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Network

Introduction​

The network layer in aelf is vital for maintaining connections and communication between nodes. It supports higher-level logic like synchronization and allows node operators to monitor and manage network operations. aelf uses gRPC for connections to keep the design simple and flexible.

Architecture​

The network consists of three layers:

  1. aelf.OS

    • Handles network events.
    • Runs background tasks for network operations.

  2. aelf.OS.Core.Network

    • Provides services to higher levels.
    • Defines infrastructure components and types.

  3. aelf.OS.Network.Grpc

    • Implements the infrastructure layer using gRPC.
    • Manages low-level functions like serialization and retrying.

aelf.OS​

This layer monitors and handles network-related events:

  • Transaction Accepted Event: When a transaction is verified.
  • Block Mined Event: When a block is packaged.
  • Block Accepted Event: When a block is executed successfully.
  • New Irreversible Block Found Event: When a new irreversible block is found.

It also performs regular tasks:

  • Peer Health Check: Ensures connected peers are healthy.
  • Peer Retry Connection: Attempts to reconnect with unhealthy peers.
  • Network Node Discovery: Finds new nodes.

aelf.OS.Core.Network​

This core module includes:

  • NetworkService: Manages sending/receiving requests, broadcasting items to peers, and handling network exceptions.
  • IPeerPool/PeerPool: Manages active peer connections.
  • IPeer: Defines peer interactions and metrics.
  • IaelfNetworkServer: Manages network lifecycle and connections.

aelf.OS.Network.Grpc​

Implements the infrastructure layer using gRPC:

  • GrpcPeer: Implements IPeer.
  • GrpcStreamPeer: Client-side IPeer implementation (node version >=1.4.0).
  • GrpcStreamBackPeer: Server-side IPeer implementation (node version >=1.4.0).
  • GrpcNetworkServer: Implements IaelfNetworkServer.
  • GrpcServerService: Manages network service interfaces and data exchange.

Extra functionalities include:

  • Serializing and deserializing requests.
  • Implementing request/response mechanisms.
  • Authentication.

Protocol​

Nodes use a defined network interface protocol for normal operation and data synchronization.

Connection​

DoHandshake​

When a node connects, it exchanges handshake information. This includes chain status, current height, and more.

  • Request: 
    rpc DoHandshake (HandshakeRequest) returns (HandshakeReply) {}
  • Handshake Message: 
    message Handshake {
        HandshakeData handshake_data = 1;
        bytes signature = 2;
        bytes session_id = 3;
    }
  • HandshakeData Message: 
    message HandshakeData {
        int32 chain_id = 1;
        int32 version = 2;
        int32 listening_port = 3;
        bytes pubkey = 4;
        aelf.Hash best_chain_hash = 5;
        int64 best_chain_height = 6;
        aelf.Hash last_irreversible_block_hash = 7;
        int64 last_irreversible_block_height = 8;
        google.protobuf.Timestamp time = 9;
    }

ConfirmHandshake​

Confirms the handshake with the target node.

  • Request: 
    rpc ConfirmHandshake (ConfirmHandshakeRequest) returns (VoidReply) {}

Broadcasting​

BlockBroadcastStream​

Receives block information after packaging.

  • Request: 
    rpc BlockBroadcastStream (stream BlockWithTransactions) returns (VoidReply) {}

TransactionBroadcastStream​

Receives forwarded transaction information.

  • Request: 
    rpc TransactionBroadcastStream (stream aelf.Transaction) returns (VoidReply) {}

AnnouncementBroadcastStream​

Receives block announcements.

  • Request: 
    rpc AnnouncementBroadcastStream (stream BlockAnnouncement) returns (VoidReply) {}

LibAnnouncementBroadcastStream​

Receives last irreversible block (LIB) announcements.

  • Request: 
    rpc LibAnnouncementBroadcastStream (stream LibAnnouncement) returns (VoidReply) {}

Block Request​

RequestBlock​

Requests a single block.

  • Request: 
    rpc RequestBlock (BlockRequest) returns (BlockReply) {}

RequestBlocks​

Requests multiple blocks.

  • Request: 
    rpc RequestBlocks (BlocksRequest) returns (BlockList) {}

Peer Management​

Ping​

Verifies network availability.

  • Request: 
    rpc Ping (PingRequest) returns (PongReply) {}

CheckHealth​

Performs health checks on peers.

  • Request: 
    rpc CheckHealth (HealthCheckRequest) returns (HealthCheckReply) {}