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"""A base class session manager."""
# Copyright (c) Jupyter Development Team.
# Distributed under the terms of the Modified BSD License.
import os
import pathlib
import uuid
from typing import Any, Dict, List, NewType, Optional, Union, cast
KernelName = NewType("KernelName", str)
ModelName = NewType("ModelName", str)
try:
import sqlite3
except ImportError:
# fallback on pysqlite2 if Python was build without sqlite
from pysqlite2 import dbapi2 as sqlite3 # type:ignore[no-redef]
from dataclasses import dataclass, fields
from jupyter_core.utils import ensure_async
from tornado import web
from traitlets import Instance, TraitError, Unicode, validate
from traitlets.config.configurable import LoggingConfigurable
from jupyter_server.traittypes import InstanceFromClasses
class KernelSessionRecordConflict(Exception):
"""Exception class to use when two KernelSessionRecords cannot
merge because of conflicting data.
"""
@dataclass
class KernelSessionRecord:
"""A record object for tracking a Jupyter Server Kernel Session.
Two records that share a session_id must also share a kernel_id, while
kernels can have multiple session (and thereby) session_ids
associated with them.
"""
session_id: Optional[str] = None
kernel_id: Optional[str] = None
def __eq__(self, other: object) -> bool:
"""Whether a record equals another."""
if isinstance(other, KernelSessionRecord):
condition1 = self.kernel_id and self.kernel_id == other.kernel_id
condition2 = all(
[
self.session_id == other.session_id,
self.kernel_id is None or other.kernel_id is None,
]
)
if any([condition1, condition2]):
return True
# If two records share session_id but have different kernels, this is
# and ill-posed expression. This should never be true. Raise an exception
# to inform the user.
if all(
[
self.session_id,
self.session_id == other.session_id,
self.kernel_id != other.kernel_id,
]
):
msg = (
"A single session_id can only have one kernel_id "
"associated with. These two KernelSessionRecords share the same "
"session_id but have different kernel_ids. This should "
"not be possible and is likely an issue with the session "
"records."
)
raise KernelSessionRecordConflict(msg)
return False
def update(self, other: "KernelSessionRecord") -> None:
"""Updates in-place a kernel from other (only accepts positive updates"""
if not isinstance(other, KernelSessionRecord):
msg = "'other' must be an instance of KernelSessionRecord." # type:ignore[unreachable]
raise TypeError(msg)
if other.kernel_id and self.kernel_id and other.kernel_id != self.kernel_id:
msg = "Could not update the record from 'other' because the two records conflict."
raise KernelSessionRecordConflict(msg)
for field in fields(self):
if hasattr(other, field.name) and getattr(other, field.name):
setattr(self, field.name, getattr(other, field.name))
class KernelSessionRecordList:
"""An object for storing and managing a list of KernelSessionRecords.
When adding a record to the list, the KernelSessionRecordList
first checks if the record already exists in the list. If it does,
the record will be updated with the new information; otherwise,
it will be appended.
"""
_records: List[KernelSessionRecord]
def __init__(self, *records: KernelSessionRecord):
"""Initialize a record list."""
self._records = []
for record in records:
self.update(record)
def __str__(self):
"""The string representation of a record list."""
return str(self._records)
def __contains__(self, record: Union[KernelSessionRecord, str]) -> bool:
"""Search for records by kernel_id and session_id"""
if isinstance(record, KernelSessionRecord) and record in self._records:
return True
if isinstance(record, str):
for r in self._records:
if record in [r.session_id, r.kernel_id]:
return True
return False
def __len__(self):
"""The length of the record list."""
return len(self._records)
def get(self, record: Union[KernelSessionRecord, str]) -> KernelSessionRecord:
"""Return a full KernelSessionRecord from a session_id, kernel_id, or
incomplete KernelSessionRecord.
