Confluence performance can be significantly affected by the performance of its caches. It is essential for the administrator of a large production installation of Confluence to tune the caches to suit its environment. There are several configurable parameters for each of the cache regions, most notably cache size, cache expiry delay and eviction policy. In the majority of the cases, cache size is the parameter you would want to change. Fortunately, from Confluence 3.0, it is very easy to adjust cache sizes through the Administration Console. However, if you need to modify parameters other than a cache size, you would need to modify the relevant configuration files manually.
The cache performance information for your Confluence installation is available under Administration > Cache Statistics. More information about the numbers displayed here is available on Cache Statistics. |
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Cache tuning example
As an example of how to tune Confluence's caches, let's have a look at the following table:
Caches | % Used | % Effectiveness | Objects/Size | Hit/Miss/Expiry |
---|---|---|---|---|
Attachments | 87% | 29% | 874/1000 | 78226/189715/187530 |
Content Attachments | 29% | 9% | 292/1000 | 4289/41012/20569 |
Content Bodies | 98% | 81% | 987/1000 | 28717/6671/5522 |
Content Label Mappings | 29% | 20% | 294/1000 | 4693/18185/9150 |
Database Queries | 96% | 54% | 968/1000 | 105949/86889/83334 |
Object Properties | 27% | 18% | 279/1000 | 5746/25386/8102 |
Page Comments | 26% | 11% | 261/1000 | 2304/17178/8606 |
Users | 98% | 5% | 982/1000 | 6561/115330/114279 |
The caches above are of size 1000 (meaning that it can contain up to 1000 objects), which is the default size for caches in the default cache scheme. Refer to Confluence Cache Schemes for more explanation.
You can tell when a cache size needs to be increased because the cache has both:
- a high usage percentage (above 75%)
- a low effectiveness percentage.
Check the 'effectiveness' versus the 'percent used'. A cache with a low percent used need not have its size lowered; it does not use more memory until the cache is filled.
Based on this, the sizes of the "Attachments", "Database Queries", and "Users" caches should be increased to improve their effectiveness.
As the stored information gets older or unused it will expire and be eliminated from the cache. Cache expiry may be based on time or on frequency of use.
There is not much that you can do with a cache that has both a low percentage of usage and effectiveness. Over time, as the cache is populated with more objects and repeat requests for them are made, the cache's effectiveness will increase.
Finding the configuration file
The caches are configured in ehcache.xml
(for standard editions) or confluence-coherence-cache-config-clustered.xml
(for clustered editions) which is stored in <confluence-home>/config/
.
![]() | Oracle Coherence Licensing Change:
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Cache Key Mappings
The cache configuration file configures caches by their keys. When you move your mouse over the the cache names displayed on the cache statistics page, a tooltip will indicate the actual cache key for that cache name.
Using our example from the table above, if we were to modify parameters for the Users
cache we would need to change the cache with the key com.atlassian.user.impl.hibernate.DefaultHibernateUser
. Do not get confused with Users (External Mappings)
and Users (External Groups)
which are in themselves, two separate caches. "Users" is the friendly name for com.atlassian.user.impl.hibernate.DefaultHibernateUser
.
Standard Editions of Confluence
In standard editions of Confluence, the caching layer is Ehcache.
Understanding the Ehcache Configuration File
For more information about the Ehcache configuration file and a full reference on Ehcache configuration, please refer to the Ehcache configuration documentation.
Converting your Coherence configuration to Ehcache
![]() | This section only applies to customers who:
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To maintain your existing cache configuration file settings, you will need to transfer any cache customisations you have implemented in the Coherence cache configuration file (confluence-coherence-cache-config.xml
) to the relevant entries in the Ehcache cache configuration file (ehcache.xml
).
Each cache has a cache-mapping
element in the Coherence file (of which there is an equivalent cache
element in the ehcache.xml
file). Unfortunately, copying across your customisations is not quite a straightforward process because the Coherence file defines several 'caching schemes' to store the actual cache values, which in turn are referenced by the cache-mapping
elements. In contrast, the ehcache.xml
file does not support caching schemes and a cache's values are expressed explicitly in separate parameters of a cache
element.
To convert your Coherence cache configuration file customisations across to the equivalent Ehcache file:
- Open both the
confluence-coherence-cache-config.xml
andehcache.xml
files in a text editor. These files are located in the<confluence-home>/config
directory.
If you implemented your customisations in a version of Confluence prior to 3.0, you will most likely find the
confluence-coherence-cache-config.xml
file in the<confluence-install>/confluence/WEB-INF/classes
directory. - In the customised
confluence-coherence-cache-config.xml
file:
- Identify the caching schemes that were customised in this file and make a note of the values of all its child elements.
