IBM WebSphere and POWER7: Powering performance for Smarter Planet Solutions

1
Best practices around Dynacache
Jonathan Marshall WebSphere Technical
Professional marshalj_at_uk.ibm.com
2
Acknowledgements

• Based on presentations by
• Geoff Tindall WebSphere level 2 support
• Rama Boggarapu WebSphere level 2 support

3
Agenda

• Why do I need caching?
• What is Dynamic Cache?
• A peak under the covers of WebSphere Application
  Server
• Replicating the Dynamic Cache
• Monitoring the Cache
• Troubleshooting Tips
• Where do we go from here?

4
Why Cache?
A cache allows you to get stuff faster and helps
youavoid doing something over and over
again(which may be redundant and may not make
sense)
(far away)
(near)
(happy)
5
Why Cache?

• Improving the performance
• Tuning the application?
• Tuning the environment?
• Tuning the backend resources?
• Not doing something at all?

6
Introducing Dynamic Caching Services (dynacache)
7
Enabling Dynamic Cache
8
What does it cache?

• Each CacheEntry will have CacheId and CacheData
• In addition to CacheId and CacheData, CacheEntry
  will have other information like dependencyIds,
  timeout information, replication type and various
  other information.
• CacheMonitor.ear application can be used to view
  most of the information about a CacheEntry.

9
Where does it cache data? The Cache Instance

• An application uses a cache instance to store,
  retrieve, and share data objects within the
  dynamic cache.
• Two types of custom cache instances can be
  configured
• Servlet Cache
• Cachespec.xml
• Object Cache
• API based cache, com.ibm.websphere.cache.Distribut
  edMap
• Three methods to create custom cache instance
• Administrative console (under Resources)
• Properties file (cacheinstances.properties)
• Resource reference in web.xml

10
Dynamic Cache Configuration for Default Cache
Instance
11
Disk Offload

• Implementation inherited from IBM Research
• Disk cache size can be controlled in terms of
  space on the disk and of entries.
• LRU Size based Disk eviction algorithms can
  configured to specify the criteria for eviction.
• 3 Performance modes HIGH, CUSTOM LOW depending
  on the JVM free heap space available.
• High ..Buffers all disk metadata in memory.
• Custom/Balanced Buffers some/most disk metadata
  in memory.
• Low Buffers NO metadata in memory. Note this
  will be deprecated in v8.
• FlushToDiskOnStop provides for the cache to be
  persisted.
• One of the strongest features of Dynacache.
  Differentiates from other open source solutions
  as well as eXtreme Scale.

12
Disk Offload

• Configure a new cache instance
• Resources Cache Instances Servlet Cache
  Instance new
• A jndi name must be given to the cache instance
  which will be used to refer back to the instance
  in cachespec.xml.
• Check Enable disk offload and specify a disk
  off load location, cache size and cache entry
  limits.

13
How does it choose what to cache?

• Cachespec.xml is a deployable XML cache policy
  file that contains caching rules
• Placed in WEB-INF directory
• Specify the cache-instance name where the cache
  rules to be applied
• What to be cached?
• command/servlet/webservice/JAXRPCClient/static/por
  tlet
• How to identify an item in cache?
• Cache-Id
• Where to cache?
• Memory only/ Disk
• When to invalidate?
• Timebased/invalidation rules
• How to handle dependencies?
• Dependency rules for invalidation

14
Cache ID

• A cacheID can be comprised of the following
• Request parameters and attributes
• The URI used to invoke the servlet or JSP
• Session information
• Cookies
• Pathinfo and servlet path
• Http header and Request method
• Servlet/JSP result caching can be used to cache
  both whole pages or fragments.
• Example
• /reference/Time.jspformatanalog
• Web Service getStockPrice but NOT setStockPrice

15
Example cachespec.xml (1/4) Define the entry

• ltcache-entrygt ltnamegt/newscontrollerlt/namegt
• ltclassgtservletlt/classgt
• lt/cache-entrygt

http//publib.boulder.ibm.com/infocenter/wasinfo
/v7r0/index.jsp?topic/com.ibm.websphere.nd.doc/in
fo/ae/ae/welc6tech_dyn_dev.html
16
Example cachespec.xml (2/4) Define the cache id

