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Content Application Developer Manual / Version 2406.0

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5.7 Managed Properties

In this section, you will find tables with several important properties and actions manageable via JMX.

File System Transformed Image Blob Cache

This is a file system cache where the results of image transformations are persisted in a dedicated directory and can survive CAE restarts. Internally it is represented as two subfolders "new" and "old". Transformed images are written to the "new" folder until it exceeds NewGenerationCacheSize. When that happens, the "new" folder is renamed to "old", and a new "new" folder is created. The process of renaming the "new" folder to "old" is called a rotation. If the "old" folder is not empty at rotation, than its files are regarded to be obsolete and get deleted. During a cache lookup, a content is first searched for in the "new" folder. If it not found there, the "old" folder is searched instead. In case it exists in "old", it is regarded to be "still needed" and moved back to the "new" folder (recalled from "old").

The content of both the "old" and the "new" folder are kept across system restarts.

The JMX attributes Level, NewGenerationLevel and OldGenerationLevel show how much data is stored in bytes in the whole cache and its "new" and "old" subfolders at a certain point of time. They correspond to the values of internal counters and are also written every 5 seconds to "level.txt" files residing in the "new" and "old" folders. Upon restart, the internal counters are initialized from these files.

Note

Note

It is possible to manipulate "level.txt" files, or the values of internal counters by setting JMX attributes NewGenerationLevel and OldGenerationLevel, as well as manually delete some cached image blob files. Make sure you know what you are doing when performing such manipulations and take care to restore consistency between the physical size of "new" and "old" folders, the state of internal counters and the values persisted in "level.txt".

The following table shows the relevant JMX attributes. They are also documented in the Javadoc of TransformedBlobCacheManager.

Attribute Type Description

BasePath

Read-only The configured path used to store cache files.

CacheSize

Read/Write The maximum allowed cache size in bytes for the whole cache consisting of two generation folders "new" and "old". The cache level of both generations is rarely higher and typically significantly lower than this value. 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 this value.

NewGenerationCacheSize

Read-only Cache size of the new generation in bytes, that is, the size at which the new generation gets rotated into the old generation. The size of new generation is hard-coded to be exactly one half of the value of CacheSize. Note that the file system overhead for storing the files does not count towards this value.

Level

Read-only The cache level in bytes as a sum of files in the new generation and old generation folders. The value of level is the sum of NewGenerationLevel and OldGenerationLevel. Note that the file system overhead for storing the files does not count towards this value.

NewGenerationLevel

Read/Write The cache level of the new generation in bytes, that is, the total size of all files in the new generation. Note that the file system overhead for storing the files does not count towards this value.

OldGenerationLevel

Read/Write The cache level of the old generation in bytes, that is, the total size of all files in the old generation.

RotateCount

Read-only The count of rotate operations since system start.

AccessCount

Read-only The count of blob accesses since system start.

RecallCount

Read-only The count of recalls since system start. During a recall, a blob is recovered from the old generation and moved back into the new generation.

FaultCount

Read-only The count of faults since system start. During a fault, a blob is computed and put into the new generation.

RecallSizeSum

Read-only The sum of sizes in bytes of all blobs recalled since system start. During a recall, a blob is recovered from the old generation and moved back into the new generation.

FaultSizeSum

Read-only The sum of sizes in bytes of all blobs faulted since system start. During a fault, a blob is computed and put into the new generation.

InitialLevel

Read-only The initial cache level for the whole cache consisting of two generation folders "new" and "old". Note that the file system overhead for storing the files does not count towards this value.

NewGenerationInitialLevel

Read-only The initial cache level of the new generation at system start, that is, the total size of all files in the new generation. Note that the file system overhead for storing the files does not count towards this value.

OldGenerationInitialLevel

Read-only The initial cache level of the old generation at system start, that is, the total size of all files in the old generation. Note that the file system overhead for storing the files does not count towards this value.

StartTime

Read-only The time of the system start in milliseconds since the Epoch.

Uptime

Read-only Uptime of the cache in milliseconds.

Table 5.13. TransformedBlobCacheManager attributes


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