Add zookeeper support

CMakeLists.txt

@@ -27,5 +27,15 @@ add_dependencies(cppkafka googletest)
 
 option(ENABLE_ZOOKEEPER "Whether to enable zookeeper support" ON)
 
+if (ENABLE_ZOOKEEPER)
+    set(CPPKAFKA_HAVE_ZOOKEEPER ON)
+endif()
+
+# Configuration file
+configure_file(
+  "${CMAKE_CURRENT_SOURCE_DIR}/include/cppkafka/config.h.in"
+  "${CMAKE_CURRENT_SOURCE_DIR}/include/cppkafka/config.h"
+)
+
 enable_testing()
 add_subdirectory(tests)

include/cppkafka/config.h.in

@@ -0,0 +1,7 @@
+#ifndef CPPKAFKA_CONFIG_H
+#define CPPKAFKA_CONFIG_H
+
+/* Define if the zookeeper extensions are enabled */
+#cmakedefine CPPKAFKA_HAVE_ZOOKEEPER
+
+#endif // CPPKAFKA_CONFIG_H

include/cppkafka/configuration.h

@@ -33,6 +33,8 @@
 #include <memory>
 #include <string>
 #include <functional>
+#include <unordered_map>
+#include <unordered_set>
 #include <chrono>
 #include <boost/optional.hpp>
 #include <librdkafka/rdkafka.h>
@@ -79,6 +81,7 @@ public:
     void set_socket_callback(SocketCallback callback);
     void set_default_topic_configuration(boost::optional<TopicConfiguration> config);
 
+    bool has_property(const std::string& name) const;
     rd_kafka_conf_t* get_handle() const;
     std::string get(const std::string& name) const;
     const DeliveryReportCallback& get_delivery_report_callback() const;
@@ -91,8 +94,10 @@ public:
     const boost::optional<TopicConfiguration>& get_default_topic_configuration() const;
     boost::optional<TopicConfiguration>& get_default_topic_configuration();
 private:
+    static const std::unordered_set<std::string> VALID_EXTENSIONS;
     using HandlePtr = ClonablePtr<rd_kafka_conf_t, decltype(&rd_kafka_conf_destroy),
                                   decltype(&rd_kafka_conf_dup)>;
+    using PropertiesMap = std::unordered_map<std::string, std::string>;
 
     Configuration(rd_kafka_conf_t* ptr);
     static HandlePtr make_handle(rd_kafka_conf_t* ptr);
@@ -106,6 +111,7 @@ private:
     LogCallback log_callback_;
     StatsCallback stats_callback_;
     SocketCallback socket_callback_;
+    PropertiesMap extension_properties_;
 };
 
 } // cppkafka

include/cppkafka/kafka_handle_base.h

@@ -42,6 +42,10 @@
 #include "topic_partition_list.h"
 #include "topic_configuration.h"
 #include "configuration.h"
+#include "config.h"
+#ifdef CPPKAFKA_HAVE_ZOOKEEPER
+    #include "zookeeper/zookeeper_subscriber.h"
+#endif // CPPKAFKA_HAVE_ZOOKEEPER
 
 namespace cppkafka {
 
@@ -93,6 +97,10 @@ private:
     Configuration config_;
     TopicConfigurationMap topic_configurations_;
     std::mutex topic_configurations_mutex_;
+    #ifdef CPPKAFKA_HAVE_ZOOKEEPER
+        // This could be an optional but apparently move construction is only supported as of 1.56
+        std::unique_ptr<ZookeeperSubscriber> zookeeper_subscriber_;
+    #endif // CPPKAFKA_HAVE_ZOOKEEPER
 };
 