• ltcache-entrygt ltnamegt/newscontrollerlt/namegt
• ltclassgtservletlt/classgt
• ltcache-idgt
• ltcomponent id"action" type"parameter"gt
• ltvaluegtviewlt/valuegt
• ltrequiredgttruelt/requiredgt
• lt/componentgt
• ltcomponent id"category" type"parameter"gt
• ltrequiredgttruelt/requiredgt
• lt/componentgt
• ltcomponent id"layout" type"session"gt
• ltrequiredgtfalselt/requiredgt
• lt/componentgt
• lt/cache-idgt
• lt/cache-entrygt

http//publib.boulder.ibm.com/infocenter/wasinfo
/v7r0/index.jsp?topic/com.ibm.websphere.nd.doc/in
fo/ae/ae/welc6tech_dyn_dev.html
17
Example cachespec.xml (3/4) Define the
dependencies

• ltcache-entrygt ltnamegt/newscontrollerlt/namegt
• ltclassgtservletlt/classgt
• ltcache-idgt
• ltcomponent id"action" type"parameter"gt
• ltvaluegtviewlt/valuegt
• ltrequiredgttruelt/requiredgt
• lt/componentgt
• ltcomponent id"category" type"parameter"gt
• ltrequiredgttruelt/requiredgt
• lt/componentgt
• ltcomponent id"layout" type"session"gt
• ltrequiredgtfalselt/requiredgt
• lt/componentgt
• lt/cache-idgt
• ltdependency-idgtcategory
• ltcomponent id"category" type"parameter"gt
• ltrequiredgttruelt/requiredgt
• lt/componentgt
• lt/dependency-idgt

http//publib.boulder.ibm.com/infocenter/wasinfo
/v7r0/index.jsp?topic/com.ibm.websphere.nd.doc/in
fo/ae/ae/welc6tech_dyn_dev.html
18
Example cachespec.xml (4/4) Define the
invalidation

• ltcache-entrygt ltnamegt/newscontrollerlt/namegt
• ...
• ltinvalidationgtcategory
• ltcomponent id"action" type"parameter"
  ignore-value"true"gt
• ltvaluegtupdatelt/valuegt
• ltrequiredgttruelt/requiredgt
• lt/componentgt
• ltcomponent id"category" type"parameter"gt
• ltrequiredgttruelt/requiredgt
• lt/componentgt
• lt/invalidationgt
• lt/cache-entrygt

http//publib.boulder.ibm.com/infocenter/wasinfo
/v7r0/index.jsp?topic/com.ibm.websphere.nd.doc/in
fo/ae/ae/welc6tech_dyn_dev.html
19
Fragment Caching

• The content of A.jsp is composed of its own
  content plus 3 jsps(fragments) B.jsp,C.jsp and
  D.jsp
• Often a mix of static and dynamic
• consume-subfragmentstells the cache to store
  fragments
• ltexcludegt allows fragments to explicitly not be
  cached

20
Going under the covers Data Replication Service
21
Data Replication Service - DRS

• Data replication service (DRS) is an internal
  WebSphere Application Server component that
  replicates data.
• Transport for sending data from one managed
  server to another.
• Uses HAManager and DCS data stack frameworks to
  accomplish replication.
• Has the notion of replicas
• Data transfer channel can be encrypted. In
  practice no-one does this.
• Benefits
• Used by DynaCache, HTTPSession, Stateful Session
  Beans and SIP
• Challenges
• DRS Bootstrap will be expensive, if aggressive
  replication occurs during startup.
• DCS uses a star topology for synchrony, can
  result in scalability bottlenecks.

22
High Availability Manager
Data Replication Services (DRS)

• New feature in V6
• Collection of services
• Highly Available Singleton Services
• Low-level Replication Abstraction
• Shared State Bulletin Board
• Several runtime features depend on HA Manager
  services
• HA Manager runs in every single JVM in the cell
• HA Manager services are only available between
  JVMs that are part of the same core group

23
HA Core Group Message Links
JVM

• N2-N links
• N2, 2 links
• N3, 6 links
• N4, 12 links
• N5, 20 links
• N6, 30 links

JVM
JVM
JVM
JVM

• With each additional JVM
• Geometrically greater messages flowing
• More connections per JVM
• More memory per JVM to hold messages

JVM
Optimizations to reduce message frequency and
size are available in WAS 6.1
24
DRS Important Tuning

