Performance Anti-Patterns in Hibernate

Patrycja Wegrzynowicz
Snippets:

• "premature optimization is the root of all evil"
• "expect unexpected"...
• avoid temporary changes
• careful with Collections: inadequate collection mappings can impact resulting # of queries
• OneToMany on owning side: lots of unnecessary locking / querying
• bulk processing through Hibernate --> use database operations instead

Conclusion

• big data = big problems -- my addition: with hibernate :-)
  • standard mappings don't handle large datasets well
  • smart model, bulk processing, projections
• read the manual
  • hibernate docs
  • think of consequences
• hibernate
  • smart policies / data structures

Nothing was said of my personal performance finding with Hibernate: maximally use readonly access whenever possible. The support for 'dirty' objects adds a lot of performance overhead if some model-parts are readonly.

Bleeding Edge HTML5

Paul Kinlan
This presentation demonstrated some ongoing - bleeding edge - development in html5:

• : section that can be collapsed: no extra javascript required
• : highlight portions of text
  • less javascript
  • easier for to handle
• input-tag adds support for speech-to-text input
• video & animations: check if the current tab is visible. Allows to stop a video when the tab is inactive
• a link can suggest the browser to pre-fetch the contents of links the user will likely click --> the page is pre-loaded
• intents: loosely coupling/integration of services from different websites. Cfr Android intents: an application asks a photo viewer and Android lets the user choose which one he wants.
• check online / offline status in javascript or use a callback. --> clean handling of unconnected status.
• paste of images in browser
• camera / microphone support
• full-screen support, callable from javascript (user must grant permission)
• WebRTC: real-time communication: Real time Video / audio for communication
• much better audio support

check out http://html5hacks.com

JDK 7, 8 and 9

Mark Reinhold


Java7

• Project Coin: small language improvements
  • diamond <> operator: easier generics
  • multi-catch clause
  • ...
• invokedynamic: bytecode opperation for dynamic languages (e.g. JRuby) and will be used for Lamba expressions in Java 8.
• fork/join framework

Java8

• Lambda expressions (aka Closures)
• Jigsaw: modularity
  • improve performance:
    • only load what's needed
    • more efficient jmod package type
  • dependencies are defined in the module configuration --> better than the current classpath hell
  • jmod modules will be easily packaged into rpm or deb packages ⁻ JavaFX 3.0
• Type annotations
• new Date/Time library (cfr. JodaTime)
• support for Sensors (accelerometer, etc.)

Java9 (not decided yet)

• self-tuning JVM's
• better JNI
• support for Big Data
• reified generics
• unified types: int <> Integer etc.
• optimize tail recursion... finally?
• resource management / accounting?

Devoxx11: Java EE Keynote

Cameron Purdy
Focus on next Java EE versions 7 & 8:

• Html 5
• Modularity
  • jigsaw
  • profiles:JEE providers can choose to not implement part of the SPEC. Eg. some older specs like EJB CMP & BMP will become optional.
• Cloud
  • elastic
  • auto provisioning
  • Paas

Platform as a Service (Paas) details

• JEE7 is the service
• auto-provisioning:
  • DB (incl. init-script)
  • LDAP
  • loadbalancer / clustering settings
• extensible for frameworks (e.g. Spring, Seam)
• Quality of Service (QOS)
• API's for the Cloud: Caching ...
• Multi-tenant: deploy the same app for multiple / isolated users.
• Cloud descriptions in meta in the ear

Other:

• Timeboxed strategy for providing JEE 7 / 8: : everything not ready for JEE7 will shift to JEE8.
• Glassfish provides the reference implementation of latest JEE developments.

Devoxx11: Java SE Keynote

Henrik Ståhl
Java Standard Edition (SE) 7 achievements:

• project coin: small language improvements
• concurrency: fork/join framework
• JavaFx as part of the java language

Java SE 8 focus:

• Jigsaw: modularity
• lambda (aka closures): opens the door for easier to use concurrency api's
• javaFx 3.0
• new devices: multi-touch etc.

Devoxx11: Jackpot 3.0 - Large Custom Refactorings

Jan Lahoda
Jackpot:

• originally from Sun labs
• uses the Abstract Syntax Tree (AST) --> knows java-language / syntax: smarter than simple regexp's
• ideal to refactor deprecated API's
• remove anti-patterns

Jackpot is now included in Netbeans 7.1

• use special 'Hint' syntax: Class.oldMethod => NewClass.newMethod ;;
• completely integrated in standard Netbeans hints / refactoring logic
  • hints are show in the IDE, directly to the developer
  • batch refactorings are allowed: completely integrated in the "Inspect and refactor" dialog (incl. managing hints)
  • run headless from the command line
• can be highly fine-tuned:
  • use instanceof checks
  • match on specific Java constructs: e.g. only look for Fields
  • check on target java version
  • combine multiple checks
  • write repeatable tests in ".test" file
• definitely worthwhile looking at for large refactorings of legace Java projects!

Devoxx11: Java 7 toolbox

Project coin brought some minor improvements to the Java language. Most notably:

• easier generics:
  • diamond operator <>: less copy/paste thanks to smarter compiler
  • less warnings on vararg's
• easier error-handling:
  • multicatch: less copy/paste
  • 'try-with-resource' contstruct: automatic & correct closing and error handling
• consistency / clarity
  • Strings in Switch
  • numbers improvements:
    • direct binary format: 0b0101001
    • logical grouping of large number in sub-chunks: 123_435_576L --> java ignores the underscores.

