Message Queues

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Incoming and outgoing message queues are maintained between P2PComm and the rest of the Zilliqa core. This helps provide some ordering in the processing of messages, and it also adds some control over the number of messages that can be buffered. Once ready for processing, messages enter a thread pool, which regulates the number of messages that can be processed concurrently.

After an incoming message is read from a socket, it is first inserted into Zilliqa::m_msgQueue, whose maximum size is controlled by MSGQUEUE_SIZE. When the queue reaches full capacity, any further incoming messages are dropped. A dedicated thread launched during startup manages dequeueing of messages and sending them to Zilliqa::m_queuePool, a thread pool limited by MAXRECVMESSAGE. Once assigned to a thread, the message gets dispatched according to the earlier section.

Equivalently, before an outgoing message is written out to a socket, it is first inserted into P2PComm::m_sendQueue, whose maximum size is controlled by SENDQUEUE_SIZE. Any further outgoing messages are also dropped once the queue is full. A dedicated thread launched during startup also manages dequeueing of messages and sending them to Zilliqa::m_SendPool, which is also limited by MAXSENDMESSAGE. One assigned to a thread, the message gets sent out according to the P2PComm::SendJob settings for the message.