Allow setting ReadPreference at a Repository and Query level [DATAMONGO-2103]

[spring-projects-issues]

João Carvalho opened DATAMONGO-2103 and commented

Currently, setting the ReadPreference can only be done at the MongoTemplate level. This forces us to move down an abstraction layer to specify custom ReadPreferences for our entities and queries.

We would like to be able to specify the ReadPreference for an entity at the Repository and Query level. Our current use case involves a specific entity which can be accessed from a secondary node node in the majority of the use cases, but requires primary reads for other use cases. As our applications scale, it becomes critical to distribute load across all nodes in the MongoDB cluster, and currently, we can either change the global level (thus sacrificing correctness) or providing custom implementations on a repository-by-repository basis.

This could be achieved using an annotation, like such:

@ReadPreference(SECONDARY_PREFERRED)
class FooRepository : CrudRepository<Foo, String> {

  fun findByName(name: String): Foo?

  @ReadPreference(PRIMARY)
  fun strongFindByName(name: String): Foo?

}

In this example, all queries to this entity (both builtin an custom) would use the 'Secondary Preferred' level, except for strongFindByName, which would use the 'Primary' level.

 

 

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1 votes, 2 watchers

[jorgerod]

Hi @christophstrobl
I am very interested in this feature. I see that @odrotbohm is assigned.

If there is no problem, I would like to contribute.

[christophstrobl]

@jorgerod I cleared the assignee, happy to review a PR. Please make sure to check out our contribution guidelines.