SERVER-29745 after a successful migration, ensure the metadata update is persisted before range deletion is schedule

1 files changed, 18 insertions, 0 deletions

diff --git a/src/mongo/s/catalog_cache.h b/src/mongo/s/catalog_cache.h
index a978642c825..9b261de3a43 100644
--- a/src/mongo/s/catalog_cache.h
+++ b/src/mongo/s/catalog_cache.h
@@ -98,6 +98,24 @@ public:
                                          const ChunkVersion& version);
 
     /**
+     * Waits for the persisted collection version to be gte to 'version', or an epoch change. Only
+     * call this function if you KNOW that a version gte WILL eventually be persisted.
+     *
+     * This function cannot wait for a version if nothing is persisted because a collection can
+     * become unsharded after we start waiting and 'version' will then never be reached. If 'nss'
+     * has no persisted metadata, even if it will shortly, a NamespaceNotFound error will be
+     * returned.
+     *
+     * A lock must not be held when calling this because it would prevent using the latest snapshot
+     * and actually seeing the change after it arrives.
+     * This function can throw a DBException if the opCtx is interrupted.
+     * This can only be called on a shard!
+     */
+    Status waitForCollectionVersion(OperationContext* opCtx,
+                                    const NamespaceString& nss,
+                                    const ChunkVersion& version);
+
+    /**
      * Retrieves the cached metadata for the specified database. The returned value is still owned
      * by the cache and should not be kept elsewhere. I.e., it should only be used as a local
      * variable. The reason for this is so that if the cache gets invalidated, the caller does not