getblockchaininfo JSON-RPC method

[mpguerra]

Motivation

lightwalletd uses the getblockchaininfo JSON-RPC method.

Dependencies

• Estimate the current chain height from the chain tip and local time #3161

Required Fields

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

But only the following fields are used by lightwalletd: https://github.com/zcash/lightwalletd/blob/master/common/common.go#L70

Field list:

{
  "chain": "xxxx",        (string) current network name as defined in BIP70 (main, test, regtest)
  "blocks": xxxxxx,         (numeric) the current number of blocks processed in the server
  "bestblockhash": "...", (string) the hash of the currently best block
  "estimatedheight": xxxx,  (numeric) if syncing, the estimated height of the chain, else the current best height
  "upgrades": {                (object) status of network upgrades
     "xxxx" : {                (string) branch ID of the upgrade, in lowercase hexadecimal
        "name": "xxxx",        (string) name of upgrade - unused by `lightwalletd`, but useful for debugging
        "activationheight": xxxxxx,  (numeric) block height of activation
        "status": "xxxx",      (string) status of upgrade: disabled/pending/active
     }, ...
  },
  "consensus": {               (object) branch IDs of the current and upcoming consensus rules
     "chaintip": "xxxxxxxx",   (string) branch ID used to validate the current chain tip, in lowercase hexadecimal
     "nextblock": "xxxxxxxx"   (string) branch ID that the next block will be validated under, in lowercase hexadecimal
  }
}

The zcashd code that generates the network upgrade JSON is here:
https://github.com/zcash/zcash/blob/6cd5b8792bbe0a3cc1064e1884914415f0c6e7d7/src/rpc/blockchain.cpp#L970

The lightwalletd code that parses the network upgrade JSON is here:
https://github.com/adityapk00/lightwalletd/blob/c1bab818a683e4de69cd952317000f9bb2932274/common/common.go#L195

Tasks

• Implement the RPC method
• 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

[ftm1000]

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[oxarbitrage]

I am unsure about the consensus object data regarding what should we return there.

I tried to get info from zcashd and i get all 00000 in that fields, however it was a not in sync chain. Anyone know what is the data that goes there ?

[teor2345]

I am unsure about the consensus object data regarding what should we return there.

I tried to get info from zcashd and i get all 00000 in that fields, however it was a not in sync chain. Anyone know what is the data that goes there ?

consensus contains the ConsensusBranchId of the current tip block and the next block.

Something like:

let next_block_height = (height + 1).expect("valid chain tips are a lot less than Height::MAX");

consensus.chaintip = NetworkUpgrade::current(network, height).branch_id();
consensus.nextblock = NetworkUpgrade::current(network, next_block_height).branch_id();