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552 lines
19 KiB
C++
552 lines
19 KiB
C++
/*
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* Copyright (c) 2017, Matias Fontanini
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met:
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*
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following disclaimer
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* in the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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#ifndef CPP_KAFKA_CONSUMER_H
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#define CPP_KAFKA_CONSUMER_H
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#include <vector>
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#include <string>
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#include <chrono>
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#include <functional>
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#include "kafka_handle_base.h"
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#include "queue.h"
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#include "macros.h"
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#include "error.h"
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#include "detail/callback_invoker.h"
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namespace cppkafka {
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class TopicConfiguration;
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/**
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* \brief High level kafka consumer class
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*
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* Wrapper for the high level consumer API provided by rdkafka. Most methods are just
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* a one to one mapping to rdkafka functions.
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*
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* This class allows hooking up to assignments/revocations via callbacks.
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*
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* Semi-simple code showing how to use this class
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*
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* \code
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* // Create a configuration and set the group.id and broker list fields
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* Configuration config = {
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* { "metadata.broker.list", "127.0.0.1:9092" },
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* { "group.id", "foo" }
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* };
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*
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* // Create a consumer
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* Consumer consumer(config);
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*
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* // Set the assignment callback
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* consumer.set_assignment_callback([&](TopicPartitionList& topic_partitions) {
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* // Here you could fetch offsets and do something, altering the offsets on the
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* // topic_partitions vector if needed
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* cout << "Got assigned " << topic_partitions.size() << " partitions!" << endl;
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* });
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*
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* // Set the revocation callback
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* consumer.set_revocation_callback([&](const TopicPartitionList& topic_partitions) {
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* cout << topic_partitions.size() << " partitions revoked!" << endl;
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* });
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*
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* // Subscribe
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* consumer.subscribe({ "my_topic" });
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* while (true) {
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* // Poll. This will optionally return a message. It's necessary to check if it's a valid
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* // one before using it
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* Message msg = consumer.poll();
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* if (msg) {
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* if (!msg.get_error()) {
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* // It's an actual message. Get the payload and print it to stdout
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* cout << msg.get_payload().as_string() << endl;
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* }
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* else if (!msg.is_eof()) {
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* // Is it an error notification, handle it.
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* // This is explicitly skipping EOF notifications as they're not actually errors,
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* // but that's how rdkafka provides them
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* }
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* }
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* }
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* \endcode
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*/
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class CPPKAFKA_API Consumer : public KafkaHandleBase {
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public:
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using AssignmentCallback = std::function<void(TopicPartitionList&)>;
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using RevocationCallback = std::function<void(const TopicPartitionList&)>;
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using RebalanceErrorCallback = std::function<void(Error)>;
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using KafkaHandleBase::pause;
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using KafkaHandleBase::resume;
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/**
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* \brief Creates an instance of a consumer.
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*
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* Note that the configuration *must contain* the group.id attribute set or this
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* will throw.
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*
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* \param config The configuration to be used
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*/
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Consumer(Configuration config);
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Consumer(const Consumer&) = delete;
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Consumer(Consumer&&) = delete;
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Consumer& operator=(const Consumer&) = delete;
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Consumer& operator=(Consumer&&) = delete;
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/**
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* \brief Closes and destroys the rdkafka handle
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*
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* This will call Consumer::close before destroying the handle
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*/
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~Consumer();
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/**
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* \brief Sets the topic/partition assignment callback
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*
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* The Consumer class will use rd_kafka_conf_set_rebalance_cb and will handle the
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* rebalance, converting from rdkafka topic partition list handles into TopicPartitionList
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* and executing the assignment/revocation/rebalance_error callbacks.
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*
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* \note You *do not need* to call Consumer::assign with the provided topic parttitions. This
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* will be handled automatically by cppkafka.
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*
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* \param callback The topic/partition assignment callback
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*/
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void set_assignment_callback(AssignmentCallback callback);
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/**
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* \brief Sets the topic/partition revocation callback
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*
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* The Consumer class will use rd_kafka_conf_set_rebalance_cb and will handle the
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* rebalance, converting from rdkafka topic partition list handles into TopicPartitionList
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* and executing the assignment/revocation/rebalance_error callbacks.
