Cold Hard Cache
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Cold Hard Cache Alex Miller (@puredanger)
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An examination of caching, Ehcache, Hibernate second level-cache, Terracotta caching, and the future.
Transcript of Cold Hard Cache
Cold Hard CacheAlex Miller (@puredanger)
Agenda
• Why cache?
• Ehcache
• Hibernate 2nd level cache
• Terracotta
• The future....
Why cache?
• Temporal locality
• Non-uniform distribution
Temporal locality
Items:
Temporal locality
Items:
Cache:
Temporal locality
Items:
Cache:
Hits: 0%
Temporal locality
Items:
Cache:
Items:
Hits: 0%
Temporal locality
Items:
Cache:
Items:
Hits: 0%
Cache:
Temporal locality
Items:
Cache:
Items:
Hits: 0%
Cache:
Hits: 65%
Non-uniform distribution
0
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1600
2400
3200
0%
25%
50%
75%
100%Web page hits, ordered by rank
Page views, ordered by rank
Pageviews per rank% of total hits per rank
Non-uniform distribution
0
800
1600
2400
3200
0%
25%
50%
75%
100%Web page hits, ordered by rank
Page views, ordered by rank
Pageviews per rank% of total hits per rank
Cache is always good right?
• Watch out for:
• Amdahl’s law
• Memory
• Concurrency
• Copy cost
Reduce latency
0
500
1000
1500
2000
No cache With cache
Page build Data retrieval
Database offload
OperationsPer Second
Amount of Data
DBs are sized to peak load
OperationsPer Second
Amount of Data
Strive to downsize DBs
OperationsPer Second
Amount of Data
Frequently accessed app data:Shared Memory (Transactional)
Business Record Data : Database
Ehcache
Ehcache history
• First created in 2003 by Greg Luck
• Most widely used Java cache - 100k’s of deployments
• Apache 2.0 license
• JSR 107 Java cache implementation
Ehcache Architecture
Ehcache Features
• In-memory and spill-to-disk storage
• Cache bootstrap loaders
• Cache replication via listener API - RMI, JGroups, JMS
• Cache server with REST and SOAP APIs
• Servlet caching filter API
• Hibernate second-level cache support
Ehcache 1.6 performance
Ehcache Performance vs memcached
Hibernate Second-Level Cache
Hibernate Caching
Application Thread
Database
Session
Application Thread
Session
CacheConcurrency
Strategy
CacheConcurrency
Strategy
CacheConcurrency
Strategy
CacheRegion
CacheRegion
CacheRegion
Hib
ern
ate
1st Level Cache
2nd Level CacheCacheProvider
Entity and collection caches
• Entity and collection cache regions
• Mark a Hibernate entity or a collection in an entity as @Cacheable
• Specify a cache concurrency strategy
• ReadOnly, ReadWrite, NonstrictReadWrite, Transactional
• Turn on second level caching in the Hibernate config
Query Cache
• Query cache regions
• Mark HQL, Criteria, Query as cacheable
• Store result set id values
• Timestamp cache region - last update time for each entity type
• Useful for caching natural key lookups (non-primary key)
• ...but lots of hidden issues
Terracotta as cache
DistributedCache
• High-throughput clustered coherent cache
• Simple interface - basically ConcurrentMap
• Eviction options
• TTI, TTL
• Max in-memory size, max total size limits
DistributedCache Example
CacheConfig config = CacheConfigFactory.newConfig();config.setMaxTTISeconds(30 * 60) .setMaxTTLSeconds(2 * 60 * 60);
DistributedCache<String, Person> cache = config.newCache();
Person person = new Person(.......);cache.put(“Alex”, person);
Person cached = cache.get(“Alex”);
DistributedCache features
• Built on high throughput ConcurrentDistributedMap
• Expiration based on either TTI or TTL
• Both in-memory and total target max limits
• Automatic memory management of caches
• Coherent clustered cache
Terracotta Hibernate Second Level Cache
• Easy integration and configuration
• Supports entity, collection, and query cache regions
• Supports read-only, read-write, and nonstrict-read-write cache concurrency strategies
• Hibernate-specific tooling
• High performance with cache coherency
Enabling Second Level Cache
• Mark your entities with a cache concurrency strategy
• In hibernate.cfg.xml: <cache usage="read-write"/>
• With annotations: @Cache(usage=CacheConcurrencyStrategy.READ_WRITE)
• hibernate.cfg.xml
• <property name="cache.use_second_level_cache">true</property>
• <property name="cache.provider_class"> org.terracotta.hibernate.TerracottaHibernateCacheProvider</property>
Enabling Second Level Cache
• Define the tc-hibernate-cache.xml in your classpath
<?xml version=”1.0” encoding=”UTF-8”?><terracotta-hibernate-cache-configuration> <default-configuration> <time-to-idle-seconds>7200</time-to-idle-seconds> <time-to-live-seconds>7200</time-to-live-seconds> </default-configuration> <cache> <region-name>org.terracotta.authinator.domain.Account</region-name> <!-- as many region-names here as you want --> <configuration> <time-to-idle-seconds>600</time-to-idle-seconds> <time-to-live-seconds>600</time-to-live-seconds> </configuration> </cache> </terracotta-hibernate-cache-configuration>
• Add the Terracotta Hibernate cache provider jar to your classpath
• -cp terracotta-hibernate-cache-1.0.0.jar
• Add the Terracotta Hibernate cache agent jar to your command line
• -javaagent:terracotta-hibernate-agent-1.0.0.jar
New Hibernate cache visibility
Performance - Read-Only Comparison
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20
40
60
80
100
Database IMDG EhcacheTerracotta
Latency
Avg
Lat
ency
(ms)
0K
50K
100K
150K
200K
Database IMDG EhcacheTerracotta
Throughput
Tran
sact
ions
per
sec
ond
The future of caching...
Wonder twin powers, activate!
• “Standard” cache apis (Ehcache / JSR 107)
• Low latency local cache
• High throughput clustered cache
• Coherent caching with options to degrade for greater performance
• Support for both “copy” and “shared object” caching
Terracotta Ehcache
Single node and replicated Ehcache
• Same license, code base, and API
• Better visibility
• Better performance testing -> improved concurrency and performance
• Smooth migration path to...
Clustered Ehcache
• Short release for initial integration (probably Ehcache 1.7)
• Clustered store - partial API support
• Smooth upgrade from single node or replicated Ehcache
• New management and visibility features
Hibernate 2nd level cache
• More efficient in-memory and total count eviction (3.1.1)
• Better visibility of memory conditions
• Improved query caching
• Improved performance of core Terracotta (lock manager and memory manager)
Thanks!
• Terracotta Open Source JVM clustering:
• http://www.terracotta.org
• Apress: “The Definitive Guide to Terracotta”
• by Ari Zilka, Alex Miller, Geert Bevin, Jonas Boner, Orion Letizi, Taylor Gautier
• 2nd edition in progress....
• Alex Miller
• @puredanger
• http://tech.puredanger.com