"""
if isinstance(record, str):
for r in self._records:
if record in (r.kernel_id, r.session_id):
return r
elif isinstance(record, KernelSessionRecord):
for r in self._records:
if record == r:
return record
msg = f"{record} not found in KernelSessionRecordList."
raise ValueError(msg)
def update(self, record: KernelSessionRecord) -> None:
"""Update a record in-place or append it if not in the list."""
try:
idx = self._records.index(record)
self._records[idx].update(record)
except ValueError:
self._records.append(record)
def remove(self, record: KernelSessionRecord) -> None:
"""Remove a record if its found in the list. If it's not found,
do nothing.
"""
if record in self._records:
self._records.remove(record)
class SessionManager(LoggingConfigurable):
"""A session manager."""
database_filepath = Unicode(
default_value=":memory:",
help=(
"The filesystem path to SQLite Database file "
"(e.g. /path/to/session_database.db). By default, the session "
"database is stored in-memory (i.e. `:memory:` setting from sqlite3) "
"and does not persist when the current Jupyter Server shuts down."
),
).tag(config=True)
@validate("database_filepath")
def _validate_database_filepath(self, proposal):
"""Validate a database file path."""
value = proposal["value"]
if value == ":memory:":
return value
path = pathlib.Path(value)
if path.exists():
# Verify that the database path is not a directory.
if path.is_dir():
msg = "`database_filepath` expected a file path, but the given path is a directory."
raise TraitError(msg)
# Verify that database path is an SQLite 3 Database by checking its header.
with open(value, "rb") as f:
header = f.read(100)
if not header.startswith(b"SQLite format 3") and header != b"":
msg = "The given file is not an SQLite database file."
raise TraitError(msg)
return value
kernel_manager = Instance("jupyter_server.services.kernels.kernelmanager.MappingKernelManager")
contents_manager = InstanceFromClasses(
[
"jupyter_server.services.contents.manager.ContentsManager",
"notebook.services.contents.manager.ContentsManager",
]
)
def __init__(self, *args, **kwargs):
"""Initialize a record list."""
super().__init__(*args, **kwargs)
self._pending_sessions = KernelSessionRecordList()
# Session database initialized below
_cursor = None
_connection = None
_columns = {"session_id", "path", "name", "type", "kernel_id"}
@property
def cursor(self):
"""Start a cursor and create a database called 'session'"""
if self._cursor is None:
self._cursor = self.connection.cursor()
self._cursor.execute(
"""CREATE TABLE IF NOT EXISTS session
(session_id, path, name, type, kernel_id)"""
)
return self._cursor
@property
def connection(self):
"""Start a database connection"""
if self._connection is None:
# Set isolation level to None to autocommit all changes to the database.
self._connection = sqlite3.connect(self.database_filepath, isolation_level=None)
self._connection.row_factory = sqlite3.Row
return self._connection
def close(self):
"""Close the sqlite connection"""
if self._cursor is not None:
self._cursor.close()
self._cursor = None
def __del__(self):
"""Close connection once SessionManager closes"""
self.close()
async def session_exists(self, path):
"""Check to see if the session of a given name exists"""
exists = False
self.cursor.execute("SELECT * FROM session WHERE path=?", (path,))
row = self.cursor.fetchone()
if row is not None:
# Note, although we found a row for the session, the associated kernel may have
# been culled or died unexpectedly. If that's the case, we should delete the
# row, thereby terminating the session. This can be done via a call to
# row_to_model that tolerates that condition. If row_to_model returns None,
# we'll return false, since, at that point, the session doesn't exist anyway.
model = await self.row_to_model(row, tolerate_culled=True)
if model is not None:
exists = True
return exists
def new_session_id(self) -> str:
"""Create a uuid for a new session"""
return str(uuid.uuid4())
async def create_session(
self,
path: Optional[str] = None,
name: Optional[ModelName] = None,
type: Optional[str] = None,
kernel_name: Optional[KernelName] = None,
kernel_id: Optional[str] = None,
) -> Dict[str, Any]:
"""Creates a session and returns its model
Parameters
----------
name: ModelName(str)
Usually the model name, like the filename associated with current
kernel.
