public Connection borrowConnection(long timeout, TimeUnit unit)
throws ConnectionException, TimeoutException {
if (isShutdown.get())
// Note: throwing a ConnectionException is probably fine in practice as it will trigger the
// creation of a new host.
// That being said, maybe having a specific exception could be cleaner.
throw new ConnectionException(host.getAddress(), "Pool is shutdown");
if (connections.isEmpty()) {
for (int i = 0; i < options().getCoreConnectionsPerHost(hostDistance); i++) {
// We don't respect MAX_SIMULTANEOUS_CREATION here because it's only to
// protect against creating connection in excess of core too quickly
scheduledForCreation.incrementAndGet();
manager.executor().submit(newConnectionTask);
}
Connection c = waitForConnection(timeout, unit);
c.setKeyspace(manager.poolsState.keyspace);
return c;
}
int minInFlight = Integer.MAX_VALUE;
Connection leastBusy = null;
for (Connection connection : connections) {
int inFlight = connection.inFlight.get();
if (inFlight < minInFlight) {
minInFlight = inFlight;
leastBusy = connection;
}
}
if (minInFlight >= options().getMaxSimultaneousRequestsPerConnectionThreshold(hostDistance)
&& connections.size() < options().getMaxConnectionsPerHost(hostDistance))
maybeSpawnNewConnection();
while (true) {
int inFlight = leastBusy.inFlight.get();
if (inFlight >= Connection.MAX_STREAM_PER_CONNECTION) {
leastBusy = waitForConnection(timeout, unit);
break;
}
if (leastBusy.inFlight.compareAndSet(inFlight, inFlight + 1)) break;
}
leastBusy.setKeyspace(manager.poolsState.keyspace);
return leastBusy;
}
