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

5 files changed, 40 insertions, 0 deletions

diff --git a/src/mongo/s/catalog_cache.cpp b/src/mongo/s/catalog_cache.cpp
index 255ed96df69..9677b8bc58f 100644
--- a/src/mongo/s/catalog_cache.cpp
+++ b/src/mongo/s/catalog_cache.cpp
@@ -178,6 +178,12 @@ void CatalogCache::notifyOfCollectionVersionUpdate(OperationContext* opCtx,
     _cacheLoader->notifyOfCollectionVersionUpdate(opCtx, nss, version);
 }
 
+Status CatalogCache::waitForCollectionVersion(OperationContext* opCtx,
+                                              const NamespaceString& nss,
+                                              const ChunkVersion& version) {
+    return _cacheLoader->waitForCollectionVersion(opCtx, nss, version);
+}
+
 StatusWith<CachedDatabaseInfo> CatalogCache::getDatabase(OperationContext* opCtx,
                                                          StringData dbName) {
     try {
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
diff --git a/src/mongo/s/catalog_cache_loader.h b/src/mongo/s/catalog_cache_loader.h
index 7405d225d5b..3257cb8fbc5 100644
--- a/src/mongo/s/catalog_cache_loader.h
+++ b/src/mongo/s/catalog_cache_loader.h
@@ -96,6 +96,13 @@ public:
                                                  const ChunkVersion& version) = 0;
 
     /**
+     * Waits for the persisted collection version to be GTE to 'version', or an epoch change.
+     */
+    virtual Status waitForCollectionVersion(OperationContext* opCtx,
+                                            const NamespaceString& nss,
+                                            const ChunkVersion& version) = 0;
+
+    /**
      * Non-blocking call, which requests the chunks changed since the specified version to be
      * fetched from the persistent metadata store and invokes the callback function with the result.
      * The callback function must never throw - it is a fatal error to do so.
diff --git a/src/mongo/s/config_server_catalog_cache_loader.cpp b/src/mongo/s/config_server_catalog_cache_loader.cpp
index 79cea4d8211..e0ca6968b91 100644
--- a/src/mongo/s/config_server_catalog_cache_loader.cpp
+++ b/src/mongo/s/config_server_catalog_cache_loader.cpp
@@ -159,6 +159,12 @@ void ConfigServerCatalogCacheLoader::notifyOfCollectionVersionUpdate(OperationCo
     MONGO_UNREACHABLE;
 }
 
+Status ConfigServerCatalogCacheLoader::waitForCollectionVersion(OperationContext* opCtx,
+                                                                const NamespaceString& nss,
+                                                                const ChunkVersion& version) {
+    MONGO_UNREACHABLE;
+}
+
 std::shared_ptr<Notification<void>> ConfigServerCatalogCacheLoader::getChunksSince(
     const NamespaceString& nss,
     ChunkVersion version,
diff --git a/src/mongo/s/config_server_catalog_cache_loader.h b/src/mongo/s/config_server_catalog_cache_loader.h
index 9f7512f30bb..1a2451628da 100644
--- a/src/mongo/s/config_server_catalog_cache_loader.h
+++ b/src/mongo/s/config_server_catalog_cache_loader.h
@@ -47,6 +47,9 @@ public:
     void notifyOfCollectionVersionUpdate(OperationContext* opCtx,
                                          const NamespaceString& nss,
                                          const ChunkVersion& version) override;
+    Status waitForCollectionVersion(OperationContext* opCtx,
+                                    const NamespaceString& nss,
+                                    const ChunkVersion& version) override;
 
     std::shared_ptr<Notification<void>> getChunksSince(
         const NamespaceString& nss,