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Dispatcher versions are independent of AEM (Adobe Experience Manager). You may have been redirected to this page if you followed a link to the Dispatcher documentation. That link was embedded in the documentation for a previous version of AEM.
The following sections describe how to configure various aspects of the Dispatcher.
Support for IPv4 and IPv6 support-for-ipv-and-ipv
All elements of AEM and Dispatcher can be installed in both IPv4 and IPv6 networks. See IPV4 and IPV6 .
Dispatcher Configuration Files dispatcher-configuration-files
By default the Dispatcher configuration is stored in the
dispatcher.any
text file, though you can change the name and location of this file during installation.
The configuration file contains a series of single-valued or multi-valued properties that control the behavior of the Dispatcher:
Using Environment Variables using-environment-variables
You can use environment variables in string-valued properties in the dispatcher.any file instead of hard-coding the values. To include the value of an environment variable, use the format
${variable_name}
.
For example, if the dispatcher.any file is in the same directory as the cache directory, the following value for the docroot property can be used:
/docroot "${PWD}/cache"
Naming the Dispatcher Instance naming-the-dispatcher-instance-name
Use the /name property to specify a unique name to identify your Dispatcher instance. The /name property is a top-level property in the configuration structure.
Defining Farms defining-farms-farms
The /farms property defines one or more sets of Dispatcher behaviors, where each set is associated with different web sites or URLs. The /farms property can include a single farm or multiple farms:
Use a single farm when you want the Dispatcher to handle all of your web pages or web sites in the same way.
Create multiple farms when different areas of your web site or different web sites require different Dispatcher behavior.
The /farms property is a top-level property in the configuration structure. To define a farm, add a child property to the /farms property. Use a property name that uniquely identifies the farm within the Dispatcher instance.
The /farmname property is multi-valued, and contains other properties that define Dispatcher behavior:
The URLs of the pages that the farm applies to.
One or more service URLs (typically of AEM publish instances) to use for rendering documents.
The statistics to use for load-balancing multiple document renderers.
Several other behaviors, such as which files to cache and where to cache.
If you use more than one render farm, the list is evaluated bottom-up. This flow is relevant when defining Virtual Hosts for your websites.
Each farm property can contain the following child properties:
Property name
Description
Default homepage (optional)(IIS only)
The headers from the client HTTP request to pass through.
This farm’s virtual hosts.
Support for session management and authentication.
The servers that provide rendered pages (typically AEM publish instances).
Defines the URLs to which the Dispatcher enables access.
Configures access to vanity URLs.
Support for the forwarding of syndication requests.
Configures caching behavior.
Defining statistic categories for load-balancing calculations.
The folder that contains sticky documents.
The URL to use to determine server availability.
The delay before retrying a failed connection.
Penalties that affect statistics for load-balancing calculations.
Resend requests to different renders when the original request fails.
For permission-sensitive caching, see Caching Secured Content.
The /homepageparameter (IIS only) no longer works. Instead, you should use the IIS URL Rewrite Module.
If you are using Apache, you should use the mod_rewrite module. See the Apache web site documentation for information about mod_rewrite (for example, Apache 2.4). When using mod_rewrite, it is advisable to use the flag ‘passthrough|PT’ (pass through to next handler) to force the rewrite engine to set the uri field of the internal request_rec structure to the value of the filename field.
Specifying the HTTP Headers to Pass Through specifying-the-http-headers-to-pass-through-clientheaders
The /clientheaders property defines a list of HTTP headers that Dispatcher passes from the client HTTP request to the renderer (AEM instance).
By default, the Dispatcher forwards the standard HTTP headers to the AEM instance. In some instances, you might want to forward additional headers, or remove specific headers:
If you customize the set of headers to pass through, you must specify an exhaustive list of headers, including those headers that are normally included by default.
For example, a Dispatcher instance that handles page activation requests for publish instances requires the PATH header in the /clientheaders section. The PATH header enables communication between the replication agent and the Dispatcher.
The following code is an example configuration for /clientheaders:
/clientheaders
"CSRF-Token"
"X-Forwarded-Proto"
"referer"
"user-agent"
"authorization"
"from"
"content-type"
"content-length"
"accept-charset"
"accept-encoding"
"accept-language"
"accept"
"host"
"max-forwards"
"proxy-authorization"
"proxy-connection"
"range"
"cookie"
"cq-action"
"cq-handle"
"handle"
"action"
"cqstats"
"depth"
"translate"
"expires"
"date"
"dav"
"ms-author-via"
"lock-token"
"x-expected-entity-length"
"destination"
"PATH"
scheme: (Optional) Either https:// or https://.host: The name or IP address of the host computer and the port number if necessary. (See https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.23)uri: (Optional) The path to the resources.The first-encountered virtual host that matches all three of the host, the scheme, and the uri of the request is used.
If no virtualhosts values have scheme and uri parts that both match the scheme and uri of the request, the first-encountered virtual host that matches the host of the request is used.
If no virtualhosts values have a host part that matches the host of the request, the topmost virtual host of the topmost farm is used.
Therefore, you should place your default virtual host at the top of the virtualhosts property. PLace it in the topmost farm of your dispatcher.any file.
Example Virtual Host Resolution example-virtual-host-resolution
The following example represents a snippet from a dispatcher.any file that defines two Dispatcher farms, and each farm defines a virtualhosts property.
/farms
/myProducts
/virtualhosts
"www.mycompany.com/products/*"
/renders
/hostname "server1.myCompany.com"
/port "80"
/myCompany
/virtualhosts
"www.mycompany.com"
/renders
/hostname "server2.myCompany.com"
/port "80"
Using this example, the following table shows the virtual hosts that are resolved for the given HTTP requests:
Request URL
Resolved virtual host
https://www.mycompany.com/products/gloves.html
www.mycompany.com/products/
https://www.mycompany.com/about.html
www.mycompany.com
Enabling Secure Sessions - /sessionmanagement enabling-secure-sessions-sessionmanagement
CAUTION
/allowAuthorized Set to "0" in the /cache section to enable this feature. As detailed in the Caching When Authentication is used section, when you set /allowAuthorized 0 requests that include authentication information are not cached. If permission-sensitive caching is required, see the Caching Secured Content page.