 } // cppkafka

include/cppkafka/zookeeper/zookeeper_pool.h

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2016, 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_ZOOKEEPER_POOL_H
+#define CPPKAFKA_ZOOKEEPER_POOL_H
+
+#include <map>
+#include <string>
+#include <chrono>
+#include <mutex>
+#include "zookeeper/zookeeper_watcher.h"
+
+namespace cppkafka {
+
+class ZookeeperSubscriber;
+
+class ZookeeperPool {
+public:
+    static ZookeeperPool& instance();
+
+    ZookeeperSubscriber subscribe(const std::string& endpoint,
+                                  std::chrono::milliseconds receive_timeout,
+                                  ZookeeperWatcher::WatcherCallback callback);
+    void unsubscribe(const ZookeeperSubscriber& subscriber);
+    std::string get_brokers(const std::string& endpoint);
+
+    size_t get_subscriber_count(const std::string& endpoint) const;
+private:
+    using WatchersMap = std::map<std::string, ZookeeperWatcher>;
+
+    WatchersMap watchers_;
+    mutable std::mutex watchers_mutex_;
+};
+
+} // cppkafka
+
+#endif // CPPKAFKA_ZOOKEEPER_POOL_H

include/cppkafka/zookeeper/zookeeper_subscriber.h

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2016, 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_ZOOKEEPER_SUBSCRIBER_H
+#define CPPKAFKA_ZOOKEEPER_SUBSCRIBER_H
+
+#include <string>
+
+namespace cppkafka {
+
+class ZookeeperSubscriber {
+public:
+    ZookeeperSubscriber(std::string endpoint, std::string subscription_id);
+    ZookeeperSubscriber(ZookeeperSubscriber&&) = default;
+    ZookeeperSubscriber(const ZookeeperSubscriber&) = delete;
+    ZookeeperSubscriber& operator=(ZookeeperSubscriber&&);
+    ZookeeperSubscriber& operator=(const ZookeeperSubscriber&) = delete;
+    ~ZookeeperSubscriber();
+
+    const std::string& get_endpoint() const;
+    const std::string& get_subscription_id() const;
+private:
+    std::string endpoint_;
+    std::string subscription_id_;
+};
+
+} // cppkafka
+
+#endif // CPPKAFKA_ZOOKEEPER_SUBSCRIBER_H

include/cppkafka/zookeeper/zookeeper_watcher.h

@@ -33,6 +33,9 @@
 #include <memory>
 #include <string>
 #include <chrono>
+#include <map>
+#include <functional>
+#include <mutex>
 #include <zookeeper/zookeeper.h>
 
 namespace cppkafka {
@@ -41,21 +44,33 @@ class ZookeeperWatcher {
 public:
     static const std::chrono::milliseconds DEFAULT_RECEIVE_TIMEOUT;
 
+    using WatcherCallback = std::function<void(const std::string& brokers)>;
+
     ZookeeperWatcher(const std::string& endpoint);
     ZookeeperWatcher(const std::string& endpoint, std::chrono::milliseconds receive_timeout);
 
+    void setup_watcher();
+
+    std::string subscribe(WatcherCallback callback); 
+    void unsubscribe(const std::string& id);
 
     std::string get_brokers();
+    size_t get_subscriber_count() const;
 private:
-    using HandlePtr = std::unique_ptr<zhandle_t, decltype(&zookeeper_close)>;
-
     static const std::string BROKERS_PATH;
 
+    using HandlePtr = std::unique_ptr<zhandle_t, decltype(&zookeeper_close)>;
+    using CallbackMap = std::map<std::string, WatcherCallback>;
+
     static void handle_event_proxy(zhandle_t* zh, int type, int state, const char* path,
                                    void* ctx);
     void handle_event(int type, int state, const char* path);
+    std::string generate_id();
 
     HandlePtr handle_;
+    CallbackMap callbacks_;
+    mutable std::mutex callbacks_mutex_;
+    size_t id_counter_{0};
 };
 
 } // cppkafka

src/CMakeLists.txt

@@ -16,8 +16,11 @@ set(SOURCES
 )
 
 if (ENABLE_ZOOKEEPER)
+    add_definitions("-DCPPKAFKA_ENABLE_ZOOKEEPER=1")
     set(ZOOKEEPER_SOURCES
-        ${CMAKE_CURRENT_SOURCE_DIR}/zookeeper/zookeeper_watcher.cpp)
+        ${CMAKE_CURRENT_SOURCE_DIR}/zookeeper/zookeeper_watcher.cpp
+        ${CMAKE_CURRENT_SOURCE_DIR}/zookeeper/zookeeper_pool.cpp
+        ${CMAKE_CURRENT_SOURCE_DIR}/zookeeper/zookeeper_subscriber.cpp)
     # Add json library as include dir (header only)
     include_directories(SYSTEM ${CMAKE_CURRENT_SOURCE_DIR}/../third_party/json)
     set(SOURCES ${SOURCES} ${ZOOKEEPER_SOURCES})

src/configuration.cpp

@@ -34,10 +34,12 @@
 #include "message.h"
 #include "producer.h"
 #include "consumer.h"
+#include "config.h"
 
 using std::string;
 using std::move;
 using std::vector;
+using std::unordered_set;
 
 using boost::optional;
 
