light-client: Add experimental light-client support #965

lexnv · 2023-05-18T17:23:41Z

This PR exposes the LightClient that uses smoldot to connect to chains.

Smoldot exposes a single non-clonable object that exposes all responses of all methods and all subscriptions via
a next() method call. Because of this, a background task is spawned to multiplex the responses back
to the appropriate submitters.

Smoldot generates some extra events while submitting an extrinsic, this is related to the new RPC Spec V2.
As a result of that, spurious events emitted by transaction_unstable_watchEvent are ignored.

The SubstrateTxStatus needed to be changed as well to support both lower camelCase and upper CamelCase.

When using the smoldot from crates-io, the implementation panics at:

thread 'main' panicked at 'attempt to subtract with overflow', /Users/lexnv/.cargo/registry/src/index.crates.io-6f17d22bba15001f/smoldot-0.6.0/src/chain_spec.rs:444:37
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

However, using the latest from the smoldot repo does not reproduce the issue.

The PR exposes 2 ways to construct the Light Client:

from a spec str
from a URL from which the chain spec is fetched

The former version is working as expected, while the latter seems to cause an overflow issue in smoldot

thread 'main' panicked at 'attempt to subtract with overflow', /Users/lexnv/.cargo/git/checkouts/smoldot-2dcbf637e11a77d4/43b3306/lib/src/chain_spec.rs:445:37
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Testing Done

Initially using smoldot to target a local node caused the client to hang with GrandPa warp sync warnings.
Using the latest branch, I was able to start a node as normal:

./polkadot-6dc9e84dde2 --dev --alice --validator
cargo run --example tx_basic_light_client

Available functionality

The following functionality is tested both on a local node, as well as on the polkadot live chain:

Submit and watch a transaction
Subscribes to all finalized blocks using the old RPC method
Subscribes to the head of the chain using the new chainHead RPC method
Dynamically query constants
Dynamically decode the events of the latest block
Various RPC calls to ensure proper shape of the response.

Known limitations

Iterating over keys is not expected to work: the light client tries its best to provide some answers, although I've encountered the same 3 responses submitted over again
chainHead_unstable_body response contains a value: ["0xhex", "0xhex"] shape, where subxt expects from substrate chains result: "0xhex"
chainHead_unstable_storage response contains a value: "0xhex" shape, where subxt expects from substrate chains result: "0xhex" (this is handled internally)
submitting a transaction using the old API will generate spurious events from the new API (chainHead_unstable_transaction -- handled internally)

Closes: #962

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

ascjones · 2023-05-19T10:43:04Z

Been dreaming about this for a long time 🚀

IIRC @rphmeier also expressed an interest in this.

subxt/src/rpc/lightclient/background.rs

Cargo.toml

subxt/src/rpc/lightclient/background.rs

subxt/src/rpc/lightclient/client.rs

niklasad1

Looks good,

How to deal with the git dependency is a blocker from my side otherwise really cool to have support for this in subxt

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

Co-authored-by: Niklas Adolfsson <niklasadolfsson1@gmail.com>

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

rphmeier · 2023-05-22T17:36:40Z

Nice, looking forward to trying this out. Is it also intended to work in-browser with Wasm compilation as well as native executables?

tomaka · 2023-06-23T10:14:31Z

subxt/src/client/lightclient/background.rs

+ let result = self.client.json_rpc_request(request, self.chain_id);
+ if let Err(err) = result {
+ tracing::warn!(
+ target: LOG_TARGET,
+ "Cannot send RPC request to lightclient {:?}",
+ err.to_string()
+ );


I just want to point out that this can realistically happen. If a TooBusy error is returned, you're supposed to back-pressure the requests sender.

I understand that from your point of view it's not very convenient, so I've opened smol-dot/smoldot#804 to clarify this thing.

To clarify: there will always be an error here. But maybe I can provide some configuration option that guarantees a minimum buffer size, so that you have a runtime guarantee that it won't happen.

Sorry I was a bit confused this morning since I was working on something else in parallel.

What you should do is pass max_pending_requests: u32::max_value() and max_subscriptions: u32::max_value() when adding the chain. There's no need to make these parameters configurable.

These parameters exist only to make sure that the memory usage of smoldot is bounded in situations where the JSON-RPC client is potentially malicious and can spam you with requests. This isn't relevant here, since you are the JSON-RPC client.

niklasad1

great PR, looks good to me

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

subxt/src/rpc/types.rs

Co-authored-by: Niklas Adolfsson <niklasadolfsson1@gmail.com>

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

tadeohepperle

Very good work, I like the multiplexing over the background task a lot.

subxt/src/book/usage/light_client.rs

subxt/src/client/lightclient/background.rs

testing/integration-tests/Cargo.toml

testing/integration-tests/src/light_client/mod.rs

testing/integration-tests/src/utils/wait_for_blocks.rs

testing/substrate-runner/src/lib.rs

testing/integration-tests/src/lib.rs

subxt/src/client/lightclient/builder.rs

subxt/examples/unstable_light_client_tx_basic.rs

jsdw

A few remaining nits and small things, but in general this is amazing stuff! Clean, well documented and tested. Good job!!