• DRS shares the HA Manager with other services
• Under load, you may see large numbers of any of
  the following Distribution and Consistency
  Services (DCS) congestion messages in your
  SystemOut.log file
• DCSV1051W, a high severity congestion event for
  outgoing messages
• DCSV1052W, a medium severity congestion event for
  outgoing messages
• DCSV1054W, a medium severity congestion event for
  incoming messages
• Tuning directions are given in the InfoCenter
  http//publib.boulder.ibm.com/infocenter/wasinfo/v
  6r1/index.jsp?topic/com.ibm.websphere.nd.doc/info
  /ae/ae/trun_ha_cfg_replication.html

25
DRS Important Tuning

• Consider increasing the size of the default
  thread pool
• In larger configurations, the Default thread pool
  size should be increased.
• Doubling the thread pool size to 40 will likely
  be sufficient.
• However, when the number of application servers
  in a replication domain is greater 10 and the
  number of replication domain consumers in each
  application server exceeds 2, it may need to be
  increased more.
• This should keep the DCS traffic moving and avoid
  the timeouts.
• The transport buffer size out of the box value
  may also be insufficient 
• For all the appservers doing replication,
• Click on Servers -gt Application Servers -gt ltYour
  appservergt -gt Coregroup service
• Change the transport buffer size to 100MB (or
  larger in more extreme loads). This changes the
  RMM buffer size.
• We also recommend changing the IBM_CS_DATASTACK_ME
  G memory config parameter
• Servers --gt Core Groups --gt Core group settings
  --gtthen the settings for your core group (e.g.
  such as DefaultCoreGroup). Choose "Additional
  Properties" to specify a "Custom Properties".
  Key would be "IBM_CS_DATASTACK_MEG" with value in
  MB. Default value is 50.

26
Cache Replication
27
Replicating data across servers in a cluster

• Currently only dealt with the scenario where data
  is cached per JVM
• The Data Replication Service replicates data
  throughout the cell for various functions
• Dynacache
• HTTP Session
• Stateful Session Beans
• The scope of replication, the Replication
  Domain allows multiple deployment patterns
• Client/Server
• Client-only/Server-only
• Creating replication domains http//publib.boulde
  r.ibm.com/infocenter/wasinfo/v6r1/index.jsp?topic
  /com.ibm.websphere.nd.doc/info/ae/ae/trun_drs_repl
  ication.html

28
Replication Topologies Peer to peer

• For dynacache and HTTP session replication

29
Replication Topologies Client/Server

• For HTTP session replication only

30
Replication Domain configuration

• Single replica
• Limits replicated data to a single backup copy
  within the Replication Domain
• Reduces the total amount of redundant data held
  throughout the domain
• E.g. HTTP Session replication
• Entire Domain
• Stores a backup copy within each DRS instance in
  the Replication Domain
• Maximises the redundancy of the data held
  throughout the domain
• E.g. Dynamic cache needs to use this
• Specify
• Stores a specified number of backup copies within
  the Replication Domain

31
Configuring Replication for Default Cache Instance
32
Replication Types

• In all of the following modes, the invalidations
  will be sent across servers for data consistency.
• PUSH mode - cacheId and Cache Data will be sent
  to all servers in cluster
• PULL mode (Not recommended) - Server requests the
  data from other servers in cluster, when not
  present in its cache
• PUSH/PULL mode - Only cacheId is sent to all
  servers in cluster. When a server needs an entry
  in the Push/Pull table, it requests it from the
  server that has the copy.
• Not Shared - Cache data will not be shared across
  servers. But invalidation events are sent to all
  servers.
• Recommendation
• Try PUSH and move to PUSH/PULL or even Not Shared
  if struggling to replicate

33
Monitoring the Cache
34
Monitoring the Cache The CacheMonitor
Application

• Shipped with WebSphere application server install
  in the installableApps dir

35
Monitoring the Cache

• Cache contents can also be displayed.
• In our example, the cacheID is
• /referenceWEB/Time.jsprequestTypeGET

36
Disk Offload
37
Extended Cache Monitor on developerWorks

• http//www.ibm.com/developerworks/websphere/downlo
  ads/cache_monitor.html
• Provides two functions that are not available
  with the cache monitor
• Monitor and Manage contents of object cache
• Monitor cache statistics for cache instances
  across all members of the cluster.
• Enhancements made for the cache monitorin
  WebSphere Application Server V7
• look at the push-pull table associated with a
  cache instance
• search memory contents, disk contents, and
  push-pull table using a regular expression
• compare cache instances

