Add get/query offset wrappers

include/cppkafka/consumer.h

@@ -41,10 +41,13 @@ public:
     void commit(const TopicPartitionList& topic_partitions);
     void async_commit(const TopicPartitionList& topic_partitions);
 
-    TopicPartitionList get_offsets_committed(const TopicPartitionList& topic_partitions);
-    TopicPartitionList get_offsets_position(const TopicPartitionList& topic_partitions);
-    TopicPartitionList get_subscription();
-    TopicPartitionList get_assignment();
+    OffsetTuple get_offsets(const std::string& topic, int partition) const;
+
+    TopicPartitionList get_offsets_committed(const TopicPartitionList& topic_partitions) const;
+    TopicPartitionList get_offsets_position(const TopicPartitionList& topic_partitions) const;
+    TopicPartitionList get_subscription() const;
+    TopicPartitionList get_assignment() const;
+    std::string get_member_id() const;
 
     Message poll();
 private:

include/cppkafka/kafka_handle_base.h

@@ -6,6 +6,7 @@
 #include <chrono>
 #include <unordered_map>
 #include <mutex>
+#include <tuple>
 #include <librdkafka/rdkafka.h>
 #include "metadata.h"
 #include "topic_partition.h"
@@ -19,6 +20,8 @@ class Topic;
 
 class KafkaHandleBase {
 public:
+    using OffsetTuple = std::tuple<int64_t, int64_t>;
+
     virtual ~KafkaHandleBase() = default;
     KafkaHandleBase(const KafkaHandleBase&) = delete;
     KafkaHandleBase(KafkaHandleBase&&) = delete;
@@ -30,18 +33,21 @@ public:
 
     void set_timeout(const std::chrono::milliseconds& timeout);
 
-    rd_kafka_t* get_handle();
+    OffsetTuple query_offsets(const std::string& topic, int partition) const;
+
+    rd_kafka_t* get_handle() const;
     Topic get_topic(const std::string& name);
     Topic get_topic(const std::string& name, TopicConfiguration config);
-    Metadata get_metadata();
-    Metadata get_metadata(const Topic& topic);
+    Metadata get_metadata() const;
+    Metadata get_metadata(const Topic& topic) const;
+    std::string get_name() const;
     std::chrono::milliseconds get_timeout() const;
     const Configuration& get_configuration() const;
 protected:
     KafkaHandleBase(Configuration config);
 
     void set_handle(rd_kafka_t* handle);
-    void check_error(rd_kafka_resp_err_t error);
+    void check_error(rd_kafka_resp_err_t error) const;
     rd_kafka_conf_t* get_configuration_handle();
 private:
     static const std::chrono::milliseconds DEFAULT_TIMEOUT;
@@ -50,7 +56,7 @@ private:
     using TopicConfigurationMap = std::unordered_map<std::string, TopicConfiguration>;
 
     Topic get_topic(const std::string& name, rd_kafka_topic_conf_t* conf);
-    Metadata get_metadata(rd_kafka_topic_t* topic_ptr);
+    Metadata get_metadata(rd_kafka_topic_t* topic_ptr) const;
     void save_topic_config(const std::string& topic_name, TopicConfiguration config);
 
     HandlePtr handle_;

src/consumer.cpp

@@ -6,6 +6,7 @@
 using std::vector;
 using std::string;
 using std::move;
+using std::make_tuple;
 
 using std::chrono::milliseconds;
 
@@ -96,7 +97,17 @@ void Consumer::async_commit(const TopicPartitionList& topic_partitions) {
     commit(topic_partitions, true);
 }
 
-TopicPartitionList Consumer::get_offsets_committed(const TopicPartitionList& topic_partitions) {
+KafkaHandleBase::OffsetTuple Consumer::get_offsets(const string& topic, int partition) const {
+    int64_t low;
+    int64_t high;
+    rd_kafka_resp_err_t result = rd_kafka_get_watermark_offsets(get_handle(), topic.data(),
+                                                                partition, &low, &high);
+    check_error(result);
+    return make_tuple(low, high);
+}
+
+TopicPartitionList
+Consumer::get_offsets_committed(const TopicPartitionList& topic_partitions) const {
     TopicPartitionsListPtr topic_list_handle = convert(topic_partitions);
     rd_kafka_resp_err_t error = rd_kafka_committed(get_handle(), topic_list_handle.get(),
                                                    get_timeout().count());
@@ -104,14 +115,15 @@ TopicPartitionList Consumer::get_offsets_committed(const TopicPartitionList& top
     return convert(topic_list_handle);
 }
 
-TopicPartitionList Consumer::get_offsets_position(const TopicPartitionList& topic_partitions) {
+TopicPartitionList
+Consumer::get_offsets_position(const TopicPartitionList& topic_partitions) const {
     TopicPartitionsListPtr topic_list_handle = convert(topic_partitions);
     rd_kafka_resp_err_t error = rd_kafka_position(get_handle(), topic_list_handle.get());
     check_error(error);
     return convert(topic_list_handle);
 }
 
-TopicPartitionList Consumer::get_subscription() {
+TopicPartitionList Consumer::get_subscription() const {
     rd_kafka_resp_err_t error;
     rd_kafka_topic_partition_list_t* list = nullptr;
     error = rd_kafka_subscription(get_handle(), &list);
@@ -119,7 +131,7 @@ TopicPartitionList Consumer::get_subscription() {
     return convert(make_handle(list));
 }
 