Create a secure session for access to the render farm so that users must log in to access any page in the farm. After logging in, users can access pages in the farm. See Creating a Closed User Group for information about using this feature with CUGs. Also, see the Dispatcher Security Checklist before going live.
The /sessionmanagement property is a subproperty of /farms.
CAUTION
If sections of your website use different access requirements, you must define multiple farms.
/sessionmanagement has several subparameters:
/directory (mandatory)
The directory that stores the session information. If the directory does not exist, it is created.
CAUTION
When configuring the directory subparameter, do not point to the root folder (/directory "/") as it can cause serious problems. Always specify the path to the folder that stores the session information. For example:
/encode (optional)
How the session information is encoded. Use md5 for encryption using the md5 algorithm, or hex for hexadecimal encoding. If you encrypt the session data, a user with access to the file system cannot read the session contents. The default is md5.
/header (optional)
The name of the HTTP header or cookie that stores the authorization information. If you store the information in the http header, use HTTP:<header-name>. To store the information in a cookie, use Cookie:<header-name>. If you do not specify a value, HTTP:authorization is used.
/timeout (optional)
The number of seconds until the session times out after it has been used last. If not specified "800" is used, so the session times out a little over 13 minutes after the last request of the user.
An example configuration looks as follows:
/sessionmanagement
/directory "/usr/local/apache/.sessions"
/encode "md5"
/header "HTTP:authorization"
/timeout "800"
# port of the renderer
/port "4503"
# connection timeout in milliseconds, "0" (default) waits indefinitely
/timeout "0"
Renders options renders-options
/timeout
Specifies the connection timeout accessing the AEM instance in milliseconds. The default is "0", causing the Dispatcher to wait indefinitely.
/receiveTimeout
Specifies the time in milliseconds that a response is allowed to take. The default is "600000", causing Dispatcher to wait for 10 Minutes. A setting of "0" eliminates the timeout.
If the timeout is reached while parsing response headers, an HTTP Status of 504 (Bad Gateway) is returned. If the timeout is reached while the response body is read, the Dispatcher returns the incomplete response to the client. It also deletes any cached files that might have been written.
/ipv4
Specifies whether Dispatcher uses the getaddrinfo function (for IPv6) or the gethostbyname function (for IPv4) for obtaining the IP address of the render. A value of 0 causes getaddrinfo to be used. A value of 1 causes gethostbyname to be used. The default value is 0.
The getaddrinfo function returns a list of IP addresses. Dispatcher iterates the list of addresses until it establishes a TCP/IP connection. Therefore, the ipv4 property is important when the render hostname is associated with multiple IP addresses. And, the host, in response to the getaddrinfo function, returns a list of IP addresses that are always in the same order. In this situation, you should use the gethostbyname function so that the IP address that Dispatcher connects with is randomized.
Amazon Elastic Load Balancing (ELB) is such a service that responds to getaddrinfo with a potentially same-ordered list of IP addresses.
/secure
If the /secure property has a value of "1", Dispatcher uses HTTPS to communicate with the AEM instance. For more details, see Configuring Dispatcher to Use SSL.
/always-resolve
With Dispatcher version 4.1.6, you can configure the /always-resolve property as follows:
When set to "1", it resolves the host-name on every request (the Dispatcher never caches any IP address). There may be a slight performance impact due to the additional call required to get the host information for each request.
If the property is not set, the IP address is cached by default.
Configuring Access to Content configuring-access-to-content-filter
Use the /filter section to specify the HTTP requests that Dispatcher accepts. All other requests are sent back to the web server with a 404 error code (page not found). If no /filter section exists, all requests are accepted.
Note: Requests for the statfile are always rejected.
CAUTION
See the Dispatcher Security Checklist for further considerations when restricting access using the AEM Dispatcher. Also, read the AEM Security Checklist for additional security details regarding your AEM installation.
The /filter section consists of a series of rules that either deny or allow access to content according to patterns in the request-line part of the HTTP request. Use an allowlist strategy for your /filter section:
Type: The /type indicates whether to allow or deny access for the requests that match the pattern. The value can be either allow or deny.
Element of the Request Line: Include /method, /url, /query, or /protocol. And, include a pattern for filtering requests. Filter them according to specific parts of the request-line part in the HTTP request. Filtering on elements of the request line (rather than on the entire request line) is the preferred filter method.
Advanced Elements of the Request Line: Starting with Dispatcher 4.2.0, four new filter elements are available for use. These new elements are /path, /selectors, /extension, and /suffix respectively. Include one or more of these items to further control URL patterns.
Filtering with globs is deprecated in Dispatcher. As such, you should avoid using globs in the /filter sections since it may lead to security issues. So, instead of:
/glob "* *.css *"
/url "*.css"
The request-line Part of HTTP Requests the-request-line-part-of-http-requests
HTTP/1.1 defines the request-line as follows:
Method Request-URI HTTP-Version<CRLF>
The <CRLF> characters represent a carriage return followed by a line feed. The following example is the request-line that is received when a client requests the US-English page of the WKND site:
GET /content/wknd/us/en.html HTTP.1.1<CRLF>
Your patterns must account for the space characters in the request-line and the <CRLF> characters.
Double-quotes vs Single-quotes double-quotes-vs-single-quotes
When creating your filter rules, use double quotation marks "pattern" for simple patterns. If you are using Dispatcher 4.2.0 or later and your pattern includes a regular expression, you must enclose the regex pattern '(pattern1|pattern2)' within single quotation marks.
Regular Expressions regular-expressions
In Dispatcher versions later than 4.2.0, you can include POSIX Extended Regular Expressions in your filter patterns.
Troubleshooting Filters troubleshooting-filters
If your filters are not triggering in the way you would expect, enable Trace Logging on Dispatcher so you can see which filter is intercepting the request.
Example Filter: Deny All example-filter-deny-all
The following example filter section causes the Dispatcher to deny requests for all files. Deny access to all files and then allow access to specific areas.
/0001 { /type "deny" /url "*" }
Requests to an explicitly denied area result in a 404 error code (page not found) being returned.