38
Cache Statistics Collector and Visualizer
http//www.alphaworks.ibm.com/tech/cacheviz/
Statistics from DynaCache JMX MBean provide
insight into the state, health, performance,
composition efficiency of the cache. Collect
cache statistics using DynaCacheStatisticsCSV.py
wsadmin jython script. Outputs statistics in
CSV file Statistics can be charted with
Microsoft Excel or OpenOffice SpreadSheet.
39
Performance Troubleshooting
40
Dynamic Cache Common Sense Tips

• WebSphere Application Server uses JVM memory to
  cache objects. Therefore, know how much memory
  can be allocated for the cache and set the cache
  size to the proper value.
• Increase the priority of cache entries that are
  expensive to regenerate.
• Modify timeout of entries so that they stay in
  memory as long as they are valid.
• If the estimated total size of all cached objects
  is bigger than the available memory, you can
  enable the disk offload option.
• Increase the cache size if memory allows.

41
Essential Dynacache Tuning

• Read the following document for cache replication
  tuning
• http//www-01.ibm.com/support/docview.wss?uidswg2
  7006431
• Set the following Dynacache JVM Custom Properties
• Name com.ibm.ws.cache.CacheConfig.ignoreValueInIn
  validationEvent Value true
• Name com.ibm.ws.cache.CacheConfig.filterTimeOutIn
  validation Value true
• Name com.ibm.ws.cache.CacheConfig.filterLRUInvalid
  ation Value true
• Name com.ibm.ws.cache.CacheConfig.cacheEntryWindo
  w Value 50
• Name com.ibm.ws.cache.CacheConfig.cacheInvalidate
  EntryWindow Value 50
• Name com.ibm.ws.cache.CacheConfig.useServerClassL
  oader Value true
• Assume to use replication type of NOT_SHARED
• Read the following Technote for Portal Server
  Cache Replication issues
• http//www-01.ibm.com/support/docview.wss?uidswg2
  1322640
• Read the following Technote for Commerce server
  replication issues
• http//www-01.ibm.com/support/docview.wss?uidswg2
  1358672

42
Objects placed in cache are not replicated

• Make sure the replication instance is launched
  (see SystemOut.log below)
• Test with PUSH mode
• If you are using PUSH_PULL mode, only CacheId
  will be pushed. Cache data will be pulled when
  needed
• The following messages in SystemOut.log file
  tells Dynamic cache instance is initialized and
  replication service is launched. Notice a small
  delay, if application is looking for replicated
  data during the delay, it may not find
  it2008-07-10 185601828 EST 0000002c
  CacheServiceI I DYNA1001I WebSphere Dynamic
  Cache instance named /cache/instance_one
  initialized successfully.2008-07-10
  185602828 EST 00000042 DRSBootstrapM A
  CWWDR0001I Replication instance launched
  /cache/instance_one
• See the following Technote for more information
• http//www-01.ibm.com/support/docview.wss?uidswg2
  1313480

43
Dynacache Congestion

• Signs of Congestion
• (1) DCSV1051W/DCSV1052W DCS Stack
  DefaultCoreGroup.MyCluster at Member
  CustomServer1 Raised a high severity congestion
  event for outgoing messages. Internal details are
  Total stored bytes 67701476, Red mark is
  41943040, Yellow mark is 37748736, Green mark is
  8388608.
• (2) HMGR0152W CPU Starvation detected. Current
  thread scheduling delay is 109 seconds.
• Congestion normally occurs when there is lot of
  data stored in cache and a member joins a
  HAManager view or if there are lot of
  invalidation events across servers.
• Workarounds
• Use the NOT_SHARED or PUSH_PULL replication mode
• Filter out of unnecessary cache invalidation
  events by configuring custom propertiesName
  com.ibm.ws.cache.CacheConfig.filterTimeOutInvalida
  tion Value trueName com.ibm.ws.cache.CacheConfi
  g.filterLRUInvalidation Value true

44
Dynacache Controlling DRS message size

• When processing BatchUpates, the DRS message
  could be huge, which can lead to fragmentation
  issues and OutOfMemory errors.
• The following custom properties introduced in
  PK32201 and PK35284 helps to control the size of
  DRS messagescom.ibm.ws.cache.CacheConfig.cachePe
  rcentageWindow 2com.ibm.ws.cache.CacheConfig.c
  acheEntryWindow 50com.ibm.ws.CacheConfig.batchU
  pdateMilliseconds - 1 seccom.ibm.ws.cache.CacheCo
  nfig.cacheInvalidateEntryWindow
  50com.ibm.ws.cache.CacheConfig.cacheInvalidatePer
  centWindow -2

