feat: implement the LogStoreRawEntryReader and `RawEntryReaderFilte…

…r` (GreptimeTeam#4030)

* feat: implement the `LogStoreRawEntryReader`

* feat: implement the `RawEntryReaderFilter`

* test: add tests

src/mito2/src/error.rs

@@ -250,6 +250,14 @@ pub enum Error {
         source: BoxedError,
     },
 
+    #[snafu(display("Failed to read WAL, topic: {}", topic))]
+    ReadKafkaWal {
+        topic: String,
+        #[snafu(implicit)]
+        location: Location,
+        source: BoxedError,
+    },
+
     #[snafu(display("Failed to decode WAL entry, region_id: {}", region_id))]
     DecodeWal {
         region_id: RegionId,
@@ -742,6 +750,7 @@ impl ErrorExt for Error {
             | ReadParquet { .. }
             | WriteWal { .. }
             | ReadWal { .. }
+            | ReadKafkaWal { .. }
             | DeleteWal { .. } => StatusCode::StorageUnavailable,
             CompressObject { .. }
             | DecompressObject { .. }

src/mito2/src/wal/raw_entry_reader.rs

@@ -12,11 +12,20 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+use std::sync::Arc;
+
+use async_stream::try_stream;
+use common_error::ext::BoxedError;
+use common_wal::options::{KafkaWalOptions, WalOptions};
 use futures::stream::BoxStream;
-use store_api::logstore::entry::RawEntry;
+use futures::TryStreamExt;
+use snafu::ResultExt;
+use store_api::logstore::entry::{Entry, RawEntry};
+use store_api::logstore::LogStore;
 use store_api::storage::RegionId;
+use tokio_stream::StreamExt;
 
-use crate::error::Result;
+use crate::error::{self, Result};
 use crate::wal::EntryId;
 
 /// A stream that yields [RawEntry].
@@ -32,6 +41,12 @@ pub struct RaftEngineNamespace {
     region_id: RegionId,
 }
 
+impl RaftEngineNamespace {
+    pub fn new(region_id: RegionId) -> Self {
+        Self { region_id }
+    }
+}
+
 /// The namespace of [RawEntryReader].
 pub(crate) enum LogStoreNamespace<'a> {
     RaftEngine(RaftEngineNamespace),
@@ -40,5 +55,298 @@ pub(crate) enum LogStoreNamespace<'a> {
 