Example Filter: Deny Access to Specific Areas example-filter-deny-access-to-specific-areas
Filters also let you deny access to various elements, for example, ASP pages and sensitive areas within a publish instance. The following filter denies access to ASP pages:
/0002 { /type "deny" /url "*.asp" }
/filter {
/0001 { /glob "*" /type "deny" }
/0002 { /type "allow" /method "POST" /url "/content/[.]*.form.html" }
Example Filter: Allow Access to the Workflow Console example-filter-allow-access-to-the-workflow-console
The following example shows a filter used to allow external access to the Workflow console:
/filter {
/0001 { /glob "*" /type "deny" }
/0002 { /type "allow" /url "/libs/cq/workflow/content/console*" }
Example filter: Filter extra Elements of a Request URL example-filter-filter-additional-elements-of-a-request-url
Below is a rule example that blocks content grabbing from the /content path and its subtree, using filters for path, selectors, and extensions:
/006 {
/type "deny"
/path "/content/*"
/selectors '(feed|rss|pages|languages|blueprint|infinity|tidy|sysview|docview|query|jcr:content|_jcr_content|search|childrenlist|ext|assets|assetsearch|[0-9-]+)'
/extension '(json|xml|html|feed))'
miscellaneous content such as designs and client libraries. For example:
/etc/designs/default*/etc/designs/mydesign*After you create filters, test page access to ensure that your AEM instance is secure.
The following /filter section of the dispatcher.any file can be used as a basis in your Dispatcher configuration file.
This example is based on the default configuration file that is provided with Dispatcher and is intended as an example for use in a production environment. Items prefixed with # are deactivated (commented out). Care should be taken if you decide to activate any of these items (by removing the # on that line). Doing so can have a security impact.
Deny access to everything, then allow access to specific (limited) elements:
/filter
# Deny everything first and then allow specific entries
/0001 { /type "deny" /url "*" }
# Open consoles
# /0011 { /type "allow" /url "/admin/*" } # allow servlet engine admin
# /0012 { /type "allow" /url "/crx/*" } # allow content repository
# /0013 { /type "allow" /url "/system/*" } # allow OSGi console
# Allow non-public content directories
# /0021 { /type "allow" /url "/apps/*" } # allow apps access
# /0022 { /type "allow" /url "/bin/*" }
/0023 { /type "allow" /url "/content*" } # disable this rule to allow mapped content only
# /0024 { /type "allow" /url "/libs/*" }
# /0025 { /type "deny" /url "/libs/shindig/proxy*" } # if you enable /libs close access to proxy
# /0026 { /type "allow" /url "/home/*" }
# /0027 { /type "allow" /url "/tmp/*" }
# /0028 { /type "allow" /url "/var/*" }
# Enable extensions in non-public content directories, using a regular expression
/0041
/type "allow"
/extension '(css|gif|ico|js|png|swf|jpe?g)'
# Enable features
/0062 { /type "allow" /url "/libs/cq/personalization/*" } # enable personalization
# Deny content grabbing, on all accessible pages, using regular expressions
/0081
/type "deny"
/selectors '((sys|doc)view|query|[0-9-]+)'
/extension '(json|xml)'
# Deny content grabbing for /content and its subtree
/0082
/type "deny"
/path "/content/*"
/selectors '(feed|rss|pages|languages|blueprint|infinity|tidy)'
/extension '(json|xml|html)'
# /0087 { /type "allow" /method "GET" /extension 'json' "*.1.json" } # allow one-level json requests
When used with Apache, design your filter URL patterns according to the DispatcherUseProcessedURL property of the Dispatcher module. (See Apache Web Server - Configure your Apache Web Server for Dispatcher.)
Consider the following recommendations if you do choose to extend access:
Care must be taken when allowing access to files in /libs. Access should be allowed on an individual basis.
Deny access to the replication configuration so it cannot be seen:
/etc/replication.xml*/etc/replication.infinity.json*Deny access to the Google Gadgets reverse proxy:
/libs/opensocial/proxy*Depending on your installation, there might be more resources under /libs, /apps or elsewhere, that must be made available. You can use the access.log file as one method of determining resources that are being accessed externally.
CAUTION
Access to consoles and directories can present a security risk for production environments. Unless you have explicit justification, they should remain deactivated (commented out).
Restricting Query Strings restricting-query-strings
Since Dispatcher version 4.1.5, use the /filter section to restrict query strings. It is recommended that you explicitly allow query strings and exclude generic allowance through allow filter elements.
A single entry can have either glob or some combination of method, url, query, and version, but not both. The following example allows the a=* query string and denies all other query strings for URLs that resolve to the /etc node:
/filter {
/0001 { /type "deny" /method "POST" /url "/etc/*" }
/0002 { /type "allow" /method "GET" /url "/etc/*" /query "a=*" }
If a rule contains a /query, it only matches requests that contain a query string and match the provided query pattern.
In above example, if requests to /etc that have no query string should be allowed as well, the following rules would be required:
/filter {
>/0001 { /type "deny" /method "*" /url "/path/*" }
>/0002 { /type "allow" /method "GET" /url "/path/*" }
>/0003 { /type "deny" /method "GET" /url "/path/*" /query "*" }
>/0004 { /type "allow" /method "GET" /url "/path/*" /query "a=*" }
Testing Dispatcher Security testing-dispatcher-security
Dispatcher filters should block access to the following pages and scripts on AEM publish instances. Use a web browser to attempt to open the following pages as a site visitor would and verify that a code 404 is returned. If any other result is obtained, adjust your filters.
You should see normal page rendering for /content/add_valid_page.html?debug=layout.