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*
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* \note You *do not need* to call Consumer::assign with an empty topic partition list or
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* anything like that. That's handled automatically by cppkafka. This is just a notifitation
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* so your application code can react to revocations
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*
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* \param callback The topic/partition revocation callback
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*/
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void set_revocation_callback(RevocationCallback callback);
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/**
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* \brief Sets the rebalance error callback
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*
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* The Consumer class will use rd_kafka_conf_set_rebalance_cb and will handle the
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* rebalance, converting from rdkafka topic partition list handles into TopicPartitionList
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* and executing the assignment/revocation/rebalance_error callbacks.
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*
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* \param callback The rebalance error callback
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*/
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void set_rebalance_error_callback(RebalanceErrorCallback callback);
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/**
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* \brief Subscribes to the given list of topics
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*
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* This translates to a call to rd_kafka_subscribe
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*
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* \param topics The topics to subscribe to
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*/
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void subscribe(const std::vector<std::string>& topics);
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/**
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* \brief Unsubscribes to the current subscription list
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*
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* This translates to a call to rd_kafka_unsubscribe
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*/
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void unsubscribe();
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/**
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* \brief Sets the current topic/partition assignment
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*
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* This translates into a call to rd_kafka_assign
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*/
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void assign(const TopicPartitionList& topic_partitions);
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/**
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* \brief Unassigns the current topic/partition assignment
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*
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* This translates into a call to rd_kafka_assign using a null as the topic partition list
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* parameter
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*/
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void unassign();
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/**
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* \brief Pauses all consumption
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*/
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void pause();
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/**
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* \brief Resumes all consumption
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*/
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void resume();
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/**
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* \brief Commits the current partition assignment
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*
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* This translates into a call to rd_kafka_commit with a null partition list.
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*
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* \remark This function is equivalent to calling commit(get_assignment())
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*/
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void commit();
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/**
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* \brief Commits the current partition assignment asynchronously
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*
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* This translates into a call to rd_kafka_commit with a null partition list.
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*
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* \remark This function is equivalent to calling async_commit(get_assignment())
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*/
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void async_commit();
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/**
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* \brief Commits the given message synchronously
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*
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* This translates into a call to rd_kafka_commit_message
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*
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* \param msg The message to be committed
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*/
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void commit(const Message& msg);
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/**
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* \brief Commits the given message asynchronously
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*
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* This translates into a call to rd_kafka_commit_message
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*
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* \param msg The message to be committed
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*/
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void async_commit(const Message& msg);
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/**
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* \brief Commits the offsets on the given topic/partitions synchronously
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*
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* This translates into a call to rd_kafka_commit
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*
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* \param topic_partitions The topic/partition list to be committed
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*/
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void commit(const TopicPartitionList& topic_partitions);
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/**
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* \brief Commits the offsets on the given topic/partitions asynchronously
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*
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* This translates into a call to rd_kafka_commit
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*
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* \param topic_partitions The topic/partition list to be committed
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*/
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void async_commit(const TopicPartitionList& topic_partitions);
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/**
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* \brief Gets the minimum and maximum offsets for the given topic/partition
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*
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* This translates into a call to rd_kafka_get_watermark_offsets
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*
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* \param topic_partition The topic/partition to get the offsets from
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*
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* \return A pair of offsets {low, high}
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*/
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OffsetTuple get_offsets(const TopicPartition& topic_partition) const;
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/**
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* \brief Gets the offsets committed for the given topic/partition list
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*
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* This translates into a call to rd_kafka_committed
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*
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* \param topic_partitions The topic/partition list to be queried
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*
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* \return The topic partition list
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*/
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TopicPartitionList get_offsets_committed(const TopicPartitionList& topic_partitions) const;
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/**
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* \brief Gets the offsets committed for the given topic/partition list with a timeout
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*
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* This translates into a call to rd_kafka_committed
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*
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* \param topic_partitions The topic/partition list to be queried
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*
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* \param timeout The timeout for this operation. Supersedes the default consumer timeout.
