Synchronization
During website initialization, the synchronization engine scans and validates available content types and properties created in code, or from the Optimizely Content Management System (CMS) admin view.
The synchronization engine runs during site initialization, and creates a content type in CMS for each ContentType attributed class found in assemblies. The database stores only enough information to satisfy constraints and to associate the database row with the class. The engine stores additional code-defined settings in memory.
Annotation detects code-defined content types by using class and property attributes. During site initialization, annotation scans assemblies in the application, and passes classes decorated with the ContentType attribute to the synchronization engine.
The properties of a class determine the properties of a content type. The content type receives a property for each public class property with public GET and SET accessors. To specify property settings, use Property attributes.
Synchronization consists of the following steps.
- Validate the models. Synchronization validates the models created from the classes, including that two models do not share a GUID value.
- Analyze the content types and properties. Synchronization determines whether each model defined in code (and its properties) matches one of the following conditions:
- The model is a new content type.
- The model is an updated version of an existing content type.
- The model is identical to an existing content type.
Synchronization also finds content types and properties in the database that no longer exist in code. The synchronization engine skips a content type if the assembly version numbers are smaller than the version numbers from the previous synchronization commit.
- Commit content types and properties. Synchronization commits any content types or properties to the database. To disable the commit phase, configure ContentModelOptions.EnableModelSyncCommit to false. The Synchronize button displays on content types to allow for more granular synchronization. The commit phase performs the following operations.
- Create a content type or property. Synchronization stores only enough information to fulfill the database constraints and to associate the row in the database with the class or class member from which it originated. It stores the remaining class settings in a separate, in-memory repository available when the content type or property is cached.
- Update a content type or property. The merge operation updates changed settings. The merge operation occurs right before a content type or property is cached.
- Rename properties. A class property can change for one of the following reasons.
- A property was renamed.
- A new property was added, and another was removed.
Synchronization handles either case as a new property, so no values are transferred to the new property. To rename a property and transfer its values, implement a MigrationStep. See Refactor content type classes.
- Delete content types and properties. Synchronization deletes automatically created content types or properties in the database that do not exist in code. Synchronization does not delete content types and properties created in the admin view.
- A content type is removed only if no instances for the type exist in the database.
- A property is removed only if no values are set for it.
- Merge database settings. Synchronization adds a content type or property definition object to the runtime cache when it loads for the first time. Before the item is cached, synchronization merges the settings stored in the database (settings made in admin view) and settings defined in code (set via attributes) to form the actual object the application uses. If model and database settings conflict, database values take precedence. Settings saved through the admin view override code-defined settings and persist after the application restarts. When you edit properties and content types, the Revert to Default button removes settings previously saved through the admin view and reapplies settings specified in code.
For more information, see Finding content type conflict reasons by Māris Krivtežs.