Once the Handler is started, it processes securities definitions retrieved from TCP connection. Afterward, the Handler starts listening for a book-related market data. At first, the Handler reconstructs all the books for all available securities. Once reconstruction is accomplished, the Handler listens for incremental updates and processes them accordingly.
The table below describes all possible states for the Handler:
HandlerStates::BooksResynchronizationStarted The Handler switches to this state when it joins the system for a market data and starts building the books for all securities whose definitions were obtained on the previous stage. Also, the Handler may move into this stage in case of message GAP detection while maintaining books.