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1"""Kernel Provisioner Classes"""
3# Copyright (c) Jupyter Development Team.
4# Distributed under the terms of the Modified BSD License.
5import os
6from abc import ABC, ABCMeta, abstractmethod
7from typing import Any, Union
9from traitlets.config import Instance, LoggingConfigurable, Unicode
11from ..connect import KernelConnectionInfo
14class KernelProvisionerMeta(ABCMeta, type(LoggingConfigurable)): # type: ignore[misc]
15 pass
18class KernelProvisionerBase(ABC, LoggingConfigurable, metaclass=KernelProvisionerMeta): # type: ignore[metaclass]
19 """
20 Abstract base class defining methods for KernelProvisioner classes.
22 A majority of methods are abstract (requiring implementations via a subclass) while
23 some are optional and others provide implementations common to all instances.
24 Subclasses should be aware of which methods require a call to the superclass.
26 Many of these methods model those of :class:`subprocess.Popen` for parity with
27 previous versions where the kernel process was managed directly.
28 """
30 # The kernel specification associated with this provisioner
31 kernel_spec: Any = Instance("jupyter_client.kernelspec.KernelSpec", allow_none=True)
32 kernel_id: Union[str, Unicode] = Unicode(None, allow_none=True)
33 connection_info: KernelConnectionInfo = {}
35 @property
36 @abstractmethod
37 def has_process(self) -> bool:
38 """
39 Returns true if this provisioner is currently managing a process.
41 This property is asserted to be True immediately following a call to
42 the provisioner's :meth:`launch_kernel` method.
43 """
44 pass
46 @abstractmethod
47 async def poll(self) -> int | None:
48 """
49 Checks if kernel process is still running.
51 If running, None is returned, otherwise the process's integer-valued exit code is returned.
52 This method is called from :meth:`KernelManager.is_alive`.
53 """
54 pass
56 @abstractmethod
57 async def wait(self) -> int | None:
58 """
59 Waits for kernel process to terminate.
61 This method is called from `KernelManager.finish_shutdown()` and
62 `KernelManager.kill_kernel()` when terminating a kernel gracefully or
63 immediately, respectively.
64 """
65 pass
67 @abstractmethod
68 async def send_signal(self, signum: int) -> None:
69 """
70 Sends signal identified by signum to the kernel process.
72 This method is called from `KernelManager.signal_kernel()` to send the
73 kernel process a signal.
74 """
75 pass
77 @abstractmethod
78 async def kill(self, restart: bool = False) -> None:
79 """
80 Kill the kernel process.
82 This is typically accomplished via a SIGKILL signal, which cannot be caught.
83 This method is called from `KernelManager.kill_kernel()` when terminating
84 a kernel immediately.
86 restart is True if this operation will precede a subsequent launch_kernel request.
87 """
88 pass
90 @abstractmethod
91 async def terminate(self, restart: bool = False) -> None:
92 """
93 Terminates the kernel process.
95 This is typically accomplished via a SIGTERM signal, which can be caught, allowing
96 the kernel provisioner to perform possible cleanup of resources. This method is
97 called indirectly from `KernelManager.finish_shutdown()` during a kernel's
98 graceful termination.
100 restart is True if this operation precedes a start launch_kernel request.
101 """
102 pass
104 @abstractmethod
105 async def launch_kernel(self, cmd: list[str], **kwargs: Any) -> KernelConnectionInfo:
106 """
107 Launch the kernel process and return its connection information.
109 This method is called from `KernelManager.launch_kernel()` during the
110 kernel manager's start kernel sequence.
111 """
112 pass
114 @abstractmethod
115 async def cleanup(self, restart: bool = False) -> None:
116 """
117 Cleanup any resources allocated on behalf of the kernel provisioner.
119 This method is called from `KernelManager.cleanup_resources()` as part of
120 its shutdown kernel sequence.
122 restart is True if this operation precedes a start launch_kernel request.
123 """
124 pass
126 async def shutdown_requested(self, restart: bool = False) -> None:
127 """
128 Allows the provisioner to determine if the kernel's shutdown has been requested.
130 This method is called from `KernelManager.request_shutdown()` as part of
131 its shutdown sequence.
133 This method is optional and is primarily used in scenarios where the provisioner
134 may need to perform other operations in preparation for a kernel's shutdown.
