@Version("0.5.1")
Package org.apache.jackrabbit.oak.composite
Composition support
This package contains support classes for implementing a composite persistence at the NodeStore level.
Design goals
- Transparency of the composition setup. Neither the NodeStores nor the code using a composite NodeStore should be aware of the specific implementation being used.
- Persistence-agnosticity. The composition support should be applicable to any conformant NodeStore implementation.
- Negligible performance impact. Composition should not add a significat performance overhead.
Implementation
The main entry point is the CompositeNodeStore
,
which wraps one or more NodeStore instances. Also of interest are the CompositeNodeState
and CompositeNodeBuilder
.
These classes maintain internal mappings of the 'native' objects. For instance, if the composite NodeStore holds two MemoryNodeStore instances, then a call to NodeStore.getRoot() will return a composite NodeState backed by two MemoryNodeState instances. Similarly, a call to NodeState.builder() will return a composite NodeBuilder backed by two MemoryNodeState instances.
Using this approach allows us to always keep related NodeStore, NodeState and NodeBuilder instances isolated from other instances.
Open items
1. Brute-force support for oak:mount nodes.
The Mount.getPathFragmentName()
method defines
a name pattern that can be used by mounted stores to contribute to a patch which is not
owned by them. For instance, a mount named apps which owns /libs,/apps
can own another subtree anywhere in the repository given that a node named :oak-mount-apps
is found.
The current implementation naively queries all stores whenever the child node list is prepared.
This is obviously correct but may be slow.
CompositionContext.getContributingStores(java.lang.String, java.util.function.Function)
-
Interface Summary Interface Description CompositeNodeStoreMonitor CompositeNodeStoreStatsMBean -
Class Summary Class Description CompositeCheckpointMBean CompositeNodeStore CompositeNodeStore.Builder CompositeNodeStoreService CompositeNodeStoreStats CrossMountReferenceValidator CrossMountReferenceValidatorProvider Validator
which detects references crossing the mount boundariesInitialContentMigrator ModifiedPathDiff MountedNodeStore MountInfoConfig MountInfoProviderService NodeMap<T> PrivateStoreValidatorProvider Validator
which detects change commits to the read only mounts.StringCache This class caches the path strings used in the CompositeNodeState to avoid keeping too many strings in the memory. -
Annotation Types Summary Annotation Type Description MountInfoConfig.Props