45

• Advanced topologies

46
Dynamic Cache Next Generation
47
WebSphere eXtreme Scale

• WebSphere eXtreme Scale provides distributed
  object caching essential for elastic scalability
  and next-generation cloud environments. It
  processes massive volumes of transactions with
  extreme efficiency and linear scalability.
• The WebSphere eXtreme Scale dynamic cache
  provider
• It uses cheaper system memory instead of SAN or
  storage solutions
• Provides a scalable replicated cache with a
  configurable number of replicas. This eliminates
  the need to use broadcast data everywhere with
  DRS.
• Scales elastically. Additional WebSphere
  eXtreme Scale containers can be added at runtime.
  WebSphere eXtreme Scale automatically
  redistributes data partitions as new containers
  are added to the grid.
• Provides better caching qualities of service and
  control, than the default cache provider.
• Uses the same runtime monitoring and
  administration tools as the classic dynamic
  cache.

48
WebSphere eXtreme Scale Example with Commerce
WXS Grid 18Gb

• Benefits
• With WXS, we offload the dynacache data store to
  WXS grid
• WCS estate needs 25 less memory for dynacache -
  potentially reduce WCS estate
• Performance improvement from not needing disk I/O
• Disk not needed cost savings
• WCS throughput improvement through reduced
  chatter between JVMs and less GC overhead
• WXS can now provide much larger in-memory cache
  if desired by adding more JVMs (disk often
  constrained by size and contention limits
• Replica WXS JVM gives the cache resilience

49
Summary
50
Summary

• Dynamic Cache is a core service provided by
  WebSphere Application Server that can provide
  significant benefits to application developers
  for
• Web content Servlets/JSPs, AJAX requests, Web
  Services
• DistributedMap API
• Java command objects
• Dynamic Cache provides a comprehensive monitoring
  support infrastructure
• Higher performance environments will need to do
  some tuning to ensure Dynamic Cache performs at
  its best

51
Reference

• IBM Redbooks
• WebSphere Application Server V6 Scalability and
  Performance Handbook
• http//www.redbooks.ibm.com/abstracts/SG246392.ht
  ml
• Mastering DynaCache in WebSphere Commerce
• http//www.redbooks.ibm.com/abstracts/sg247393.ht
  ml
• WebSphere Dynamic Cache Improving J2EE
  application performance
• http//www.research.ibm.com/journal/sj/432/bakalo
  va.pdf

52
Backup
53
Cache Invalidation

• It is essential that timely invalidations of
  cached content take place for the integrity of
  the website.
• Mechanisms for invalidation are
• timeout or inactivity directives within
  cachespec.xml
• group-based invalidation mechanism through
  dependency IDs.
• Programmatic invalidation via the cache API
  'com.ibm.websphere.cache.
• The CacheMonitor

54
Data Oriented
Session management
Elastic DynaCache
DataPower XC10 Appliance
Web side cache

• Drop-in cache solution optimized and hardened for
  data oriented scenarios
• High density, low footprint improves datacenter
  efficiency

Petabyte analytics
Data buffer
eXtreme Scale
Event Processing

• Ultimate flexibility across a broad range of
  caching scenarios
• In-memory capabilities for application oriented
  scenarios

Worldwide cache
In-memory OLTP
In-memory SOA
Application Oriented
Elastic caching for linear scalability High
availability data replication Simplified
management, monitoring and administration
55
Caching Rules in cachespec.xml

• Consider the simple JSP, Display.jsp.
• The request to Display.jsp returns itself, as the
  parent, plus the included fragment Time.jsp.

