Package io.datareplication.producer.feed

Interface FeedEntityRepository

  • public interface FeedEntityRepository
    Repository to store feed entities and what page they are assigned to.

    Entities are uniquely identified by their ContentId. Different methods alternatively take and return either full entities (Entity) or a subset of header fields (FeedEntityRepository.PageAssignment). All these methods act on the same data, they just provide different views onto the same records, to avoid having to load full entity bodies when they're not needed. The fields that need to be stored in this repository is the union of all fields in both classes. See the documentation for FeedEntityRepository.PageAssignment on how to match the fields.

    As an exception to the rule above, the following fields don't need to be accurately saved:

    • FeedEntityHeader.extraHeaders() may be ignored if you don't intend to use it
    • Entity.userData() explicitly does not have any meaning ascribed to it by the library; consequently, it is entirely up to the repository implementation how to handle this field

    Consistency Requirements

    This repository must fulfill the common requirements for all feed producer repositories.

    All write operations must be atomic for an individual entity, i.e. it must never be possible to observe a partially-written entity

    Ordering

    Any returned lists of entities must be sorted in the following way:
    1. by their last-modified timestamp (FeedEntityRepository.PageAssignment.lastModified()), oldest to newest
    2. any entities with the same timestamp must be sorted using their content ID as a tie breaker
    It's important that the ordering for any two entities remains stable so long as their last-modified timestamps don't change.

    • Method Detail

      • append

        @NonNull
@NonNull java.util.concurrent.CompletionStage<java.lang.Void> append​(@NonNull
                                                                     @NonNull Entity<@NonNull FeedEntityHeader> entity)
        Add an entity to the repository. Once an entity has been saved successfully, this method won't be called again with the same content ID.

        The Entity object does not contain all fields that need to be saved in the repository. See FeedEntityRepository.PageAssignment for the expected default values for any fields missing from the entity.

        Parameters:
        entity - the entity to save
        Returns:
        CompletionStage

      • get

        @NonNull
@NonNull java.util.concurrent.CompletionStage<@NonNull java.util.List<@NonNull Entity<@NonNull FeedEntityHeader>>> get​(@NonNull
                                                                                                                       @NonNull PageId pageId)
        Load all entities whose FeedEntityRepository.PageAssignment.pageId() field is set to the given page.

        All fields necessary to create the Entity must be loaded, including the body. The returned list must be sorted by the entities' timestamps as described in the class documentation.

        Parameters:
        pageId - the page ID to load
        Returns:
        CompletionStage of all entities assigned to the given page

      • getUnassigned

        @NonNull
@NonNull java.util.concurrent.CompletionStage<@NonNull java.util.List<@NonNull FeedEntityRepository.PageAssignment>> getUnassigned​(int limit)
        Load all entities whose FeedEntityRepository.PageAssignment.pageId() field is empty.

        The returned list must be sorted by the entities' timestamps as described in the class documentation. Note that the limit must take place after sorting, i.e. logically the list of all available records is sorted and then the first 

        limit
        elements from the sorted list are returned.
        Parameters:
        limit - the maximum number of records to load
        Returns:
        CompletionStage of all entities not assigned to a page

      • getPageAssignments

        @NonNull
@NonNull java.util.concurrent.CompletionStage<@NonNull java.util.List<@NonNull FeedEntityRepository.PageAssignment>> getPageAssignments​(@NonNull
                                                                                                                                        @NonNull PageId pageId)
        Load all entities whose FeedEntityRepository.PageAssignment.pageId() field is set to the given page.

        The returned list must be sorted by the entities' timestamps as described in the class documentation.

        Parameters:
        pageId - the page ID to load
        Returns:
        CompletionStage of all entities assigned to the given page

      • savePageAssignments

        @NonNull
@NonNull java.util.concurrent.CompletionStage<java.lang.Void> savePageAssignments​(@NonNull
                                                                                  @NonNull java.util.List<@NonNull FeedEntityRepository.PageAssignment> pageAssignments)
        Update the given entities.

        This method will only ever update existing entities, i.e. all content IDs in the list are guaranteed to exist in the repository.

        Parameters:
        pageAssignments - a list of updates to save to the repository
        Returns:
        CompletionStage