-TopicPartitionList Consumer::get_assignment() {
+TopicPartitionList Consumer::get_assignment() const {
     rd_kafka_resp_err_t error;
     rd_kafka_topic_partition_list_t* list = nullptr;
     error = rd_kafka_assignment(get_handle(), &list);
@@ -127,6 +139,10 @@ TopicPartitionList Consumer::get_assignment() {
     return convert(make_handle(list));
 }
 
+string Consumer::get_member_id() const {
+    return rd_kafka_memberid(get_handle());
+}
+
 Message Consumer::poll() {
     rd_kafka_message_t* message = rd_kafka_consumer_poll(get_handle(), 
                                                          get_timeout().count());

src/kafka_handle_base.cpp

@@ -6,6 +6,7 @@
 using std::string;
 using std::vector;
 using std::move;
+using std::make_tuple;
 using std::lock_guard;
 using std::mutex;
 using std::chrono::milliseconds;
@@ -42,7 +43,7 @@ void KafkaHandleBase::set_timeout(const milliseconds& timeout) {
     timeout_ms_ = timeout;
 }
 
-rd_kafka_t* KafkaHandleBase::get_handle() {
+rd_kafka_t* KafkaHandleBase::get_handle() const {
     return handle_.get();
 }
 
@@ -57,14 +58,29 @@ Topic KafkaHandleBase::get_topic(const string& name, TopicConfiguration config)
     return get_topic(name, rd_kafka_topic_conf_dup(handle));
 }
 
-Metadata KafkaHandleBase::get_metadata() {
+KafkaHandleBase::OffsetTuple KafkaHandleBase::query_offsets(const string& topic,
+                                                            int partition) const {
+    int64_t low;
+    int64_t high;
+    rd_kafka_resp_err_t result = rd_kafka_query_watermark_offsets(handle_.get(), topic.data(),
+                                                                  partition, &low, &high,
+                                                                  timeout_ms_.count());
+    check_error(result);
+    return make_tuple(low, high);
+}
+
+Metadata KafkaHandleBase::get_metadata() const {
     return get_metadata(nullptr);
 }
 
-Metadata KafkaHandleBase::get_metadata(const Topic& topic) {
+Metadata KafkaHandleBase::get_metadata(const Topic& topic) const {
     return get_metadata(topic.get_handle());
 }
 
+string KafkaHandleBase::get_name() const {
+    return rd_kafka_name(handle_.get());
+}
+
 milliseconds KafkaHandleBase::get_timeout() const {
     return timeout_ms_;
 }
@@ -85,7 +101,7 @@ Topic KafkaHandleBase::get_topic(const string& name, rd_kafka_topic_conf_t* conf
     return Topic(topic);
 }
 
-Metadata KafkaHandleBase::get_metadata(rd_kafka_topic_t* topic_ptr) {
+Metadata KafkaHandleBase::get_metadata(rd_kafka_topic_t* topic_ptr) const {
     const rd_kafka_metadata_t* metadata;
     rd_kafka_resp_err_t error = rd_kafka_metadata(get_handle(), topic_ptr != nullptr, 
                                                   topic_ptr, &metadata, timeout_ms_.count());
@@ -99,7 +115,7 @@ void KafkaHandleBase::save_topic_config(const string& topic_name, TopicConfigura
     iter->second.set_as_opaque();
 }
 
-void KafkaHandleBase::check_error(rd_kafka_resp_err_t error) {
+void KafkaHandleBase::check_error(rd_kafka_resp_err_t error) const {
     if (error != RD_KAFKA_RESP_ERR_NO_ERROR) {
         throw HandleException(error);
     }

tests/consumer_test.cpp

@@ -14,6 +14,7 @@ using std::string;
 using std::thread;
 using std::set;
 using std::mutex;
+using std::tie;
 using std::condition_variable;
 using std::lock_guard;
 using std::unique_lock;
@@ -131,6 +132,12 @@ TEST_F(ConsumerTest, AssignmentCallback) {
 
     assignment = consumer.get_assignment();
     EXPECT_EQ(3, assignment.size());
+
+    int64_t low;
+    int64_t high;
+    tie(low, high) = consumer.get_offsets(KAFKA_TOPIC, partition);
+    EXPECT_GT(high, low);
+    EXPECT_EQ(high, runner.get_messages().back().get_offset() + 1);
 }
 
 TEST_F(ConsumerTest, Rebalance) {

tests/producer_test.cpp

@@ -10,6 +10,7 @@
 using std::string;
 using std::to_string;
 using std::set;
+using std::tie;
 using std::move;
 using std::thread;
 using std::mutex;
@@ -124,6 +125,11 @@ TEST_F(ProducerTest, OneMessageOnFixedPartition) {
     EXPECT_EQ(KAFKA_TOPIC, message.get_topic());
     EXPECT_EQ(partition, message.get_partition());
     EXPECT_EQ(0, message.get_error());
+
+    int64_t low;
+    int64_t high;
+    tie(low, high) = producer.query_offsets(KAFKA_TOPIC, partition);
+    EXPECT_GT(high, low);
 }
 
 TEST_F(ProducerTest, OneMessageUsingKey) {