Typically, each caching scheme is located inside a
local-scheme
element and all of these are enclosed within thecache-schemes
element, which appears towards the end of this file. - Note each customised caching scheme by the content of its
scheme-name
element. - For each
cache-mapping
element (which typically appears towards the top of this file), identify if it has ascheme-name
element whose content matches one noted in the previous step and if so, make a note of its associatedcache-name
element.
- Identify the caching schemes that were customised in this file and make a note of the values of all its child elements.
- In the
ehcache.xml
file:
- Identify each
cache
element whose 'name' parameter matches thecache-name
elements noted in step '2c'. - Using the mappings table below, apply the values noted in step '2a' to the appropriate parameters of the
cache
elements identified in the previous step ('3a').
- Identify each
Mappings table showing how elements of the Coherence cache configuration file map to parameters of the equivalent Ehcache file.
Coherence Element | Ehcache Attribute |
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Clustered Editions of Confluence
Understanding the Coherence configuration file
The Coherence configuration file is a mapping of cache keys to cache schemes. Each cache scheme controls the expiry, eviction policy and size of the caches linked to it. A cache scheme can extend another scheme.
For a full reference, see the Oracle's Coherence cache configuration documentation.
Defining Caching Scheme Mappings in Coherence Cache config file
If a cache key does not have an explicit definition in the caching scheme mappings (defined in confluence-coherence-cache-config.xml
) then it will use the "default" cache-mapping
.
In our example, com.atlassian.user.impl.hibernate.DefaultHibernateUser
is not explicitly defined in the caching scheme mappings. Hence to increase the expiry-delay to 2 hours, we will need to define the mapping ourselves and add the following within the <caching-scheme-mapping>...</caching-scheme-mapping>
tags:
<cache-mapping> <cache-name>com.atlassian.user.impl.hibernate.DefaultHibernateUser</cache-name> <scheme-name>cache:com.atlassian.user.impl.hibernate.DefaultHibernateUser</scheme-name> </cache-mapping>
Then we will need to define a cache schema with name cache:com.atlassian.user.impl.hibernate.DefaultHibernateUser
within <caching-schemes>...</caching-schemes>
tags.
<local-scheme> <scheme-name>cache:com.atlassian.user.impl.hibernate.DefaultHibernateUser</scheme-name> <scheme-ref>default</scheme-ref> <high-units>10000</high-units> <expiry-delay>7200</expiry-delay> </local-scheme>
It's possible to define a local-scheme mapping for a cache key without defining certain parameters (e.g. <high-units>
). In such a cases, their parameters will be inherited from scheme-ref
scheme, which is the default
scheme in our case.
Important Caches
![]() | The following suggestions are general guidelines. In cases of large databases, 20-30% of the size of the table may be unnecessarily large. Check the effectiveness and Percent Used categories in the cache for more specific assessments. |
com.atlassian.confluence.core.ContentEntityObject
(known asContent Objects
cache)
should be set to at least 20-30% of the number of content entity objects (pages, comments, emails, news items) in your system. To find the number of content entity objects, use the queryselect count(*) from CONTENT where prevver is null
.com.atlassian.confluence.core.ContentEntityObject.bodyContents
(known asContent Body Mappings
cache)
should be set to at least 20% of the number of content entity objects (pages, comments, emails, news items) in your system. To find the number of content entity objects, use the queryselect count(*) from CONTENT where prevver is null
.com.atlassian.confluence.security.PermissionCheckDispatcher.isPermitted()
(known asUser Authorized URLs
cache)
should be set to at least the number of concurrent users you expect to access Confluence at the same timecom.atlassian.user.impl.hibernate.DefaultHibernateUser
(known asUsers
cache)
should be set to the number of users you have:select count (*) from users
. Note that by default, this will also control the LDAP user's cache, including expiration.com.atlassian.confluence.security.SpacePermission
(known asPermissions
cache)
should be set to the number of space permissions in your deployment (a good rule of thumb is 20 times the number of spaces). You can find the number of space permissions using the queryselect count(*) from SPACEPERMISSIONS
.
Cache Tuning Follow-Up
After you have made changes to your cache config, doing a follow up on the changes in the next week or after the expected performance spike would be important.
Make sure that you take a screenshot of the cache statistics before and after the change. Then compare them with the cache statistics in the later period where performance improvement is expected.
![]() | You can monitor what's in the cache by using a JSP included in the Confluence distribution. Browse to <base-URL>/admin/cachecontents.jsp to monitor the cache contents. |
RELATED TOPICS
Cache Performance Tuning for Specific Problems
Confluence Cache Schemes
Performance Testing Scripts
Working with Confluence Logs
Operating Large or Mission-Critical Confluence Installations
Confluence Clustering Overview
Requesting Performance Support
Confluence Administrator's Guide
Confluence Configuration Guide