feat(sync): add gRPC-based block downloader

[kariy]

Adds gRPC as a third sync source for full node block synchronization, alongside the existing feeder gateway and JSON-RPC downloaders. Usage: --sync.grpc http://host:5051. This is a Katana-specific endpoint — it only works when syncing from another Katana node with --grpc enabled.

Implementation

Block downloader (crates/sync/stage/src/blocks/downloader.rs):

• GrpcBatchBlockDownloader implements BlockDownloader using BatchDownloader<GrpcDownloader> for concurrent downloads with retry logic
• Downloads GetBlockWithReceipts and GetStateUpdate concurrently per block via tokio::try_join!
• Converts proto responses directly to BlockData (proto → primitives), avoiding intermediate rpc_types conversions and keeping the code self-contained in the sync crate
• Lazy connection via OnceCell<GrpcClient> — connects on first download rather than at startup, so Node::build() stays synchronous and transient connection failures are handled by the existing retry logic in BatchDownloader
• Clones GrpcClient per download call since tonic's Channel is Arc-backed (cheap to clone), avoiding Mutex contention on concurrent downloads where &mut self is required by tonic

Class downloader (crates/sync/stage/src/classes/downloader.rs):

• GrpcClassDownloader implements ClassDownloader using the same lazy connection and clone-per-download patterns
• Deserializes the class from the JSON payload in the gRPC response's abi field

gRPC server fix (crates/grpc/src/handlers/starknet.rs):

• Fixed get_class and get_class_at handlers which previously returned stubbed/empty responses
• JSON-serializes the full Class (Sierra or Legacy) and stores it in the abi field of the appropriate proto variant (ContractClass or DeprecatedContractClass)
• Uses JSON rather than a binary format (e.g. postcard) because the class types are not compatible with non-human-readable serialization

CLI (crates/cli/src/options.rs):

• --sync.grpc <URL> flag, mutually exclusive with --sync.gateway and --sync.rpc

Error handling:

• Retryable gRPC status codes (Unavailable, ResourceExhausted, DeadlineExceeded) and transport errors trigger BatchDownloader's exponential backoff retry
• All other status codes are treated as permanent failures

🤖 Generated with Claude Code

[github-actions]

