advanced apache cayenne
TRANSCRIPT
Advanced Apache Cayenne(practical demonstration)by Andrus Adamchik, ObjectStyle LLC
CMS: Admin appTapestry stack
Admin App(demo)
Admin App - Takeaway
• We can reuse Cayenne and service code between the apps
• When editing objects, ObjectContext is placed in the page scope and should be reset when we start editing a new object
• Scope in Tapestry is managed with @Persist annotation
Lifecycle Events(demo)
Lifecycle Events - Takeway
• Two ways to receive events - callbacks and listeners
• Use callbacks on persistent objects for simple things like initialization
• Use listeners for more complex workflows, cross-entity workflows
• Check out DataChannelFilter (will be discussed later)
Caching
Types of Cache
• What is cached?
• Object cache - objects cached by ID
• Query cache - lists cached by generated cache key
Types of Cache
• Where is it cached?
• Local cache - attached to an ObjectContext
• Shared cache - attached to a DataDomain (a common parent of all ObjectContexts)
Object Cache (very much like EOF)
• Stores objects (or DataRows) by ObjectId
• Prevents unneeded DB trips when navigating object graph
• Ensures uniquing
• Can be auto-synchronized across contexts or VMs
• Memory leak-free (shared - LRU; local - weak refs)
Query Cache (nothing like EOF)
• Stores lists of objects (or lists of DataRows) by query key
• Prevents unneeded DB trips when running queries
• Fully “managed” - time-based or event-based expiration policies
• Lightweight synchronization via cache groups (in VM, cross-VM)
• Scales much better
Query Cache(demo)
Caching and Performance
Turn off Cross-Context Synchronization
• Good for desktop apps, terrible for webapps
• unrelated contexts receiving events they don’t care about
• Clustering of object cache doesn’t perform well
• Without clustering, behavior differs for contexts in same VM vs different VM
• Object auto-sync will interfere with optimistic locking
Turn off Cross-Context Synchronization
binder.bindMap(Constants.PROPERTIES_MAP).put(Constants.SERVER_CONTEXTS_SYNC_PROPERTY, "false");
Use Query Cache
• Design your app with cache groups in mind
• Implement refresh based on expiration policies
• Implement refresh based on events and CacheInvalidationFilter
• Cluster refresh events. Clustering is lightweight, not prone to breaking on code version changes
Consider Optimistic Locking
Caching and Performance
• Don’t try to sync individual objects
• Turn off cross-context synchronization
• Use query cache. Cluster it.
• Use optimistic locking