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*
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* \return The topic partition list
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*/
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TopicPartitionList get_offsets_committed(const TopicPartitionList& topic_partitions,
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std::chrono::milliseconds timeout) const;
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/**
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* \brief Gets the offset positions for the given topic/partition list
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*
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* This translates into a call to rd_kafka_position
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*
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* \param topic_partitions The topic/partition list to be queried
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*
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* \return The topic partition list
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*/
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TopicPartitionList get_offsets_position(const TopicPartitionList& topic_partitions) const;
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#if (RD_KAFKA_VERSION >= RD_KAFKA_STORE_OFFSETS_SUPPORT_VERSION)
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/**
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* \brief Stores the offsets on the currently assigned topic/partitions (legacy).
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*
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* This translates into a call to rd_kafka_offsets_store with the offsets prior to the current assignment positions.
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* It is equivalent to calling rd_kafka_offsets_store(get_offsets_position(get_assignment())).
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*
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* \note When using this API it's recommended to set enable.auto.offset.store=false and enable.auto.commit=true.
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*/
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void store_consumed_offsets() const;
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/**
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* \brief Stores the offsets on the given topic/partitions (legacy).
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*
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* This translates into a call to rd_kafka_offsets_store.
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*
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* \param topic_partitions The topic/partition list to be stored.
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*
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* \note When using this API it's recommended to set enable.auto.offset.store=false and enable.auto.commit=true.
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*/
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void store_offsets(const TopicPartitionList& topic_partitions) const;
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#endif
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/**
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* \brief Stores the offset for this message (legacy).
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*
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* This translates into a call to rd_kafka_offset_store.
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*
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* \param msg The message whose offset will be stored.
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*
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* \note When using this API it's recommended to set enable.auto.offset.store=false and enable.auto.commit=true.
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*/
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void store_offset(const Message& msg) const;
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/**
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* \brief Gets the current topic subscription
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*
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* This translates to a call to rd_kafka_subscription
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*/
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std::vector<std::string> get_subscription() const;
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/**
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* \brief Gets the current topic/partition list assignment
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*
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* This translates to a call to rd_kafka_assignment
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*
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* \return The topic partition list
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*/
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TopicPartitionList get_assignment() const;
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/**
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* \brief Gets the group member id
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*
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* This translates to a call to rd_kafka_memberid
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*
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* \return The id
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*/
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std::string get_member_id() const;
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/**
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* \brief Gets the partition assignment callback.
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*
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* \return The callback reference
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*/
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const AssignmentCallback& get_assignment_callback() const;
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/**
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* \brief Gets the partition revocation callback.
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*
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* \return The callback reference
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*/
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const RevocationCallback& get_revocation_callback() const;
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/**
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* \brief Gets the rebalance error callback.
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*
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* \return The callback reference
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*/
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const RebalanceErrorCallback& get_rebalance_error_callback() const;
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/**
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* \brief Polls for new messages
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*
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* This will call rd_kafka_consumer_poll.
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*
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* Note that you need to call poll periodically as a keep alive mechanism, otherwise the broker
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* will think this consumer is down and will trigger a rebalance (if using dynamic
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* subscription).
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*
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* The timeout used on this call will be the one configured via Consumer::set_timeout.
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*
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* \return A message. The returned message *might* be empty. It's necessary to check
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* that it's valid before using it:
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*
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* \code
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* Message msg = consumer.poll();
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* if (msg) {
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* // It's a valid message!
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* }
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* \endcode
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*/
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Message poll();
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/**
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* \brief Polls for new messages
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*
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* Same as the other overload of Consumer::poll but the provided timeout will be used
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* instead of the one configured on this Consumer.
