The idxmap package provides an enhanced mapping structure to help in the following use cases:
- Exposing read-only access to plugin local data for other plugins
- Secondary indexing
- Data caching for key-value store (such as etcd)
For more detailed description see the godoc.
App plugins often need to expose some structured information to other plugins inside the agent (see the following diagram).
Structured data stored in idxmap are available for (possibly concurrent) read access to other plugins:
- either via lookup using primary keys or secondary indices;
- or via watching for data changes in the map using channels or callbacks (subscribe for changes and receive notification once an item is added, changed or removed).
TODO: remove "<<cache>>" string from the image
It is useful to have the data from a key-value store cached when you need to:
- minimize the number of lookups into the key-value store
- execute lookups by secondary indexes for key-value stores that do not necessarily support secondary indexing (e.g. etcd)
CacheHelper turns idxmap (injected as field
IDX) into an indexed local copy of remotely stored key-value data.
CacheHelper watches the target key-value store for data changes
and resync events. Received key-value pairs are transformed into
the name-value (+ secondary indices if defined) pairs and stored into
the injected idxmap instance.
For a visual explanation, see the diagram below:
Packages that use index map.
The constructor that combines CacheHelper with idxmap to build the cache from the example
can be found there as well.