fms: extract entry_size to log_entry::get_size

We intend to reuse it in subsequent commit.

raft/fsm.cc

@@ -855,27 +855,6 @@ void fsm::request_vote_reply(server_id from, vote_reply&& reply) {
     }
 }
 
-static size_t entry_size(const log_entry& e) {
-    struct overloaded {
-        size_t operator()(const command& c) {
-            return c.size();
-        }
-        size_t operator()(const configuration& c) {
-            size_t size = 0;
-            for (auto& s : c.current) {
-                size += sizeof(s.addr.id);
-                size += s.addr.info.size();
-                size += sizeof(s.can_vote);
-            }
-            return size;
-        }
-        size_t operator()(const log_entry::dummy& d) {
-            return 0;
-        }
-    };
-    return std::visit(overloaded{}, e.data) + sizeof(e);
-}
-
 void fsm::replicate_to(follower_progress& progress, bool allow_empty) {
 
     logger.trace("replicate_to[{}->{}]: called next={} match={}",
@@ -935,7 +914,7 @@ void fsm::replicate_to(follower_progress& progress, bool allow_empty) {
                 req.entries.push_back(entry);
                 logger.trace("replicate_to[{}->{}]: send entry idx={}, term={}",
                              _my_id, progress.id, entry->idx, entry->term);
-                size += entry_size(*entry);
+                size += entry->get_size();
                 next_idx++;
                 if (progress.state == follower_progress::state::PROBE) {
                     break; // in PROBE mode send only one entry

raft/raft.cc

@@ -12,6 +12,27 @@ namespace raft {
 
 seastar::logger logger("raft");
 
+size_t log_entry::get_size() const {
+    struct overloaded {
+        size_t operator()(const command& c) {
+            return c.size();
+        }
+        size_t operator()(const configuration& c) {
+            size_t size = 0;
+            for (auto& s : c.current) {
+                size += sizeof(s.addr.id);
+                size += s.addr.info.size();
+                size += sizeof(s.can_vote);
+            }
+            return size;
+        }
+        size_t operator()(const log_entry::dummy& d) {
+            return 0;
+        }
+    };
+    return std::visit(overloaded{}, this->data) + sizeof(*this);
+}
+
 } // end of namespace raft
 
 auto fmt::formatter<raft::server_address>::format(const raft::server_address& addr,

raft/raft.hh

@@ -239,6 +239,8 @@ struct log_entry {
     term_t term;
     index_t idx;
     std::variant<command, configuration, dummy> data;
+
+    size_t get_size() const;
 };
 
 using log_entry_ptr = seastar::lw_shared_ptr<const log_entry>;