@@ -45,6 +47,12 @@ using std::chrono::milliseconds;
 
 namespace cppkafka {
 
+const unordered_set<string> Configuration::VALID_EXTENSIONS = {
+    #ifdef CPPKAFKA_HAVE_ZOOKEEPER
+    "zookeeper", "zookeeper.receive.timeout.ms"
+    #endif // CPPKAFKA_HAVE_ZOOKEEPER
+};
+
 // Callback proxies
 
 void delivery_report_callback_proxy(rd_kafka_t*, const rd_kafka_message_t* msg, void *opaque) {
@@ -125,6 +133,11 @@ Configuration::Configuration(rd_kafka_conf_t* ptr)
 }
 
 void Configuration::set(const string& name, const string& value) {
+    if (VALID_EXTENSIONS.count(name)) {
+        // This is one of cppkafka's extensions
+        extension_properties_.emplace(name, value);
+    }
+    else {
         char error_buffer[512];
         rd_kafka_conf_res_t result;
         result = rd_kafka_conf_set(handle_.get(), name.data(), value.data(), error_buffer,
@@ -133,6 +146,7 @@ void Configuration::set(const string& name, const string& value) {
             throw ConfigException(name, error_buffer);
         }
     }
+}
 
 void Configuration::set_delivery_report_callback(DeliveryReportCallback callback) {
     delivery_report_callback_ = move(callback);
@@ -173,11 +187,29 @@ void Configuration::set_default_topic_configuration(optional<TopicConfiguration>
     default_topic_config_ = move(config);
 }
 
+bool Configuration::has_property(const string& name) const {
+    if (VALID_EXTENSIONS.count(name)) {
+        return extension_properties_.count(name) == 1;
+    }
+    else {
+        size_t size = 0;
+        return rd_kafka_conf_get(handle_.get(), name.data(), nullptr, &size) == RD_KAFKA_CONF_OK;
+    }
+}
+
 rd_kafka_conf_t* Configuration::get_handle() const {
     return handle_.get();
 }
 
 string Configuration::get(const string& name) const {
+    if (VALID_EXTENSIONS.count(name)) {
+        auto iter = extension_properties_.find(name);
+        if (iter == extension_properties_.end()) {
+            throw ConfigOptionNotFound(name);
+        }
+        return iter->second;
+    }
+    else {
         size_t size = 0;
         auto result = rd_kafka_conf_get(handle_.get(), name.data(), nullptr, &size);
         if (result != RD_KAFKA_CONF_OK) {
@@ -187,6 +219,7 @@ string Configuration::get(const string& name) const {
         rd_kafka_conf_get(handle_.get(), name.data(), buffer.data(), &size);
         return string(buffer.data());
     }
+}
 
 const Configuration::DeliveryReportCallback& Configuration::get_delivery_report_callback() const {
     return delivery_report_callback_;

src/kafka_handle_base.cpp

@@ -31,6 +31,9 @@
 #include "exceptions.h"
 #include "topic.h"
 #include "topic_partition_list.h"
+#ifdef CPPKAFKA_HAVE_ZOOKEEPER
+    #include "zookeeper/zookeeper_pool.h"
+#endif // CPPKAFKA_HAVE_ZOOKEEPER
 
 using std::string;
 using std::vector;
@@ -38,6 +41,7 @@ using std::move;
 using std::make_tuple;
 using std::lock_guard;
 using std::mutex;
+using std::exception;
 using std::chrono::milliseconds;
 
 namespace cppkafka {
@@ -120,6 +124,32 @@ const Configuration& KafkaHandleBase::get_configuration() const {
 
