hops::MHO_PythonSubprocessRunner Class Reference

Pure-C++ (no pybind, no libpython) helper that runs the user's python3 and exchanges JSON with it. This is the interprocess comms primitive used by the no-embed subprocess backends (control-file evaluation and default plotting). One process is spawned per action (no persistent worker!), which is slow and a lot of overhead, but this is ok for a fallback. More...

#include <MHO_PythonSubprocessRunner.hh>

Classes
struct	Result

Static Public Member Functions
static std::string	ResolveInterpreter ()
	Resolve the python interpreter to use: $HOPS_PYTHON, else "python3" (left for PATH resolution by the shell). More...
static std::string	ResolvePackageDir ()
	Install-prefix-relative directory holding the shipped hops_* python packages, resolved at runtime against GetHopsInstallPrefix() (or $HOPS_INSTALL). Empty if it cannot be determined. More...
static Result	RunModule (const std::string &module, const std::string &request_json)
	Run python -m <module> <request_file>, feeding the JSON request_json via a temp file, and capture stdout/stderr. The child's PYTHONPATH is prepended with ResolvePackageDir() so the shipped hops packages import cleanly. More...

Detailed Description

Pure-C++ (no pybind, no libpython) helper that runs the user's python3 and exchanges JSON with it. This is the interprocess comms primitive used by the no-embed subprocess backends (control-file evaluation and default plotting). One process is spawned per action (no persistent worker!), which is slow and a lot of overhead, but this is ok for a fallback.

Author

J. Barrett - barre.nosp@m.ttj@.nosp@m.mit.e.nosp@m.du

Implementation note: we use popen() (a unidirectional pipe) and pass the JSON request as a temp file given on the child's command line, reading the JSON response back off the child's stdout. This sidesteps the bidirectional-pipe deadlock concerns of a hand-rolled fork/exec while keeping the code small.

Interpreter discovery: $HOPS_PYTHON if set, else "python3" on PATH. Package discovery: the shipped pure-python hops_* packages are located via MHO_DirectoryInterface::GetHopsInstallPrefix() + the install-relative site subdir (baked in as HOPS_PYTHON_SITE_SUBDIR, matching hops_pypath.sh.in), and prepended to the child's PYTHONPATH so the default control/plot entry points are self-contained (no user pip install required).

Member Function Documentation

ResolveInterpreter()

std::string hops::MHO_PythonSubprocessRunner::ResolveInterpreter ( )

static

Resolve the python interpreter to use: $HOPS_PYTHON, else "python3" (left for PATH resolution by the shell).

ResolvePackageDir()

std::string hops::MHO_PythonSubprocessRunner::ResolvePackageDir ( )

static

Install-prefix-relative directory holding the shipped hops_* python packages, resolved at runtime against GetHopsInstallPrefix() (or $HOPS_INSTALL). Empty if it cannot be determined.

RunModule()

MHO_PythonSubprocessRunner::Result hops::MHO_PythonSubprocessRunner::RunModule ( const std::string &  module, const std::string &  request_json  )

static

Run python -m <module> <request_file>, feeding the JSON request_json via a temp file, and capture stdout/stderr. The child's PYTHONPATH is prepended with ResolvePackageDir() so the shipped hops packages import cleanly.

Parameters

module	python module to run with -m (e.g. "hops_control").
request_json	the JSON request payload written to the temp file.

Returns

Result with capture + exit status. spawned==false means the interpreter could not be launched at all.

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The documentation for this class was generated from the following files:

• MHO_PythonSubprocessRunner.hh
• MHO_PythonSubprocessRunner.cc