Transcript Document

Are You “Cashing In” on
Caching?
An in-depth look at the caching methods
available within ColdFusion applications
Tyson Vanek
Senior Technical Consultant
Webapper Services, LLC
Presentation Overview
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Caching overview and basic concepts
Identifying candidates for caching
ColdFusion’s template caching options
ColdFusion’s native query caching methods
ColdFusion’s native page/content caching
methods
 Alternatives to ColdFusion’s native caching
methods
June 27th- 30th 2007
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About Tyson Vanek
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Independent Consultant
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12 years of ColdFusion experience
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Began working with ColdFusion v1.0
Using ColdFusion on every project since July, 1995
Former employee of Allaire/Macromedia Consulting Services Division
Noteworthy Accomplishments
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Currently engaged full-time with Webapper Services, LLC
Certified ColdFusion Developer
Contributing author - “Inside ColdFusion MX”
Contributing author - Adobe’s ColdFusion Developer Center
2 year author of BrainBench ColdFusion certification exams (5 & MX6)
Noteworthy Clients
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Footlocker
Eastbay
Lockheed Martin
Abbott Laboratories
University of Virginia
Adelphia Communications
Williams-Sonoma
Chicago Mercantile Exchange
International Broadcast Bureau / Voice of America
Discovery Communications / Discovery Channel / unitedstreaming
June 27th- 30th 2007
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Caching Basics
June 27th- 30th 2007
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What is Caching?
 A way of saving data after it has been originally
computed so that subsequent requests for the
same data are executed more quickly than the
original call by retrieving the saved data instead of
computing real-time
June 27th- 30th 2007
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What Can Be Cached?
 CFML Templates at the Server level
 Trusted Cache
 Class files
 Data Objects
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Query record sets
Complex variables (e.g. structures, arrays, objects)
Simple variables (e.g. strings, text blocks)
Web Service Invocation Responses
CFCs
 Rendered HTML Content
 Entire pages
 HTML blocks
June 27th- 30th 2007
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Why Should I Be Caching?
 Alleviates load from the server(s)
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Makes the server faster and “healthier”
Allows the server to support more load
 Decreases page load time for the end
user
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Improves the user’s experience
Allows the user to accomplish tasks more
quickly
June 27th- 30th 2007
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Defining Good Cache Candidates
Items that can be described by any/all of
the following characteristics:
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Global to all users
Used throughout the application and accessed frequently
Not subject to frequent change
Not subject to a high number of variants
o Limited number of input arguments and distinct values
 Takes a significant amount of time to render in real-time
when not cached (application performance bottlenecks)
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June 27th- 30th 2007
Complex nested CFML logic
Database I/O
CFC invocation
CFHTTP calls
Web Service calls
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Methods for Identifying Application
Performance Bottlenecks
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The Old Fashioned Way
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Examination of ColdFusion log files
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Pages logged when ColdFusion Administrator “Log slow pages taking longer
than X seconds” option is enabled.
Examination of ColdFusion debugging output
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Displays execution times of templates, includes, custom tags, and CFC methods
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Query execution times
Cumulative template execution time
CFML Language
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Displayed in detail when ColdFusion Admin “Report Execution Times” option is enabled
with “summary” mode selected
getTickCount()
<cflog>
<cftrace>
Using New Server Analytics Tools
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SeeFusion
FusionReactor
CFMX 8 Administrator
June 27th- 30th 2007
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Important Questions to Ask Yourself
When Evaluating a Caching Candidate
1. How often do changes take place that will
affect and/or invalidate the cached data?
2. Is up-to-the-second data absolutely critical?
3. How many cache variants are possible
based on the variable input arguments?
4. What is the average count/size/length of
each cache variant?
June 27th- 30th 2007
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What is a “Cache Variant”?
A “cache variant” is a single set of data or content derived from the
application code and based on a single combination of values for any variable
input arguments
Examples
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Variant #1
<cfset lastNameLetter = “A”>
<cfquery name=“qUsers” datasource=“myDSN”>
SELECT *
FROM tblUser
WHERE left(lastName,1) = ‘#lastNameLetter#’
</cfquery>
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Variant #2
<cfset lastNameLetter = “Z”>
<cfquery name=“qUsers” datasource=“myDSN”>
SELECT *
FROM tblUse
WHERE left(lastName,1) = ‘#lastNameLetter#’
</cfquery>
June 27th- 30th 2007
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Calculating Cache Variants
Query Example #1
Query Example #2
SQL Statement:
SELECT *
FROM tblUser
WHERE userid = #userid#
AND active = #active#
SQL Statement:
SELECT *
FROM tblUser
WHERE department = #department#
AND age = #age#
AND gender = #gender#
AND active = #active#
But how many likely variants exist?