 void KafkaHandleBase::set_handle(rd_kafka_t* handle) {
     handle_ = HandlePtr(handle, &rd_kafka_destroy);
+
+    #ifdef CPPKAFKA_HAVE_ZOOKEEPER
+    
+    if (config_.has_property("zookeeper")) {
+        string endpoint = config_.get("zookeeper");
+        milliseconds timeout = ZookeeperWatcher::DEFAULT_RECEIVE_TIMEOUT;
+        if (config_.has_property("zookeeper.receive.timeout.ms")) {
+            try {
+                timeout = milliseconds(stoi(config_.get("zookeeper.receive.timeout.ms")));
+            }
+            catch (exception&) {
+                throw ZookeeperException("Invalid zookeeper receive timeout");
+            }
+        }
+        auto& pool = ZookeeperPool::instance();
+        auto callback = [&](const string& brokers) {
+            // Add the brokers and poll
+            rd_kafka_brokers_add(handle_.get(), brokers.data());
+            rd_kafka_poll(handle_.get(), 10);
+        };
+        ZookeeperSubscriber subscriber = pool.subscribe(endpoint, timeout, callback);
+        zookeeper_subscriber_.reset(new ZookeeperSubscriber(move(subscriber)));
+        callback(pool.get_brokers(endpoint));
+    }
+    
+    #endif // CPPKAFKA_HAVE_ZOOKEEPER
 }
 
 Topic KafkaHandleBase::get_topic(const string& name, rd_kafka_topic_conf_t* conf) {

src/zookeeper/zookeeper_pool.cpp

@@ -0,0 +1,89 @@
+/*
+ * Copyright (c) 2016, 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.
+ *
+ */
+
+#include "zookeeper/zookeeper_pool.h"
+#include "zookeeper/zookeeper_subscriber.h"
+#include "exceptions.h"
+
+using std::string;
+using std::mutex;
+using std::lock_guard;
+using std::forward_as_tuple;
+using std::piecewise_construct;
+using std::chrono::milliseconds;
+
+namespace cppkafka {
+
+ZookeeperPool& ZookeeperPool::instance() {
+    static ZookeeperPool the_instance;
+    return the_instance;
+}
+
+ZookeeperSubscriber ZookeeperPool::subscribe(const string& endpoint,
+                                             milliseconds receive_timeout,
+                                             ZookeeperWatcher::WatcherCallback callback) {
+    lock_guard<mutex> _(watchers_mutex_);
+    auto iter = watchers_.find(endpoint);
+    if (iter == watchers_.end()) {
+        iter = watchers_.emplace(piecewise_construct, forward_as_tuple(endpoint),
+                                 forward_as_tuple(endpoint, receive_timeout)).first;
+    }
+    string id = iter->second.subscribe(move(callback));
+    return ZookeeperSubscriber(endpoint, id);
+}
+
+void ZookeeperPool::unsubscribe(const ZookeeperSubscriber& subscriber) {
+    lock_guard<mutex> _(watchers_mutex_);
+    auto iter = watchers_.find(subscriber.get_endpoint());
+    if (iter != watchers_.end()) {
+        iter->second.unsubscribe(subscriber.get_subscription_id());
+    }
+}
+
+string ZookeeperPool::get_brokers(const string& endpoint) {
+    lock_guard<mutex> _(watchers_mutex_);
+    auto iter = watchers_.find(endpoint);
+    if (iter == watchers_.end()) {
+        throw ZookeeperException("No zookeeper watcher for given endpoint");
+    }
+    return iter->second.get_brokers();
+}
+
+size_t ZookeeperPool::get_subscriber_count(const string& endpoint) const {
+    lock_guard<mutex> _(watchers_mutex_);
+    auto iter = watchers_.find(endpoint);
+    if (iter == watchers_.end()) {
+        return 0;
+    }
+    else {
+        return iter->second.get_subscriber_count();
+    }
+}
+
+} // cppkafka

