presto-main/src/main/java/io/prestosql/operator/ExchangeClient.java/ExchangeClient/isFinished
class ExchangeClient:    public boolean isFinished()
    {
        throwIfFailed();
        // For this to works, locations must never be added after is closed is set
        return isClosed() && completedClients.size() == allClients.size();
    }