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*
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* \param timeout The timeout to be used on this call
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*
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* \return A message
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*/
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Message poll(std::chrono::milliseconds timeout);
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/**
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* \brief Polls for a batch of messages
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*
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* This can return zero or more messages
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*
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* \param max_batch_size The maximum amount of messages expected
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* \param alloc The optionally supplied allocator for allocating messages
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*
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* \return A list of messages
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*/
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template <typename Allocator>
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std::vector<Message, Allocator> poll_batch(size_t max_batch_size,
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const Allocator& alloc);
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/**
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* \brief Polls for a batch of messages
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*
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* This can return zero or more messages
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*
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* \param max_batch_size The maximum amount of messages expected
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*
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* \return A list of messages
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*/
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std::vector<Message> poll_batch(size_t max_batch_size);
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/**
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* \brief Polls for a batch of messages
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*
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* This can return zero or more messages
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*
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* \param max_batch_size The maximum amount of messages expected
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* \param timeout The timeout for this operation
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* \param alloc The optionally supplied allocator for allocating messages
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*
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* \return A list of messages
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*/
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template <typename Allocator>
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std::vector<Message, Allocator> poll_batch(size_t max_batch_size,
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std::chrono::milliseconds timeout,
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const Allocator& alloc);
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/**
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* \brief Polls for a batch of messages
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*
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* This can return one or more messages
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*
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* \param max_batch_size The maximum amount of messages expected
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* \param timeout The timeout for this operation
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*
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* \return A list of messages
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*/
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std::vector<Message> poll_batch(size_t max_batch_size,
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std::chrono::milliseconds timeout);
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/**
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* \brief Get the global event queue servicing this consumer corresponding to
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* rd_kafka_queue_get_main and which is polled via rd_kafka_poll
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*
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* \return A Queue object
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*
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* \remark Note that this call will disable forwarding to the consumer_queue.
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* To restore forwarding if desired, call Queue::forward_to_queue(consumer_queue)
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*/
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Queue get_main_queue() const;
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/**
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* \brief Get the consumer group queue servicing corresponding to
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* rd_kafka_queue_get_consumer and which is polled via rd_kafka_consumer_poll
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*
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* \return A Queue object
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*/
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Queue get_consumer_queue() const;
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/**
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* \brief Get the queue belonging to this partition. If the consumer is not assigned to this
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* partition, an empty queue will be returned
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*
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* \param partition The partition object
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*
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* \return A Queue object
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*
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* \remark Note that this call will disable forwarding to the consumer_queue.
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* To restore forwarding if desired, call Queue::forward_to_queue(consumer_queue)
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*/
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Queue get_partition_queue(const TopicPartition& partition) const;
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private:
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static void rebalance_proxy(rd_kafka_t *handle, rd_kafka_resp_err_t error,
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rd_kafka_topic_partition_list_t *partitions, void *opaque);
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void close();
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void commit(const Message& msg, bool async);
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void commit(const TopicPartitionList* topic_partitions, bool async);
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void handle_rebalance(rd_kafka_resp_err_t err, TopicPartitionList& topic_partitions);
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AssignmentCallback assignment_callback_;
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RevocationCallback revocation_callback_;
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RebalanceErrorCallback rebalance_error_callback_;
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};
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// Implementations
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template <typename Allocator>
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std::vector<Message, Allocator> Consumer::poll_batch(size_t max_batch_size,
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const Allocator& alloc) {
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return poll_batch(max_batch_size, get_timeout(), alloc);
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}
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template <typename Allocator>
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std::vector<Message, Allocator> Consumer::poll_batch(size_t max_batch_size,
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std::chrono::milliseconds timeout,
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const Allocator& alloc) {
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std::vector<rd_kafka_message_t*> raw_messages(max_batch_size);
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// Note that this will leak the queue when using rdkafka < 0.11.5 (see get_queue comment)
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Queue queue = Queue::make_queue(rd_kafka_queue_get_consumer(get_handle()));
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ssize_t result = rd_kafka_consume_batch_queue(queue.get_handle(),
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timeout.count(),
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raw_messages.data(),
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raw_messages.size());
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if (result == -1) {
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check_error(rd_kafka_last_error());
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// on the off-chance that check_error() does not throw an error
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return std::vector<Message, Allocator>(alloc);
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}
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return std::vector<Message, Allocator>(raw_messages.begin(),
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raw_messages.begin() + result,
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alloc);
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}
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} // cppkafka
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#endif // CPP_KAFKA_CONSUMER_H
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