Principles
Nuxeo provides a Redis integration via the nuxeo-core-redis bundle.
The idea is that, at least for now, Redis is not a hard requirement for running the Nuxeo Platform; We simply use Redis as a backend to provide alternate implementation of some services inside the platform. However, we do provide these implementations because we think they can be useful.
Nuxeo uses Redis to store transient data, after a normal cluster shutdown, the content of Redis can be flushed (erased). Note however that Nuxeo can not work with a Redis configured as LRU cache, there should be no eviction under memory pressure, hopefully this is the default policy of Reds.
Nuxeo Core Cache
Nuxeo Core Cache provides a service to declare and use caches. This cache system:
- is used in Nuxeo Directories (caching directories entries)
- is used in UserManager (caching principals)
- is used in Nuxeo Drive (caching synchronization roots)
- can be used in your custom code
The Cache has a default "in memory" implementation, but nuxeo-core-redis provides another implementation that allows:
- To have out of JVM memory cache storage. It opens the way to have big caches without hurting the JVM.
- To share the same cache between several Nuxeo nodes. In cluster mode this can increase cache efficiency.
- To manage cluster wide invalidations. Updating the user on one node will impact the central cache: all nodes see the exact same data.
You can configure the backend storage on a per cache basis: Directory A could use Redis while directory B could use in memory.
Work Manager
The WorkManager handles asynchronous jobs:
- Schedule Jobs and store them in queues
- Assign execution slots to queues
- Execute the jobs
In the default implementation, job queues are in the JVM memory. But this model has some limitations:
- Stacking a lot of jobs will consume JVM Memory
- In cluster mode each Nuxeo node maintains its own queue
- When a Nuxeo server is restarted, all the queued jobs are lost
nuxeo-core-redis provides an alternate implementation of the queuing system based on Redis:
- Jobs are then stored outside of JVM memory. That's why Work have to be serializable: they are serialized and stored inside Redis.
- Jobs can be shared across cluster nodes. This allows to dedicate some nodes to some specific processing.
- Jobs survive a Nuxeo restart. When Redis persistence is activated, the jobs even survive a Redis restart.
Lock Manager
By default Lock managed on documents are stored inside the repository backend.When the locking system is heavily used, it can create a lot of very small transactions against the database backend.
nuxeo-core-redis provides a Redis-based implementation of the locking system that is resilient as the database implementation, but easier to scale.
Clustering invalidation
VCS Row Cache Invalidation
Managing VCS row cache invalidations with Redis instead of using the database can improve performance on concurrent writes and provides synchronous invalidations.
DBS Cache Invalidation
Since Nuxeo 8.10 the DBS layer (used by MongoDB or Marklogic backends) has a cache its invalidation in cluster mode requires Redis.
Transient Store
The RedisTransientStore is a Redis-based implementation of the Transient Store.
It is the one used by the default Transient Store if Redis is enabled.
It allows the parameters associated to the stored blobs to be shared accross cluster nodes.