The exchange_app module is the top-level assembly for the BetaTrader Exchange server. It acts as the "braid" that weaves together the matching partitions, risk management, and protocol gateways into a single functional daemon.

Overview

Unlike the micro-modules it contains, exchange_app is responsible for global lifecycle management. It handles the instantiation of singleton resources (like DatabaseWorker and ID Generators), initializes the instrument-specific matching partitions, and provides the public submitCommand interface used by networking gateways.

Key Responsibilities

Initialize the global DatabaseWorker for asynchronous persistence.
Construct and own the Partition array based on the Instrument enumeration.
Provide a centralized TradingCore facade for command dispatch.
Orchestrate orderly shutdown and queue draining during maintenance.
Maintain the instance singleton for global access.

Architecture

graph TD
    SERVER(fix_server Executable) --> CORE[exchange_app: TradingCore]
    
    subgraph "exchange_app internals"
        CORE --> P1(exchange_routing: Partition 1)
        CORE --> P2(exchange_routing: Partition 2)
        CORE --> DB(exchange_persistence: DatabaseWorker)
        CORE --> IDG(exchange_state: OrderIDGenerator)
    end
    
    subgraph "Networking Layers"
        FIX(exchange_fix: FIX Server)
        API(exchange_api: REST Server)
    end
 
    FIX -->|submitCommand| CORE
    API -->|submitCommand| CORE

Class Diagram

classDiagram
    class TradingCore {
        +start()
        +stop()
        +submitCommand(unique_ptr~Command~)
        +getPartition(Instrument) : Partition*
        +TradingCore(dbWorker*, bool autoInit)
        +TradingCore(dbWorkerUptr, authRepoUptr, tradeIDRepoUptr, tradeIDGenUptr, orderIDGenUptr, autoInit)
        -initPartitions()
        -m_partitions: unique_ptr~Partition~[]
        -m_dbWorker: DatabaseWorker*
    }
 
    class Main {
        +main()
        -setupSignalHandlers()
    }
 
    Main --> TradingCore : Instantiates

Component Responsibilities

Component	Description
`TradingCore`	The central facade. It routes incoming commands to the specific `Partition` responsible for a given instrument.
`Main`	Entry point. Parses CLI arguments, sets up logging, and blocks on the `io_context` while the engine runs.

Critical Design Conventions

Partition Isolation: TradingCore ensures that a command for EURUSD never touches the state of USDJPY by routing exclusively to the dedicated partition.
Resource Ownership: This module is the "parent" of the server stack; objects created here are passed by reference down into the child micro-modules to enforce a clear ownership hierarchy.