fix(sync): resolve multi-chain gossip block propagation and sync across nodes

apps/blockchain-node/src/aitbc_chain/consensus/poa.py

@@ -174,6 +174,7 @@ class PoAProposer:
             await gossip_broker.publish(
                 "blocks",
                 {
+                    "chain_id": self._config.chain_id,
                     "height": block.height,
                     "hash": block.hash,
                     "parent_hash": block.parent_hash,
@@ -210,6 +211,7 @@ class PoAProposer:
             await gossip_broker.publish(
                 "blocks",
                 {
+                    "chain_id": self._config.chain_id,
                     "height": genesis.height,
                     "hash": genesis.hash,
                     "parent_hash": genesis.parent_hash,

apps/blockchain-node/src/aitbc_chain/main.py

@@ -8,6 +8,8 @@ from .config import settings
 from .consensus import PoAProposer, ProposerConfig, CircuitBreaker
 from .database import init_db, session_scope
 from .logger import get_logger
+from .gossip import gossip_broker, create_backend
+from .sync import ChainSync
 from .mempool import init_mempool
 
 logger = get_logger(__name__)
@@ -18,8 +20,57 @@ class BlockchainNode:
         self._stop_event = asyncio.Event()
         self._proposers: dict[str, PoAProposer] = {}
 
+    async def _setup_gossip_subscribers(self) -> None:
+        # Transactions
+        tx_sub = await gossip_broker.subscribe("transactions")
+        
+        async def process_txs():
+            from .mempool import get_mempool
+            mempool = get_mempool()
+            while True:
+                try:
+                    tx_data = await tx_sub.queue.get()
+                    if isinstance(tx_data, str):
+                        import json
+                        tx_data = json.loads(tx_data)
+                    chain_id = tx_data.get("chain_id", "ait-devnet")
+                    mempool.add(tx_data, chain_id=chain_id)
+                except Exception as exc:
+                    logger.error(f"Error processing transaction from gossip: {exc}")
+                    
+        asyncio.create_task(process_txs())
+
+        # Blocks
+        block_sub = await gossip_broker.subscribe("blocks")
+        
+        async def process_blocks():
+            while True:
+                try:
+                    block_data = await block_sub.queue.get()
+                    logger.info(f"Received block from gossip")
+                    if isinstance(block_data, str):
+                        import json
+                        block_data = json.loads(block_data)
+                    chain_id = block_data.get("chain_id", "ait-devnet")
+                    logger.info(f"Importing block for chain {chain_id}: {block_data.get('height')}")
+                    sync = ChainSync(session_factory=session_scope, chain_id=chain_id)
+                    res = sync.import_block(block_data)
+                    logger.info(f"Import result: accepted={res.accepted}, reason={res.reason}")
+                except Exception as exc:
+                    logger.error(f"Error processing block from gossip: {exc}")
+                    
+        asyncio.create_task(process_blocks())
+
     async def start(self) -> None:
         logger.info("Starting blockchain node", extra={"supported_chains": getattr(settings, 'supported_chains', settings.chain_id)})
+        
+        # Initialize Gossip Backend
+        backend = create_backend(
+            settings.gossip_backend,
+            broadcast_url=settings.gossip_broadcast_url,
+        )
+        await gossip_broker.set_backend(backend)
+        
         init_db()
         init_mempool(
             backend=settings.mempool_backend,
@@ -28,6 +79,7 @@ class BlockchainNode:
             min_fee=settings.min_fee,
         )
         self._start_proposers()
+        await self._setup_gossip_subscribers()
         try:
             await self._stop_event.wait()
         finally:
@@ -61,6 +113,7 @@ class BlockchainNode:
         for chain_id, proposer in list(self._proposers.items()):
             await proposer.stop()
         self._proposers.clear()
+        await gossip_broker.shutdown()
 
 
 @asynccontextmanager