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mod batch;
mod sidx_fast_path;
mod tail;
pub(crate) use batch::BatchRecoveryState;
use tail::PayloadReadFailure;
use super::{read_frame_header_or_clean_eof, FrameScanTailPolicy, Reader, ScannedIndexEntry};
use crate::event::{EventHeader, EventKind, HashChain};
use crate::store::segment::{self, SegmentHeader, SEGMENT_MAGIC};
use crate::store::{EncodedBytes, ExtensionKey, StoreError};
use serde::Deserialize;
use std::collections::BTreeMap;
use std::io::{Read, Seek, SeekFrom};
use std::path::Path;
impl Reader {
/// Scan only the metadata required to rebuild the in-memory index.
/// Tries the SIDX footer first (O(1) seek + bulk read); falls back to
/// frame-by-frame msgpack deserialization if no SIDX footer is present.
/// Accepts optional `batch_state` for cross-segment batch recovery.
///
/// **SIDX fast-path contract.** The SIDX fast-path may be used only
/// when the caller has no pending batch (`batch_state.in_batch ==
/// false`) AND this segment does not itself carry a cross-segment
/// batch — i.e., its SIDX entries cover every frame in the segment.
/// If a BEGIN marker in this segment rotates before its COMMIT, the
/// SIDX written at rotation is empty of that batch's items (items
/// are recorded to the collector only after COMMIT succeeds), and
/// the next segment's frame-scan needs the batch-in-progress state
/// to match its COMMIT against. In that case we must frame-scan this
/// segment so the BEGIN and staged items propagate via
/// `BatchRecoveryState`. Otherwise a cross-segment batch is silently
/// dropped on recovery.
///
/// This lets cold-start rebuild stream scanned entries straight into the
/// replay cursor instead of allocating a per-segment `Vec` only to fold it
/// again immediately afterward.
pub(crate) fn scan_segment_index_into_with_tail_policy<F>(
&self,
path: &Path,
mut batch_state: Option<&mut BatchRecoveryState>,
tail_policy: FrameScanTailPolicy,
mut sink: F,
) -> Result<(), StoreError>
where
F: FnMut(ScannedIndexEntry) -> Result<(), StoreError>,
{
// Fast path: try SIDX footer for sealed segments only.
// Sealed segments cannot have incomplete batches, so SIDX is safe.
// Active segment might have incomplete batches, so use slow path.
// A malformed filename is soft-skipped: we cannot safely attribute
// its frames to any segment id, so the safe move is to log and
// return rather than guess.
let segment_id = match segment::SegmentId::from_filename(path) {
Ok(parsed) => parsed.as_u64(),
Err(error) => {
tracing::warn!(
path = %path.display(),
%error,
"skipping malformed segment filename"
);
return Ok(());
}
};
let batch_in_progress = batch_state.as_ref().is_some_and(|state| state.in_batch);
if self.try_sidx_fast_path(path, segment_id, batch_in_progress, &mut sink)? {
return Ok(());
}
let mut file = crate::store::platform::fs::open_file(path).map_err(StoreError::Io)?;
let file_len = file.seek(SeekFrom::End(0)).map_err(StoreError::Io)?;
let frames_end = segment::detect_sidx_boundary(&mut file, file_len)?.unwrap_or(file_len);
file.seek(SeekFrom::Start(0)).map_err(StoreError::Io)?;
let mut magic = [0u8; 4];
file.read_exact(&mut magic).map_err(StoreError::Io)?;
if &magic != SEGMENT_MAGIC {
return Err(StoreError::corrupt_magic(segment_id));
}
let mut header_len_buf = [0u8; 4];
file.read_exact(&mut header_len_buf)
.map_err(StoreError::Io)?;
let header_len = u32::from_be_bytes(header_len_buf) as usize;
let mut header_buf = vec![0u8; header_len];
file.read_exact(&mut header_buf).map_err(StoreError::Io)?;
let header: SegmentHeader = crate::encoding::from_bytes(&header_buf)
.map_err(|e| StoreError::Serialization(Box::new(e)))?;
if header.version != 1 {
return Err(StoreError::corrupt_version(segment_id, header.version));
}
let mut cursor = (8 + header_len) as u64;
let mut local_state = BatchRecoveryState::default();
let state_ref: &mut BatchRecoveryState = match batch_state {
Some(ref mut s) => s,
None => &mut local_state,
};
loop {
if cursor >= frames_end {
break;
}
let frame_offset = cursor;
let Some(frame_header) =
read_frame_header_or_clean_eof(&mut file).map_err(StoreError::Io)?