135 """
136 pass
138 async def pre_launch(self, **kwargs: Any) -> dict[str, Any]:
139 """
140 Perform any steps in preparation for kernel process launch.
142 This includes applying additional substitutions to the kernel launch command
143 and environment. It also includes preparation of launch parameters.
145 NOTE: Subclass implementations are advised to call this method as it applies
146 environment variable substitutions from the local environment and calls the
147 provisioner's :meth:`_finalize_env()` method to allow each provisioner the
148 ability to cleanup the environment variables that will be used by the kernel.
150 This method is called from `KernelManager.pre_start_kernel()` as part of its
151 start kernel sequence.
153 Returns the (potentially updated) keyword arguments that are passed to
154 :meth:`launch_kernel()`.
155 """
156 env = kwargs.pop("env", os.environ).copy()
157 env.update(self.__apply_env_substitutions(env))
158 self._finalize_env(env)
159 kwargs["env"] = env
161 return kwargs
163 async def post_launch(self, **kwargs: Any) -> None:
164 """
165 Perform any steps following the kernel process launch.
167 This method is called from `KernelManager.post_start_kernel()` as part of its
168 start kernel sequence.
169 """
170 pass
172 async def get_provisioner_info(self) -> dict[str, Any]:
173 """
174 Captures the base information necessary for persistence relative to this instance.
176 This enables applications that subclass `KernelManager` to persist a kernel provisioner's
177 relevant information to accomplish functionality like disaster recovery or high availability
178 by calling this method via the kernel manager's `provisioner` attribute.
180 NOTE: The superclass method must always be called first to ensure proper serialization.
181 """
182 provisioner_info: dict[str, Any] = {}
183 provisioner_info["kernel_id"] = self.kernel_id
184 provisioner_info["connection_info"] = self.connection_info
185 return provisioner_info
187 async def load_provisioner_info(self, provisioner_info: dict) -> None:
188 """
189 Loads the base information necessary for persistence relative to this instance.
191 The inverse of `get_provisioner_info()`, this enables applications that subclass
192 `KernelManager` to re-establish communication with a provisioner that is managing
193 a (presumably) remote kernel from an entirely different process that the original
194 provisioner.
196 NOTE: The superclass method must always be called first to ensure proper deserialization.
197 """
198 self.kernel_id = provisioner_info["kernel_id"]
199 self.connection_info = provisioner_info["connection_info"]
201 def get_shutdown_wait_time(self, recommended: float = 5.0) -> float:
202 """
203 Returns the time allowed for a complete shutdown. This may vary by provisioner.
205 This method is called from `KernelManager.finish_shutdown()` during the graceful
206 phase of its kernel shutdown sequence.
208 The recommended value will typically be what is configured in the kernel manager.
209 """
210 return recommended
212 def get_stable_start_time(self, recommended: float = 10.0) -> float:
213 """
214 Returns the expected upper bound for a kernel (re-)start to complete.
215 This may vary by provisioner.
217 The recommended value will typically be what is configured in the kernel restarter.
218 """
219 return recommended
221 def _finalize_env(self, env: dict[str, str]) -> None:
222 """
223 Ensures env is appropriate prior to launch.
225 This method is called from `KernelProvisionerBase.pre_launch()` during the kernel's
226 start sequence.
228 NOTE: Subclasses should be sure to call super()._finalize_env(env)
229 """
230 if self.kernel_spec.language and self.kernel_spec.language.lower().startswith("python"):
231 # Don't allow PYTHONEXECUTABLE to be passed to kernel process.
232 # If set, it can bork all the things.
233 env.pop("PYTHONEXECUTABLE", None)
235 def __apply_env_substitutions(self, substitution_values: dict[str, str]) -> dict[str, str]:
236 """
237 Walks entries in the kernelspec's env stanza and applies substitutions from current env.
239 This method is called from `KernelProvisionerBase.pre_launch()` during the kernel's
240 start sequence.
242 Returns the substituted list of env entries.
244 NOTE: This method is private and is not intended to be overridden by provisioners.
245 """
246 substituted_env = {}
247 if self.kernel_spec:
248 from string import Template
250 # For each templated env entry, fill any templated references
251 # matching names of env variables with those values and build
252 # new dict with substitutions.
253 templated_env = self.kernel_spec.env
254 for k, v in templated_env.items():
255 substituted_env.update({k: Template(v).safe_substitute(substitution_values)})
256 return substituted_env