Preserve artifact cache unless stale (#1918)

Co-authored-by: Marcin S <marcin@realemail.net>

polkadot/node/core/candidate-validation/src/lib.rs

@@ -25,7 +25,7 @@
 
 use polkadot_node_core_pvf::{
 	InternalValidationError, InvalidCandidate as WasmInvalidCandidate, PrepareError,
-	PrepareJobKind, PrepareStats, PvfPrepData, ValidationError, ValidationHost,
+	PrepareJobKind, PvfPrepData, ValidationError, ValidationHost,
 };
 use polkadot_node_primitives::{
 	BlockData, InvalidCandidate, PoV, ValidationResult, POV_BOMB_LIMIT, VALIDATION_CODE_BOMB_LIMIT,
@@ -794,7 +794,7 @@ trait ValidationBackend {
 		validation_result
 	}
 
-	async fn precheck_pvf(&mut self, pvf: PvfPrepData) -> Result<PrepareStats, PrepareError>;
+	async fn precheck_pvf(&mut self, pvf: PvfPrepData) -> Result<(), PrepareError>;
 }
 
 #[async_trait]
@@ -824,7 +824,7 @@ impl ValidationBackend for ValidationHost {
 		})?
 	}
 
-	async fn precheck_pvf(&mut self, pvf: PvfPrepData) -> Result<PrepareStats, PrepareError> {
+	async fn precheck_pvf(&mut self, pvf: PvfPrepData) -> Result<(), PrepareError> {
 		let (tx, rx) = oneshot::channel();
 		if let Err(err) = self.precheck_pvf(pvf, tx).await {
 			// Return an IO error if there was an error communicating with the host.

polkadot/node/core/candidate-validation/src/tests.rs

@@ -377,7 +377,7 @@ impl ValidationBackend for MockValidateCandidateBackend {
 		result
 	}
 
-	async fn precheck_pvf(&mut self, _pvf: PvfPrepData) -> Result<PrepareStats, PrepareError> {
+	async fn precheck_pvf(&mut self, _pvf: PvfPrepData) -> Result<(), PrepareError> {
 		unreachable!()
 	}
 }
@@ -1014,11 +1014,11 @@ fn pov_decompression_failure_is_invalid() {
 }
 
 struct MockPreCheckBackend {
-	result: Result<PrepareStats, PrepareError>,
+	result: Result<(), PrepareError>,
 }
 
 impl MockPreCheckBackend {
-	fn with_hardcoded_result(result: Result<PrepareStats, PrepareError>) -> Self {
+	fn with_hardcoded_result(result: Result<(), PrepareError>) -> Self {
 		Self { result }
 	}
 }
@@ -1034,7 +1034,7 @@ impl ValidationBackend for MockPreCheckBackend {
 		unreachable!()
 	}
 
-	async fn precheck_pvf(&mut self, _pvf: PvfPrepData) -> Result<PrepareStats, PrepareError> {
+	async fn precheck_pvf(&mut self, _pvf: PvfPrepData) -> Result<(), PrepareError> {
 		self.result.clone()
 	}
 }
@@ -1051,7 +1051,7 @@ fn precheck_works() {
 
 	let (check_fut, check_result) = precheck_pvf(
 		ctx.sender(),
-		MockPreCheckBackend::with_hardcoded_result(Ok(PrepareStats::default())),
+		MockPreCheckBackend::with_hardcoded_result(Ok(())),
 		relay_parent,
 		validation_code_hash,
 	)
@@ -1113,7 +1113,7 @@ fn precheck_invalid_pvf_blob_compression() {
 
 	let (check_fut, check_result) = precheck_pvf(
 		ctx.sender(),
-		MockPreCheckBackend::with_hardcoded_result(Ok(PrepareStats::default())),
+		MockPreCheckBackend::with_hardcoded_result(Ok(())),
 		relay_parent,
 		validation_code_hash,
 	)

polkadot/node/core/pvf/Cargo.toml

@@ -8,6 +8,7 @@ license.workspace = true
 
 [dependencies]
 always-assert = "0.1"
+blake3 = "1.5"
 cfg-if = "1.0"
 futures = "0.3.21"
 futures-timer = "3.0.2"

polkadot/node/core/pvf/benches/host_prepare_rococo_runtime.rs

@@ -56,7 +56,7 @@ impl TestHost {
 		&self,
 		code: &[u8],
 		executor_params: ExecutorParams,
-	) -> Result<PrepareStats, PrepareError> {
+	) -> Result<(), PrepareError> {
 		let (result_tx, result_rx) = futures::channel::oneshot::channel();
 
 		let code = sp_maybe_compressed_blob::decompress(code, 16 * 1024 * 1024)

polkadot/node/core/pvf/common/Cargo.toml

@@ -36,6 +36,9 @@ seccompiler = "0.4.0"
 assert_matches = "1.4.0"
 tempfile = "3.3.0"
 
