From 4c14bbe38b0593ed2db9f0d35c689f450f30c8f3 Mon Sep 17 00:00:00 2001
From: Chris Lu <chris.lu@gmail.com>
Date: Sun, 8 Mar 2026 10:23:50 -0700
Subject: [PATCH] feat(storage): implement makeup_diff for safe concurrent
 compaction

---
 seaweed-volume/src/storage/volume.rs | 122 +++++++++++++++++++++++++++
 1 file changed, 122 insertions(+)

diff --git a/seaweed-volume/src/storage/volume.rs b/seaweed-volume/src/storage/volume.rs
index 2b1ad1aec..29258539d 100644
--- a/seaweed-volume/src/storage/volume.rs
+++ b/seaweed-volume/src/storage/volume.rs
@@ -1701,6 +1701,11 @@ impl Volume {
 
     /// Commit a previously completed compaction: swap .cpd/.cpx to .dat/.idx and reload.
     pub fn commit_compact(&mut self) -> Result<(), VolumeError> {
+        self.makeup_diff().map_err(|e| {
+            warn!("makeup_diff failed: {}", e);
+            e
+        })?;
+
         // Close current files
         if let Some(ref mut nm) = self.nm {
             nm.close();
@@ -1768,6 +1773,123 @@ impl Volume {
         Ok(())
     }
 
+    /// Read any new needles appended during compaction and append them to .cpd/.cpx
+    fn makeup_diff(&mut self) -> Result<(), VolumeError> {
+        let old_idx_size = self.nm.as_ref().map_or(0, |nm| nm.index_file_size());
+        if old_idx_size == 0 || old_idx_size <= self.last_compact_index_offset {
+            return Ok(());
+        }
+
+        let old_super_block = &self.super_block;
+        if old_super_block.compaction_revision != self.last_compact_revision {
+            return Err(VolumeError::Io(io::Error::new(
+                io::ErrorKind::Other,
+                format!(
+                    "current old dat file's compact revision {} is not the expected one {}",
+                    old_super_block.compaction_revision, self.last_compact_revision
+                ),
+            )));
+        }
+
+        let old_idx_path = self.file_name(".idx");
+        let mut old_idx_file = File::open(&old_idx_path)?;
+        
+        // Read new entries from .idx
+        let mut incremented_entries = std::collections::HashMap::new();
+        let offset = self.last_compact_index_offset;
+        
+        old_idx_file.seek(SeekFrom::Start(offset))?;
+        let entry_count = (old_idx_size - offset) / NEEDLE_MAP_ENTRY_SIZE as u64;
+        for _ in 0..entry_count {
+            let mut buf = [0u8; NEEDLE_MAP_ENTRY_SIZE];
+            old_idx_file.read_exact(&mut buf)?;
+            let (key, needle_offset, size) = crate::storage::types::idx_entry_from_bytes(&buf);
+            incremented_entries.insert(key, (needle_offset, size));
+        }
+
+        if incremented_entries.is_empty() {
+            return Ok(());
+        }
+
+        let cpd_path = self.file_name(".cpd");
+        let cpx_path = self.file_name(".cpx");
+        
+        let mut dst_dat = OpenOptions::new().read(true).write(true).open(&cpd_path)?;
+        let mut dst_idx = OpenOptions::new().write(true).append(true).open(&cpx_path)?;
+
+        let mut dat_offset = dst_dat.seek(SeekFrom::End(0))?;
+        let padding_rem = dat_offset % NEEDLE_PADDING_SIZE as u64;
+        if padding_rem != 0 {
+            dat_offset += NEEDLE_PADDING_SIZE as u64 - padding_rem;
+            dst_dat.seek(SeekFrom::Start(dat_offset))?;
+        }
+
+        let version = self.version();
+        let old_dat_path = self.file_name(".dat");
+        let old_dat_file = File::open(&old_dat_path)?;
+
+        for (key, (needle_offset, size)) in incremented_entries {
+            if !needle_offset.is_zero() && !size.is_deleted() && size.0 > 0 {
+                let actual_size = crate::storage::needle::needle::get_actual_size(size, version);
+                let mut blob = vec![0u8; actual_size as usize];
+                
+                #[cfg(unix)]
+                {
+                    use std::os::unix::fs::FileExt;
+                    old_dat_file.read_exact_at(&mut blob, needle_offset.to_actual_offset() as u64)?;
+                }
+                #[cfg(windows)]
+                {
+                    crate::storage::volume::read_exact_at(&old_dat_file, &mut blob, needle_offset.to_actual_offset() as u64)?;
+                }
+                
+                dst_dat.write_all(&blob)?;
+                
+                let mut idx_entry_buf = [0u8; NEEDLE_MAP_ENTRY_SIZE];
+                crate::storage::types::idx_entry_to_bytes(
+                    &mut idx_entry_buf,
+                    key,
+                    Offset::from_actual_offset(dat_offset as i64),
+                    size,
+                );
+                dst_idx.write_all(&idx_entry_buf)?;
+                
+                dat_offset += actual_size as u64;
+            } else {
+                let mut fake_del_needle = Needle {
+                    id: key,
+                    cookie: Cookie(0x12345678),
+                    append_at_ns: SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_nanos() as u64,
+                    ..Needle::default()
+                };
+                let bytes = fake_del_needle.write_bytes(version);
+                dst_dat.write_all(&bytes)?;
+                
+                let mut idx_entry_buf = [0u8; NEEDLE_MAP_ENTRY_SIZE];
+                crate::storage::types::idx_entry_to_bytes(
+                    &mut idx_entry_buf,
+                    key,
+                    Offset::from_actual_offset(0),
+                    Size(crate::storage::types::TOMBSTONE_FILE_SIZE.into()),
+                );
+                dst_idx.write_all(&idx_entry_buf)?;
+                
+                dat_offset += bytes.len() as u64;
+            }
+            
+            let padding = NEEDLE_PADDING_SIZE as u64 - (dat_offset % NEEDLE_PADDING_SIZE as u64);
+            if padding != NEEDLE_PADDING_SIZE as u64 {
+                dat_offset += padding;
+                dst_dat.seek(SeekFrom::Start(dat_offset))?;
+            }
+        }
+        
+        dst_dat.sync_all()?;
+        dst_idx.sync_all()?;
+        
+        Ok(())
+    }
+
     // ---- Sync / Close ----
 
     pub fn sync_to_disk(&mut self) -> io::Result<()> {