local_provisioner.py

"""Kernel Provisioner Classes"""
# Copyright (c) Jupyter Development Team.
# Distributed under the terms of the Modified BSD License.
import asyncio
import os
import signal
import sys
from typing import Any, Dict, List, Optional

from ..connect import KernelConnectionInfo, LocalPortCache
from ..launcher import launch_kernel
from ..localinterfaces import is_local_ip, local_ips
from .provisioner_base import KernelProvisionerBase


class LocalProvisioner(KernelProvisionerBase):  # type:ignore[misc]
    """
    :class:`LocalProvisioner` is a concrete class of ABC :py:class:`KernelProvisionerBase`
    and is the out-of-box default implementation used when no kernel provisioner is
    specified in the kernel specification (``kernel.json``).  It provides functional
    parity to existing applications by launching the kernel locally and using
    :class:`subprocess.Popen` to manage its lifecycle.

    This class is intended to be subclassed for customizing local kernel environments
    and serve as a reference implementation for other custom provisioners.
    """

    process = None
    _exit_future = None
    pid = None
    pgid = None
    ip = None
    ports_cached = False

    @property
    def has_process(self) -> bool:
        return self.process is not None

    async def poll(self) -> Optional[int]:
        """Poll the provisioner."""
        ret = 0
        if self.process:
            ret = self.process.poll()
        return ret

    async def wait(self) -> Optional[int]:
        """Wait for the provisioner process."""
        ret = 0
        if self.process:
            # Use busy loop at 100ms intervals, polling until the process is
            # not alive.  If we find the process is no longer alive, complete
            # its cleanup via the blocking wait().  Callers are responsible for
            # issuing calls to wait() using a timeout (see kill()).
            while await self.poll() is None:
                await asyncio.sleep(0.1)

            # Process is no longer alive, wait and clear
            ret = self.process.wait()
            # Make sure all the fds get closed.
            for attr in ['stdout', 'stderr', 'stdin']:
                fid = getattr(self.process, attr)
                if fid:
                    fid.close()
            self.process = None  # allow has_process to now return False
        return ret

    async def send_signal(self, signum: int) -> None:
        """Sends a signal to the process group of the kernel (this
        usually includes the kernel and any subprocesses spawned by
        the kernel).

        Note that since only SIGTERM is supported on Windows, we will
        check if the desired signal is for interrupt and apply the
        applicable code on Windows in that case.
        """
        if self.process:
            if signum == signal.SIGINT and sys.platform == 'win32':
                from ..win_interrupt import send_interrupt

                send_interrupt(self.process.win32_interrupt_event)
                return

            # Prefer process-group over process
            if self.pgid and hasattr(os, "killpg"):
                try:
                    os.killpg(self.pgid, signum)
                    return
                except OSError:
                    pass  # We'll retry sending the signal to only the process below

            # If we're here, send the signal to the process and let caller handle exceptions
            self.process.send_signal(signum)
            return

    async def kill(self, restart: bool = False) -> None:
        """Kill the provisioner and optionally restart."""
        if self.process:
            if hasattr(signal, "SIGKILL"):
                # If available, give preference to signalling the process-group over `kill()`.
                try:
                    await self.send_signal(signal.SIGKILL)
                    return
                except OSError:
                    pass
            try:
                self.process.kill()
            except OSError as e:
                LocalProvisioner._tolerate_no_process(e)

    async def terminate(self, restart: bool = False) -> None:
        """Terminate the provisioner and optionally restart."""
        if self.process:
            if hasattr(signal, "SIGTERM"):
                # If available, give preference to signalling the process group over `terminate()`.
                try:
                    await self.send_signal(signal.SIGTERM)
                    return
                except OSError:
                    pass
            try:
                self.process.terminate()
            except OSError as e:
                LocalProvisioner._tolerate_no_process(e)