/jcr:system/jcr:versionStorage.json/_jcr_system/_jcr_versionStorage.json/libs/wcm/core/content/siteadmin.html/libs/collab/core/content/admin.html/libs/cq/ui/content/dumplibs.html/var/linkchecker.html/etc/linkchecker.html/home/users/a/admin/profile.json/home/users/a/admin/profile.xml/libs/cq/core/content/login.json/content/../libs/foundation/components/text/text.jsp/content/.{.}/libs/foundation/components/text/text.jsp/apps/sling/config/org.apache.felix.webconsole.internal.servlet.OsgiManager.config/jcr%3acontent/jcr%3adata/libs/foundation/components/primary/cq/workflow/components/participants/json.GET.servlet/content.pages.json/content.languages.json/content.blueprint.json/content.-1.json/content.10.json/content.infinity.json/content.tidy.json/content.tidy.-1.blubber.json/content/dam.tidy.-100.json/content/content/geometrixx.sitemap.txt/content/add_valid_page.query.json?statement=//*/content/add_valid_page.qu%65ry.js%6Fn?statement=//*/content/add_valid_page.query.json?statement=//*[@transportPassword]/(@transportPassword%20|%20@transportUri%20|%20@transportUser)/content/add_valid_path_to_a_page/_jcr_content.json/content/add_valid_path_to_a_page/jcr:content.json/content/add_valid_path_to_a_page/_jcr_content.feed/content/add_valid_path_to_a_page/jcr:content.feed/content/add_valid_path_to_a_page/pagename._jcr_content.feed/content/add_valid_path_to_a_page/pagename.jcr:content.feed/content/add_valid_path_to_a_page/pagename.docview.xml/content/add_valid_path_to_a_page/pagename.docview.json/content/add_valid_path_to_a_page/pagename.sysview.xml/etc.xml/content.feed.xml/content.rss.xml/content.feed.html/content/add_valid_page.html?debug=layout/projects/tagging/etc/replication.html/etc/cloudservices.html/welcomeTo determine whether anonymous write access is enabled, issue the following command in a terminal or command prompt. Writing data to the node should not be possible.
curl -X POST "https://anonymous:anonymous@hostname:port/content/usergenerated/mytestnode"
To attempt to invalidate the Dispatcher cache and ensure that you receive a code 403 response, issue the following command in a terminal or command prompt:
curl -H "CQ-Handle: /content" -H "CQ-Path: /content" https://yourhostname/dispatcher/invalidate.cache
Enabling Access to Vanity URLs enabling-access-to-vanity-urls-vanity-urls
Configure the Dispatcher to enable access to vanity URLs that are configured for your AEM pages.
When access to vanity URLs is enabled, Dispatcher periodically calls a service that runs on the render instance to obtain a list of vanity URLs. Dispatcher stores this list in a local file. When a request for a page is denied due to a filter in the /filter section, Dispatcher consults the list of vanity URLs. If the denied URL is on the list, Dispatcher allows access to the vanity URL.
To enable access to vanity URLs, add a /vanity_urls section to the /farms section, similar to the following example:
/vanity_urls {
/url "/libs/granite/dispatcher/content/vanityUrls.html"
/file "/tmp/vanity_urls"
/delay 300
/url: The path to the vanity URL service that runs on the render instance. The value of this property must be "/libs/granite/dispatcher/content/vanityUrls.html".
/file: The path to the local file where Dispatcher stores the list of vanity URLs. Make sure that the Dispatcher has write-access to this file.
/delay: (Seconds) The time between calls to the vanity URL service.
If your render is an instance of AEM, you must install the VanityURLS-Components package from Software Distribution to enable the vanity URL service. (See Software Distribution for more details.)
Use the following procedure to enable access to vanity URLs.
If your render service is an AEM instance, install the com.adobe.granite.dispatcher.vanityurl.content package on the publish instance (see the note above).
For each vanity URL that you have configured for an AEM or CQ page, ensure that the /filter configuration denies the URL. If necessary, add a filter that denies the URL.
Add the /vanity_urls section below /farms.
Restart Apache web server.
Forwarding Syndication Requests - /propagateSyndPost forwarding-syndication-requests-propagatesyndpost
Syndication requests are intended for Dispatcher only, so by default they are not sent to the renderer (for example, an AEM instance).
If necessary, set the /propagateSyndPost property to "1" to forward syndication requests to Dispatcher. If set, you must make sure that POST requests are not denied in the filter section.
Configuring the Dispatcher Cache - /cache configuring-the-dispatcher-cache-cache
The /cache section controls how Dispatcher caches documents. Configure several subproperties to implement your caching strategies:
/docroot "/opt/dispatcher/cache"
/statfile "/tmp/dispatcher-website.stat"
/allowAuthorized "0"
/rules
# List of files that are cached
/invalidate
# List of files that are auto-invalidated
Specifying the Cache Directory specifying-the-cache-directory
The /docroot property identifies the directory where cached files are stored.
The value must be the same path as the document root of the web server so that the Dispatcher and the web server handle the same files.
The web server is responsible for delivering the correct status code when the Dispatcher cache file is used, that’s why it is important that it can find it as well.
If you use multiple farms, each farm must use a different document root.
Naming the Statfile naming-the-statfile
The /statfile property identifies the file to use as the statfile. Dispatcher uses this file to register the time of the most recent content update. The statfile can be any file on the web server.
The statfile has no content. When content is updated, the Dispatcher updates the timestamp. The default statfile is named .stat and is stored in the docroot. Dispatcher blocks access to the statfile.
If /statfileslevel is configured, Dispatcher ignores the /statfile property and uses .stat as the name.
Serving Stale Documents When Errors Occur serving-stale-documents-when-errors-occur
The /serveStaleOnError property controls whether Dispatcher returns invalidated documents when the render server returns an error. By default, when a statfile is touched and invalidates cached content, the Dispatcher deletes the cached content. This action is done the next time it is requested.
If /serveStaleOnError is set to "1", Dispatcher does not delete invalidated content from the cache. That is, unless the render server returns a successful response. A 5xx response from AEM or a connection timeout causes the Dispatcher to serve the outdated content and respond with and HTTP Status of 111 (Revalidation Failed).
Caching When Authentication is Used caching-when-authentication-is-used
The /allowAuthorized property controls whether requests that contain any of the following authentication information are cached:
By default, requests that include this authentication information are not cached because authentication is not performed when a cached document is returned to the client. This configuration prevents Dispatcher from serving cached documents to users who do not have the necessary rights.
However, if your requirements permit the caching of authenticated documents, set /allowAuthorized to one:
/allowAuthorized "1"
To enable session management (using the /sessionmanagement property), the /allowAuthorized property must be set to "0".
The GET or HEAD (for the HTTP header) methods are cacheable by the Dispatcher. For additional information on response header caching, see the Caching HTTP Response Headers section.
