Method minInFlight

lib/host-connection-pool.js:130–167

* Gets the connection with the minimum number of in-flight requests. * Only checks for 2 connections (round-robin) and gets the one with minimum in-flight requests, as long as * the amount of in-flight requests is lower than maxRequests. * @param {Array. } connections * @param

(connections, maxRequests, previousConnection)

   * @returns {Connection!}
   */
  static minInFlight(connections, maxRequests, previousConnection) {
    const length = connections.length;
    if (length === 1) {
      return connections[0];
    }

    // Use a single index for all hosts as a simplified way to balance the load between connections
    connectionIndex++;
    if (connectionIndex >= connectionIndexOverflow) {
      connectionIndex = 0;
    }

    let current;
    for (let index = connectionIndex; index < connectionIndex + length; index++) {
      current = connections[index % length];
      if (current === previousConnection) {
        // Increment the index and skip
        current = connections[(++index) % length];
      }

      let next = connections[(index + 1) % length];
      if (next === previousConnection) {
        // Skip
        next = connections[(index + 2) % length];
      }

      if (next.getInFlight() < current.getInFlight()) {
        current = next;
      }

      if (current.getInFlight() < maxRequests) {
        // Check as few connections as possible, as long as the amount of in-flight
        // requests is lower than maxRequests
        break;
      }
    }
    return current;
  }

  /**
   * Creates all the connections in the pool and switches the keyspace of each connection if needed.