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Content Application Developer Manual / Version 2010

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3.2.2 File System Cache for Transformed Image Blobs

Additionally, you can configure a separate cache where results of image transformations are stored persistently and can survive CAE restarts. Enabling this cache helps solving the problem of high CPU load in the first hours of operation after restart. This could happen because the transformation of large image blobs to compute scaled crops can be quite expensive. After system restart, the in-memory cache (UAPI cache) is empty, and without this file system cache all needed images would have to be transformed again.

Note

Note

Due to the specifics of file locking on Windows, the timely and correct deletion/rename of files and directories on this operation system cannot be guaranteed. Therefore, the file system transformed blob cache must not be used on Windows systems.

The configuration properties for the transformed blob cache are listed in the table:

Property Description

com.coremedia.transform.blobCache.size

The maximum allowed size that the transformed blobs cache can occupy on the disk. Note that the file system overhead for storing the files does not count towards this value. So the physical space that has to be reserved on the disk for the cache has to be slightly higher than value of this configuration property.

If several concurrent threads write large blobs at the same time, the deletion of the folder with the old unused files can be postponed for later, thus this is the second reason why the maximum allowed cache size can grow slightly higher than this configuration property. The size of such deviation depend on the blobs size as well as the amount of parallel threads.

com.coremedia.transform.blobCache.basePath

The path to the transformed blobs cache. If not set, then this cache is deactivated and the results of blob transformations are stored using UAPI cache. It is recommended to set this property to a folder that is not cleared during CAE restart, for example /var/cache/coremedia/persistent-transformed-blobcache.

Table 3.3.  Properties for transformed blob cache


Pay attention, not to purge the directory with the transformed blobs cache on CAE restarts.

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