Each item in the /rules property includes a glob pattern and a type:
For information about Glob properties, see Designing Patterns for Glob Properties.
If there are some sections of your page that are dynamic (for example a news application) or within a closed user group, you can define exceptions:
Do not cache closed user groups. The reason is because user rights are not checked for cached pages.
/0000 { /glob "*" /type "allow" }
/0001 { /glob "/en/news/*" /type "deny" }
/0002 { /glob "*/private/*" /type "deny" }
Dispatcher creates .statfiles in each folder from the docroot folder to the level that you specify. The docroot folder is level 0.
Files are invalidated by touching the .stat file. The .stat file’s last modification date is compared to the last modification date of a cached document. The document is refetched if the .stat file is newer.
When a file at a certain level is invalidated, all .stat files from the docroot to the level of the invalidated file or the configured statsfilevel (whichever is smaller) are touched.
For example: if you set the statfileslevel property to 6 and a file is invalidated at level 5 then every .stat file from docroot to 5 are touched. Continuing with this example, if a file is invalidated at level 7 then every stat file from docroot to six are touched (since /statfileslevel = "6").
When a file in /content/myWebsite/xx is invalidated, then every .stat file from docroot down to /content/myWebsite/xxis touched. This scenario is the case only for /content/myWebsite/xx and not for example /content/myWebsite/yy or /content/anotherWebSite.
Invalidation can be prevented by sending an extra Header CQ-Action-Scope:ResourceOnly. This method can be used to flush particular resources without invalidating other parts of the cache. See this page and Manually Invalidating the Dispatcher Cache for additional details.
Automatically Invalidating Cached Files automatically-invalidating-cached-files
The /invalidate property defines the documents that are automatically invalidated when content is updated.
With automatic invalidation, Dispatcher does not delete cached files after a content update, but checks their validity when they are next requested. Documents in the cache that are not auto-invalidated remain in the cache until a content update explicitly deletes them.
Automatic invalidation is typically used for HTML pages. HTML pages often contain links to other pages, making it difficult to determine whether a content update affects a page. To make sure that all relevant pages are invalidated when content is updated, automatically invalidate all HTML pages. The following configuration invalidates all HTML pages:
/invalidate
/0000 { /glob "*" /type "deny" }
/0001 { /glob "*.html" /type "allow" }
All the files with pattern en.* are removed from the /content/wknd/us folder.
The /content/wknd/us/en./_jcr_content folder is removed.
All the other files that match the /invalidate configuration are not immediately deleted. These files are deleted when the next request occurs. In the example, /content/wknd.html is not deleted; it is deleted when /content/wknd.html is requested.
/0000 { /glob "*" /type "deny" }
/0001 { /glob "*.html" /type "allow" }
/0002 { /glob "*.zip" /type "allow" }
/0003 { /glob "*.pdf" /type "allow" }
Using custom invalidation scripts using-custom-invalidation-scripts
The /invalidateHandler property lets you define a script that is called for each invalidation request received by Dispatcher.
It is called with the following arguments:
Handle - The content path that is invalidated
Action - The replication Action (for example, Activate, Deactivate)
Action Scope - The replication Action’s Scope (empty, unless a header of CQ-Action-Scope: ResourceOnly is sent, see Invalidating Cached Pages from AEM for details)
This method can be used to cover several different use cases. For example, invalidating other application-specific caches, or to handle cases where the externalized URL of a page, and its place in the docroot, does not match the content path.
The following example script logs each invalidated request to a file.
/invalidateHandler "/opt/dispatcher/scripts/invalidate.sh"
Limiting the Clients That Can Flush the Cache limiting-the-clients-that-can-flush-the-cache
The /allowedClients property defines specific clients that are allowed to flush the cache. The globbing patterns are matched against the IP.
The following example:
When a parameter is ignored for a page, the page is cached the first time that the page is requested. Subsequent requests for the page are served to the cached page, regardless of the value of the parameter in the request.
It is recommended that you configure the ignoreUrlParams setting in an allowlist manner. As such, all query parameters are ignored and only known or expected query parameters are exempt (“denied”) from being ignored. For more details and examples, see this page.
To specify which parameters are ignored, add glob rules to the ignoreUrlParams property:
To cache a page regardless of the request containing a URL parameter, create a glob property that allows the parameter (to be ignored).
To prevent the page from being cached, create a glob property that denies the parameter (to be ignored).
When configuring the glob property, it should match the query parameter name. For example, if you want to ignore the “p1” parameter from the following URL http://example.com/path/test.html?p1=test&p2=v2, then the glob property should be:
/0002 { /glob "p1" /type "allow" }
The following example causes Dispatcher to ignore all parameters, except the nocache parameter. As such, Dispatcher never caches request URLs that include the nocache parameter:
/ignoreUrlParams
# ignore-all-url-parameters-by-dispatcher-and-requests-are-cached
/0001 { /glob "*" /type "allow" }
# allow-the-url-parameter-nocache-to-bypass-dispatcher-on-every-request
/0002 { /glob "nocache" /type "deny" }
The /headers property lets you define the HTTP header types that Dispatcher is going to cache. On the first request to an uncached resource, all headers matching one of the configured values (see the configuration sample below) are stored in a separate file, next to the cache file. On subsequent requests to the cached resource, the stored headers are added to the response.
Below is a sample from the default configuration:
/cache {
/headers {
"Cache-Control"
"Content-Disposition"
"Content-Type"
"Expires"
"Last-Modified"
"X-Content-Type-Options"
"Last-Modified"
0400 Allow read by owner.0200 Allow write by owner.0100 Allow the owner to search in directories.0040 Allow read by group members.0020 Allow write by group members.0010 Allow group members to search in the directory.0004 Allow read by others.0002 Allow write by others.0001 Allow others to search in the directory.The default value is 0755, which allows the owner to read, write, or search and the group and others to read or search.
Throttling .stat file touching throttling-stat-file-touching
With the default /invalidate property, every activation effectively invalidates all .html files (when their path matches the /invalidate section). On a website with considerable traffic, multiple, subsequent activations increase the cpu load on the backend. In such a scenario, it is desirable to “throttle” .stat file touching to keep the website responsive. You can accomplish this action by using the /gracePeriod property.