IDE support

• Netbeans & Intellij have excellent support for Java 7
  • inline hints and refactorings are offered
  • batch refactorings throughout the 'inspect and transform' dialog
• Eclipse is somewhat lagging behind.

Devoxx11: Real-world deep-dive into Infinispan - the open source data grid platform

Sanne Grinovero, Pete Muir and Mircea Markus
Infinispan details

• developed & provided by JBoss
• Open Source license
• distributed, in-memory data structure
• High Available: configuration options depending on your safety / performance considerations
  • Total replication
  • Partial replication ("distribution mode")
• Elastic:
  • easy to scale up / down
  • deal with node stops / crashes
  • accept additional nodes
  • managed through JGroups

Capabilities:

• Transactions
• Map / Reduce
• Query
• JMX access

Two access modes to inifinispan:

• embedded mode: in the JVM
• client / server mode: different protocols supported:
  • REST
  • memcached
  • hotrod

Possible setups:

• local cache: Simple Map-like interface, with advanced cache-features (eviction, etc.)
• cluster cache: all caches are kept in sync between JVM's, the developer is responsible for accessing the persistence layer (DB)
• grid cache: the cache itself handles the persisting of the data to the DB.

JGroups

• reliable cluster communication
• developed by JBoss, and used by Infinispan
• Node / cluster config (incl. auto-discover setup)
• focus on performance: e.g. UDP, but with reliability handled by JGroups
• support for reliable multicast messages

Devoxx11: Building Web Applications with MongoDB

Brendan McAdams

mongoDB is a nosql DB, ie. a "non-relational" DB

• no joins
• no referential integrity
• no complex transactions --> not suitable for higly transactional apps
• but: focus on horizontal scalability
  • sharding
  • replica's
• a scheme-less DB
  • unique ObjectID is automatically generated (based on time, machine, pid & counter)
  • flexible structures: adding/omitting elements is easy
• native JSON support
  • hierarchical 'documents'
  • arrays
  • internally, an optimized format is used: BSON:http://bsonspec.org
• support for indexes (+ 'multi-indexes' on arrays)

technical specifics:

• based on memory mapped files:
  • OS maps the files in the RAM.
  • pagefaults are expensive --> keep working set in RAM
    • provide sufficient RAM
    • prewarm the DB
  • only use 64bit OS & binaries
• Intel-only (little endian)
• filesystem
  • Ext4 & Xfs: only filesystems with support for posix_fallocate()
  • set noatime, noadirtime in /etc/fstab
• 'documents' (i.e. objects) have a max. size of 16mb
• accessible over tcp/ip: Mongo Wire Protocol
• UTF-8
• the data is stored in fysical files / 'extents'

modeling for mongoDB:

• think of 'documents' instead of 'rows'
• favor embedding over referencing -- mongoDB offers no referential integrity (aka foreign keys)
• think of the access patterns of your data

other specifics:

• support for MapReduce
• geospatial indexing
• indexes (internally btrees)
• query optimization
• advanced queries ($lt, $all, $in...)
• gridfs:
  • large 'chunked' files
  • distributed (sharded)
  • accessible through a regular java.io.File

Devoxx11: Codereview with GIT / Gerrit

Matthias Sohn

Git:

• decentralized source version control
• good at merging
• cryptographic hashes to prevent modifications to history
• works well off-line
• personal branches
• JGit: written in Java
• eGit: eclipse plugin for Git

Adopters of GIT:

• Linux
• CVS will be deprecated in 2012
• eclipse.org: converting from CVS to Git

Gerrit:

• Code-review based on Git
• parallel work-flow based on branches
• web based interface

Devoxx11: Android awesomeness

Chet Haase, Romain Guy and Philip Milne

Android 4.0: Tablet (3.0) & Phone (2.3) reunited

GridLayout: powerful & flexible lay-outing -- way too complex explanation.

Tools for profiling / debugging Android apps. "Experience matters"

• Memory
  • dumpsys: dump info of processes running on the device
    • adb shell dumpsys meminfocom.android.Launcher: dumps heap usage details
    • dumpsys gfxinfo: graphics chip
    • dumpsys window: decompose window objects used
  • DDMS: heap dump
  • jhat:
    • generate hprof
    • convert it with hprof-conv
    • in eclipse
    • check out "rootset references" for potentially memory leaks
  • MAT: Eclipse Allocation Tracker - http://eclipse.org/mat
• Performance
  • "use your eyes"
  • DDMS
  • track frames per second -> "trackFPS()" call in a PreDrawListener
• UI
  • 'crazy' stuff like high speed cams: Casio Ex-F1: replay the animation in slow motion
  • HierarchyViewer:
    • ViewTree
    • PixelPerfectTree
  • ViewServer

Devoxx11: Android Jumpstart

Lars Vogel

Excellent introduction to the Android development experience.

• tutorials on Android: www.vogella.de
• java --> class -- through dx-tool --> dex
• development environment: ADT for eclipse.
  • emulator: QEMU
  • DDMS: very powerful device debug mode
• API Components:
  • View for single views & ViewGroup for combining
  • Activity: app lifecycle - onPause() is the guaranteed last call to persist data
  • Intent: transitions to other apps
    • Implicit: Android decides
    • explicit: hard coded coupling to called app
  • Toast class: display quick temporary message
  • Preferences
  • DIY Views:
    • onDraw() method
    • Path class
    • selective invalidate() call to improve performance
  • ListActivity & ListAdapter
  • Threading & Async behaviour:
    • Threads: use runOnUiThread for async updates of the UI
    • Services
    • Broadcast & Receiver