src/zookeeper/zookeeper_subscriber.cpp

@@ -0,0 +1,25 @@
+#include "zookeeper/zookeeper_subscriber.h"
+#include "zookeeper/zookeeper_pool.h"
+
+using std::string;
+
+namespace cppkafka {
+
+ZookeeperSubscriber::ZookeeperSubscriber(string endpoint, string subscription_id) 
+: endpoint_(move(endpoint)), subscription_id_(move(subscription_id)) {
+
+}
+
+ZookeeperSubscriber::~ZookeeperSubscriber() {
+    ZookeeperPool::instance().unsubscribe(*this);
+}
+
+const string& ZookeeperSubscriber::get_endpoint() const {
+    return endpoint_;
+}
+
+const string& ZookeeperSubscriber::get_subscription_id() const {
+    return subscription_id_;
+}
+
+} // cppkafka

src/zookeeper/zookeeper_watcher.cpp

@@ -29,15 +29,20 @@
 
 #include <stdexcept>
 #include <sstream>
+#include <chrono>
 #include <picojson.h>
 #include "zookeeper/zookeeper_watcher.h"
 #include "exceptions.h"
 
 using std::string;
+using std::lock_guard;
+using std::mutex;
 using std::unique_ptr;
 using std::ostringstream;
 using std::runtime_error;
+using std::make_shared;
 using std::chrono::milliseconds;
+using std::chrono::system_clock;
 
 using picojson::value;
 using picojson::object;
@@ -63,10 +68,23 @@ ZookeeperWatcher::ZookeeperWatcher(const string& endpoint, milliseconds receive_
     handle_ = HandlePtr(raw_handle, &zookeeper_close);
 }
 
+string ZookeeperWatcher::subscribe(WatcherCallback callback) {
+    lock_guard<mutex> _(callbacks_mutex_);
+    string id = generate_id();
+    callbacks_.emplace(id, move(callback));
+    return id;
+}
+
+void ZookeeperWatcher::unsubscribe(const string& id) {
+    lock_guard<mutex> _(callbacks_mutex_);
+    callbacks_.erase(id);
+}
+
 string ZookeeperWatcher::get_brokers() {
+    auto handle = handle_.get();
     using VectorPtr = unique_ptr<String_vector, decltype(&deallocate_String_vector)>;
     String_vector brokers;
-    if (zoo_get_children(handle_.get(), BROKERS_PATH.data(), 1, &brokers) != ZOK) {
+    if (zoo_get_children(handle, BROKERS_PATH.data(), 1, &brokers) != ZOK) {
         throw ZookeeperException("Failed to get broker list from zookeeper");
     }
     // RAII up this pointer
@@ -76,7 +94,7 @@ string ZookeeperWatcher::get_brokers() {
         char config_line[1024];
         string path = "/brokers/ids/" + string(brokers.data[i]);
         int config_len = sizeof(config_line);
-        zoo_get(handle_.get(), path.data(), 0, config_line, &config_len, NULL);
+        zoo_get(handle, path.data(), 0, config_line, &config_len, NULL);
         if (config_len > 0) {
             config_line[config_len] = 0;
 
@@ -102,6 +120,11 @@ string ZookeeperWatcher::get_brokers() {
     return oss.str();
 }
 
+size_t ZookeeperWatcher::get_subscriber_count() const {
+    lock_guard<mutex> _(callbacks_mutex_);
+    return callbacks_.size();
+}
+
 void ZookeeperWatcher::handle_event_proxy(zhandle_t*, int type, int state, const char* path,
                                           void* ctx) {
     auto self = static_cast<ZookeeperWatcher*>(ctx);
@@ -111,8 +134,17 @@ void ZookeeperWatcher::handle_event_proxy(zhandle_t*, int type, int state, const
 void ZookeeperWatcher::handle_event(int type, int state, const char* path) {
     if (type == ZOO_CHILD_EVENT && path == BROKERS_PATH) {
         string brokers = get_brokers();
-        // TODO: Callback!
+        lock_guard<mutex> _(callbacks_mutex_);
+        for (const auto& callbackPair : callbacks_) {
+            callbackPair.second(brokers);
+        }        
     }   
 }
 
