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feat: persist.c WAL writer with chained CRC32 and dedicated fsync pthread (P0-1)

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- Expose persist_t struct concretely in persist.h (opaque pattern deferred)
- persist_set_workdir() derives wal/snap paths from workdir+name
- persist_init() creates WAL/snap directories, rejects NFS mounts
- persist_wal_async() writes WAL entries with chained CRC32 via zlib
- Dedicated fsync pthread fires every wal_sync_ms milliseconds
- persist_flush() forces fdatasync for tests and clean shutdown
- WAL_CHECKPOINT type rejected with -EINVAL (never written via async path)
- Stubs: persist_recover, persist_wal_sync_append, persist_checkpoint
- Add fsync_thread_running flag to guard persist_stop when thread not started
- Add zlib_dep to controller and unit test meson targets
- 3 new TDD tests: init_creates_directories, wal_async_writes_entry,
  checkpoint_type_rejected — all GREEN
This commit is contained in:
Rongsong Shen 2026-05-07 10:00:10 +00:00
parent d66a8a98b6
commit b0a5fbb4e9
5 changed files with 502 additions and 2 deletions
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43
src/include/persist.h
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@ -81,10 +81,48 @@ typedef struct {
} slot_key_t;
/* ============================================================
* persist_t — opaque; defined in persist.c (Task 7)
* persist_t — concrete definition (exposed for stack/calloc allocation)
* The opaque pattern can be restored in a later refactor once the
* full API surface is stable.
* ============================================================ */
struct persist_s {
/* WAL state */
int wal_fd;
uint64_t current_lsn;
uint64_t last_crc;
uint64_t last_replicated_crc;
uint64_t term;
uint32_t seg_offset;
uint64_t checkpoint_lsn;
uint64_t total_wal_bytes;
char seg_path[4096];
/* Paths (derived from workdir + name via persist_set_workdir) */
char wal_path[4096];
char snap_path[4096];
/* Config */
persist_config_t config;
/* Concurrency */
pthread_mutex_t lock;
atomic_int fsync_stop;
atomic_int fsync_thread_running;
pthread_t fsync_thread;
/* Checkpoint (stubs for now — wired in Task 10) */
atomic_int checkpoint_in_progress;
atomic_int checkpoint_requested;
pthread_cond_t checkpoint_done;
pthread_mutex_t checkpoint_mutex;
pthread_t snap_thread;
};
typedef struct persist_s persist_t;
/* Set workdir and controller name before persist_init().
* Derives wal_path and snap_path as <workdir>/<name>/data/{wal,snap}. */
void persist_set_workdir(persist_t* p, const char* workdir, const char* name);
/* Lifecycle */
int persist_init(persist_t* p, persist_config_t* config, cluster_t* c);
int persist_start(persist_t* p);
@ -99,6 +137,9 @@ int persist_wal_sync_append(persist_t* p, uint32_t type,
const void* payload, uint32_t len,
int* sync_rc_out);
/* Force WAL fdatasync (for tests and clean shutdown) */
int persist_flush(persist_t* p);
/* Checkpoint */
int persist_checkpoint(persist_t* p);