The /gracePeriod property defines the number of seconds a stale, auto-invalidated resource may still be served from the cache after the last occurring activation. The property can be used in a setup where a batch of activations would otherwise repeatedly invalidate the entire cache. The recommended value is 2 seconds.
For more details, see /invalidate and /statfileslevelearlier.
Configuring Time Based Cache Invalidation - /enableTTL configuring-time-based-cache-invalidation-enablettl
Time-based cache invalidation depends on the /enableTTL property and the presence of regular expiration headers from the HTTP standard. If you set the property to 1 (/enableTTL "1"), it evaluates the response headers from the backend. If the headers contain a Cache-Control, max-age or Expires date, an auxiliary, empty file next to the cached file is created, with the modification time equal to the expiry date. When the cached file is requested past the modification time, it is automatically re-requested from the backend.
Before Dispatcher 4.3.5, the TTL invalidation logic was based only on the configured TTL value. With Dispatcher 4.3.5, both the set TTL and the Dispatcher cache invalidation rules are accounted for. As such, for a cached file:
If /enableTTL is set to 1, the file expiration is checked. If the file has expired according to the set TTL, no other checks are performed and the cached file is re-requested from the backend.
If the file has either not expired, or /enableTTL is not configured, then the standard cache invalidation rules are applied such as those rules that /statfileslevel and /invalidate set. This flow means that the Dispatcher can invalidate files for which the TTL has not expired.
This new implementation supports use cases where files have a longer TTL (for example, on the CDN). But those file can still be invalidated even if the TTL has not expired. It favors content freshness over cache-hit ratio on the Dispatcher.
Conversely, in case you need only the expiration logic applied to a file then set /enableTTL to 1 and exclude that file from the standard cache invalidation mechanism. For example, you can:
/0000 { /glob "*" /type "deny" }
/0001 { /glob "*.html" /type "allow" }
/0002 { /glob "*.example.html" /type "deny" }
Doing so ensures that .stat file invalidation is not used and only TTL expiration is active for the specified files.
Keep in mind that setting /enableTTL to 1 enables TTL caching only on the Dispatcher side. As such, the TTL information contained in the additional file (see above) is not provided to any other user agent requesting such a file type from the Dispatcher. If you want to provide caching headers to downstream systems like a CDN or a browser, you should configure the /cache/headers section accordingly.
Configuring Load Balancing - /statistics configuring-load-balancing-statistics
The /statistics section defines categories of files for which Dispatcher scores the responsiveness of each render. Dispatcher uses the scores to determine which render to send a request.
Each category that you create defines a glob pattern. Dispatcher compares the URI of the requested content to these patterns to determine the category of the requested content:
Dispatcher supports a maximum of eight statistics categories. If you define more than eight categories, only the first 8 are used.
Render Selection
Each time the Dispatcher requires a rendered page, it uses the following algorithm to select the render:
If the request contains the render name in a renderid cookie, Dispatcher uses that render.
If the request includes no renderid cookie, Dispatcher compares the render statistics:
Dispatcher determines the category of the request URI.
Dispatcher determines which render has the lowest response score for that category, and selects that render.
If no render is selected yet, use the first render in the list.
The score for a render’s category is based on previous response times, and previous failed and successful connections that Dispatcher attempts. For each attempt, the score for the category of the requested URI is updated.
If you do not use load balancing, you can omit this section.
Defining Statistics Categories defining-statistics-categories
Define a category for each type of document for which you want to keep statistics for render selection. The /statistics section contains a /categories section. To define a category, add a line below the /categories section that has the following format:
/name { /glob "pattern"}
The category name must be unique to the farm. The pattern is described in the Designing Patterns for glob Properties section.
To determine the category of a URI, the Dispatcher compares the URI with each category pattern until a match is found. Dispatcher begins with the first category in the list and continues in order. Therefore, place categories with more specific patterns first.
For example, Dispatcher the default dispatcher.any file defines an HTML category and an others category. The HTML category is more specific and so it appears first:
/statistics
/categories
/html { /glob "*.html" }
/others { /glob "*" }
Reflecting Server Unavailability in Dispatcher Statistics reflecting-server-unavailability-in-dispatcher-statistics
The /unavailablePenalty property sets the time (in tenths of a second) that is applied to the render statistics when a connection to the render fails. Dispatcher adds the time to the statistics category that matches the requested URI.
For example, the penalty is applied when the TCP/IP connection to the designated hostname/port cannot be established. The reason is either because AEM is not running (and not listening) or because of a network-related problem.
The /unavailablePenalty property is a direct child of the /farm section (a sibling of the /statistics section).
If no /unavailablePenalty property exists, a value of "1" is used.
/unavailablePenalty "1"
Identifying a Sticky Connection Folder - /stickyConnectionsFor identifying-a-sticky-connection-folder-stickyconnectionsfor
The /stickyConnectionsFor property defines one folder that contains sticky documents. This property is accessed using the URL. Dispatcher sends all requests, from a single user that are in this folder, to the same render instance. Sticky connections ensure that session data is present and consistent for all documents. This mechanism uses the renderid cookie.
The following example defines a sticky connection to the /products folder:
/stickyConnectionsFor "/products"
When a page is composed of content from several content nodes, include the /paths property that lists the paths to the content. For example, a page contains content from /content/image, /content/video, and /var/files/pdfs. The following configuration enables sticky connections for all content on the page:
/stickyConnections {
/paths {
"/content/image"
"/content/video"
"/var/files/pdfs"
httpOnly httponly
When sticky connections are enabled, the Dispatcher module sets the renderid cookie. This cookie does not have the httponly flag, which should be added to enhance security. You add the httponly flag by setting the httpOnly property in the /stickyConnections node of a dispatcher.any configuration file. The property’s value (either 0 or 1) defines whether the renderid cookie has the HttpOnly attribute appended. The default value is 0, which means the attribute is not added.
For additional information about the httponly flag, read this page.
secure secure
When sticky connections are enabled, the Dispatcher module sets the renderid cookie. This cookie does not have the secure flag, which should be added to enhance security. You add the secure flag setting the secure property in the /stickyConnections node of a dispatcher.any configuration file. The property’s value (either 0 or 1) defines whether the renderid cookie has the secure attribute appended. The default value is 0, which means the attribute is added if the incoming request is secure. If the value is set to 1, then the secure flag is added regardless of whether the incoming request is secure or not.