+[build-dependencies]
+substrate-build-script-utils = { path = "../../../../../substrate/utils/build-script-utils" }
+
 [features]
 # This feature is used to export test code to other crates without putting it in the production build.
 test-utils = []

polkadot/node/core/pvf/common/build.rs

@@ -0,0 +1,19 @@
+// Copyright (C) Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+fn main() {
+	substrate_build_script_utils::generate_wasmtime_version();
+}

polkadot/node/core/pvf/common/src/error.rs

@@ -14,16 +14,24 @@
 // You should have received a copy of the GNU General Public License
 // along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
 
-use crate::prepare::PrepareStats;
+use crate::prepare::{PrepareSuccess, PrepareWorkerSuccess};
 use parity_scale_codec::{Decode, Encode};
 use std::fmt;
 
-/// Result of PVF preparation performed by the validation host. Contains stats about the preparation
-/// if successful
-pub type PrepareResult = Result<PrepareStats, PrepareError>;
+/// Result of PVF preparation from a worker, with checksum of the compiled PVF and stats of the
+/// preparation if successful.
+pub type PrepareWorkerResult = Result<PrepareWorkerSuccess, PrepareError>;
+
+/// Result of PVF preparation propagated all the way back to the host, with path to the concluded
+/// artifact and stats of the preparation if successful.
+pub type PrepareResult = Result<PrepareSuccess, PrepareError>;
+
+/// Result of prechecking PVF performed by the validation host. Contains stats about the preparation
+/// if successful.
+pub type PrecheckResult = Result<(), PrepareError>;
 
 /// An error that occurred during the prepare part of the PVF pipeline.
-// Codec indexes are intended to stabilize pre-encoded payloads (see `OOM_PAYLOAD` below)
+// Codec indexes are intended to stabilize pre-encoded payloads (see `OOM_PAYLOAD`)
 #[derive(Debug, Clone, Encode, Decode)]
 pub enum PrepareError {
 	/// During the prevalidation stage of preparation an issue was found with the PVF.

polkadot/node/core/pvf/common/src/lib.rs

@@ -31,6 +31,8 @@ pub use sp_tracing;
 
 const LOG_TARGET: &str = "parachain::pvf-common";
 
+pub const RUNTIME_VERSION: &str = env!("SUBSTRATE_WASMTIME_VERSION");
+
 use std::{
 	io::{self, Read, Write},
 	mem,

polkadot/node/core/pvf/common/src/prepare.rs

@@ -15,6 +15,25 @@
 // along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
 
 use parity_scale_codec::{Decode, Encode};
+use std::path::PathBuf;
+
+/// Result from prepare worker if successful.
+#[derive(Debug, Clone, Default, Encode, Decode)]
+pub struct PrepareWorkerSuccess {
+	/// Checksum of the compiled PVF.
+	pub checksum: String,
+	/// Stats of the current preparation run.
+	pub stats: PrepareStats,
+}
+
+/// Result of PVF preparation if successful.
+#[derive(Debug, Clone, Default)]
+pub struct PrepareSuccess {
+	/// Canonical path to the compiled artifact.
+	pub path: PathBuf,
+	/// Stats of the current preparation run.
+	pub stats: PrepareStats,
+}
 
 /// Preparation statistics, including the CPU time and memory taken.
 #[derive(Debug, Clone, Default, Encode, Decode)]

polkadot/node/core/pvf/common/src/pvf.rs

@@ -115,7 +115,7 @@ impl fmt::Debug for PvfPrepData {
 	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 		write!(
 			f,
-			"Pvf {{ code, code_hash: {:?}, executor_params: {:?}, prep_timeout: {:?} }}",
+			"Pvf {{ code: [...], code_hash: {:?}, executor_params: {:?}, prep_timeout: {:?} }}",
 			self.code_hash, self.executor_params, self.prep_timeout
 		)
 	}

polkadot/node/core/pvf/prepare-worker/Cargo.toml

@@ -7,6 +7,7 @@ edition.workspace = true
 license.workspace = true
 
 [dependencies]
+blake3 = "1.5"
 cfg-if = "1.0"
 gum = { package = "tracing-gum", path = "../../../gum" }
 libc = "0.2.139"

polkadot/node/core/pvf/prepare-worker/src/lib.rs

@@ -40,10 +40,10 @@ use nix::{
 use os_pipe::{self, PipeReader, PipeWriter};
 use parity_scale_codec::{Decode, Encode};
 use polkadot_node_core_pvf_common::{
-	error::{PrepareError, PrepareResult},
+	error::{PrepareError, PrepareWorkerResult},
 	executor_intf::create_runtime_from_artifact_bytes,
 	framed_recv_blocking, framed_send_blocking,
-	prepare::{MemoryStats, PrepareJobKind, PrepareStats},
+	prepare::{MemoryStats, PrepareJobKind, PrepareStats, PrepareWorkerSuccess},
 	pvf::PvfPrepData,
 	worker::{
 		cpu_time_monitor_loop, run_worker, stringify_panic_payload,
@@ -106,7 +106,7 @@ fn recv_request(stream: &mut UnixStream) -> io::Result<PvfPrepData> {
 }
 