56
Caching Rules in cachespec.xml

• consume-subfragments
• The consume-subfragments property tells the cache
  not to stop saving content when it includes a
  child servlet. The parent entry will include all
  the content from all fragments in its cache
  entry, resulting in one big cache entry.
• Use the ltexcludegt element to tell the cache to
  stop consuming for the excluded fragment and
  instead, create a placeholder for the include or
  forward. For example, exclude Time.jsp from the
  consume-subfragment, as follows

57
Caching Rules in cachespec.xml

• ltcachegt
• ltcache-entrygt
• ltclassgtservletlt/classgt
• ltnamegt/Display.jsplt/namegt
• ltproperty name"consume-subfragments"gttrue
• ltexcludegt/Time.jsplt/excludegt
• h
• ltcache-idgt
• lttimeoutgt30lt/timeoutgt
• lt/cache-idgt
• lt/cache-entrygt
• lt/cachegt

58
Caching Rules in cachespec.xml

• do-not-consume
• As discussed, the consume-subfragments property
  tells the cache to save all content including
  child fragments.
• A fragment can be excluded from the rules of the
  parent by using the do-not-consume property.
• In this cachespec, Time.jsp is labeled
  do-not-consume and can specify its own timeout or
  other rules.

ltcachegt ltcache-entrygt
ltclassgtservletlt/classgt ltnamegt/Display.jsplt/n
amegt ltproperty name"consume-subfragments"gt
truelt/propertygt ltcache-idgt
lttimeoutgt30lt/timeoutgt lt/cache-idgt
lt/cache-entrygt ltcache-entrygt
ltclassgtservletlt/classgt ltnamegt/Time.jsplt/name
gt ltproperty name"do-not-consume"gt
truelt/propertygt ltcache-idgt
lttimeoutgt10lt/timeoutgt lt/cache-idgt
lt/cache-entrygt lt/cachegt
59
Caching Rules in cachespec.xml

• Inactivity.
• While the timeout directive dictates how long
  content can remain in cache before being
  refreshed, the Inactivity directive can cause a
  refresh prior to the timeout when a page is not
  used frequently.
• ltcache-idgt
• lttimeoutgt600lt/timeoutgt
• ltinactivitygt30lt/inactivitygt
• lt/cache-idgt

60
Dependency IDs

• Dynamic Cache provides a group-based invalidation
  mechanism through dependency IDs.
• A dependencyID identifies a cache entries
  dependency based on certain factors, such that
  when those factors occur they trigger an
  invalidation of all the cache entries that share
  this dependency.
• An example of such a dependency could be the
  invalidation of a page which lists customer
  names. (Customer.jsp) Cached entries for this
  list should be invalidated when a customer is
  added to or removed from the list.

61
Troubleshooting Dynamic Cache

• Dynamic Cache Trace
• Use the WebSphere trace facility to review key
  trace points and verify expected caching
  behavior.
• Enabling Trace
• Dynamic Cache issues can be traced using the
  following trace specification
• Dynacache replication is disabled
• infocom.ibm.ws.cache.all
• Dynacache replication is enabled
• infocom.ibm.ws.cache.allcom.ibm.ws.drs.all
  
• For information regarding trace setting please
  refer to the WebSphere information center or see
  this this link
• http//www-1.ibm.com/support/docview.wss?rs180u
  idswg21254706

62
Troubleshooting Dynamic Cache

• Binding to cache instance
• ResourceMgrIm I WSVR0049I Binding
  services/cache/diskoffload as services/cache/disko
  ffload
• First request
• CacheHook 3 handleServlet absoluteUri
  /referenceWEB/Display.jsp
• EntryInfo 3 set id/referenceWEB/Display.jsp
  nameFredrequestTypeGET
• FragmentCompo 3 setConsumeSubfragments
  /Display.jsp consumeSubfragmentstrue
• FragmentCompo 3 setDoNotConsume /Display.jsp
  doNotConsumefalse
• CacheStatisti 3 CACHE Cache Miss
  /referenceWEB/Display.jspnameFredrequestTypeGE
  T
• CacheHook 3 CACHE MISS id
  /referenceWEB/Display.jspnameFredrequestTypeGE
  T
• CacheHook 3 servicing /referenceWEB/Display.
  jspnameFredrequestTypeGET
• FragmentCompo 3 saveCachedData uri/Display.jsp
• Next request
• CacheStatisti 3 CACHE Local Cache Hit
  /referenceWEB/Display.jspnameFredrequestTypeGE
  T
• CacheHook 3 CACHE HIT id/referenceWEB/Displ
  ay.jspnameFredrequestTypeGET
• Invalidation due to cache timeout
• Cache gt internalInvalidateById()
  cacheNamebaseCache id/referenceWEB/Display.jspn
  ameFredrequestTypeGET Entry
• Cache lt internalInvalidateById()
  id/referenceWEB/Display.jspnameFredrequestType
  GET Exit