Handling Render Connection Errors handling-render-connection-errors
Configure Dispatcher behavior when the render server returns a 500 error, or is unavailable.
Specifying a Health Check Page specifying-a-health-check-page
Use the /health_check property to specify a URL that is checked when a 500 status code occurs. If this page also returns a 500 status code, the instance is considered to be unavailable and a configurable time penalty ( /unavailablePenalty) is applied to the render before retrying.
/health_check
# Page gets contacted when an instance returns a 500
/url "/health_check.html"
Specifying the Page Retry Delay specifying-the-page-retry-delay
The /retryDelay property sets the time (in seconds) that Dispatcher waits between rounds of connection attempts with the farm renders. For each round, the maximum number of times the Dispatcher attempts a connection to a render is the number of renders in the farm.
Dispatcher uses a value of "1" if /retryDelay is not explicitly defined. The default value is usually appropriate.
/retryDelay "1"
Configuring the Number of Retries configuring-the-number-of-retries
The /numberOfRetries property sets the maximum number of rounds of connection attempts that Dispatcher performs with the renders. If Dispatcher cannot successfully connect to a render after this number of retries, Dispatcher returns a failed response.
For each round, the maximum number of times the Dispatcher attempts a connection to a render is the number of renders in the farm. Therefore, the maximum number of times that the Dispatcher attempts a connection is ( /numberOfRetries) x (the number of renders).
If the value is not explicitly defined, the default value is 5.
/numberOfRetries "5"
When a request to a render returns HTTP Status 503 (UNAVAILABLE), Dispatcher sends the request to a different render.
When a request to a render returns HTTP Status 50x (other than 503), Dispatcher sends a request for the page that is configured for the health_check property.
If the health check returns 500 (INTERNAL_SERVER_ERROR), Dispatcher sends the original request to a different render.
If the health check returns HTTP Status 200, the Dispatcher returns the initial HTTP 500 error to the client.
Any file system-oriented system call can be interrupted EINTR if the object of the system call is on a remote system accessed by way of NFS. Whether these system calls can time out or be interrupted is based on how the underlying file system was mounted on the local machine.
Use the /ignoreEINTR parameter if your instance has such a configuration and the log contains the following message:
Error while reading response: Interrupted system call
Internally, Dispatcher reads the response from the remote server (that is, AEM) using a loop that can be represented as:
while (response not finished) {
read more data
Such messages can be generated when the EINTR occurs in the read more data section. And, the reception of a signal before any data was received is the cause.
To ignore such interrupts, you can add the following parameter to dispatcher.any (before /farms):
/ignoreEINTR "1"
Setting /ignoreEINTR to "1" causes Dispatcher to continue to attempt to read data until the complete response is read. The default value is 0 and deactivates the option.
Designing Patterns for Glob Properties designing-patterns-for-glob-properties
Several sections in the Dispatcher configuration file use the glob properties as selection criteria for client requests. The values of glob properties are patterns that Dispatcher compares to an aspect of the request, such as the path of the requested resource, or the IP address of the client. For example, the items in the /filter section use glob patterns to identify the paths of the pages that Dispatcher acts on or rejects.
The glob values can include wildcard characters and alphanumeric characters to define the pattern.
Wildcard character
Description
Examples
Matches zero or more contiguous instances of any character in the string. Either of the following situations determines the final character of the match:
A character in the string matches the next character in the pattern, and the pattern character has the following characteristics:
Not a *
Not a ?
A literal character (including a space) or a character class.
The end of the pattern is reached.
Inside a character class, the character is interpreted literally.
*/geo* Matches any page below the /content/geometrixx node and the /content/geometrixx-outdoors node. The following HTTP requests match the glob pattern:
"GET /content/geometrixx/en.html""GET /content/geometrixx-outdoors/en.html"*outdoors/*
Matches any page below the /content/geometrixx-outdoors node. For example, the following HTTP request matches the glob pattern:
"GET /content/geometrixx-outdoors/en.html"*outdoors/??/*
Matches the pages for any language in the geometrixx-outdoors site. For example, the following HTTP request matches the glob pattern:
"GET /content/geometrixx-outdoors/en/men.html"The following request does not match the glob pattern:
“GET /content/geometrixx-outdoors/en.html”
[ and ]
Demarks the beginning and end of a character class. Character classes can include one or more character ranges and single characters.
A match occurs if the target character matches any of the characters in the character class, or within a defined range.
If the closing bracket is not included, the pattern produces no matches.
*[o]men.html*
Matches the following HTTP request:
"GET /content/geometrixx-outdoors/en/women.html"It does not match the following HTTP request:
"GET /content/geometrixx-outdoors/en/men.html"*[o/]men.html*
Matches the following HTTP requests:
"GET /content/geometrixx-outdoors/en/women.html""GET /content/geometrixx-outdoors/en/men.html"*[m-p]men.html* Matches the following HTTP request:
"GET /content/geometrixx-outdoors/en/women.html"It does not match the following HTTP request:
"GET /content/geometrixx-outdoors/en/men.html"^ wildcard.
Outside of a character class, this character is interpreted literally.
*[!o]men.html*
Matches the following HTTP request:
"GET /content/geometrixx-outdoors/en/men.html"It does not match the following HTTP request:
"GET /content/geometrixx-outdoors/en/women.html"*[!o!/]men.html*
It does not match the following HTTP request:
"GET /content/geometrixx-outdoors/en/women.html" or "GET /content/geometrixx-outdoors/en/men. html"! wildcard character.
Outside of a character class, this character is interpreted literally.
The examples for the ! wildcard character apply, substituting the ! characters in the example patterns with ^ characters.
Refer to the web server documentation and the readme file of your Dispatcher instance for more information.
Apache Rotated or Piped Logs
If using an Apache web server, you can use the standard functionality for Log Rotations, or Piped Logs, or both. For example, using Piped Logs:
DispatcherLog "| /usr/apache/bin/rotatelogs logs/dispatcher.log%Y%m%d 604800"
This functionality automatically rotates:
the Dispatcher log file, with a timestamp in the extension (logs/dispatcher.log%Y%m%d).
on a weekly basis (60 x 60 x 24 x 7 = 604800 seconds).