 /// Send a worker response.
-fn send_response(stream: &mut UnixStream, result: PrepareResult) -> io::Result<()> {
+fn send_response(stream: &mut UnixStream, result: PrepareWorkerResult) -> io::Result<()> {
 	framed_send_blocking(stream, &result.encode())
 }
 
@@ -186,8 +186,8 @@ fn end_memory_tracking() -> isize {
 ///
 /// 7. If compilation succeeded, write the compiled artifact into a temporary file.
 ///
-/// 8. Send the result of preparation back to the host. If any error occurred in the above steps, we
-///    send that in the `PrepareResult`.
+/// 8. Send the result of preparation back to the host, including the checksum of the artifact. If
+///    any error occurred in the above steps, we send that in the `PrepareWorkerResult`.
 pub fn worker_entrypoint(
 	socket_path: PathBuf,
 	worker_dir_path: PathBuf,
@@ -439,11 +439,11 @@ fn handle_child_process(
 				Err(err) => Err(err),
 				Ok(ok) => {
 					cfg_if::cfg_if! {
-					if #[cfg(target_os = "linux")] {
-						let (artifact, max_rss) = ok;
-					} else {
-						let artifact = ok;
-					}
+						if #[cfg(target_os = "linux")] {
+							let (artifact, max_rss) = ok;
+						} else {
+							let artifact = ok;
+						}
 					}
 
 					// Stop the memory stats worker and get its observed memory stats.
@@ -511,7 +511,7 @@ fn handle_parent_process(
 	worker_pid: u32,
 	usage_before: Usage,
 	timeout: Duration,
-) -> Result<PrepareStats, PrepareError> {
+) -> Result<PrepareWorkerSuccess, PrepareError> {
 	// Read from the child. Don't decode unless the process exited normally, which we check later.
 	let mut received_data = Vec::new();
 	pipe_read
@@ -554,7 +554,7 @@ fn handle_parent_process(
 
 			match result {
 				Err(err) => Err(err),
-				Ok(response) => {
+				Ok(JobResponse { artifact, memory_stats }) => {
 					// The exit status should have been zero if no error occurred.
 					if exit_status != 0 {
 						return Err(PrepareError::JobError(format!(
@@ -577,13 +577,14 @@ fn handle_parent_process(
 						temp_artifact_dest.display(),
 					);
 					// Write to the temp file created by the host.
-					if let Err(err) = fs::write(&temp_artifact_dest, &response.artifact) {
+					if let Err(err) = fs::write(&temp_artifact_dest, &artifact) {
 						return Err(PrepareError::IoErr(err.to_string()))
 					};
 
-					Ok(PrepareStats {
-						memory_stats: response.memory_stats,
-						cpu_time_elapsed: cpu_tv,
+					let checksum = blake3::hash(&artifact.as_ref()).to_hex().to_string();
+					Ok(PrepareWorkerSuccess {
+						checksum,
+						stats: PrepareStats { memory_stats, cpu_time_elapsed: cpu_tv },
 					})
 				},
 			}
@@ -657,13 +658,13 @@ fn error_from_errno(context: &'static str, errno: Errno) -> PrepareError {
 
 type JobResult = Result<JobResponse, PrepareError>;
 
-/// Pre-encoded length-prefixed `Result::Err(PrepareError::OutOfMemory)`
+/// Pre-encoded length-prefixed `JobResult::Err(PrepareError::OutOfMemory)`
 const OOM_PAYLOAD: &[u8] = b"\x02\x00\x00\x00\x00\x00\x00\x00\x01\x08";
 
 #[test]
 fn pre_encoded_payloads() {
 	// NOTE: This must match the type of `response` in `send_child_response`.
-	let oom_unencoded: JobResult = Result::Err(PrepareError::OutOfMemory);
+	let oom_unencoded: JobResult = JobResult::Err(PrepareError::OutOfMemory);
 	let oom_encoded = oom_unencoded.encode();
 	// The payload is prefixed with	its length in `framed_send`.
 	let mut oom_payload = oom_encoded.len().to_le_bytes().to_vec();