AOF_FSYNC_EVERYSEC higher resolution, change aof_last_fsync to use ms…

…time

Currently aof_last_fsync is using a low resolution unixtime is really bad,
depending on which side of the second barrier it falls, we can get very
different results.

Change it to use mstime, see discussion in redis#8612.

src/aof.c

@@ -833,7 +833,7 @@ int openNewIncrAofForAppend(void) {
      * is already synced at this point so fsync doesn't matter. */
     if (server.aof_fd != -1) {
         aof_background_fsync_and_close(server.aof_fd);
-        server.aof_last_fsync = server.unixtime;
+        server.aof_last_fsync = server.mstime;
     }
     server.aof_fd = newfd;
 
@@ -954,7 +954,7 @@ void stopAppendOnly(void) {
     if (redis_fsync(server.aof_fd) == -1) {
         serverLog(LL_WARNING,"Fail to fsync the AOF file: %s",strerror(errno));
     } else {
-        server.aof_last_fsync = server.unixtime;
+        server.aof_last_fsync = server.mstime;
     }
     close(server.aof_fd);
 
@@ -998,7 +998,7 @@ int startAppendOnly(void) {
             return C_ERR;
         }
     }
-    server.aof_last_fsync = server.unixtime;
+    server.aof_last_fsync = server.mstime;
     /* If AOF fsync error in bio job, we just ignore it and log the event. */
     int aof_bio_fsync_status;
     atomicGet(server.aof_bio_fsync_status, aof_bio_fsync_status);
@@ -1074,7 +1074,7 @@ void flushAppendOnlyFile(int force) {
          * the data in page cache cannot be flushed in time. */
         if (server.aof_fsync == AOF_FSYNC_EVERYSEC &&
             server.aof_last_incr_fsync_offset != server.aof_last_incr_size &&
-            server.unixtime > server.aof_last_fsync &&
+            server.mstime - server.aof_last_fsync >= 1000 &&
             !(sync_in_progress = aofFsyncInProgress())) {
             goto try_fsync;
 
@@ -1260,15 +1260,15 @@ void flushAppendOnlyFile(int force) {
         latencyEndMonitor(latency);
         latencyAddSampleIfNeeded("aof-fsync-always",latency);
         server.aof_last_incr_fsync_offset = server.aof_last_incr_size;
-        server.aof_last_fsync = server.unixtime;
+        server.aof_last_fsync = server.mstime;
         atomicSet(server.fsynced_reploff_pending, server.master_repl_offset);
     } else if (server.aof_fsync == AOF_FSYNC_EVERYSEC &&
-               server.unixtime > server.aof_last_fsync) {
+               server.mstime - server.aof_last_fsync >= 1000) {
         if (!sync_in_progress) {
             aof_background_fsync(server.aof_fd);
             server.aof_last_incr_fsync_offset = server.aof_last_incr_size;
         }
-        server.aof_last_fsync = server.unixtime;
+        server.aof_last_fsync = server.mstime;
     }
 }
 

src/server.c

@@ -2053,7 +2053,7 @@ void initServerConfig(void) {
     server.aof_rewrite_base_size = 0;
     server.aof_rewrite_scheduled = 0;
     server.aof_flush_sleep = 0;
-    server.aof_last_fsync = time(NULL);
+    server.aof_last_fsync = time(NULL) * 1000;
     server.aof_cur_timestamp = 0;
     atomicSet(server.aof_bio_fsync_status,C_OK);
     server.aof_rewrite_time_last = -1;

src/server.h

@@ -1779,7 +1779,7 @@ struct redisServer {
     int aof_fd;       /* File descriptor of currently selected AOF file */
     int aof_selected_db; /* Currently selected DB in AOF */
     time_t aof_flush_postponed_start; /* UNIX time of postponed AOF flush */
-    time_t aof_last_fsync;            /* UNIX time of last fsync() */
+    time_t aof_last_fsync;            /* mstime of last fsync() */
     time_t aof_rewrite_time_last;   /* Time used by last AOF rewrite run. */
     time_t aof_rewrite_time_start;  /* Current AOF rewrite start time. */
     time_t aof_cur_timestamp;       /* Current record timestamp in AOF */