See the Apache Web Server documentation on Log Rotation and Piped Logs. For example, Apache 2.4.
After installation, the default log level is high (that is, level 3 = Debug), so that the Dispatcher logs all errors and warnings. This level is useful in the initial stages.
However, such a level requires more resources. When the Dispatcher is working smoothly according to your requirements, you can lower the log level.
Trace Logging trace-logging
Among other enhancements for the Dispatcher, version 4.2.0 also introduces Trace Logging.
This ability is a higher level than Debug logging that shows additional information in the logs. It adds logging for:
[Thu Mar 03 16:05:38 2016] [T] [17183] request.headers[Host] = "localhost:8443"
[Thu Mar 03 16:05:38 2016] [T] [17183] request.headers[User-Agent] = "curl/7.43.0"
[Thu Mar 03 16:05:38 2016] [T] [17183] request.headers[Accept] = "*/*"
[Thu Mar 03 16:05:38 2016] [T] [17183] request.headers[X-Forwarded-SSL-Client-Cert] = "(null)"
[Thu Mar 03 16:05:38 2016] [T] [17183] request.headers[Via] = "1.1 localhost:8443 (dispatcher)"
[Thu Mar 03 16:05:38 2016] [T] [17183] request.headers[X-Forwarded-For] = "::1"
[Thu Mar 03 16:05:38 2016] [T] [17183] request.headers[X-Forwarded-SSL] = "on"
[Thu Mar 03 16:05:38 2016] [T] [17183] request.headers[X-Forwarded-SSL-Cipher] = "DHE-RSA-AES256-SHA"
[Thu Mar 03 16:05:38 2016] [T] [17183] request.headers[X-Forwarded-SSL-Session-ID] = "ba931f5e4925c2dde572d766fdd436375e15a0fd24577b91f4a4d51232a934ae"
[Thu Mar 03 16:05:38 2016] [T] [17183] request.headers[X-Forwarded-Port] = "8443"
[Thu Mar 03 16:05:38 2016] [T] [17183] request.headers[Server-Agent] = "Communique-Dispatcher"
Depending on your web server, you should see messages such as:
[Thu May 30 05:16:36 2002] [notice] Apache/2.0.50 (Unix) configured and[Fri Jan 19 17:22:16 2001] [I] [19096] Dispatcher initialized (build XXXX)Surf the website via the web server. Confirm that content is being shown as required.
For example, on a local installation where AEM runs on port 4502 and the web server on 80 access the Websites console using both:
https://localhost:4502/libs/wcm/core/content/siteadmin.htmlhttps://localhost:80/libs/wcm/core/content/siteadmin.htmlThe results should be identical. Confirm access to other pages with the same mechanism.
Check that the cache directory is being filled.
To check that the cache is being flushed correctly, activate a page.
If everything is operating correctly, you can reduce the loglevel to 0.
In such a case, make sure that each request goes through only one Dispatcher. A Dispatcher does not handle requests that come from another Dispatcher. Therefore, make sure that both Dispatchers access the AEM website directly.
Debugging debugging
When adding the header X-Dispatcher-Info to a request, Dispatcher answers whether the target was cached, returned from cached, or not cacheable at all. The response header X-Cache-Info contains this information in a readable form. You can use these response headers to debug issues involving responses cached by the Dispatcher.
This functionality is not enabled by default, so for the response header X-Cache-Info to be included, the farm must contain the following entry:
/info "1"
/mywebsite
# Include X-Cache-Info response header if X-Dispatcher-Info is in request header
/info "1"
target file cached
The target file is contained in the cache and the Dispatcher has determined that it is valid to deliver it.
caching
The target file isn’t contained in the cache and the Dispatcher has determined that it is valid to cache the output and deliver it.
caching: stat file is more recent
The target file is contained in the cache. However, a more recent stat file can invalidate it. The Dispatcher deletes the target file, recreates it from the output and delivers it.
not cacheable: document root non-existent
The farm’s configuration does not contain a document root (configuration element cache.docroot).
not cacheable: cache file path too long
The target file - the concatenation of document root and URL file - exceeds the longest possible file name on the system.
not cacheable: temporary file path too long
The temporary file name template exceeds the longest possible file name on the system. The Dispatcher creates a temporary file first, before actually creating or overwriting the cached file. The temporary file name is the target file name with the characters _YYYYXXXXXX appended to it, where the Y and X are replaced to create a unique name.
not cacheable: request URL is missing extension
The request URL has no extension, or there is a path following the file extension, for example: /test.html/a/path.
not cacheable: request needed to be a GET or HEAD
The HTTP method is not a GET or a HEAD. The Dispatcher assumes that the output contains dynamic data that should not be cached.
not cacheable: request contained a query string
The request contained a query string. The Dispatcher assumes that the output depends on the query string given and therefore does not cache.
not cacheable: session manager needs to authenticate
A session manager (the configuration contains a sessionmanagement node) governs the farm’s cache and the request did not contain the appropriate authentication information.
not cacheable: request contains authorization
The farm is not allowed to cache output ( allowAuthorized 0) and the request contains authentication information.
not cacheable: target is a directory
The target file is a directory. This location might point to some conceptual mistake, where a URL and some sub-URL both contain cacheable output. For example, if a request to /test.html/a/file.ext comes first and contains cacheable output, the Dispatcher is not able to cache the output of a subsequent request to /test.html.
not cacheable: request URL has a trailing slash
The request URL has a trailing slash.
not cacheable: request URL is missing in cache rules
The farm’s cache rules explicitly deny caching the output of some request URL.
not cacheable: authorization checker denied access
The farm’s authorization checker denied access to the cached file.
not cacheable: session is invalid
A session manager (configuration contains a sessionmanagement node) governs the farm’s cache and the user’s session is not or no longer valid.
not cacheable: response contains no_cache
The remote server returned a Dispatcher: no_cache header, forbidding the Dispatcher to cache the output.
not cacheable: response content length is zero
The content length of the response is zero; the Dispatcher does not create a zero-length file.
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