added test case for polling strategy refactored the strategy class

include/cppkafka/utils/poll_interface.h

@@ -0,0 +1,130 @@
+/*
+ * 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.
+ *
+ */
+
+#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 RoundRobinPollStrategy::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 RoundRobinPollStrategy::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 RoundRobinPollStrategy::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