wlan-cloud-lib-cppkafka/include/cppkafka/utils/poll_interface.h

/*
 * Copyright (c) 2017, Matias Fontanini
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following disclaimer
 *   in the documentation and/or other materials provided with the
 *   distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */

#ifndef CPPKAFKA_POLL_INTERFACE_H
#define CPPKAFKA_POLL_INTERFACE_H

#include "../consumer.h"

namespace cppkafka {

/**
 * \interface PollInterface
 *
 * \brief Interface defining polling methods for the Consumer class
 */
struct PollInterface {
    virtual ~PollInterface() = default;
    
    /**
     * \brief Get the underlying consumer controlled by this strategy
     *
     * \return A reference to the consumer instance
     */
    virtual Consumer& get_consumer() = 0;
    
    /**
     * \brief Sets the timeout for polling functions
     *
     * This calls Consumer::set_timeout
     *
     * \param timeout The timeout to be set
     */
    virtual void set_timeout(std::chrono::milliseconds timeout) = 0;
    
    /**
     * \brief Gets the timeout for polling functions
     *
     * This calls Consumer::get_timeout
     *
     * \return The timeout
     */
    virtual std::chrono::milliseconds get_timeout() = 0;
    
    /**
     * \brief Polls all assigned partitions for new messages in round-robin fashion
     *
     * Each call to poll() will first consume from the global event queue and if there are
     * no pending events, will attempt to consume from all partitions until a valid message is found.
     * The timeout used on this call will be the one configured via PollInterface::set_timeout.
     *
     * \return A message. The returned message *might* be empty. It's necessary to check
     * that it's a valid one before using it (see example above).
     *
     * \remark You need to call poll() or poll_batch() periodically as a keep alive mechanism,
     * otherwise the broker will think this consumer is down and will trigger a rebalance
     * (if using dynamic subscription)
     */
    virtual Message poll() = 0;
    
    /**
     * \brief Polls for new messages
     *
     * Same as the other overload of PollInterface::poll but the provided
     * timeout will be used instead of the one configured on this Consumer.
     *
     * \param timeout The timeout to be used on this call
     */
    virtual Message poll(std::chrono::milliseconds timeout) = 0;

    /**
     * \brief Polls all assigned partitions for a batch of new messages in round-robin fashion
     *
     * Each call to poll_batch() will first attempt to consume from the global event queue
     * and if the maximum batch number has not yet been filled, will attempt to fill it by
     * reading the remaining messages from each partition.
     *
     * \param max_batch_size The maximum amount of messages expected
     *
     * \return A list of messages
     *
     * \remark You need to call poll() or poll_batch() periodically as a keep alive mechanism,
     * otherwise the broker will think this consumer is down and will trigger a rebalance
     * (if using dynamic subscription)
     */
    virtual MessageList poll_batch(size_t max_batch_size) = 0;

    /**
     * \brief Polls all assigned partitions for a batch of new messages in round-robin fashion
     *
     * Same as the other overload of PollInterface::poll_batch but the provided
     * timeout will be used instead of the one configured on this Consumer.
     *
     * \param max_batch_size The maximum amount of messages expected
     *
     * \param timeout The timeout for this operation
     *
     * \return A list of messages
     */
    virtual MessageList poll_batch(size_t max_batch_size, std::chrono::milliseconds timeout) = 0;
};

} //cppkafka

#endif //CPPKAFKA_POLL_INTERFACE_H