rpc: Implement chainHead RPC API

[lexnv]

This PR implements the chainHead methods.

The chainHead methods include:

• chainHead_unstable_follow - Subscription for new, new best and finalized blocks
• chainHead_unstable_body - Get the extrinsics of a reported block by the follow method
• chainHead_unstable_call - Runtime API call at a reported block
• chainHead_unstable_header - Get the header of a reported block
• chainHead_unstable_storage - Query storage for a reported block
• chainHead_unstable_unpin - Unpin a reported block

This PR also includes the unsubscribe methods.

This PR relies on, but not blocked by the delayed pruning from #12497.

The PR should follow after a new jsonrpsee release and merge into substrate for
exposing the subscription_id API.

Part of: #12071.

Testing Done

Manual Testing

Created an app using jsonrpsee to subscribe to block production and compare the results
with the OLD API V1.

chainHead_unstable_follow

Event: Ok(Object({"event": String("initialized"), "finalizedBlockHash": String("0xb83c6a7c4666843f38293b85d8191fdbd4c054fa1ee49650bcdf2ac2867121e2"), "finalizedBlockRuntime": Object({"spec": Object({"apis": Array([Array([String("0xdf6acb689907609b"), Number(4)]), Array([String("0x37e397fc7c91f5e4"), Number(1)]), Array([String("0x40fe3ad401f8959a"), Number(6)]), Array([String("0xd2bc9897eed08f15"), Number(3)]), Array([String("0xf78b278be53f454c"), Number(2)]), Array([String("0xed99c5acb25eedf5"), Number(3)]), Array([String("0x17a6bc0d0062aeb3"), Number(1)]), Array([String("0xcbca25e39f142387"), Number(2)]), Array([String("0x687ad44ad37f03c2"), Number(1)]), Array([String("0xbc9d89904f5b923f"), Number(1)]), Array([String("0x68b66ba122c93fa7"), Number(1)]), Array([String("0x37c8bb1350a9a2a8"), Number(2)]), Array([String("0xf3ff14d5ab527059"), Number(2)]), Array([String("0x91d5df18b0d2cf58"), Number(1)]), Array([String("0xab3c0572291feb8b"), Number(1)])]), "authoringVersion": Number(10), "implName": String("substrate-node"), "implVersion": Number(0), "specName": String("node"), "specVersion": Number(268), "stateVersion": Number(1), "transactionVersion": Number(2)}), "type": String("valid")})}))
Event: Ok(Object({"blockHash": String("0x9039ce8530314f50325408dff4a82fabaa05a54269be90b2ca0bfc98bd8bc77c"), "event": String("newBlock"), "newRuntime": Null, "parentBlockHash": String("0xb83c6a7c4666843f38293b85d8191fdbd4c054fa1ee49650bcdf2ac2867121e2")}))
Event: Ok(Object({"blockHash": String("0x653b74aab0b8767ea86e4a4d91792203a1ec230e5499ec4c6dcd16bf1929570e"), "event": String("newBlock"), "newRuntime": Null, "parentBlockHash": String("0x9039ce8530314f50325408dff4a82fabaa05a54269be90b2ca0bfc98bd8bc77c")}))
Event: Ok(Object({"bestBlockHash": String("0x653b74aab0b8767ea86e4a4d91792203a1ec230e5499ec4c6dcd16bf1929570e"), "event": String("bestBlockChanged")}))
Event: Ok(Object({"blockHash": String("0x3cb58c4a14615bed81d007460f4825e6b49ef5f1ed7b2272ac5dcde250919a43"), "event": String("newBlock"), "newRuntime": Null, "parentBlockHash": String("0x653b74aab0b8767ea86e4a4d91792203a1ec230e5499ec4c6dcd16bf1929570e")}))
Event: Ok(Object({"bestBlockHash": String("0x3cb58c4a14615bed81d007460f4825e6b49ef5f1ed7b2272ac5dcde250919a43"), "event": String("bestBlockChanged")}))
Event: Ok(Object({"event": String("finalized"), "finalizedBlockHashes": Array([String("0x9039ce8530314f50325408dff4a82fabaa05a54269be90b2ca0bfc98bd8bc77c")]), "prunedBlockHashes": Array([])}))
  Block is finalized hash="0x9039ce8530314f50325408dff4a82fabaa05a54269be90b2ca0bfc98bd8bc77c"
  [OLD::chain_getBlock] hash="0x9039ce8530314f50325408dff4a82fabaa05a54269be90b2ca0bfc98bd8bc77c"
         Result=Object({"block": Object({"extrinsics": Array([String("0x280403000b8952a1858401")]), "header": Object({"digest": Object({"logs": Array([String("0x0642414245b5010100000000776427210000000034d2c861ee7b8a2976744790de52081141238aee7a468ff6fadefb45c7789522572085cb94adeed7d33da3abf978d628af6149bc55f93224e0451e03b616cb01693fd1a503a4a257238fc368e8e8f05d517ae62e26b160f63bc318caa5229e0b"), String("0x054241424501017291330f162229c740ef277948fd64c39347e0cd8dd6d1faa59254d6b3bd83176d9dd9866dc0e1d2afead08066c184ad54acaf21e96ecfdae5501403cd76898b")])}), "extrinsicsRoot": String("0xdfd8970b4bb466a3021d64eea94325b6feb8b85c2a6f90c016d5efde4a82ccaf"), "number": String("0x4"), "parentHash": String("0xb83c6a7c4666843f38293b85d8191fdbd4c054fa1ee49650bcdf2ac2867121e2"), "stateRoot": String("0x0f038ffc5a2a139b5f2a7b4715d23f1827c57ef2de3f7e2019ea7c3e4263b622")})}), "justifications": Null})
  [OLD::state_getStorage] hash="0x9039ce8530314f50325408dff4a82fabaa05a54269be90b2ca0bfc98bd8bc77c"
         Result=String("0x0040fa7f398074858a02000000000000")

  [chainHead_unstable_body] result=Some(Ok(Object({"event": String("done"), "result": String("0x04280403000b8952a1858401")})))
  [chainHead_unstable_storage] result=Some(Ok(Object({"event": String("done"), "result": String("0x0040fa7f398074858a02000000000000")})))
  [chainHead_unstable_call] result=Some(Ok(Object({"event": String("done"), "result": String("0x00000000")})))

Unit Tests

./src/chain_head/subscription.rs

Integration Tests

./src/chain_head/tests.rs

CC: @paritytech/tools-team.

[skunert]

Just minor nits, logic looks good to me 👍

[skunert]

LGTM

[niklasad1]

Return value: String containing an opaque value representing the subscription.

It's technically possible to provide a custom SubscriptionId such number but perhaps we could enforce substrate to only accept something that serializes to a String.

I think it's better to reject the subscription if the subscription ID is a number feels like bug if someone tries to use another custom subscription ID generator but it's converted to a String under the hood.

This is a edge-case and we could deal with it in another PR.

[lexnv]

Yep, we could change the logic to reject subscription IDs represented by numbers.

I'd like to tackle that in another PR, it seems that chain_head/tests infrastructure is providing by default numbers.

Thanks

[niklasad1]

nice work, LGTM

[Polkadot-Forum]

This pull request has been mentioned on Polkadot Forum. There might be relevant details there:

https://forum.polkadot.network/t/polkadot-release-analysis-v0-9-37/1736/1