Example fixes (#96)

* Add example for kafka buffered producer

* Add notes regarding bool returned in produce failure callback

* Fix example names

examples/CMakeLists.txt

@@ -4,12 +4,14 @@ include_directories(SYSTEM ${RDKAFKA_INCLUDE_DIR})
 
 add_custom_target(examples)
 macro(create_example example_name)
-    add_executable(${example_name} EXCLUDE_FROM_ALL "${example_name}.cpp")
-    add_dependencies(examples ${example_name})
+    string(REPLACE "_" "-" sanitized_name ${example_name})
+    add_executable(${sanitized_name} EXCLUDE_FROM_ALL "${example_name}_example.cpp")
+    add_dependencies(examples ${sanitized_name})
 endmacro()
 
-create_example(kafka_producer)
-create_example(kafka_consumer)
-create_example(kafka_consumer_dispatcher)
+create_example(producer)
+create_example(buffered_producer)
+create_example(consumer)
+create_example(consumer_dispatcher)
 create_example(metadata)
 create_example(consumers_information)

examples/buffered_producer_example.cpp

@@ -0,0 +1,96 @@
+#include <stdexcept>
+#include <iostream>
+#include <boost/program_options.hpp>
+#include "cppkafka/utils/buffered_producer.h"
+#include "cppkafka/configuration.h"
+
+using std::string;
+using std::exception;
+using std::getline;
+using std::cin;
+using std::cout;
+using std::endl;
+
+using cppkafka::BufferedProducer;
+using cppkafka::Configuration;
+using cppkafka::Topic;
+using cppkafka::MessageBuilder;
+using cppkafka::Message;
+
+namespace po = boost::program_options;
+
+int main(int argc, char* argv[]) {
+    string brokers;
+    string topic_name;
+    int partition_value = -1;
+
+    po::options_description options("Options");
+    options.add_options()
+        ("help,h",      "produce this help message")
+        ("brokers,b",   po::value<string>(&brokers)->required(), 
+                        "the kafka broker list")
+        ("topic,t",     po::value<string>(&topic_name)->required(),
+                        "the topic in which to write to")
+        ("partition,p", po::value<int>(&partition_value),
+                        "the partition to write into (unassigned if not provided)")
+        ;
+
+    po::variables_map vm;
+
+    try {
+        po::store(po::command_line_parser(argc, argv).options(options).run(), vm);
+        po::notify(vm);
+    }
+    catch (exception& ex) {
+        cout << "Error parsing options: " << ex.what() << endl;
+        cout << endl;
+        cout << options << endl;
+        return 1;
+    }
+
+    // Create a message builder for this topic
+    MessageBuilder builder(topic_name);
+
+    // Get the partition we want to write to. If no partition is provided, this will be
+    // an unassigned one
+    if (partition_value != -1) {
+        builder.partition(partition_value);
+    }
+
+    // Construct the configuration
+    Configuration config = {
+        { "metadata.broker.list", brokers }
+    };
+
+    // Create the producer
+    BufferedProducer<string> producer(config);
+
+    // Set a produce success callback
+    producer.set_produce_success_callback([](const Message& msg) {
+        cout << "Successfully produced message with payload " << msg.get_payload() << endl;
+    });
+    // Set a produce failure callback
+    producer.set_produce_failure_callback([](const Message& msg) {
+        cout << "Failed to produce message with payload " << msg.get_payload() << endl;
+        // Return false so we stop trying to produce this message
+        return false;
+    });
+
+    cout << "Producing messages into topic " << topic_name << endl;
+
+    // Now read lines and write them into kafka
+    string line;
+    while (getline(cin, line)) {
+        // Set the payload on this builder
+        builder.payload(line);
+
+        // Add the message we've built to the buffered producer
+        producer.add_message(builder);
+
+        // Now flush so we:
+        // * emit the buffered message
+        // * poll the producer so we dispatch on delivery report callbacks and
+        // therefore get the produce failure/success callbacks
+        producer.flush();
+    }
+}

include/cppkafka/utils/buffered_producer.h

@@ -99,7 +99,10 @@ public:
     using ProduceSuccessCallback = std::function<void(const Message&)>;
 
     /**
-     * Callback to indicate a message failed to be produced by the broker
+     * Callback to indicate a message failed to be produced by the broker.
+     *
+     * The returned bool indicates whether the BufferedProducer should try to produce
+     * the message again after each failure.
      */
     using ProduceFailureCallback = std::function<bool(const Message&)>;