SERVER-50272 Make RoutingTableHistory movable

4 files changed, 13 insertions, 50 deletions

diff --git a/src/mongo/s/catalog_cache.cpp b/src/mongo/s/catalog_cache.cpp
index 8330c76f74b..fd4ef9f5d06 100644
--- a/src/mongo/s/catalog_cache.cpp
+++ b/src/mongo/s/catalog_cache.cpp
@@ -668,9 +668,9 @@ void CatalogCache::_scheduleCollectionRefresh(WithLock lk,
         setOperationShouldBlockBehindCatalogCacheRefresh(opCtx.get(), false);
 
         // TODO(SERVER-49876): remove clang-tidy NOLINT comments.
-        if (existingRoutingInfo && newRoutingInfo &&     // NOLINT(bugprone-use-after-move)
-            existingRoutingInfo->getSequenceNumber() ==  // NOLINT(bugprone-use-after-move)
-                newRoutingInfo->getSequenceNumber()) {   // NOLINT(bugprone-use-after-move)
+        if (existingRoutingInfo && newRoutingInfo &&  // NOLINT(bugprone-use-after-move)
+            existingRoutingInfo->getVersion() ==      // NOLINT(bugprone-use-after-move)
+                newRoutingInfo->getVersion()) {       // NOLINT(bugprone-use-after-move)
             // If the routingInfo hasn't changed, we need to manually reset stale shards.
             newRoutingInfo->setAllShardsRefreshed();
         }
diff --git a/src/mongo/s/chunk_manager.cpp b/src/mongo/s/chunk_manager.cpp
index 49ba0907017..3107a05a7a0 100644
--- a/src/mongo/s/chunk_manager.cpp
+++ b/src/mongo/s/chunk_manager.cpp
@@ -49,9 +49,6 @@
 namespace mongo {
 namespace {
 
-// Used to generate sequence numbers to assign to each newly created RoutingTableHistory
-AtomicWord<unsigned> nextCMSequenceNumber(0);
-
 bool allElementsAreOfType(BSONType type, const BSONObj& obj) {
     for (auto&& elem : obj) {
         if (elem.type() != type) {
@@ -309,8 +306,7 @@ RoutingTableHistory::RoutingTableHistory(NamespaceString nss,
                                          std::unique_ptr<CollatorInterface> defaultCollator,
                                          bool unique,
                                          ChunkMap chunkMap)
-    : _sequenceNumber(nextCMSequenceNumber.addAndFetch(1)),
-      _nss(std::move(nss)),
+    : _nss(std::move(nss)),
       _uuid(uuid),
       _shardKeyPattern(shardKeyPattern),
       _defaultCollator(std::move(defaultCollator)),
diff --git a/src/mongo/s/chunk_manager.h b/src/mongo/s/chunk_manager.h
index 77c636c0043..a5863b064b2 100644
--- a/src/mongo/s/chunk_manager.h
+++ b/src/mongo/s/chunk_manager.h
@@ -136,6 +136,9 @@ class RoutingTableHistory : public std::enable_shared_from_this<RoutingTableHist
     RoutingTableHistory& operator=(const RoutingTableHistory&) = delete;
 
 public:
+    RoutingTableHistory(RoutingTableHistory&&) = default;
+    RoutingTableHistory& operator=(RoutingTableHistory&&) = default;
+
     /**
      * Makes an instance with a routing table for collection "nss", sharded on
      * "shardKeyPattern".
@@ -165,13 +168,6 @@ public:
      */
     std::shared_ptr<RoutingTableHistory> makeUpdated(const std::vector<ChunkType>& changedChunks);
 
-    /**
-     * Returns an increasing number of the reload sequence number of this chunk manager.
-     */
-    unsigned long long getSequenceNumber() const {
-        return _sequenceNumber;
-    }
-
     const NamespaceString& getns() const {
         return _nss;
     }
@@ -274,24 +270,20 @@ private:
 
     ChunkVersion _getVersion(const ShardId& shardName, bool throwOnStaleShard) const;
 
-    // The shard versioning mechanism hinges on keeping track of the number of times we reload
-    // ChunkManagers.
-    const unsigned long long _sequenceNumber;
-
     // Namespace to which this routing information corresponds
-    const NamespaceString _nss;
+    NamespaceString _nss;
 
     // The invariant UUID of the collection.  This is optional in 3.6, except in change streams.
-    const boost::optional<UUID> _uuid;
+    boost::optional<UUID> _uuid;
 
     // The key pattern used to shard the collection
-    const ShardKeyPattern _shardKeyPattern;
+    ShardKeyPattern _shardKeyPattern;
 
     // Default collation to use for routing data queries for this collection
-    const std::unique_ptr<CollatorInterface> _defaultCollator;
+    std::unique_ptr<CollatorInterface> _defaultCollator;
 
     // Whether the sharding key is unique
-    const bool _unique;
+    bool _unique;
 
     // Map from the max for each chunk to an entry describing the chunk. The union of all chunks'
     // ranges must cover the complete space from [MinKey, MaxKey).
@@ -314,13 +306,6 @@ public:
     ChunkManager(std::shared_ptr<RoutingTableHistory> rt, boost::optional<Timestamp> clusterTime)
         : _rt(std::move(rt)), _clusterTime(std::move(clusterTime)) {}
 
-    /**
-     * Returns an increasing number of the reload sequence number of this chunk manager.
-     */
-    unsigned long long getSequenceNumber() const {
-        return _rt->getSequenceNumber();
-    }
-
     const NamespaceString& getns() const {
         return _rt->getns();
     }
diff --git a/src/mongo/s/write_ops/chunk_manager_targeter.cpp b/src/mongo/s/write_ops/chunk_manager_targeter.cpp
index f8bada7ced4..ec79a4ec1e4 100644
--- a/src/mongo/s/write_ops/chunk_manager_targeter.cpp
+++ b/src/mongo/s/write_ops/chunk_manager_targeter.cpp
@@ -335,24 +335,6 @@ bool isMetadataDifferent(const ChunkManager* managerA,
     return !databaseVersion::equal(dbVersionA, dbVersionB);
 }
 
-/**
- * Whether or not the manager/primary pair was changed or refreshed from a previous version
- * of the metadata.
- */
-bool wasMetadataRefreshed(const ChunkManager* managerA,
-                          const DatabaseVersion dbVersionA,
-                          const ChunkManager* managerB,
-                          const DatabaseVersion dbVersionB) {
-    if (isMetadataDifferent(managerA, dbVersionA, managerB, dbVersionB))
-        return true;
-
-    if (managerA) {
-        return managerA->getSequenceNumber() != managerB->getSequenceNumber();
-    }
-
-    return false;
-}
-
 }  // namespace
 
 ChunkManagerTargeter::ChunkManagerTargeter(OperationContext* opCtx,
@@ -728,7 +710,7 @@ void ChunkManagerTargeter::refreshIfNeeded(OperationContext* opCtx, bool* wasCha
         // If we couldn't target, we might need to refresh if we haven't remotely refreshed
         // the metadata since we last got it from the cache.
 
-        bool alreadyRefreshed = wasMetadataRefreshed(
+        bool alreadyRefreshed = isMetadataDifferent(
             lastManager, lastDbVersion, _routingInfo->cm(), _routingInfo->db().databaseVersion());
 
         // If didn't already refresh the targeting information, refresh it