decrease _next_index when when the request with the minimum log

ehds · Apr 7, 2024 · 731c0b1 · 731c0b1
1 parent 59c40e5
commit 731c0b1
Showing 1 changed file with 15 additions and 7 deletions.
diff --git a/src/braft/replicator.cpp b/src/braft/replicator.cpp
@@ -447,18 +447,26 @@ void Replicator::_on_rpc_returned(ReplicatorId id, brpc::Controller* cntl,
                        << " is " << response->last_log_index();
             // The peer contains less logs than leader
             r->_next_index = response->last_log_index() + 1;
-        } else {  
+        } else {
             // The peer contains logs from old term which should be truncated,
             // decrease _last_log_at_peer by one to test the right index to keep
             if (BAIDU_LIKELY(r->_next_index > 1)) {
-                BRAFT_VLOG << "Group " << r->_options.group_id 
-                           << " log_index=" << r->_next_index << " mismatch";
+                BRAFT_VLOG << "Group " << r->_options.group_id
+                         << " log_index=" << r->_next_index << " mismatch";
+              // Decrease the next_index when the request with the minimum log
+              // index mismatch.
+              // Because when we enable pipeline replication and disable cache,
+              // the request with larger log index would be handled before the
+              // smaller request, we should ignore it.
+              // See https://github.com/baidu/braft/issues/421
+              if (request->prev_log_index() == r->_next_index - 1) {
                 --r->_next_index;
+              }
             } else {
-                LOG(ERROR) << "Group " << r->_options.group_id 
-                           << " peer=" << r->_options.peer_id
-                           << " declares that log at index=0 doesn't match,"
-                              " which is not supposed to happen";
+              LOG(ERROR) << "Group " << r->_options.group_id
+                         << " peer=" << r->_options.peer_id
+                         << " declares that log at index=0 doesn't match,"
+                            " which is not supposed to happen";
             }
         }
         // dummy_id is unlock in _send_heartbeat