Actor execution and debug modes

Image Added

Kepler actor, could be run in two main execution modes: JNI and 'standalone' and related debugger modes.

 Execution modes 

 JNI mode

User codes are run directly from an actor, within a Kepler process, using Java JNI mechanism.

 Standalone mode

When 'standalone' mode is set, Kepler runs an actor, as an independent system process, waiting only for its finish and produced outcomes.

'Standalone' mode uses more system resources (it is a separate system process!), however running actor in this mode may solve memory issues related with: insufficient memory owned by JVM or memory overriding (user code is run in separate memory space). 

More in details - when actor with is fired in 'standalone' mode:

• All actors files (user library, wrapper, standalone.exe) are copied to ~/public/KEPLEREXECUTION/<actor_dir> folder
• An input.txt file is created (it contains all actor inputs, like CPO/IDS meta descriptions, strings, primitives values, XML params strings, etc)
• A standalone C/Fortran executable  (<actor_name>.exe) is run. It:
  • reads input data from input.txt
  • calls actor wrapper (defined in FortranWrapper.f90)

Please notice that 'standalone' mode  is different from JNI execution:

• Actor is run separately (e.g. no preceding actors in w-f can affect its execution)
• User code is run from C/Fortran binary (in real case, in w-f, it is run by JNI)
• It is run with different memory settings as in real w-f execution

 Debugging a user code

Sequential codes

A user codes could be debugged using a chosen debugger in a way corresponding to execution modes described above. 

1. JNI/Attach - Debugger attaches to a running Kepler process:

   • User could debug what REALLY happens in w-f, including JNI calls, influence of previous actors, etc, etc...

   • Proces cannot be restarted. Stopping or killing the proces being debugged kills JVM. 
2. Standalone - debugger 'owning' executable  (<actor_name>.exe)  is started with as a separate process
   • The code being debugged is run in somehow 'artificial' environment that differs from (usually used) JNI mode of an actor 
   • No preceding actors in w-f can affect its execution so error related with memory issues usually cannot be reproduce

MPI codes

Debugging MPI codes is available only from commandline. User should go to an actor folder (~/public/KEPLEREXECUTION/<actor_dir>), and run  'mpiexec' providing appropriate debug options

An example:

mpiexec <debugger switch>  -np 2 ./<actor_name>_exe 

Unfortunately not only switches values differ regarding to MPI implementation, but also 'intel's' and 'gnu's' mpiexec behaves differently: under intel one it is impossible to restart an application that already finished...

Actor cache

...