LTS (Long term support mechanism)
The FX data exchange format between Flux and e.g. RA control creates the need of a mechanism to avoid issues if the compatibility gets compromised. The situation is:
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Customers update their desktop software quite frequently but don’t want to update the machine. We will have different FX versions between Flux and RA.
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FX is a self descriptive data format where additional data could be added without a compatibility issue. The only problem comes if we change the interpretation of the data / data format but the FX format is already quite mature.
In order to allow the customer to run different versions of RA and Flux, a stepping mechanism is introduced from Flux build 602 and RA 182.
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We start with stepping version 1 in all systems
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We increase the stepping version in case we need to do an incompatible change in the FX format.
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Flux checks the stepping version while loading a FX file. If it is identical or lower, then the file could be loaded without issues
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If Flux identifies that a file has a higher stepping version then it will raise Flux.APIException with VersionMismatch code. RA catches the exception, checks the code and tries to call an external downgrade application "Flux.Stepper.exe" which is located in the binary folder of RA. It will save a fx file with a lower stepping version and can be loaded into RA.
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External application takes 3 arguments which are source fx file, target fx file name and target stepping version.
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External application can contain different version of Flux.API than the one installed in the machine and can be installed at any location. In that case, environmental variable FLUXSTEPPER should be set to the directory containing Flux.Stepper.exe.
This means that if we need to introduce a new stepping version we will deliver to all customers this Flux.Stepper.exe which could be installed instead of upgrading the machine.
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If the build version of Flux and RA is different but the stepping version is identical we will not display a warning message.
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If the stepping downgrader gets executed we will display a warning message in RA that we are using an external application to downgrade the fx file.