[ModelicaSystem] only local omc process allowed

[syntron]

ModelicaSystem relies on read access to files and the possibility to execute the compiled model; thus, it only works if OMC is started locally

Use OMCProcessLocal to ensure that this requirement is defined

Based on PR #295

[adeas31]

Does this mean we can't use docker and wsl instances with ModelicaSystem? Is this just because if I/O permission issues?

[syntron]

Does this mean we can't use docker and wsl instances with ModelicaSystem? Is this just because if I/O permission issues?

@adeas31 no, the reason is that ModelicaSystem accesses the file system directly without using OMC (create csv file; read result data, etc.). Due to this, the class can only used locally ...

[syntron]

Here some more analyses:

ModelicaSystem(Cmd) are using Python functions to access files from the OMC model; if this code is replaced by calls to OMC, the ModelicaSystem classes would be completly independent from the use OMCSessionZMQ(OMCProcess) version used.

However, it would also mean, that some simple functionality is replaced by code which has to go through OMC in the case of a local usage - but it should be possible to abstract the access to the local filesystem! Thus, ModelicaSystem can be used for all systems for which OMCSessionZMQ is defined.

Use cases (line numbers based on master):

• pathlib.Path().exists() / pathlib.Path().is_file() / pathlib.is_dir()
  • L246 ModelicaSystemCmd.run() - check for *.bat file
  • L426 ModelicaSystem.init() - check if fileName exists
  • L486 ModelicaSystem.setTempDirectory() - check if dir exists + mkdir + check again
  • L543 ModelicaSystem.xmlparse() - check if *.xml file exists
  • L887 / L929 / L934 ModelicaSystem.simulate() - check if resultfile exists
  • L958 ModelicaSystem.getSolution() - check if resultfile exists
  • L1217 ModelicaSystem.convertMo2FMU() - check if file exists
  • L1234 ModelicaSystem.convertFMU2Mo() - check if file exists
  • L1332 / L1335 ModelicaSystem.linearize() - check if linearFile exists - python file!
  • => https://build.openmodelica.org/Documentation/OpenModelica.Scripting.regularFileExists.html
  • => https://build.openmodelica.org/Documentation/OpenModelica.Scripting.mkdir.html
  • => https://build.openmodelica.org/Documentation/OpenModelica.Scripting.directoryExists.html
• open(r)
  • L249 ModelicaSystemCmd.run() - open for *.bat file (read all content)
  • L546 ModelicaSystem.xmlparse() - read file via xml.etree.ElementTree - could be replaced by open() / write temp / read
  • => https://build.openmodelica.org/Documentation/OpenModelica.Scripting.readFile.html
• open(w)
  • L906 ModelicaSystem.simulate() - write overridefile
  • L1190 ModelicaSystem.createCSVData() - write csvfile
  • L1294 ModelicaSystem.linearize() - write overrideLinearFile
  • => https://build.openmodelica.org/Documentation/OpenModelica.Scripting.writeFile.html
• unlink
  • L930 ModelicaSystem.simulate() - remove resultfile from previous run
  • => https://build.openmodelica.org/Documentation/OpenModelica.Scripting.remove.html

[syntron]

Another big issue is the call to the executable in simulate() and linearize() using ModelicaSystemCmd(). A solution for this case is also needed - how to call / run the executable from the host within docker / wsl and also local?

[syntron]

Another point: if the model executeable is used, the evaluation of the library paths is done for Windows (using *.bat file). However, I never tested this part for linux (docker, wsl). How can we ensure, that the needed (external) libraries are found in this case?

[adeas31]

All of this filesystem access is needed because we are running the executable directly instead of using simulate api. This was an intentional change a while back to keep the control in OMPython. OMC might crash/hang during simulation so to have the control over the simulation we run the executable directly from OMPython.

The batch file is only needed in Windows to set the executable PATH so it can find all the dependencies. I think we don't need this in linux as it is handled automatically using rpath.

[syntron]

I think this is a quite good descission as it allows to run control the execution of the model in more detail; see also the possibility of running DoEs (see PR #312).

However, it also limits the usability of the class ModelicaSystem if it is not run locally, i.e. in docker or WSL. I do not know the history - was ModelicaSystem in the past useable via docker?

The linux case still needs to be tested (including external C libraries like SDF) ... currently I'm only able to run OMC in docker or on Windows.

[adeas31]

However, it also limits the usability of the class ModelicaSystem if it is not run locally, i.e. in docker or WSL. I do not know the history - was ModelicaSystem in the past useable via docker?

@arun3688 can you please comment on this? Is ModelicaSystem useable via docker?

Saw that docker test is skipped so I enabled it in PR #319. However, the test is very basic. We should try to enhance it to see if we can test model simulation using docker.

@syntron I am assuming that ModelicaSystem is always used locally, @arun3688 will confirm it, so this PR makes sense to restrict it to local process. For now I will review this PR as it is and we will see if we can fix #315 in future.

[adeas31]

LGTM.