SERVER-33097 make shards put a request's databaseVersion on the OperationShardingState

1 files changed, 38 insertions, 37 deletions

diff --git a/src/mongo/db/s/operation_sharding_state.h b/src/mongo/db/s/operation_sharding_state.h
index 4a55173c09c..2f57f849830 100644
--- a/src/mongo/db/s/operation_sharding_state.h
+++ b/src/mongo/db/s/operation_sharding_state.h
@@ -33,6 +33,7 @@
 #include "mongo/base/disallow_copying.h"
 #include "mongo/db/namespace_string.h"
 #include "mongo/s/chunk_version.h"
+#include "mongo/s/database_version_gen.h"
 #include "mongo/util/concurrency/notification.h"
 
 namespace mongo {
@@ -40,12 +41,9 @@ namespace mongo {
 class OperationContext;
 
 /**
- * A decoration on OperationContext representing per-operation shard version metadata sent to mongod
- * from mongos as a command parameter.
- *
- * The metadata for a particular operation can be retrieved using the get() method.
- *
- * Note: This only supports storing the version for a single namespace.
+ * A decoration on OperationContext tracking per-operation sharding state, such as the client's
+ * sent shardVersion, databaseVersion, and allowImplicitCollectionCreation fields, and whether this
+ * operation should wait for a migration critical section to complete before returning.
  */
 class OperationShardingState {
     MONGO_DISALLOW_COPYING(OperationShardingState);
@@ -72,41 +70,50 @@ public:
     bool allowImplicitCollectionCreation() const;
 
     /**
-     * Parses shard version from the command parameters 'cmdObj' and stores the results in this
-     * object along with the give namespace that is associated with the version. Does nothing
-     * if no shard version is attached to the command.
-     *
-     * Expects the format { ..., shardVersion: [<version>, <epoch>] }.
-     *
-     * This initialization may only be performed once for the lifetime of the object, which
-     * coincides with the lifetime of the request.
+     * Returns whether a shardVersion for 'nss' was sent by the client.
      */
-    void initializeShardVersion(NamespaceString nss, const BSONElement& shardVersionElement);
+    bool hasClientShardVersion(const NamespaceString& nss) const;
 
     /**
-     * Returns whether or not there is a shard version associated with this operation.
+     * Returns whether a shardVersion for any namespace was sent by the client.
      */
-    bool hasShardVersion() const;
+    bool hasClientShardVersionForAnyNamespace() const;
 
     /**
-     * Returns the shard version (i.e. maximum chunk version) of a namespace being used by the
-     * operation. Documents in chunks which did not belong on this shard at this shard version
-     * will be filtered out.
-     *
-     * Returns ChunkVersion::UNSHARDED() if this operation has no shard version information
-     * for the requested namespace.
+     * Returns whether a database version for 'db' was sent by the client.
+     */
+    bool hasClientDbVersion(const std::string& db) const;
+
+    /**
+     * Returns whether a database version for any database was sent by the client.
+     */
+    bool hasClientDbVersionForAnyDb() const;
+
+    /**
+     * Inspects 'cmdObj' for shardVersion and databaseVersion fields, and sets them as the client's
+     * shardVersion and dbVersion for 'nss'.
      */
-    ChunkVersion getShardVersion(const NamespaceString& nss) const;
+    void setClientRoutingVersions(NamespaceString nss, BSONObj cmdObj);
 
     /**
-     * Stores the given chunk version of a namespace into this object.
+     * Returns the client's sent shardVersion for 'nss', if one was sent, otherwise returns the
+     * UNSHARDED version. This is for two historical reasons:
+     *
+     * 1) Some commands operate on multiple namespaces (such as agg with $out, agg with $lookup, and
+     *    eval), but it's not possible to send a shardVersion for more than one namespace.
+     *    Luckily, the secondary namespaces in all such commands are required to be unsharded. So,
+     *    we return UNSHARDED for any namespace besides the (primary) namespace the client sent an
+     *    explicit shardVersion for.
+     * 2) Not all paths on mongos attached a shardVersion when targeting an unsharded collection.
+     *
+     * Operations that need to completely opt out of shardVersion checks set the IGNORED version.
      */
-    void setShardVersion(NamespaceString nss, ChunkVersion newVersion);
+    ChunkVersion getClientShardVersion(const NamespaceString& nss) const;
 
     /**
-     * Undoes setting the shard version for the given namespace. Needed for views.
+     * Returns the client's sent dbVersion for 'db', if one was sent, otherwise returns boost::none.
      */
-    void unsetShardVersion(NamespaceString nss);
+    boost::optional<DatabaseVersion> getClientDbVersion(const std::string& db) const;
 
     /**
      * This call is a no op if there isn't a currently active migration critical section. Otherwise
@@ -125,18 +132,12 @@ public:
     void setMigrationCriticalSectionSignal(std::shared_ptr<Notification<void>> critSecSignal);
 
 private:
-    /**
-     * Resets this object back as if it was default constructed (ie _hasVersion is false,
-     * _shardVersion is UNSHARDED, _ns is empty).
-     */
-    void _clear();
-
     // Specifies whether the request is allowed to create database/collection implicitly
     bool _allowImplicitCollectionCreation{true};
 
-    bool _hasVersion = false;
-    ChunkVersion _shardVersion{ChunkVersion::UNSHARDED()};
-    NamespaceString _ns;
+    boost::optional<NamespaceString> _nss;
+    boost::optional<ChunkVersion> _shardVersion;
+    boost::optional<DatabaseVersion> _dbVersion;
 
     // This value will only be non-null if version check during the operation execution failed due
     // to stale version and there was a migration for that namespace, which was in critical section.