Consistent List Entity Children
- John Hill
Introduction
Currently, the GET /query service provides consistent query results as long as the caller does not filter by annotations. In order to address scalability issues with the query services, we plan to change the query to run against replicated data in the index database. This will change the query service from providing consistent query results to eventually-consistent results.
For most use cases, eventual-consistency of the query services is acceptable. For example, the UI uses the query services to list the children of a container. For the use case where a user is browsing children of a container using the UI, it is okay if newly created children do not appear immediately. The user will not know that children are missing. However for the user case where the users creates a new child, if the new child does not appear in the list, there will be a perception of data loss.
In order to prevent the perception of data loss, we need to provide a consistent service for listing the children of a container before we change the query service to be eventually consistent.
New API
Object Models
| EntityChildrenRequest |
|---|
| String parentId |
| List<EntityType> includeTypes |
| Enum{NAME,CREATED_ON} sortBy |
| Enum{ASC,DESC} sortDirection |
| EntityChildrenReponse |
|---|
| List<EntityHeader> page |
| String nextPageToken |
REST call
| Response Body | URI | Request Body |
|---|---|---|
| EntityChildrenReponse | /entity/{entity_id}/children | EntityChildrenRequest |