Add get_watermark_offsets

Author: mattusifer

src/consumer/base_consumer.rs

@@ -656,6 +656,27 @@ where
         }
     }
 
+    fn get_watermark_offsets(&self, topic: &str, partition: i32) -> KafkaResult<(i64, i64)> {
+        let mut low = -1;
+        let mut high = -1;
+        let topic_c = CString::new(topic.to_string())?;
+        let result = unsafe {
+            rdsys::rd_kafka_get_watermark_offsets(
+                self.client.native_ptr(),
+                topic_c.as_ptr(),
+                partition,
+                &mut low as *mut i64,
+                &mut high as *mut i64,
+            )
+        };
+
+        if result.is_error() {
+            Err(KafkaError::MetadataFetch(result.into()))
+        } else {
+            Ok((low, high))
+        }
+    }
+
     fn position(&self) -> KafkaResult<TopicPartitionList> {
         let tpl = self.assignment()?;
         let error = unsafe { rdsys::rd_kafka_position(self.client.native_ptr(), tpl.ptr()) };

src/consumer/mod.rs

@@ -369,6 +369,15 @@ where
         T: Into<Timeout>,
         Self: Sized;
 
+    /// Get last known low (oldest/beginning) and high (newest/end) offsets for partition.
+    ///
+    /// The low offset is updated periodically (if statistics.interval.ms is set) while the
+    /// high offset is updated on each fetched message set from the broker.
+    ///
+    /// If there is no cached offset (either low or high, or both) then OFFSET_INVALID will
+    /// be returned for the respective offset.
+    fn get_watermark_offsets(&self, topic: &str, partition: i32) -> KafkaResult<(i64, i64)>;
+
     /// Retrieve current positions (offsets) for topics and partitions.
     fn position(&self) -> KafkaResult<TopicPartitionList>;
 

src/consumer/stream_consumer.rs

@@ -493,6 +493,10 @@ where
         self.base.offsets_for_times(timestamps, timeout)
     }
 
+    fn get_watermark_offsets(&self, topic: &str, partition: i32) -> KafkaResult<(i64, i64)> {
+        self.base.get_watermark_offsets(topic, partition)
+    }
+
     fn position(&self) -> KafkaResult<TopicPartitionList> {
         self.base.position()
     }

tests/test_high_consumers.rs

@@ -314,6 +314,19 @@ async fn test_consumer_commit_message() {
         (0, 12)
     );
 
+    assert_eq!(
+        consumer.get_watermark_offsets(&topic_name, 0).unwrap(),
+        (0, 10)
+    );
+    assert_eq!(
+        consumer.get_watermark_offsets(&topic_name, 1).unwrap(),
+        (0, 11)
+    );
+    assert_eq!(
+        consumer.get_watermark_offsets(&topic_name, 2).unwrap(),
+        (0, 12)
+    );
+
     let mut assignment = TopicPartitionList::new();
     assignment
         .add_partition_offset(&topic_name, 0, Offset::Stored)
@@ -399,6 +412,19 @@ async fn test_consumer_store_offset_commit() {
         (0, 12)
     );
 
+    assert_eq!(
+        consumer.get_watermark_offsets(&topic_name, 0).unwrap(),
+        (0, 10)
+    );
+    assert_eq!(
+        consumer.get_watermark_offsets(&topic_name, 1).unwrap(),
+        (0, 11)
+    );
+    assert_eq!(
+        consumer.get_watermark_offsets(&topic_name, 2).unwrap(),
+        (0, 12)
+    );
+
     let mut assignment = TopicPartitionList::new();
     assignment
         .add_partition_offset(&topic_name, 0, Offset::Stored)