Package: bethel.silva.purge
bethel.silva.purgeTable of Contentsbethel.silva.purgeIntroductionOperation in SilvaOn modificationOn PublishWhat PURGE urls are generated?Object EventsPublishing EventsInstallationConfiguration1. Enable the service2. Set Cache Proxies3. Complex Virtual Hosting (a.k.a. Path Translations)4. Domain Translationsbethel.silva.purge changesIntroductionThis package is a wrapper aroundplone.cachepurging, providing purge support for
for Silva content. Purges of Silva content are triggered when that content is
changed or published.Many Silva sites sit behind a caching proxy server (e.g. varnish, squid,
pound, etc).  The cache server will cache Silva content until it expires.  For
the most part this is positive and a good thing, so long as the caching
headers are set correctly in Silva.There becomes a problem, however, when a cached page is republished or
closed. The caching server will continue to serve the cached page until it
expires, even though there is newer content in Silva.  The old content on
the caching server is referred to as ‘stale’.This extension adds a PurgingService to the Silva root.  This service has
options to enable purging, specifying the caching servers, and configuring
plone.cachepurging-style simple virtualhosting (renamed to domain translations).
There is also support for complex virtualhost situations, where many
virtualhosts are served from different areas of a single Silva root (this is
called path translations).The actual PURGE requests occur AFTER the request is finished, via a
ZPublisher.pubevents.PubSuccess event.  Each PURGE path is put into a queue
and multiple worker threads operate on the queue until empty.  This is a sweet
feature of plone.cachepurging, as it does not slow down the response to the
client.Note: while installing and configuring this extension is easy, do you homework!
Read through the plone.cachepurging documentation and make sure you understand
the fundamentals of PURGE.Operation in SilvaWhen content is modified or published in Silva, a Purge event is triggered.On modificationThis package markes SilvaObject with the IPurgeable interface. This enables
purging on IObjectMovedEvent and IObjectModifiedEvent. This ought to include
containers (e.g. saving a container’s metadata). FMI see:purging objects automaticallyIf the object event is for an index document, the container is also purged.On PublishIVersions have an IPublishingEvent subscriber, which is triggered on every
publishing event (publish, approval requesting, expires, approved, etc). While
this will cause PURGEs to occur on events which to not affect the published
version, the only effect is that the content is purged and needs to be
re-fetched.This causes a Purge of the IContent object, NOT the IVersion object, since the version
isn’t cached.If the object event is for an index document, the container is also purged.What PURGE urls are generated?Multiple PURGE urls are generated for each event.  The following illustrates the
paths generated BEFORE being translated by domain or path.Object EventsStandard plone.cachepurging path: the full rooted path to object. For
publishable content, this would be the path to the version, e.g./silva/example.com/doc/1.[with path translations enabled] Index objects will add paths for the container,
both with and without a trailing slash.  e.g. for an event on /silva/example.com/folder/index:/silva/example.com/folder
/silva/example.com/folder/[with domain translations enabled] The path relative to the silva root. e.g. for
/silva/folder/doc:/folder/docPublishing EventsStandard plone.cachepurging path: the full rooted path to object. For
publishable content, this would be the path to the version, e.g.:/silva/example.com/doc/1[with path translations enabled] Path to IContent, e.g.:/silva/example.com/doc[with path translations enabled] Index objects will add paths for the
container, both with and without a trailing slash.  e.g. for an event on
/silva/example.com/folder/index:/silva/example.com/folder
/silva/example.com/folder/[with domain translations enabled] The path relative to the silva root.
e.g. for /silva/folder/doc:/folder/docInstallationTo install the service, activate the “Silva Purging Service’ extension in the
service_extensions. Installing this extension installs aplone.registryinto
the silva root and registers it as a local utility. The registry is used by
plone.cachepurging to store it’s configuration.ConfigurationThe service is configured via a ZMI management screen. Configuration will
change the plone.registry settings for plone.cachepurging, and configure the
path translations for complex vhosting.1. Enable the serviceThis field represents the value of plone.cachepurging.interfaces.ICacheSettings.enabled.Checking this will enable cache purging.2. Set Cache ProxiesAll frontend caching servers need to be added to this field. The format for each
is a URI, e.g.http://cachingserver.example.com:60813. Complex Virtual Hosting (a.k.a. Path Translations)Some Silva installations may serve multiple domains from within a single Silva
root. These domains may be located underneath the Silva root, e.g.
/silva_root/domain1, /silva_root/domain2, etc.  When this is the case,
plone.cachepurging vhosting support is not sufficient. Path Translations need
to be used instead.A path translation is simply an rule on how to translate a rooted path into
a virtualhosting string.To enable complex vhosting, check the “use path translations” field.Configure the path translations by adding them one per line.  The format for
each line is the “rooted path + ‘ ‘ + translated path”.  As an example, let’s say
there is a vhost at /silva/example.com/.  This is accessed from the domainhttp://example.com.  The line for this path translation would then be:/silva/example.com /VirtualHostBase/http/example.com:80/silva/www/VirtualHostRootPath Translations support multiple vhosts to the same root.  If www.example.com
also points /silva/example.com, an additional line can be added:/silva/example.com /VirtualHostBase/http/www.example.com:80/silva/www/VirtualHostRootAdditionally https vhosts can be supplied:/silva/example.com /VirtualHostBase/https/www.example.com:443/silva/www/VirtualHostRootSupport for inside-out hosting (using _vh_ segments) is supported, and in fact
any string can be supplied as the “translated path”.  The critical thing here
is that the path generated match the path cached by the caching server, or no
content will be purged.When purging urls are being generated, any matching paths will have the matching
part replaced with the vhost string, for all matches.  The search for matchingpaths begins with the full path to the object then proceeds down the path,
removing the last path component on each pass.4. Domain TranslationsConfigures plone.cachepurging virtual host support. This package includes two
types of virtual hosting support, so the plone.cachepurging style is renamed
to ‘domain translations’.  This approach rewrites the path from the silva root
to a virtual hosting url.To enable, check “Use domain translations”, and add the domains in the “Domains”
field.For more information on how this type of virtualhost works, see theplone.cachepurging documentation.bethel.silva.purge changesbethel.silva.purge 1.0b (2012-05-29)initial release for bethel.silva.purge