lei.chen/myxce
1
0
Fork 1
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

fix(raft-ha-core-safety): close 5.10a — WAL segment rotation + endpoint UAF blocking real snapshot catch-up

Browse source 
Chain of fixes needed to get --force-snapshot soak to a real live PASS
(raft-ha-core-safety task 5.10a / ha-entity-snapshots task 7.1):

1. WAL segment rotation was gated on a hardcoded 64MB compile-time
   constant; trim_wal_segments() never deletes the active (currently-open)
   segment. At soak job counts a segment never rotated, so nothing was
   ever physically trimmable and ha_evaluate_repl_action always chose
   STREAM_WAL over SEND_SNAPSHOT for an empty-rejoining node. Fixed by
   threading a wal_segment_bytes override through persist_config_t
   (mirrors the --max-wal-records pattern: config.h default, persist.h
   setter, persist.c 3 usage sites + minimum-floor enforcement, 6-point
   CLI wiring through main.c/myconf.h/myapp.c/cluster.c) plus a new
   --wal-segment-bytes CLI flag. run-ha-soak.sh's --force-snapshot mode
   now sets WAL_SEGMENT_BYTES=4096 to force real rotation at soak scale.

2. This unmasked a genuine heap-use-after-free in INVOKE_MSG_HANDLER
   (include/netio.h): the macro calls ep->msg_handler(ep) synchronously
   (not via the vtask dispatcher, so the bug-1298 vtask ref/unref pairing
   doesn't cover it) then writes ep->fsm_in.pkt = NULL. A stale vote-reply
   handler chain (raft_on_vote_reply -> raft_cb_become_follower ->
   endpoint_unref) could drop the endpoint's last ref and free it inside
   the handler call, so the trailing write hit freed memory. This is the
   first-ever live exercise of a node receiving a snapshot transfer while
   mid-election. Fixed by holding a ref across the synchronous call, same
   pattern task 5.8 established for the async path.

With both fixes: --force-snapshot soak now PASSES live (committed
divergence=0, job_loss=0, confirmed real "HA: snapshot" install on the
restarted node) — first genuine live proof of this scenario. 3-round
--chaotic regression clean. Full 217-test controller suite green
before/after every fix in the chain.

Builds on the delaymgr starvation fix (b9ad018) and walcompare
checkpoint-floor fix (f3c86a6) from earlier in this investigation.
This commit is contained in:
Rongsong Shen 2026-07-02 04:11:20 +00:00
parent b9ad01878c
commit 1439e2655e
11 changed files with 115 additions and 40 deletions
Download patch file Download diff file Expand all files Collapse all files

16
src/controller/persist.c
View file

@ -94,7 +94,6 @@ static int capnp_encode_worker(const xce_worker_t* w, uint8_t** out, size_t* out
/* Constants */
/* ------------------------------------------------------------------ */
#define WAL_SEGMENT_SIZE_BYTES (64UL * 1024 * 1024) /* 64 MB per segment */
#define WAL_SEG_FMT "%s/seg-%016" PRIx64 ".wal"
/* NFS_SUPER_MAGIC — reject WAL on NFS mounts (unreliable fsync) */
@ -148,7 +147,7 @@ static int open_new_segment(persist_t* p)
/* Pre-allocate segment space to avoid fragmentation and metadata updates
* on every write. posix_fallocate is best-effort — ignore errors. */
posix_fallocate(fd, 0, (off_t)WAL_SEGMENT_SIZE_BYTES);
posix_fallocate(fd, 0, (off_t)p->config.wal_segment_bytes);
p->wal_fd = fd;
p->seg_offset = 0;
@ -571,6 +570,15 @@ int persist_init(persist_t* p, persist_config_t* cfg, cluster_t* c)
p->config.max_wal_records = 100;
}
/* Enforce minimum value for wal_segment_bytes to prevent a rotation storm
* (must comfortably fit at least one max-payload entry: header + up to
* MAX_WAL_PAYLOAD_BYTES). */
if (p->config.wal_segment_bytes < 4096) {
ERROR("persist: wal_segment_bytes=%u too low (minimum 4096) — setting to 4096",
p->config.wal_segment_bytes);
p->config.wal_segment_bytes = 4096;
}
/* Initialise atomic checkpoint-trigger counters */
atomic_store(&p->wal_record_count, 0);
atomic_store(&p->checkpoint_in_progress, 0);
@ -790,7 +798,7 @@ int persist_wal_async(persist_t* p, uint32_t type,
repl_broadcast(&p->repl, &hdr, payload, len, prev_log_term);
/* Rotate segment when full */
if (p->seg_offset >= WAL_SEGMENT_SIZE_BYTES) {
if (p->seg_offset >= p->config.wal_segment_bytes) {
if (rotate_segment(p) != 0) {
pthread_mutex_unlock(&p->lock);
return -EIO;
@ -1204,7 +1212,7 @@ int persist_wal_write_replicated(persist_t* p, uint64_t lsn, uint32_t type,
}
/* Rotate segment when full (same threshold as the primary append). */
if (p->seg_offset >= WAL_SEGMENT_SIZE_BYTES) {
if (p->seg_offset >= p->config.wal_segment_bytes) {
if (rotate_segment(p) != 0) {
pthread_mutex_unlock(&p->lock);
return -EIO;