 /// [RawEntryReader] provides the ability to read [RawEntry] from the underlying [LogStore].
 pub(crate) trait RawEntryReader: Send + Sync {
-    fn read(&self, ctx: LogStoreNamespace, start_id: EntryId) -> Result<RawEntryStream<'static>>;
+    fn read<'a>(
+        &'a self,
+        ctx: LogStoreNamespace<'a>,
+        start_id: EntryId,
+    ) -> Result<RawEntryStream<'a>>;
+}
+
+/// Implement the [RawEntryReader] for the [LogStore].
+pub struct LogStoreRawEntryReader<S> {
+    store: Arc<S>,
+}
+
+impl<S: LogStore> LogStoreRawEntryReader<S> {
+    pub fn new(store: Arc<S>) -> Self {
+        Self { store }
+    }
+
+    fn read_region(&self, ns: RaftEngineNamespace, start_id: EntryId) -> Result<RawEntryStream> {
+        let region_id = ns.region_id;
+        let stream = try_stream!({
+            // TODO(weny): refactor the `namespace` method.
+            let namespace = self.store.namespace(region_id.into(), &Default::default());
+            let mut stream = self
+                .store
+                .read(&namespace, start_id)
+                .await
+                .map_err(BoxedError::new)
+                .context(error::ReadWalSnafu { region_id })?;
+
+            while let Some(entries) = stream.next().await {
+                let entries = entries
+                    .map_err(BoxedError::new)
+                    .context(error::ReadWalSnafu { region_id })?;
+
+                for entry in entries {
+                    yield entry.into_raw_entry()
+                }
+            }
+        });
+
+        Ok(Box::pin(stream))
+    }
+
+    fn read_topic<'a>(
+        &'a self,
+        ns: KafkaNamespace<'a>,
+        start_id: EntryId,
+    ) -> Result<RawEntryStream> {
+        let topic = ns.topic;
+        let stream = try_stream!({
+            // TODO(weny): refactor the `namespace` method.
+            let namespace = self.store.namespace(
+                RegionId::from_u64(0).into(),
+                &WalOptions::Kafka(KafkaWalOptions {
+                    topic: topic.to_string(),
+                }),
+            );
+
+            let mut stream = self
+                .store
+                .read(&namespace, start_id)
+                .await
+                .map_err(BoxedError::new)
+                .context(error::ReadKafkaWalSnafu { topic })?;
+
+            while let Some(entries) = stream.next().await {
+                let entries = entries
+                    .map_err(BoxedError::new)
+                    .context(error::ReadKafkaWalSnafu { topic })?;
+
+                for entry in entries {
+                    yield entry.into_raw_entry()
+                }
+            }
+        });
+
+        Ok(Box::pin(stream))
+    }
+}
+
+impl<S: LogStore> RawEntryReader for LogStoreRawEntryReader<S> {
+    fn read<'a>(
+        &'a self,
+        ctx: LogStoreNamespace<'a>,
+        start_id: EntryId,
+    ) -> Result<RawEntryStream<'a>> {
+        let stream = match ctx {
+            LogStoreNamespace::RaftEngine(ns) => self.read_region(ns, start_id)?,
+            LogStoreNamespace::Kafka(ns) => self.read_topic(ns, start_id)?,
+        };
+
+        Ok(Box::pin(stream))
+    }
+}
+
+/// A filter implement the [RawEntryReader]
+pub struct RawEntryReaderFilter<R, F> {
+    reader: R,
+    filter: F,
+}
+
+impl<R, F> RawEntryReaderFilter<R, F>
+where
+    R: RawEntryReader,
+    F: Fn(&RawEntry) -> bool + Sync + Send,
+{
+    pub fn new(reader: R, filter: F) -> Self {
+        Self { reader, filter }
+    }
+}
+
+impl<R, F> RawEntryReader for RawEntryReaderFilter<R, F>
+where
+    R: RawEntryReader,
+    F: Fn(&RawEntry) -> bool + Sync + Send,
+{
+    fn read<'a>(
+        &'a self,
+        ctx: LogStoreNamespace<'a>,
+        start_id: EntryId,
+    ) -> Result<RawEntryStream<'a>> {
+        let mut stream = self.reader.read(ctx, start_id)?;
+        let filter = &(self.filter);
+        let stream = try_stream!({
+            while let Some(entry) = stream.next().await {
+                let entry = entry?;
+                if filter(&entry) {
+                    yield entry
+                }
+            }
+        });
+
+        Ok(Box::pin(stream))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::sync::Arc;
+
+    use common_wal::options::WalOptions;
+    use futures::stream;
+    use store_api::logstore::entry::{Entry, RawEntry};
+    use store_api::logstore::entry_stream::SendableEntryStream;
+    use store_api::logstore::namespace::Namespace;
+    use store_api::logstore::{
+        AppendBatchResponse, AppendResponse, EntryId, LogStore, NamespaceId,
+    };
+    use store_api::storage::RegionId;
+
+    use super::*;
+    use crate::error;
+
+    #[derive(Debug)]
+    struct MockLogStore {
+        entries: Vec<RawEntry>,
+    }
+
+    #[derive(Debug, Eq, PartialEq, Clone, Copy, Default, Hash)]
+    struct MockNamespace;
+
+    impl Namespace for MockNamespace {