Variable Input Arguments:
userid
(1,000 distinct values)
active
(2 distinct values)
Variable Input Arguments:
department
age
gender
active
Variants:
1,000 x 2 = 2,000
Variants:
2,000 potential query variants exist
June 27th- 30th 2007
(50 distinct values)
(100 distinct values)
(2 distinct values)
(2 distinct values)
50 x 100 x 2 x 2 = 20,000
20,000 potential query variants exist
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Why Calculating the Cache Variants is
Important
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Each variant represents an instance of data/content
that could potentially be cached
The more items in the cache, the larger the cache
becomes in size and complexity
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Size may affect storage decisions
Complexity may affect access/seek time to cached items
With larger caches, attention must be given to
server resources (e.g. disk space, memory
allocation, etc)
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The size of the cache may play a role in determining the
best location to store the cache
June 27th- 30th 2007
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A Simple Measure of the Effects of
Caching
Example #1 – No Caching
Example #2 - Caching
Request execution time:
500ms
Average requests per minute:
Calculation:
60
First request execution time:
Cache TTL:
Cached request execution time:
Average requests per minute:
Calculation:
500ms
60s
20ms
60
500ms x 60 = 30s
(500ms x 1) + (20ms x 59) = 1.7s
30 seconds of server time
allocated per minute
1.7 seconds of server time
allocated per minute
30s x 60m = 1,800s
1.7s x 60m = 102s
1,800 seconds of server time
allocated per hour
102 seconds of server time
allocated per hour
Result: 94.3% Improvement!
June 27th- 30th 2007
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ColdFusion Server
Template Caching Techniques
June 27th- 30th 2007
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Understanding ColdFusion’s Template
Request Workflow
June 27th- 30th 2007
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Template Caching with Trusted Cached
 ColdFusion Administrator “Trusted Cache” setting
 Bypasses disk checks for more recent changes to the CFML
template, caching the CFML template into RAM
 Impacts the “STARTUP, PARSING, COMPILING, LOADING,
& SHUTDOWN” timer located in ColdFusion debugging
output
 Typically only enabled on production servers where
templates change infrequently or with scheduled releases
 Server-wide setting with no application-specific control
 Templates are cached based on file date/time stamps
o May cause unexpected behavior when templates are deployed
via FTP or source control promotion of a previous version of the
template
June 27th- 30th 2007
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Template Caching with Trusted Cached
(cont.)
 Clearing cached items
 Individually
o Execute cached template while “Trusted Cache” setting is
disabled in CF Administrator
• Re-enable the “Trusted Cache” setting once the template has
been executed
 Entire Cache
o Restart ColdFusion Application Server (YIKES!)
o ColdFusion Administrator “Clear Template Cache Now” button
(CFMX 7+)
o Admin API call (may be programmatically invoked)
o Event Gateway/Admin API Tool developed by Brian Szoszorek
(CFMX 7+)
• http://www.adobe.com/devnet/coldfusion/articles/cacheclear.html
June 27th- 30th 2007
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The “Save Class Files” Option
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New option added with ColdFusion MX 6.1
Found in the CF Admin “Caching” settings
When enabled, generates and saves a *.class file
for each CFML template executed
Files are stored in WEB-INF/cfclasses/ directory
File-based storage means that cache persists even
if ColdFusion is restarted
Server-wide setting with no application-specific
control
June 27th- 30th 2007
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Why You Should Consider NOT
Enabling It
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Feature was automatically enabled (behind the scenes) in CFMX 6.0 due to
performance issues with the compiler (javac/jikes) that was being used at the time
Compiler in CFMX 6.1+ was replaced and improved
CFMX 6.1 compiler is much faster, converting CFML files into bytecode
Improved performance of the 6.1+ compiler has more or less eliminated the need
for .class file generation/caching
Creates additional overhead
Potential for thousands of files in the /cfclasses/ directory
ColdFusion will continue to check the date/time stamp of the .class file with every
call to the corresponding .cfm template to ensure that the cached .class file is still
valid (unless Trusted Cache is enabled or the template is not present in the
Template Cache)
Significant file/directory IO (500+ ms or more)
Most customers report little or no difference with this option enabled or disabled on
CFMX 6.1 or higher
If there’s little or no performance to be gained, why bother with the option at all?
Enabling this option adds more decision points to the ColdFusion Template
Request Workflow, inherently slowing the request process.
Does it even work?
