protected void checkDisconnects(final long currentTimeMs) {
        // Check the connection of the unsent request. Disconnect the disconnected node if it is unable to be connected.
        Iterator<UnsentRequest> iter = unsentRequests.iterator();
        while (iter.hasNext()) {
            UnsentRequest u = iter.next();
            if (u.node.isPresent() && client.connectionFailed(u.node.get())) {
                iter.remove();
                AuthenticationException authenticationException = client.authenticationException(u.node.get());
                u.handler.onFailure(currentTimeMs, authenticationException);
            }
        }
    }
Tries to send the requests in the unsentRequest queue. If the request doesn't have an assigned node, it will
find the leastLoadedOne, and will be retried in the next {@code poll()}. If the request is expired, a
{@link TimeoutException} will be thrown.
clients/src/main/java/org/apache/kafka/clients/consumer/internals/NetworkClientDelegate.java