+string ZookeeperWatcher::generate_id() {
+    ostringstream oss;
+    oss << id_counter_++ << "-" << system_clock::now().time_since_epoch().count();
+    return oss.str();
+}
+
 } // cppkafka

tests/CMakeLists.txt

@@ -18,6 +18,10 @@ endmacro()
 add_definitions("-DKAFKA_TEST_INSTANCE=\"${KAFKA_TEST_INSTANCE}\"")
 add_definitions("-DZOOKEEPER_TEST_INSTANCE=\"${ZOOKEEPER_TEST_INSTANCE}\"")
 
+if (ENABLE_ZOOKEEPER)
+    link_libraries(zookeeper_mt)
+endif()
+
 create_test(consumer)
 create_test(producer)
 create_test(kafka_handle_base)
@@ -25,5 +29,4 @@ create_test(topic_partition_list)
 create_test(configuration)
 if (ENABLE_ZOOKEEPER)
     create_test(zookeeper_watcher)
-    target_link_libraries(zookeeper_watcher_test zookeeper_mt)
 endif()

tests/producer_test.cpp

@@ -276,3 +276,46 @@ TEST_F(ProducerTest, PartitionerCallbackOnDefaultTopicConfig) {
     EXPECT_EQ(partition, message.get_partition());
     EXPECT_TRUE(callback_called);   
 }
+
+#ifdef CPPKAFKA_HAVE_ZOOKEEPER
+
+#include "zookeeper/zookeeper_pool.h"
+
+TEST_F(ProducerTest, ConnectUsingZookeeper) {
+    int partition = 0;
+
+    Configuration producer_config;
+    producer_config.set("zookeeper", ZOOKEEPER_TEST_INSTANCE);
+
+    Configuration consumer_config = producer_config;
+    consumer_config.set("enable.auto.commit", false);
+    consumer_config.set("group.id", "producer_test");
+
+    // Create a consumer and assign this topic/partition
+    Consumer consumer(consumer_config);
+    consumer.assign({ TopicPartition(KAFKA_TOPIC, partition) });
+    ConsumerRunner runner(consumer, 1, 1);
+
+    // Now create a producer and produce a message
+    Producer producer(producer_config);
+    Topic topic = producer.get_topic(KAFKA_TOPIC);
+    string payload = "Hello world! 2";
+    string key = "such key";
+    producer.produce(topic, partition, Buffer(payload.data(), payload.size()),
+                     Buffer(key.data(), key.size()));
+    runner.try_join();
+
+    const auto& messages = runner.get_messages();
+    ASSERT_EQ(1, messages.size());
+    const auto& message = messages[0];
+    EXPECT_EQ(payload, message.get_payload().as_string());
+    EXPECT_EQ(key, message.get_key().as_string());
+    EXPECT_EQ(KAFKA_TOPIC, message.get_topic());
+    EXPECT_EQ(partition, message.get_partition());
+    EXPECT_EQ(0, message.get_error());
+
+    // We should have 2 watchers
+    EXPECT_EQ(2, ZookeeperPool::instance().get_subscriber_count(ZOOKEEPER_TEST_INSTANCE));
+}
+
+#endif // CPPKAFKA_HAVE_ZOOKEEPER

tests/zookeeper_watcher_test.cpp

@@ -1,5 +1,6 @@
 #include <gtest/gtest.h>
 #include "cppkafka/zookeeper/zookeeper_watcher.h"
+#include "cppkafka/exceptions.h"
 
 using std::string;
 
@@ -15,3 +16,16 @@ TEST_F(ZookeeperWatcherTest, GetBrokers) {
     string brokers = watcher.get_brokers();
     EXPECT_EQ(KAFKA_TEST_INSTANCE, brokers);
 }
+
+TEST_F(ZookeeperWatcherTest, InvalidEndpointThrows) {
+    ZookeeperWatcher watcher("127.0.0.1:1212");
+    EXPECT_THROW(watcher.get_brokers(), ZookeeperException);
+}
+
+TEST_F(ZookeeperWatcherTest, SubscribeUnsubscribe) {
+    ZookeeperWatcher watcher(ZOOKEEPER_TEST_INSTANCE);
+    string id = watcher.subscribe([](const string&) { });
+    EXPECT_EQ(1, watcher.get_subscriber_count());
+    watcher.unsubscribe(id);
+    EXPECT_EQ(0, watcher.get_subscriber_count());
+}