Example fixes (#96)

* Add example for kafka buffered producer

* Add notes regarding bool returned in produce failure callback

* Fix example names

examples/consumers_information_example.cpp

@@ -0,0 +1,97 @@
+#include <stdexcept>
+#include <iostream>
+#include <boost/program_options.hpp>
+#include "cppkafka/producer.h"
+#include "cppkafka/configuration.h"
+#include "cppkafka/group_information.h"
+#include "cppkafka/topic.h"
+
+using std::string;
+using std::exception;
+using std::vector;
+using std::cout;
+using std::endl;
+
+using cppkafka::Producer;
+using cppkafka::Exception;
+using cppkafka::Configuration;
+using cppkafka::Topic;
+using cppkafka::GroupInformation;
+using cppkafka::GroupMemberInformation;
+using cppkafka::MemberAssignmentInformation;
+
+namespace po = boost::program_options;
+
+int main(int argc, char* argv[]) {
+    string brokers;
+    string group_id;
+    bool show_assignment = false;
+
+    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")
+        ("group-id,g",   po::value<string>(&group_id),
+                         "only fetch consumer group information for the specified one")
+        ("assignment,a", po::value<bool>(&show_assignment)->implicit_value(true),
+                         "show topic/partition assignment for each consumer group")
+        ;
+
+    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;
+    }
+
+    // Construct the configuration
+    Configuration config = {
+        { "metadata.broker.list", brokers },
+        // Disable auto commit
+        { "enable.auto.commit", false }
+    };
+
+    try {
+        // Construct a producer
+        Producer producer(config);
+
+        // Fetch the group information
+        vector<GroupInformation> groups = [&]() {
+            if (!group_id.empty()) {
+                return vector<GroupInformation>{producer.get_consumer_group(group_id)};
+            }
+            else {
+                return producer.get_consumer_groups();
+            }
+        }();
+
+        if (groups.empty()) {
+            cout << "Found no consumers" << endl;
+            return 0;
+        }
+        cout << "Found the following consumers: " << endl;
+        for (const GroupInformation& group : groups) {
+            cout << "* \"" << group.get_name() << "\" having the following (" <<
+                    group.get_members().size() << ") members: " << endl;
+            for (const GroupMemberInformation& info : group.get_members()) {
+                cout << "    - " << info.get_member_id() << " @ " << info.get_client_host();
+                if (show_assignment) {
+                    MemberAssignmentInformation assignment(info.get_member_assignment());
+                    cout << " has assigned: " << assignment.get_topic_partitions();
+                }
+                cout << endl;
+            }
+            cout << endl;
+        }
+    }
+    catch (const Exception& ex) {
+        cout << "Error fetching group information: " << ex.what() << endl;
+    }
+}