Caching (In-Memory)

In Foresight Analytics Platform data caching and repository object caching are implemented to speed up work.

To cache data in Foresight Analytics Platform, In-Memory is applied. In-Memory is a subsystem that enables data loading from sources (cube caching), data local storage, quick multiuser access and high performance. Caching enables to avoid sending request each time the data sample from DBMS is required. The following repository objects support In-Memory caching:

To cache objects of various types, the various mechanisms speeding up access to objects and their work are developed. Description of object caching principles is given below.

In-Memory Data Caching

Data is stored in file cache. Cache stores values from definite point and coordinates identifying point binding to data source. Files containing the data currently in use are mapped to computer memory. Memory paging mechanism provides a possibility to work in limited RAM with almost unlimited size of data stored in files. In case of out-of-memory state, data loading/downloading is page-by-page.

When the In-Memory mechanism is used, a special structure with source data is loaded to RAM memory. Further data processing (creating data slice, filtering, aggregation, sorting, and so on) is executed in the RAM memory, without addressing data source. Thus, the platform response time is reduced and user work interactivity increases. Cache provides incremental data processing where if some cells are modified, then only related with those cells data is recalculated and not the whole source. On working user access permissions to data are taken into account. Data segments that are set up on creating a role model for Foresight Budgeting are also taken into account

In the desktop application, the cache management of separate objects is performed on the Cache tab of the Object Properties dialog box. BI server will apply data caching for objects which cache was enabled in the desktop application.

NOTE. Users that will work with cache must have read and write permissions to specified folders.

The caching mechanism settings are changed in the Settings.xml file or in registry. Settings are determined on client workstations if the desktop application is used, or at BI server.

After data is changed and saved, updated data will be in the cache of the computer used for work. To update cache on computers of other users of the Foresight Analytics Platform desktop application, click the Update Cache button on the Cache tab of the Object Properties dialog box. It is also possible to set up scheduled cache update on each user's computer using task scheduler.

Constraints and Features of Working

The current implementation has the following constraints and features when working with data caching:

Factors of In-Memory Cache Effectiveness Decrease

The list given below presents factors that can speed down work with cached data. In some cases, speeding down can be considerable:

Caching Repository Objects

On caching dictionary elements and time series database dictionaries the system creates temporary copies of the object containing element attribute values and links to the used objects on the user computer.

NOTE. Dictionary and time series database element cache is stored and used within the same repository connection.

Caching of dictionaries and time series database is intelligent and available for a number of users if they have similar access permissions and parameter values. It means that several copies of one object can be cached at a time (for example, for various parameter values).

Cache provides speeding up start of custom forms and execute application code on application projects work.

On compiling units/forms/assemblies (Fore or Fore.NET), a file cache, which stores a compiled object version, is created on the local drive. By default, cache is located in the user profile, in the subdirectory "\AppData\Local\Foresight\Foresight Analytics Platform\AsmCache<n>\Mod\<Repository ID>\<assembly number>\". If required, file cache storage path can be changed. To do it in the [HKEY_CURRENT_USER\Software\Foresight\Foresight Analytics Platform\9.0\9.2] registry branch create the CachefilePath string parameter and set up required path in it.

To speed up the first starting of application projects on an industrial scale, compiled objects of development environment can also be stored in the repository base. The Caching Assemblies on the Local Disk checkbox is used to control storing mode of compiled objects in the repository base. This checkbox is located in the Repository Parameters dialog box. On the first start compiled versions of objects are copied into the file cache. After that, the rest of the work is performed with file cache.

Possible Consequences

By default the Caching Assemblies on the Local Disk checkbox is deselected, the compiled version of object is saved both on the local disk and in the repository.

If different platform versions are used to work within the same repository, and the compiled assemblies are saved to the repository, one project can store forms and units compiled by different platform versions. This may cause errors like Access Violation or Internal Runtime Error, that occur, for example, when a form is started from another form compiled by other release of the Platform. These errors are caused by incompatibility of formats in different platform versions.

This may also slow down development process. On compiling objects on the same computer, their compiled versions are saved into the repository base. If these objects are used at the same time to work on another computer, local compiled versions and repository versions are compared. This will cause constant detecting of differences, which in turn will overload server because versions are constantly loaded the local disk and unloaded back to the repository base.

Solution

To avoid such consequences:

Select the Caching Assemblies on the Local Disk checkbox at the stage of project development
Delete complied assemblies from repository.

Recommendations

On developing application code, select the Caching Assemblies on the Local Disk checkbox. This will enable the user to work with code in different platform versions.
It is not recommended to select the Caching Assemblies on the Local Disk checkbox if the system is installed on the users' workstations belonged to a customer.
Remove compiled assemblies from the repository before commissioning the system to a customer. Then deselect the Caching Assemblies on the Local Disk checkbox and start users' forms to compile and save assemblies in the repository. The users' forms must be started with the platform version, which will be also installed at customer's place in the future. This will prevent compiling objects on decompressing and first starting of the system, as the previously compiled objects are loaded into the file cache.
In order not to prevent users from working in the system, when the system is developed for a customer, it is necessary to select the Caching Assemblies on the Local Disk checkbox on the workstations used for development.
Remember that a modified unit or form is saved when compiled from the development environment. After this it cannot be guaranteed that a previous platform version can open the saved unit or form.
Developed units and forms are recommended to be arranged and stored inside the assemblies. This reduces the number of created cache files that reduces the number of file system calls and speeds up start of cached objects.
Selection or deselection of the Caching Assemblies on the Local Disk checkbox does not slow down general development process, as in any case file cache is used at the start. This checkbox can have influence only at the first start and decompressing of a new version of application on the customer's computers.

On caching of regular report instances of an object are created, which are opened with certain parameter values. On opening an object with some parameters the cache is checked for availability of a record corresponding to these parameters. If such a record is found, cached object version is extracted and opened. If no record is found for the specified parameters, the last object version is opened from the repository. All the objects, on which this object depends, are also opened. Instance cache of the regular report is stored in repository base. Caching is managed in the Object Cache dialog box.

To speed up map rendering in reports, maps are cached. On opening the report, it is checked whether its cache contains a map. If the map is found in cache, the cached map will be shown in the report. If there is no map in cache, the repository map opens, and cache will be refreshed.

If there are several connections to the same repository, one common cache with maps will be used for all connections. On closing all connections, cache of maps is cleared.

On selecting object view in object navigator as large icons images are cached for preview. Icon caching is used only for reports created by means of the Dashboards, Analytical Queries (OLAP), Reports, Time Series Analysis tools.

Caching In Web Application

On Foresight Analytics Platform working, extraction and storage of data required for web application running is made in the BI server memory. The system can be also expanded by introducing additional (more performing) BI servers with function of data extracting and caching from repository base. BI server with web application will request those BI servers and get the flow with required data without additional request of DBMS.

In the registry or in the settings.xml it is required to fill in the Service section. This section contains addresses of removed BI servers and repository settings for which the specified data caching scheme is applied.

NOTE. The specified caching mode is relevant only for the subjects for which caching is enabled in repository.

Cache Clearing

To clear dictionary and time series database cache, select the Clear Cache item in the Tools menu in the object navigator.

To clear development environment object cache, select the Repository > Clear Assembly Cache item of security manager.

To clear data cache of different objects, click the Clear Cache item on the Cache tab of the Object properties window.

To clear repository cache, select the Clear Cache item in the Tools main menu of the object navigator.