+        fn id(&self) -> NamespaceId {
+            0
+        }
+    }
+
+    #[async_trait::async_trait]
+    impl LogStore for MockLogStore {
+        type Entry = RawEntry;
+        type Error = error::Error;
+        type Namespace = MockNamespace;
+
+        async fn stop(&self) -> Result<(), Self::Error> {
+            unreachable!()
+        }
+
+        async fn append(&self, entry: Self::Entry) -> Result<AppendResponse, Self::Error> {
+            unreachable!()
+        }
+
+        async fn append_batch(
+            &self,
+            entries: Vec<Self::Entry>,
+        ) -> Result<AppendBatchResponse, Self::Error> {
+            unreachable!()
+        }
+
+        async fn read(
+            &self,
+            ns: &Self::Namespace,
+            id: EntryId,
+        ) -> Result<SendableEntryStream<Self::Entry, Self::Error>, Self::Error> {
+            Ok(Box::pin(stream::iter(vec![Ok(self.entries.clone())])))
+        }
+
+        async fn create_namespace(&self, ns: &Self::Namespace) -> Result<(), Self::Error> {
+            unreachable!()
+        }
+
+        async fn delete_namespace(&self, ns: &Self::Namespace) -> Result<(), Self::Error> {
+            unreachable!()
+        }
+
+        async fn list_namespaces(&self) -> Result<Vec<Self::Namespace>, Self::Error> {
+            unreachable!()
+        }
+
+        async fn obsolete(
+            &self,
+            ns: Self::Namespace,
+            entry_id: EntryId,
+        ) -> Result<(), Self::Error> {
+            unreachable!()
+        }
+
+        fn entry(&self, data: &mut Vec<u8>, entry_id: EntryId, ns: Self::Namespace) -> Self::Entry {
+            unreachable!()
+        }
+
+        fn namespace(&self, _ns_id: NamespaceId, _wal_options: &WalOptions) -> Self::Namespace {
+            MockNamespace
+        }
+    }
+
+    #[tokio::test]
+    async fn test_raw_entry_reader() {
+        let expected_entries = vec![RawEntry {
+            region_id: RegionId::new(1024, 1),
+            entry_id: 1,
+            data: vec![],
+        }];
+        let store = MockLogStore {
+            entries: expected_entries.clone(),
+        };
+
+        let reader = LogStoreRawEntryReader::new(Arc::new(store));
+        let entries = reader
+            .read(
+                LogStoreNamespace::RaftEngine(RaftEngineNamespace::new(RegionId::new(1024, 1))),
+                0,
+            )
+            .unwrap()
+            .try_collect::<Vec<_>>()
+            .await
+            .unwrap();
+        assert_eq!(expected_entries, entries);
+    }
+
+    #[tokio::test]
+    async fn test_raw_entry_reader_filter() {
+        let all_entries = vec![
+            RawEntry {
+                region_id: RegionId::new(1024, 1),
+                entry_id: 1,
+                data: vec![1],
+            },
+            RawEntry {
+                region_id: RegionId::new(1024, 2),
+                entry_id: 2,
+                data: vec![2],
+            },
+            RawEntry {
+                region_id: RegionId::new(1024, 3),
+                entry_id: 3,
+                data: vec![3],
+            },
+        ];
+        let store = MockLogStore {
+            entries: all_entries.clone(),
+        };
+
+        let expected_region_id = RegionId::new(1024, 3);
+        let reader =
+            RawEntryReaderFilter::new(LogStoreRawEntryReader::new(Arc::new(store)), |entry| {
+                entry.region_id == expected_region_id
+            });
+        let entries = reader
+            .read(
+                LogStoreNamespace::RaftEngine(RaftEngineNamespace::new(RegionId::new(1024, 1))),
+                0,
+            )
+            .unwrap()
+            .try_collect::<Vec<_>>()
+            .await
+            .unwrap();
+        assert_eq!(
+            all_entries
+                .into_iter()
+                .filter(|entry| entry.region_id == expected_region_id)
+                .collect::<Vec<_>>(),
+            entries
+        );
+    }
 }

src/store-api/src/logstore/entry.rs

@@ -19,12 +19,35 @@ use crate::storage::RegionId;
 pub type Id = u64;
 
 /// The raw Wal entry.
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub struct RawEntry {
     pub region_id: RegionId,
     pub entry_id: Id,
     pub data: Vec<u8>,
 }
 
+impl Entry for RawEntry {
+    fn into_raw_entry(self) -> RawEntry {
+        self
+    }
+
+    fn data(&self) -> &[u8] {
+        &self.data
+    }
+
+    fn id(&self) -> Id {
+        self.entry_id
+    }
+
+    fn region_id(&self) -> RegionId {
+        self.region_id
+    }
+
+    fn estimated_size(&self) -> usize {
+        std::mem::size_of_val(self)
+    }
+}
+
 /// Entry is the minimal data storage unit through which users interact with the log store.
 /// The log store implementation may have larger or smaller data storage unit than an entry.
 pub trait Entry: Send + Sync {