    @staticmethod
    def _tolerate_no_process(os_error: OSError) -> None:
        # In Windows, we will get an Access Denied error if the process
        # has already terminated. Ignore it.
        if sys.platform == 'win32':
            if os_error.winerror != 5:
                raise
        # On Unix, we may get an ESRCH error (or ProcessLookupError instance) if
        # the process has already terminated. Ignore it.
        else:
            from errno import ESRCH

            if not isinstance(os_error, ProcessLookupError) or os_error.errno != ESRCH:
                raise

    async def cleanup(self, restart: bool = False) -> None:
        """Clean up the resources used by the provisioner and optionally restart."""
        if self.ports_cached and not restart:
            # provisioner is about to be destroyed, return cached ports
            lpc = LocalPortCache.instance()
            ports = (
                self.connection_info['shell_port'],
                self.connection_info['iopub_port'],
                self.connection_info['stdin_port'],
                self.connection_info['hb_port'],
                self.connection_info['control_port'],
            )
            for port in ports:
                lpc.return_port(port)

    async def pre_launch(self, **kwargs: Any) -> Dict[str, Any]:
        """Perform any steps in preparation for kernel process launch.

        This includes applying additional substitutions to the kernel launch command and env.
        It also includes preparation of launch parameters.

        Returns the updated kwargs.
        """

        # This should be considered temporary until a better division of labor can be defined.
        km = self.parent
        if km:
            if km.transport == 'tcp' and not is_local_ip(km.ip):
                msg = (
                    "Can only launch a kernel on a local interface. "
                    "This one is not: {}."
                    "Make sure that the '*_address' attributes are "
                    "configured properly. "
                    "Currently valid addresses are: {}".format(km.ip, local_ips())
                )
                raise RuntimeError(msg)
            # build the Popen cmd
            extra_arguments = kwargs.pop('extra_arguments', [])

            # write connection file / get default ports
            # TODO - change when handshake pattern is adopted
            if km.cache_ports and not self.ports_cached:
                lpc = LocalPortCache.instance()
                km.shell_port = lpc.find_available_port(km.ip)
                km.iopub_port = lpc.find_available_port(km.ip)
                km.stdin_port = lpc.find_available_port(km.ip)
                km.hb_port = lpc.find_available_port(km.ip)
                km.control_port = lpc.find_available_port(km.ip)
                self.ports_cached = True

            km.write_connection_file()
            self.connection_info = km.get_connection_info()

            kernel_cmd = km.format_kernel_cmd(
                extra_arguments=extra_arguments
            )  # This needs to remain here for b/c
        else:
            extra_arguments = kwargs.pop('extra_arguments', [])
            kernel_cmd = self.kernel_spec.argv + extra_arguments

        return await super().pre_launch(cmd=kernel_cmd, **kwargs)

    async def launch_kernel(self, cmd: List[str], **kwargs: Any) -> KernelConnectionInfo:
        """Launch a kernel with a command."""
        scrubbed_kwargs = LocalProvisioner._scrub_kwargs(kwargs)
        self.process = launch_kernel(cmd, **scrubbed_kwargs)
        pgid = None
        if hasattr(os, "getpgid"):
            try:
                pgid = os.getpgid(self.process.pid)
            except OSError:
                pass

        self.pid = self.process.pid
        self.pgid = pgid
        return self.connection_info

    @staticmethod
    def _scrub_kwargs(kwargs: Dict[str, Any]) -> Dict[str, Any]:
        """Remove any keyword arguments that Popen does not tolerate."""
        keywords_to_scrub: List[str] = ['extra_arguments', 'kernel_id']
        scrubbed_kwargs = kwargs.copy()
        for kw in keywords_to_scrub:
            scrubbed_kwargs.pop(kw, None)
        return scrubbed_kwargs

    async def get_provisioner_info(self) -> Dict:
        """Captures the base information necessary for persistence relative to this instance."""
        provisioner_info = await super().get_provisioner_info()
        provisioner_info.update({'pid': self.pid, 'pgid': self.pgid, 'ip': self.ip})
        return provisioner_info

    async def load_provisioner_info(self, provisioner_info: Dict) -> None:
        """Loads the base information necessary for persistence relative to this instance."""
        await super().load_provisioner_info(provisioner_info)
        self.pid = provisioner_info['pid']
        self.pgid = provisioner_info['pgid']
        self.ip = provisioner_info['ip']