fix(rln-relay): chunk event fetching

waku/v2/waku_rln_relay/group_manager/on_chain/group_manager.nim

@@ -62,6 +62,8 @@ type
 const DefaultKeyStorePath* = "rlnKeystore.json"
 const DefaultKeyStorePassword* = "password"
 
+const BlockChunkSize* = 100'u64
+
 template initializedGuard(g: OnchainGroupManager): untyped =
   if not g.initialized:
     raise newException(ValueError, "OnchainGroupManager is not initialized")
@@ -316,16 +318,28 @@ proc startListeningToEvents(g: OnchainGroupManager): Future[void] {.async.} =
 proc startOnchainSync(g: OnchainGroupManager): Future[void] {.async.} =
   initializedGuard(g)
 
-  let fromBlock = if g.latestProcessedBlock.isSome():
+  let latestBlock = cast[BlockNumber](await g.ethRpc.get().provider.eth_blockNumber())
+
+  var fromBlock = if g.latestProcessedBlock.isSome():
     info "resuming onchain sync from block", fromBlock = g.latestProcessedBlock.get()
     g.latestProcessedBlock.get()
   else:
     info "starting onchain sync from scratch"
+    # chunk size is 1000 blocks
     BlockNumber(0)
 
   try:
     # we always want to sync from last processed block => latest
-    await g.getAndHandleEvents(fromBlock, some(BlockNumber(0)))
+    if fromBlock == BlockNumber(0) or 
+       fromBlock + BlockNumber(BlockChunkSize) < latestBlock:
+      # chunk events
+      for i in 0..(latestBlock - fromBlock) div BlockChunkSize:
+        let toBlock = fromBlock + BlockNumber(BlockChunkSize)
+        info "chunking events", fromBlock = fromBlock, toBlock = toBlock
+        await g.getAndHandleEvents(fromBlock, some(toBlock))
+        fromBlock = toBlock
+    else:
+      await g.getAndHandleEvents(fromBlock, some(BlockNumber(0)))
   except CatchableError:
     raise newException(ValueError, "failed to get the history/reconcile missed blocks: " & getCurrentExceptionMsg())