Benchmark

Details

Benchmark suite	Current: aaff16f	Previous: b4121df	Ratio
CompiledClass(fixture)/compress	2625505 ns/iter (± 48439)	2625621 ns/iter (± 88165)	1.00
CompiledClass(fixture)/decompress	2912041 ns/iter (± 183236)	2905010 ns/iter (± 12454)	1.00
ExecutionCheckpoint/compress	33 ns/iter (± 0)	32 ns/iter (± 3)	1.03
ExecutionCheckpoint/decompress	27 ns/iter (± 11)	27 ns/iter (± 3)	1
PruningCheckpoint/compress	32 ns/iter (± 5)	33 ns/iter (± 6)	0.97
PruningCheckpoint/decompress	27 ns/iter (± 4)	27 ns/iter (± 5)	1
VersionedHeader/compress	653 ns/iter (± 14)	655 ns/iter (± 25)	1.00
VersionedHeader/decompress	812 ns/iter (± 42)	806 ns/iter (± 7)	1.01
StoredBlockBodyIndices/compress	76 ns/iter (± 5)	76 ns/iter (± 6)	1
StoredBlockBodyIndices/decompress	36 ns/iter (± 8)	35 ns/iter (± 5)	1.03
StorageEntry/compress	140 ns/iter (± 1)	140 ns/iter (± 10)	1
StorageEntry/decompress	141 ns/iter (± 2)	139 ns/iter (± 3)	1.01
ContractNonceChange/compress	140 ns/iter (± 2)	140 ns/iter (± 11)	1
ContractNonceChange/decompress	235 ns/iter (± 3)	248 ns/iter (± 4)	0.95
ContractClassChange/compress	207 ns/iter (± 1)	209 ns/iter (± 3)	0.99
ContractClassChange/decompress	253 ns/iter (± 3)	252 ns/iter (± 3)	1.00
ContractStorageEntry/compress	147 ns/iter (± 2)	155 ns/iter (± 3)	0.95
ContractStorageEntry/decompress	310 ns/iter (± 12)	309 ns/iter (± 15)	1.00
GenericContractInfo/compress	137 ns/iter (± 2)	138 ns/iter (± 2)	0.99
GenericContractInfo/decompress	107 ns/iter (± 3)	108 ns/iter (± 4)	0.99
Felt/compress	72 ns/iter (± 3)	71 ns/iter (± 6)	1.01
Felt/decompress	56 ns/iter (± 4)	54 ns/iter (± 4)	1.04
BlockHash/compress	72 ns/iter (± 1)	71 ns/iter (± 5)	1.01
BlockHash/decompress	56 ns/iter (± 4)	55 ns/iter (± 5)	1.02
TxHash/compress	72 ns/iter (± 1)	71 ns/iter (± 4)	1.01
TxHash/decompress	56 ns/iter (± 6)	54 ns/iter (± 4)	1.04
ClassHash/compress	72 ns/iter (± 2)	71 ns/iter (± 6)	1.01
ClassHash/decompress	56 ns/iter (± 9)	54 ns/iter (± 5)	1.04
CompiledClassHash/compress	71 ns/iter (± 1)	71 ns/iter (± 5)	1
CompiledClassHash/decompress	56 ns/iter (± 5)	54 ns/iter (± 5)	1.04
BlockNumber/compress	35 ns/iter (± 2)	34 ns/iter (± 2)	1.03
BlockNumber/decompress	26 ns/iter (± 0)	26 ns/iter (± 1)	1
TxNumber/compress	35 ns/iter (± 2)	34 ns/iter (± 2)	1.03
TxNumber/decompress	25 ns/iter (± 1)	25 ns/iter (± 1)	1
FinalityStatus/compress	1 ns/iter (± 0)	1 ns/iter (± 0)	1
FinalityStatus/decompress	12 ns/iter (± 1)	12 ns/iter (± 1)	1
TypedTransactionExecutionInfo/compress	15949 ns/iter (± 152)	18191 ns/iter (± 108)	0.88
TypedTransactionExecutionInfo/decompress	3609 ns/iter (± 63)	3570 ns/iter (± 71)	1.01
VersionedContractClass/compress	379 ns/iter (± 4)	370 ns/iter (± 5)	1.02
VersionedContractClass/decompress	760 ns/iter (± 4)	780 ns/iter (± 29)	0.97
MigratedCompiledClassHash/compress	148 ns/iter (± 4)	142 ns/iter (± 5)	1.04
MigratedCompiledClassHash/decompress	143 ns/iter (± 6)	151 ns/iter (± 4)	0.95
ContractInfoChangeList/compress	1705 ns/iter (± 40)	1692 ns/iter (± 34)	1.01
ContractInfoChangeList/decompress	2092 ns/iter (± 377)	2100 ns/iter (± 375)	1.00
BlockChangeList/compress	711 ns/iter (± 57)	714 ns/iter (± 19)	1.00
BlockChangeList/decompress	847 ns/iter (± 154)	860 ns/iter (± 152)	0.98
ReceiptEnvelope/compress	31151 ns/iter (± 419)	31191 ns/iter (± 302)	1.00
ReceiptEnvelope/decompress	6096 ns/iter (± 534)	6149 ns/iter (± 299)	0.99
TrieDatabaseValue/compress	182 ns/iter (± 3)	188 ns/iter (± 3)	0.97
TrieDatabaseValue/decompress	244 ns/iter (± 1)	243 ns/iter (± 2)	1.00
TrieHistoryEntry/compress	321 ns/iter (± 1)	319 ns/iter (± 21)	1.01
TrieHistoryEntry/decompress	263 ns/iter (± 8)	267 ns/iter (± 9)	0.99

This comment was automatically generated by workflow using github-action-benchmark.

[github-actions]

Runner: AMD EPYC 7763 64-Core Processor (4 cores) · 15Gi RAM

[codecov]

Codecov Report

❌ Patch coverage is 0.79745% with 622 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.37%. Comparing base (9bde0ae) to head (aaff16f).
⚠️ Report is 330 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/sync/stage/src/blocks/downloader.rs	0.00%	506 Missing ⚠️
crates/sync/stage/src/classes/downloader.rs	0.00%	63 Missing ⚠️
crates/node/full/src/lib.rs	0.00%	41 Missing ⚠️
crates/grpc/src/handlers/starknet.rs	35.71%	9 Missing ⚠️
crates/cli/src/full.rs	0.00%	2 Missing ⚠️
crates/cli/src/options.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #503      +/-   ##
==========================================
- Coverage   73.32%   67.37%   -5.95%     
==========================================
  Files         209      292      +83     
  Lines       23132    37388   +14256     
==========================================
+ Hits        16961    25191    +8230     
- Misses       6171    12197    +6026     

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