June 27th- 30th 2007
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ColdFusion Query Caching
June 27th- 30th 2007
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Native Query Caching with ColdFusion
 Adding the cachedWithin or cachedAfter argument to the CFQUERY tag
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Places the query result set into ColdFusion’s application server memory for the defined
length of time
Queries cached using cachedWithin or cachedAfter are placed in the same cache, so
there’s a possibility of re-use
 ColdFusion Administrator “Maximum Number of Cached Queries” setting
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Controls the physical number of queries that may be stored in the cache at any given
time
Once this threshold is reached, least recently used items in the cache will be dropped
to make room for new items
Setting value to “0”
o In earlier versions of ColdFusion, setting this value to “0” resulted in “unlimited” query caching
(extremely dangerous)
o In CFMX 6.1 (6,1,0,83762)+ and CFMX 7+, setting this value to “0” results in disabling query
caching
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Technically, allows a single cached query
 Important point about query caching variants
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Every cached query is driven by a combination of the following items:
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Query Name
SQL Statement (including formatting, tabs, spaces, etc.)
Datasource
Username/Password
Any input arguments to the SQL statement
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Query Caching Examples
Example #1 - Using cachedWithin:
Example #2 - Using cachedAfter:
Query without caching:
Query without caching:
<cfquery
name=“qTop10NewsStories”
datasource=“#myDSN#”
>
select top 10 *
from tblNews
order by storyDate desc
</cfquery>
<cfquery
name=“qTop10Videos_January2007”
datasource=“#myDSN#”
>
select top 10 sum(countView), videoName
from tblVideoView
where viewDate >= ’01/01/2007’
and viewDate < ’02/01/2007’
order by sum(countView) desc
</cfquery>
Query with caching (15 minute cache):
<cfquery
name=“qTop10NewsStories”
datasource=“#myDSN#”
cachedWithin=“#createTimeSpan(0,0,15,0)#”
>
select top 10 *
from tblNews
order by storyDate desc
</cfquery>
June 27th- 30th 2007
Query with caching (after 2/1/2007):
<cfquery
name=“qTop10Videos_January2007”
datasource=“#myDSN#”
cachedAfter=“#createDateTime(2007,2,1,0,0,0)#”
>
select top 10 sum(countView), videoName
from tblVideoView
where viewDate >= ’01/01/2007’
and viewDate < ’02/01/2007’
order by sum(countView) desc
</cfquery>
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Clearing the Query Cache
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In Part
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Execute query with
cachedWithin=“#createTimeSpan(0,0,0,0)#” or
cachedAfter=“#createDateTime(2100,1,1,0,0,0)#”
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Only clears the single cache variant being executed
Does not clear all variants of the same cached query
In Whole
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<cfobjectcache action=“clear”>
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Clears all cached queries for the entire server/instance
Not application specific
ColdFusion’s ServiceFactory purgeQueryCache() method
<cfset factory = createObject(“java”, “coldfusion.server.ServiceFactory”)>
<cfset datasourceService = factory.datasourceService>
<cfset datasourceService.purgeQueryCache()>
June 27th- 30th 2007
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Pros and Cons of ColdFusion’s Native
Query Caching
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Pros
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It’s built-in to ColdFusion and ready to use
Cached queries are placed in memory for fastest possible access time
ColdFusion’s debug output will automatically display whether a query was executed real-time or if the
results were pulled from the query cache
Cons
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No control over where the cached queries are stored or how they are organized
“Maximum Number of Cached Queries” setting is server-wide, not application-specific
Difficult to clear items from the cache
Difficult to clear multiple items from the cache without clearing the entire cache
Clearing items from the cache forces them to execute again
Queries cannot be cached if they make use of <cfqueryparam>
Query caching cannot be used with <cfstoredproc>
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Stored procedure calls can, however, be cached if called within a <cfquery> tag (using exec, call, etc.)
No way of viewing/dumping the cache in whole or in part
No way to control how ColdFusion manages the cache and cache pops
No way to track the size/usage of the cache
Query Cache is server/instance wide, not application specific
o
June 27th- 30th 2007
Code from other applications may be using <cfobjectcache> or the purgeQueryCache(), thereby clearing the cache
for the entire server/instance
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Alternative Data Caching Methods
June 27th- 30th 2007
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Alternative Methods for Caching Data
 Placing data in shared scopes instead of local variables scope
 <cfquery name=“scopeName.queryName”>
o Server, Application, or Session scope
 Requires that you programmatically manage/flush cached items
o Items will automatically timeout if shared scope variable times out
 Can be applied to queries as well as any other ColdFusion data type
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Structures
Arrays
Objects
Simple Values
 Must beware of application code that might be performing a duplicate() of
shared scopes
o Placing these additional items in the shared scope for caching could negatively
impact the performance of duplicating the scope
 No native support for clustered cache synchronization
o Currently designing and developing a cross-node in-memory cache
synchronization system for clustered environments
June 27th- 30th 2007
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Alternative Methods for Caching Data
(cont.)
