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use std::io::Error as IoError; use std::io::ErrorKind; use tracing::{debug, trace}; use dataplane::ReplicaKey; use fluvio_spu_schema::server::fetch_offset::FetchOffsetsRequest; use fluvio_spu_schema::server::fetch_offset::FetchOffsetPartitionResponse; use crate::FluvioError; use crate::client::SerialFrame; #[derive(Debug, Clone, PartialEq)] pub(crate) enum OffsetInner { Absolute(i64), FromBeginning(i64), FromEnd(i64), } /// Describes the location of an event stored in a Fluvio partition /// /// All Fluvio events are stored as a log inside a partition. A log /// is just an ordered list, and an `Offset` is just a way to select /// an item from that list. There are several ways that an `Offset` /// may identify an element from a log. Suppose you sent some /// multiples of `11` to your partition. The various offset types /// would look like this: /// /// ```text /// Partition Log: [ 00, 11, 22, 33, 44, 55, 66 ] /// Absolute Offset: 0, 1, 2, 3, 4, 5, 6 /// FromBeginning Offset: 0, 1, 2, 3, 4, 5, 6 /// FromEnd Offset: 6, 5, 4, 3, 2, 1, 0 /// ``` /// /// When a new partition is created, it always starts counting new /// events at the `Absolute` offset of 0. An absolute offset is a /// unique index that represents the event's distance from the very /// beginning of the partition. The absolute offset of an event never /// changes. /// /// Fluvio allows you to set a retention policy that determines how /// long your events should live. Once an event has outlived your /// retention policy, Fluvio may delete it to save resources. Whenever /// it does this, it keeps track of the latest non-deleted event. This /// allows the `FromBeginning` offset to select an event which is a /// certain number of places in front of the deleted range. For example, /// let's say that the first two events from our partition were deleted. /// Our new offsets would look like this: /// /// ```text /// These events were deleted! /// | /// vvvvvv /// Partition Log: [ .., .., 22, 33, 44, 55, 66 ] /// Absolute Offset: 0, 1, 2, 3, 4, 5, 6 /// FromBeginning Offset: 0, 1, 2, 3, 4 /// FromEnd Offset: 6, 5, 4, 3, 2, 1, 0 /// ``` /// /// Just like the `FromBeginning` offset may change if events are deleted, /// the `FromEnd` offset will change when new events are added. Let's take /// a look: /// /// ```text /// These events were added! /// | /// vvvvvvvvvv /// Partition Log: [ .., .., 22, 33, 44, 55, 66, 77, 88, 99 ] /// Absolute Offset: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 /// FromBeginning Offset: 0, 1, 2, 3, 4, 5, 6, 7 /// FromEnd Offset: 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 /// ``` /// /// # Example /// /// All offsets must be constructed with a positive index. Negative /// numbers are meaningless for offsets and therefore are not allowed. /// Trying to construct an offset with a negative number will yield `None`. /// /// ``` /// use fluvio::Offset; /// let absolute_offset = Offset::absolute(5).unwrap(); /// let offset_from_beginning = Offset::from_beginning(100); /// let offset_from_end = Offset::from_end(10); /// /// // Negative values are not allowed for absolute offsets /// assert!(Offset::absolute(-10).is_err()); /// ``` #[derive(Debug, Clone, PartialEq)] pub struct Offset { inner: OffsetInner, } impl Offset { /// Creates an absolute offset with the given index /// /// The index must not be less than zero. /// /// # Example /// /// ``` /// # use fluvio::Offset; /// assert!(Offset::absolute(100).is_ok()); /// assert!(Offset::absolute(0).is_ok()); /// assert!(Offset::absolute(-10).is_err()); /// ``` pub fn absolute(index: i64) -> Result<Offset, FluvioError> { if index < 0 { return Err(FluvioError::NegativeOffset(index)); } Ok(Self { inner: OffsetInner::Absolute(index), }) } /// Creates a relative offset starting at the beginning of the saved log /// /// A relative `FromBeginning` offset will not always match an `Absolute` /// offset. In order to save space, Fluvio may sometimes delete events /// from the beginning of the log. When this happens, the `FromBeginning` /// relative offset starts counting from the first non-deleted log entry. /// /// ```text /// These events were deleted! /// | /// vvvvvv /// Partition Log: [ .., .., 22, 33, 44, 55, 66 ] /// Absolute Offset: 0, 1, 2, 3, 4, 5, 6 /// FromBeginning Offset: 0, 1, 2, 3, 4 /// ^ /// | /// Offset::beginning() /// ``` /// /// # Example /// /// ``` /// # use fluvio::Offset; /// let offset: Offset = Offset::beginning(); /// ``` pub fn beginning() -> Offset { Self::from_beginning(0) } /// Creates a relative offset a fixed distance after the oldest log entry /// /// A relative `FromBeginning` offset will not always match an `Absolute` /// offset. In order to save space, Fluvio may sometimes delete events /// from the beginning of the log. When this happens, the `FromBeginning` /// relative offset starts counting from the first non-deleted log entry. /// /// ```text /// These events were deleted! /// | /// vvvvvv /// Partition Log: [ .., .., 22, 33, 44, 55, 66 ] /// Absolute Offset: 0, 1, 2, 3, 4, 5, 6 /// FromBeginning Offset: 0, 1, 2, 3, 4 /// ^ /// | /// Offset::from_beginning(4) /// ``` /// /// # Example /// /// ``` /// # use fluvio::Offset; /// // Creates an offset pointing 4 places after the oldest log entry /// let offset: Offset = Offset::from_beginning(4); /// ``` pub fn from_beginning(offset: u32) -> Offset { Self { inner: OffsetInner::FromBeginning(offset as i64), } } /// Creates a relative offset pointing to the newest log entry /// /// A relative `FromEnd` offset will point to the last "stable committed" /// event entry in the log. Since a log may continue growing at any time, /// a `FromEnd` offset may refer to different entries depending on when a /// query is made. /// /// For example, `Offset::end()` will refer to the event with content /// `66` at this point in time: /// /// ```text /// Partition Log: [ .., .., 22, 33, 44, 55, 66 ] /// Absolute Offset: 0, 1, 2, 3, 4, 5, 6 /// FromEnd Offset: 6, 5, 4, 3, 2, 1, 0 /// ``` /// /// But when these new events are added, `Offset::end()` will refer to the /// event with content `99`. /// /// ```text /// These events were added! /// | /// vvvvvvvvvv /// Partition Log: [ .., .., 22, 33, 44, 55, 66, 77, 88, 99 ] /// Absolute Offset: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 /// FromEnd Offset: 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 /// ``` /// /// # Example /// /// ``` /// # use fluvio::Offset; /// // Creates an offset pointing to the latest log entry /// let offset: Offset = Offset::end(); /// ``` pub fn end() -> Offset { Offset::from_end(0) } /// Creates a relative offset a fixed distance before the newest log entry /// /// A relative `FromEnd` offset will begin counting from the last /// "stable committed" event entry in the log. Increasing the offset will /// select events in reverse chronological order from the most recent event /// towards the earliest event. Therefore, a relative `FromEnd` offset may /// refer to different entries depending on when a query is made. /// /// For example, `Offset::from_end(3)` will refer to the event with content /// `33` at this point in time: /// /// ```text /// Partition Log: [ .., .., 22, 33, 44, 55, 66 ] /// Absolute Offset: 0, 1, 2, 3, 4, 5, 6 /// FromEnd Offset: 6, 5, 4, 3, 2, 1, 0 /// ``` /// /// But when these new events are added, `Offset::from_end(3)` will refer to /// the event with content `66`: /// /// ```text /// These events were added! /// | /// vvvvvvvvvv /// Partition Log: [ .., .., 22, 33, 44, 55, 66, 77, 88, 99 ] /// Absolute Offset: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 /// FromEnd Offset: 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 /// ``` /// /// # Example /// /// ``` /// # use fluvio::Offset; /// // Creates an offset pointing 3 places before the latest log entry /// let offset: Offset = Offset::from_end(3); /// ``` pub fn from_end(offset: u32) -> Offset { Self { inner: OffsetInner::FromEnd(offset as i64), } } /// Converts this offset into an absolute offset /// /// If this offset is relative from the beginning (i.e. it was created /// using the [`from_beginning`] function), then using `to_absolute` will /// calculate the absolute offset by finding the first still-persisted /// event offset and adding the relative offset to it. /// /// Similarly, if this offset is relative from the end (i.e. it was created /// using the [`from_end`] function), then using `to_absolute` will calculate /// the absolute offset by finding the last stably-committed event and subtracting /// the relative offset from it. /// /// Calling `to_absolute` on an offset that is already absolute just returns /// that same offset. /// /// Note that calculating relative offsets requires connecting to Fluvio, and /// therefore it is `async` and returns a `Result`. pub(crate) async fn to_absolute<F, S: Into<String>>( &self, client: &mut F, topic: S, partition: i32, ) -> Result<i64, FluvioError> where F: SerialFrame, { let offset = match self.inner { OffsetInner::Absolute(offset) => offset, OffsetInner::FromBeginning(offset) => { let replica = ReplicaKey::new(topic, partition); let offsets = fetch_offsets(client, &replica).await?; offsets.start_offset + offset } OffsetInner::FromEnd(offset) => { let replica = ReplicaKey::new(topic, partition); let offsets = fetch_offsets(client, &replica).await?; offsets.last_stable_offset - offset } }; Ok(offset) } } async fn fetch_offsets<F: SerialFrame>( client: &mut F, replica: &ReplicaKey, ) -> Result<FetchOffsetPartitionResponse, FluvioError> { debug!("fetching offset for replica: {}", replica); let response = client .send_receive(FetchOffsetsRequest::new( replica.topic.to_owned(), replica.partition, )) .await?; trace!( "receive fetch response replica: {}, {:#?}", replica, response ); match response.find_partition(&replica) { Some(partition_response) => { debug!("replica: {}, fetch offset: {}", replica, partition_response); Ok(partition_response) } None => Err(IoError::new( ErrorKind::InvalidData, format!("no replica offset for: {}", replica), ) .into()), } }