Fix: The snapshot installation blindly applies config to the server. (#…

…566) * Fix: The snapshot installation blindly applies config to the server. If the server was previously in the member set which was captured in the config of this snapshot, then the peer will appear to have "caught_up" in ::reconfigure. I do not believe there is value in rolling back the config just to reapply it later once log_sync occurs. `::commit_conf` performs a similar check. * Simplify * [Update PR] Leave a log when snapshot config is skipped --------- Co-authored-by: Jung-Sang Ahn <[email protected]>
eBay · Jan 23, 2025 · f9c7462 · f9c7462
1 parent cf80969
commit f9c7462
Showing 1 changed file with 16 additions and 3 deletions.
diff --git a/src/handle_snapshot_sync.cxx b/src/handle_snapshot_sync.cxx
@@ -20,6 +20,7 @@ limitations under the License.
 
 #include "raft_server.hxx"
 
+#include "cluster_config.hxx"
 #include "context.hxx"
 #include "error_code.hxx"
 #include "event_awaiter.hxx"
@@ -565,10 +566,22 @@ bool raft_server::handle_snapshot_sync_req(snapshot_sync_req& req, std::unique_l
                 // LCOV_EXCL_STOP
             }
 
-            reconfigure(req.get_snapshot().get_last_config());
-
+            auto snap_conf = req.get_snapshot().get_last_config();
             ptr<cluster_config> c_conf = get_config();
-            ctx_->state_mgr_->save_config(*c_conf);
+            if (snap_conf->get_log_idx() > c_conf->get_log_idx()) {
+                ctx_->state_mgr_->save_config(*snap_conf);
+                reconfigure(snap_conf);
+                c_conf = get_config();
+            } else {
+                p_in("snapshot config idx %" PRIu64 " prev idx %" PRIu64
+                     " is not newer than "
+                     "current config idx %" PRIu64 " prev idx %" PRIu64
+                     ", will not apply it",
+                     snap_conf->get_log_idx(),
+                     snap_conf->get_prev_log_idx(),
+                     c_conf->get_log_idx(),
+                     c_conf->get_prev_log_idx());
+            }
 
             precommit_index_ = req.get_snapshot().get_last_log_idx();
             sm_commit_index_ = req.get_snapshot().get_last_log_idx();