 Various available custom solutions
 Tyson Vanek’s <cf_extremeQueryCache> custom tag
o http://www.adobe.com/devnet/coldfusion/articles/query_cache.html
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Only supports caching of query record sets
Supports caching to memory or disk
 Tyson Vanek’s cacheItAll.cfc component
o http://www.coldfusionmaster.com/cacheItAll/
 Tyson Vanek’s <cf_accelerate2> custom tag
o http://www.coldfusionmaster.com/accelerate2/
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June 27th- 30th 2007
Modified version of Brandon Purcell’s <cf_accelerate> custom tag
Supports caching of both simple and complex variables
Supports caching to memory or to disk
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ColdFusion Content Caching
June 27th- 30th 2007
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Content Caching with ColdFusion’s
<CFCACHE> Tag
<CFCACHE> Tag
 Place tag at beginning of any page that should be cached
 Options include server-side or client-side caching (action argument)
 Creates rendered HTML output and saves file to disk on the server or client
depending on the action indicated
o Cache files have .tmp extension
o Cache files are simply an HTML representation of the generated content
o First line of the .tmp cache file is an HTML comment that identifies the template
and URL parameters used to generate the cached file
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This comment might cause browser validation issues
 Caches content based on the timeSpan argument, much like CFQUERYs
cachedWithin argument.
o If no value is specified for timeSpan, the content will be cached indefinitely
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Cache would have to be cleared manually
 Cached files (.tmp) can be stored in a directory of your specification (using
the cacheDirectory argument)
o Default location is $cfroot$\cache
 Automatically creates unique caches based on URL variables
 Support for unique caching by session (does it work?)
June 27th- 30th 2007
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Pros and Cons of Caching with
<CFCACHE>
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Pros
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It’s built-in to ColdFusion and ready to use
CFCACHE tag evaluates each unique URL parameter to ensure that different combinations result in
different cached pages
Supports both server-side and client-side caching for maximum efficiency
Supports unique caching by session
Cached entry is automatically expired if the CFML template is changed
Cache can be cleared programmatically
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action=“flush”
expireURL=“*/view.cfm?id=*”
Cons
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Can only be used to cache an entire page, not smaller sections of HTML
Limited control over how the cached pages are stored or how they are organized
Difficult to view/dump the cache in whole or in part
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Can view/delete HTML .tmp file written to the cacheDirectory
Files are named using an MD5 hash of the CGI.SCRIPT_NAME and CGI.QUERY_STRING
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Might make it difficult to identify the .tmp file(s) you are looking for
Programmatic clearing of cached items can be challenging
Variants are not created with consideration to CGI.PATH_INFO (SES URLs)
No way to control how ColdFusion manages the cache and cache pops
ColdFusion will not automatically remove “expired” cache items
June 27th- 30th 2007
www.cfunited.com
Alternative Methods for Caching
Content
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HTML Block caching with <cfsavecontent variable=“yourVarName”>
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Captures all content generated within <cfoutput> tags and saves it to the specified variable name
Variable can also be placed in shared scope for caching purposes
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Management options similar to those discussed earlier regarding shared scope caching of complex variables
Various available custom solutions
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<cf_superCache>
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http://www.cfprimer.com/download.cfm?ffFile=supercache.cfm
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<cf_accelerate>
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<cf_cacheOmatic>
o
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http://www.bpurcell.org/blog/index.cfm?mode=entry&entry=963
http://www.devx.com/webdev/Article/27618
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<cf_turboCache>
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<cf_hyperCache>
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Ray Camden’s ScopeCache
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http://www.hotfusion.co.uk/TurboCache/index.htm
http://www.pixl8.co.uk/index.cfm/pcms/site.products.CF_Hypercache/
http://ray.camdenfamily.com/downloads/scopecache.zip
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Andy Powell’s JohnnyCache
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Tyson Vanek’s cacheItAll.cfc component
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http://johnnycache.riaforge.org/
http://www.coldfusionmaster.com/cacheItAll/
Tyson Vanek’s <cf_accelerate2> custom tag
o
June 27th- 30th 2007
http://www.coldfusionmaster.com/accelerate2/
www.cfunited.com
Summary
 Discussed basic caching concepts and considerations
 Outlined methods for finding and qualifying good cache
candidates
 Outlined methods for identifying application bottlenecks
 Reviewed ColdFusion’s built-in template caching settings and
effects
 Reviewed ColdFusion’s built-in query caching mechanisms
 Presented alternative methods for caching queries and complex
data types
 Reviewed ColdFusion’s built-in page caching mechanisms
 Presented alternative methods for caching entire pages or
smaller sections of content
June 27th- 30th 2007
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Questions?
June 27th- 30th 2007
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