else {
if state_ref.in_batch {
tracing::warn!(
segment_id,
staged_count = state_ref.staged.len(),
"incomplete batch at EOF, will discard or continue in next segment"
);
}
break;
};
let payload_len = u32::from_be_bytes([
frame_header[0],
frame_header[1],
frame_header[2],
frame_header[3],
]) as usize;
if Self::payload_len_exceeds_max(payload_len) {
if tail_policy.can_recover_torn_tail() {
tracing::warn!(
segment_id,
payload_len,
"frame payload exceeds MAX_FRAME_PAYLOAD, stopping segment scan as torn tail"
);
break;
}
return Err(StoreError::CorruptFrame {
segment_id,
offset: frame_offset,
reason: format!("frame payload length {payload_len} exceeds MAX_FRAME_PAYLOAD"),
});
}
let frame_tail = frame_offset
.checked_add(8)
.and_then(|base| base.checked_add(u64::try_from(payload_len).ok()?))
.ok_or_else(|| {
StoreError::corrupt_segment_with_detail(segment_id, "frame tail overflow")
})?;
if frame_tail > frames_end {
if tail_policy.can_recover_torn_tail() && frames_end == file_len {
break;
}
return Err(StoreError::CorruptFrame {
segment_id,
offset: frame_offset,
reason: "frame payload extends past the frame region".into(),
});
}
let mut frame_buf = self.acquire_buffer(8 + payload_len);
frame_buf[..8].copy_from_slice(&frame_header);
if let Err(error) = file.read_exact(&mut frame_buf[8..]) {
self.release_buffer(frame_buf);
match tail::classify_payload_read_error(segment_id, error, tail_policy)? {
PayloadReadFailure::RecoverTornTail => {
break;
}
}
}
match segment::frame_decode(&frame_buf) {
Ok((msgpack, frame_size)) => {
match crate::encoding::from_bytes::<IndexScanFramePayload>(msgpack) {
Ok(payload) => {
let kind = payload.event.header.event_kind;
if !state_ref.in_batch {
if kind == EventKind::SYSTEM_BATCH_BEGIN {
let batch_count = Self::checked_batch_count(
segment_id,
frame_offset,
payload.event.header.payload_size,
)?;
state_ref.in_batch = true;
state_ref.remaining = batch_count;
state_ref.started_count = batch_count;
let batch_capacity = usize::try_from(batch_count).map_err(
|_| StoreError::CorruptFrame {
segment_id,
offset: frame_offset,
reason: format!(
"validated batch count {batch_count} does not fit usize"
),
},
)?;
state_ref.staged.reserve(batch_capacity);
} else if kind == EventKind::SYSTEM_BATCH_COMMIT {
tracing::warn!(
segment_id,
offset = frame_offset,
"orphaned COMMIT marker, skipping"
);
} else {
let hash_chain = Self::required_index_hash_chain(
&payload.event,
segment_id,
frame_offset,
)?;
let length = u32::try_from(frame_size).map_err(|_| {
StoreError::CorruptFrame {
segment_id,
offset: frame_offset,
reason: format!(
"frame size {frame_size} overflows u32"
),
}
})?;
sink(ScannedIndexEntry {
header: payload.event.header,
entity: payload.entity,
scope: payload.scope,
hash_chain,
segment_id,
offset: frame_offset,
length,
receipt_extensions: payload.receipt_extensions,
global_sequence: None,
})?;
}
} else if kind == EventKind::SYSTEM_BATCH_COMMIT {
if state_ref.remaining == 0 {
let completed_batch = std::mem::take(&mut state_ref.staged);
for entry in completed_batch {
sink(entry)?;
}
state_ref.in_batch = false;
tracing::debug!(
segment_id,
batch_count = state_ref.started_count,
