numinnex commented on code in PR #2916:
URL: https://github.com/apache/iggy/pull/2916#discussion_r2941469906
##########
core/journal/src/lib.rs:
##########
@@ -30,16 +34,40 @@ where
fn header(&self, idx: usize) -> Option<Self::HeaderRef<'_>>;
fn previous_header(&self, header: &Self::Header) ->
Option<Self::HeaderRef<'_>>;
- fn append(&self, entry: Self::Entry) -> impl Future<Output = ()>;
+ fn append(&self, entry: Self::Entry) -> impl Future<Output =
io::Result<()>>;
fn entry(&self, header: &Self::Header) -> impl Future<Output =
Option<Self::Entry>>;
+
+ /// Advance the snapshot watermark so entries at or below `op` may be
+ /// evicted from the journal's in-memory index. The default is a no-op
+ /// for journals that do not require this watermark.
+ fn set_snapshot_op(&self, _op: u64) {}
+
+ /// Number of entries that can be appended before the journal would need
+ /// to evict un-snapshotted slots. Returns `None` for journals that don't
persist to disk.
+ fn remaining_capacity(&self) -> Option<usize> {
+ None
+ }
+
+ /// Remove snapshotted entries from the WAL to reclaim disk space.
+ /// The default is a no-op for journals that do not persist to disk.
+ ///
+ /// # Errors
+ /// Returns an I/O error if compaction fails.
+ fn compact(&self) -> impl Future<Output = io::Result<()>> {
+ async { Ok(()) }
+ }
Review Comment:
The drain api would take `op` as the input e.g you would provide op_range
rather than index_range, so the wrapping of the journal doesn't matter.
The cost of deserialization isn't that big, if not existent in-fact, since
we store `Message<PrepareHeader>` as entries in our `IggyMetadata` journal, so
it's just reading opaque bytes from disk and constructing the
`Message<PrepareHeader>` from them (only cost there is the validation).
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