[SLING-8946] Non-deterministic shadowing of resource observation

• Type: Bug
• Status: Reopened
• Priority: Critical
• Resolution: Unresolved
• Affects Version/s: Resource Resolver 1.5.34
• Component/s: ResourceResolver
• Assignee: Unassigned
• Reporter: Dirk Rudolph
• Created: 20/Dec/19 18:11
• Updated: 08/Dec/20 10:32

Description

The BasicObservationReporter implements shadowing of events being propagated per ResourceProvider instance [1]. Assuming we do have 2 ResourceProviders registered, where the one shadows the other like this:

• RP A registered on /
• RP B registered on /path

then currently the excludes given to the BasicObservationReporter are different depending on either RP A or RP B gets registered first:

• RP A before RP B => excludes are empty
• RP B before RP A => excludes contain /path

This is because only the newly registered RP gets its ProviderContext updated [2]

Same applies if RP B is registered before RP A and gets unregistered. In that case the ObservationReporter of RP A stays untouched.

[1] https://github.com/apache/sling-org-apache-sling-resourceresolver/blob/master/src/main/java/org/apache/sling/resourceresolver/impl/observation/BasicObservationReporter.java#L102
[2] https://github.com/apache/sling-org-apache-sling-resourceresolver/blob/master/src/main/java/org/apache/sling/resourceresolver/impl/providers/ResourceProviderTracker.java#L358

Issue Links

• causes: SLING-9040 High resource consumption when activating/deactivating ResourceProviders
• is duplicated by: SLING-9040 High resource consumption when activating/deactivating ResourceProviders
• is related to: SLING-9077 Improve runtime complexity of o.a.s.api.resource.path.PathSet's factory methods
• is related to: SLING-9365 Optionally don't create resource providers for servlets
• links to: GitHub Pull Request #16