rgw/multisite: in order to sleep between mdlog polling events, we check if the mdlog_...

mdlog_marker and max_marker. but max_marker is exposed to changes from RGWReadMDLogEntriesCR, and if there is a race
coming from mdlog trimming which could render max_marker empty, then its comparison with mdlog polling can be incorrect.
To fix this, we now save the previous mdlog marker and compare with the updated mdlog marker.

Signed-off-by: Shilpa Jagannath <smanjara@redhat.com>
(cherry picked from commit bae10f22e8b008088f0861db2785d8c0ba7ee506)

diff --git a/src/rgw/driver/rados/rgw_sync.cc b/src/rgw/driver/rados/rgw_sync.cc
index a9ea2ecf5491d5dd6a9760442626c2c57ee14a72..583e2d1098e1c2ae2c74923d640dbc8fd773655e 100644 (file)
--- a/src/rgw/driver/rados/rgw_sync.cc
+++ b/src/rgw/driver/rados/rgw_sync.cc
@@ -1481,6 +1481,7 @@ class RGWMetaSyncShardCR : public RGWCoroutine {
   bool done_with_period = false;
 
   int total_entries = 0;
+  string old_mdlog_marker;
 
   RGWSyncTraceNodeRef tn;
 public:
@@ -1832,6 +1833,7 @@ public:
        if (mdlog_marker <= max_marker || !truncated) {
          /* we're at the tip, try to bring more entries */
           ldpp_dout(sync_env->dpp, 20) << __func__ << ":" << __LINE__ << ": shard_id=" << shard_id << " syncing mdlog for shard_id=" << shard_id << dendl;
+          old_mdlog_marker = mdlog_marker;
           yield call(new RGWCloneMetaLogCoroutine(sync_env, mdlog,
                                                   period, shard_id,
                                                   mdlog_marker, &mdlog_marker));
@@ -1902,7 +1904,8 @@ public:
           tn->log(10, SSTR(*this << ": done with period"));
           break;
         }
-       if (mdlog_marker == max_marker && can_adjust_marker) {
+       if (mdlog_marker == old_mdlog_marker && can_adjust_marker) {
+          tn->log(20, SSTR("mdlog_marker=" << mdlog_marker << " old_mdlog_marker=" << old_mdlog_marker));
           tn->unset_flag(RGW_SNS_FLAG_ACTIVE);
          yield wait(utime_t(cct->_conf->rgw_meta_sync_poll_interval, 0));
        }