NAME, CLIENT_VERSION, uacomments
}

Tasks

• Implement the RPC method
  • build: app_version()
  • subversion: USER_AGENT
• Add RPC acceptance tests to CI
• Test that the RPC method works with lightwalletd

API Reference

We plan to use jsonrpc_core with:

• jsonrpc_http_server
• jsonrpc-derive

Example Code

Here are examples of:

• declaring RPC methods as Rust functions
• testing RPC methods

[ftm1000]

Hey team! Please add your planning poker estimate with ZenHub @conradoplg @dconnolly @gustavovalverde @jvff @oxarbitrage @teor2345 @upbqdn

[oxarbitrage]

I think it will make sense to put the app_version() function we need (currently in zebrad) in the new crate zebra-node-services of #3626

So this is partially blocked by that, however the PR that creates the crate should be merged soon and some work can be advanced without it so i will not tag this as blocked.

[teor2345]

I think it will make sense to put the app_version() function we need (currently in zebrad) in the new crate zebra-node-services of #3626

app_version() returns the version of the zebrad cargo package or git, so it can't be moved to another crate. (The other crate's version could be different.)

We could pass app_version().to_string() to RpcServer::spawn, and store the string in RpcServer?

[oxarbitrage]

Oh, I did not think on that, thanks!

We could pass app_version().to_string() to RpcServer::spawn, and store the string in RpcServer?

Yea, i think this is doable. Thanks again.