Package com.privatechain.network.sync

Class BlockFetcher

java.lang.Object

com.privatechain.network.sync.BlockFetcher

public final class BlockFetcher
extends Object

Fetches missing blocks from a specific remote peer during chain synchronization.

BlockFetcher is used by SyncManager to download blocks that the local node is missing. It sends GET_BLOCKS requests to a chosen peer and returns the decoded block list for validation and persistence.

Batch size

Block fetching is chunked into batches of at most BATCH_SIZE blocks to avoid creating excessively large TCP messages. For large sync gaps the fetcher issues multiple requests until all blocks are obtained.

Thread safety

Instances are stateless and safe for concurrent use once constructed.

Since:

1.0.0

See Also:

• SyncManager
• NodeClient

Field Summary

Fields

Modifier and Type	Field	Description
static final int	BATCH_SIZE	Maximum number of blocks requested in a single GET_BLOCKS message.

Constructor Summary

Constructors

Constructor	Description
BlockFetcher(String localNodeId, NodeClient nodeClient, MessageCodec codec)	Constructs a BlockFetcher.

Method Summary

Modifier and Type	Method	Description
List<Block>	fetchBlocks(Peer peer, int fromHeight, int toHeight)	Fetches all blocks from fromHeight (inclusive) to toHeight (inclusive) from the given peer, in ascending order.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

BATCH_SIZE

public static final int BATCH_SIZE

Maximum number of blocks requested in a single GET_BLOCKS message.

See Also:

• Constant Field Values

Constructor Details

BlockFetcher

public BlockFetcher(String localNodeId,
 NodeClient nodeClient,
 MessageCodec codec)

Constructs a BlockFetcher.

Parameters:

localNodeId - this node's stable logical identifier (non-null, non-blank)

nodeClient - outbound connection client (non-null)

codec - message codec (non-null)

Throws:

NullPointerException - if any parameter is null

IllegalArgumentException - if localNodeId is blank

Method Details

fetchBlocks

public List<Block> fetchBlocks(Peer peer,
 int fromHeight,
 int toHeight)

Fetches all blocks from fromHeight (inclusive) to toHeight (inclusive) from the given peer, in ascending order.

Blocks are fetched in batches of at most BATCH_SIZE. If any batch fails to download, the method returns whatever blocks were collected before the failure (partial result). The caller (SyncManager) is responsible for detecting gaps and retrying if needed.

Parameters:

peer - the peer to fetch from (non-null)

fromHeight - the first block height to request (≥ 0)

toHeight - the last block height to request (≥ fromHeight)

Returns:

ordered list of fetched blocks; empty if the peer does not respond

Throws:

NullPointerException - if peer is null

IllegalArgumentException - if fromHeight > toHeight