"batch committed via COMMIT marker"
);
} else {
tracing::warn!(
segment_id,
expected = state_ref.started_count,
remaining = state_ref.remaining,
staged_count = state_ref.staged.len(),
"batch COMMIT mismatch, discarding"
);
}
state_ref.in_batch = false;
state_ref.staged.clear();
} else if kind == EventKind::SYSTEM_BATCH_BEGIN {
tracing::warn!(
segment_id,
staged_count = state_ref.staged.len(),
"nested BEGIN without COMMIT, discarding incomplete batch"
);
let batch_count = Self::checked_batch_count(
segment_id,
frame_offset,
payload.event.header.payload_size,
)?;
state_ref.remaining = batch_count;
state_ref.started_count = batch_count;
state_ref.staged.clear();
let batch_capacity =
usize::try_from(batch_count).map_err(|_| {
StoreError::CorruptFrame {
segment_id,
offset: frame_offset,
reason: format!(
"validated batch count {batch_count} does not fit usize"
),
}
})?;
state_ref.staged.reserve(batch_capacity);
} else {
let hash_chain = Self::required_index_hash_chain(
&payload.event,
segment_id,
frame_offset,
)?;
let length = u32::try_from(frame_size).map_err(|_| {
StoreError::CorruptFrame {
segment_id,
offset: frame_offset,
reason: format!("frame size {frame_size} overflows u32"),
}
})?;
let entry = ScannedIndexEntry {
header: payload.event.header,
entity: payload.entity,
scope: payload.scope,
hash_chain,
segment_id,
offset: frame_offset,
length,
receipt_extensions: payload.receipt_extensions,
global_sequence: None,
};
if !state_ref.stage_entry(entry) {
tracing::warn!(
segment_id,
offset = frame_offset,
expected = state_ref.started_count,
"batch contains more items than declared, discarding"
);
state_ref.discard_incomplete();
}
}
}
Err(error) => {
if state_ref.in_batch {
tracing::warn!(
segment_id,
staged_count = state_ref.staged.len(),
"discarding incomplete batch due to unreadable frame metadata"
);
state_ref.staged.clear();
state_ref.in_batch = false;
}
return Err(StoreError::CorruptSegment {
segment_id,
detail: format!(
"frame at offset {frame_offset} has unreadable index metadata: {error}"
),
});
}
}
cursor += frame_size as u64;
}
Err(error) => {
let is_crc_mismatch =
matches!(&error, segment::FrameDecodeError::CrcMismatch { .. });
if state_ref.in_batch {
if is_crc_mismatch {
tracing::warn!(
segment_id,
staged_count = state_ref.staged.len(),
"discarding incomplete batch due to CRC mismatch"
);
} else {
tracing::warn!(
segment_id,
staged_count = state_ref.staged.len(),
"discarding incomplete batch due to decode error"
);
}
state_ref.staged.clear();
state_ref.in_batch = false;
}
self.release_buffer(frame_buf);
return Err(Self::frame_decode_error(segment_id, frame_offset, error));
}
}
self.release_buffer(frame_buf);
}
Ok(())
}
}
#[derive(Deserialize)]
pub(crate) struct IndexScanFramePayload {
pub(crate) event: IndexScanEvent,
pub(crate) entity: String,
pub(crate) scope: String,
#[serde(default)]
pub(crate) receipt_extensions: BTreeMap<ExtensionKey, EncodedBytes>,
}
#[derive(Deserialize)]
pub(crate) struct IndexScanEvent {
pub(crate) header: EventHeader,
#[serde(rename = "payload")]
pub(crate) _payload: serde::de::IgnoredAny,
pub(crate) hash_chain: Option<HashChain>,
}
#[cfg(test)]
mod tests;