UseLastModified

Enable last-modified response headers. Enables or disables inclusion of the Last-Modified header in cacheable HTTP responses emitted by Image Rendering.

The server uses the most recent vignette::TimeStamp and catalog::TimeStamp value of all vignette and material catalogs/catalog records involved in a response as the Last-Modified header value.

Should be enabled only if a distributed caching network, such as Akamai, is used which does not support etag headers.

NOTE

Care must be taken when using Last-Modified headers in a load-balanced environment involving multiple Image Serving/Rendering hosts. Client caching may be defeated and server load increase if for some reason the servers have different time stamps for the same catalog entries. Such a situation can occur as follows:

  • Neither catalog::TimeStamp, vignette::TimeStamp, nor attribute::TimeStamp is defined, so that the modification time of the catalog.ini file is used as the default for catalog::TimeStamp.

  • Instead of sharing the material catalog files via a network mount, each server has its own instance of the catalog files on a local file system.

  • Two or more instances of the same catalog.ini file have different file modification dates, possibly caused by improper copying of the files.

Properties

Flag. 0 to disable, 1 to enable Last-Modified HTTP headers.

Default

Inherited from default::UseLastModified if not defined or if empty.

See also

catalog::TimeStamp , vignette::TimeStamp

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