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

…support

* rpc/types: Decode `SubstrateTxStatus` for substrate and smoldot Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * lightclient: Add light client Error Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * lightclient: Add background task to manage RPC responses Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * lightclient: Implement the light client RPC in subxt Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * subxt: Expose light client under experimental feature-flag Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * artifacts: Add development chain spec for local nodes Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Update cargo lock Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * examples: Add light client example Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Update sp-* crates and smoldot to use git with branch / rev Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Apply cargo fmt Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Fix clippy Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Import hashmap entry Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * lightclient: Fetch spec only if jsonrpsee feature is enabled Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Update subxt/src/rpc/lightclient/background.rs Co-authored-by: Niklas Adolfsson <niklasadolfsson1@gmail.com> * Fix typo Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * artifacts: Update dev chain spec Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * types: Handle storage replies from chainHead_storage Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * artifacts: Add polkadot spec Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * lightclient: Handle RPC error responses Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * examples: Tx basic with light client for local nodes Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * example: Light client coprehensive example for live chains Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * examples: Remove prior light client example Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * feature: Rename experimental to unstable Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * book: Add light client section Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * testing: Fix clippy Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * lightclient: Ignore validated events Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Adjust tests for light-clients and normal clients Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * testing: Keep lightclient variant Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Remove support for chainHead_storage for light client Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Update light client to point to crates.io Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Update sp-crates from crates.io Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Replace Atomic with u64 Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Add LightClientBuilder Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Adjust chainspec with provided bootnodes Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Add potential_relay_chains to light client builder Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Move the light-client to the background task Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Adjust tracing logs Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Update book and example Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Apply cargo fmt Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Remove dev_spec.json artifact Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Examples fix duplicate Cargo.toml Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Use tracing_subscriber crate Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Fix clippy for different features Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Add comment about bootNodes Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Add comment about tracing-sub dependency Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Run integration-tests with light-client Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Feature guard some incompatible tests Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * ci: Enable light-client tests under feature flag Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * ci: Fix git step name Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Adjust flags for testing Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Adjust warnings Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Rename feature flag jsonrpsee-ws to jsonrpsee Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Fix cargo check Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * ci: Run tests on just 2 threads Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Move light-client to subxt/src/client Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Adjust LightClientBuilder Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Use ws_url to construct light client for testing Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Refactor background Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Address feedback Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Remove polkadot.spec and trim sub_id Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Wait for substrate to produce block before connecting light client Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Adjust builder and tests Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Apply fmt Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * ci: Use release for light client testing Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Add single test for light-client Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Wait for more blocks Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Use polkadot endpoint for testing Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Adjust cargo check Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * examples: Remove light client chain connection example Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Adjust cargo.toml section for the old example Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Adjust background task to use usize for subscription Id Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Build bootnodes with serde_json::Value directly Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Make channel between subxt user and subxt background unbounded Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Update subxt/src/client/lightclient/builder.rs Co-authored-by: Niklas Adolfsson <niklasadolfsson1@gmail.com> * Switch to smoldot 0.6.0 from 0.5.0 Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Move testing to `full_client` and `light_client` higher modules Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Remove subscriptionID type Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Remove subxt/integration-testing feature flag Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Adjust wait_for_blocks documentation Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Adjust utils import for testing Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> * Remove into_iter from builder construction Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> --------- Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io> Co-authored-by: Niklas Adolfsson <niklasadolfsson1@gmail.com>

lexnv added 8 commits May 18, 2023 20:02

rpc/types: Decode SubstrateTxStatus for substrate and smoldot

68e239a

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

lightclient: Add light client Error

e54aa6a

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

lightclient: Add background task to manage RPC responses

aaace2c

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

lightclient: Implement the light client RPC in subxt

e9a6491

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

subxt: Expose light client under experimental feature-flag

2efdef1

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

artifacts: Add development chain spec for local nodes

f715092

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

Update cargo lock

0dc47f2

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

examples: Add light client example

d59a331

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

lexnv requested a review from a team as a code owner May 18, 2023 17:23

lexnv self-assigned this May 18, 2023

lexnv mentioned this pull request May 19, 2023

wasm: Update from v6.0.2 to v8.0.1 paritytech/substrate#14178

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lexnv mentioned this pull request May 22, 2023

smoldot-light: GrandPa warp sync idle at block smol-dot/smoldot#592

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lexnv and others added 7 commits May 22, 2023 17:31

Update sp-* crates and smoldot to use git with branch / rev

d25c133

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

Apply cargo fmt

96b428c

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

Fix clippy

5a04b21

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

Import hashmap entry

4140615

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

lightclient: Fetch spec only if jsonrpsee feature is enabled

c6668f6

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

Update subxt/src/rpc/lightclient/background.rs

890a0e1

Co-authored-by: Niklas Adolfsson <niklasadolfsson1@gmail.com>

Fix typo

5b15e2d

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

tomaka reviewed Jun 23, 2023

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lexnv added 2 commits June 23, 2023 13:46

Build bootnodes with serde_json::Value directly

e84cc09

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

Make channel between subxt user and subxt background unbounded

0bde689

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

tomaka reviewed Jun 23, 2023

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lexnv and others added 2 commits June 23, 2023 14:05

Update subxt/src/client/lightclient/builder.rs

4d53500

Co-authored-by: Niklas Adolfsson <niklasadolfsson1@gmail.com>

Switch to smoldot 0.6.0 from 0.5.0

0adfed4

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

lexnv mentioned this pull request Jun 23, 2023

Unreachable code submitting transaction smol-dot/smoldot#807

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Move testing to full_client and light_client higher modules

3f01f92

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

tadeohepperle approved these changes Jun 23, 2023

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