"""
session_id = self.new_session_id()
record = KernelSessionRecord(session_id=session_id)
self._pending_sessions.update(record)
if kernel_id is not None and kernel_id in self.kernel_manager:
pass
else:
kernel_id = await self.start_kernel_for_session(
session_id, path, name, type, kernel_name
)
record.kernel_id = kernel_id
self._pending_sessions.update(record)
result = await self.save_session(
session_id, path=path, name=name, type=type, kernel_id=kernel_id
)
self._pending_sessions.remove(record)
return cast(Dict[str, Any], result)
def get_kernel_env(
self, path: Optional[str], name: Optional[ModelName] = None
) -> Dict[str, str]:
"""Return the environment variables that need to be set in the kernel
Parameters
----------
path : str
the url path for the given session.
name: ModelName(str), optional
Here the name is likely to be the name of the associated file
with the current kernel at startup time.
"""
if name is not None:
cwd = self.kernel_manager.cwd_for_path(path)
path = os.path.join(cwd, name)
assert isinstance(path, str)
return {**os.environ, "JPY_SESSION_NAME": path}
async def start_kernel_for_session(
self,
session_id: str,
path: Optional[str],
name: Optional[ModelName],
type: Optional[str],
kernel_name: Optional[KernelName],
) -> str:
"""Start a new kernel for a given session.
Parameters
----------
session_id : str
uuid for the session; this method must be given a session_id
path : str
the path for the given session - seem to be a session id sometime.
name : str
Usually the model name, like the filename associated with current
kernel.
type : str
the type of the session
kernel_name : str
the name of the kernel specification to use. The default kernel name will be used if not provided.
"""
# allow contents manager to specify kernels cwd
kernel_path = await ensure_async(self.contents_manager.get_kernel_path(path=path))
kernel_env = self.get_kernel_env(path, name)
kernel_id = await self.kernel_manager.start_kernel(
path=kernel_path,
kernel_name=kernel_name,
env=kernel_env,
)
return cast(str, kernel_id)
async def save_session(self, session_id, path=None, name=None, type=None, kernel_id=None):
"""Saves the items for the session with the given session_id
Given a session_id (and any other of the arguments), this method
creates a row in the sqlite session database that holds the information
for a session.
Parameters
----------
session_id : str
uuid for the session; this method must be given a session_id
path : str
the path for the given session
name : str
the name of the session
type : str
the type of the session
kernel_id : str
a uuid for the kernel associated with this session
Returns
-------
model : dict
a dictionary of the session model
"""
self.cursor.execute(
"INSERT INTO session VALUES (?,?,?,?,?)",
(session_id, path, name, type, kernel_id),
)
result = await self.get_session(session_id=session_id)
return result
async def get_session(self, **kwargs):
"""Returns the model for a particular session.
Takes a keyword argument and searches for the value in the session
database, then returns the rest of the session's info.
Parameters
----------
**kwargs : dict
must be given one of the keywords and values from the session database
(i.e. session_id, path, name, type, kernel_id)
Returns
-------
model : dict
returns a dictionary that includes all the information from the
session described by the kwarg.
"""
if not kwargs:
msg = "must specify a column to query"
raise TypeError(msg)
conditions = []
for column in kwargs:
if column not in self._columns:
msg = f"No such column: {column}"
raise TypeError(msg)
conditions.append("%s=?" % column)
query = "SELECT * FROM session WHERE %s" % (" AND ".join(conditions)) # noqa: S608
self.cursor.execute(query, list(kwargs.values()))
try:
row = self.cursor.fetchone()
except KeyError:
# The kernel is missing, so the session just got deleted.
row = None
if row is None:
q = []
for key, value in kwargs.items():
q.append(f"{key}={value!r}")
raise web.HTTPError(404, "Session not found: %s" % (", ".join(q)))
try:
model = await self.row_to_model(row)
except KeyError as e:
raise web.HTTPError(404, "Session not found: %s" % str(e)) from e
return model
async def update_session(self, session_id, **kwargs):
"""Updates the values in the session database.
Changes the values of the session with the given session_id
with the values from the keyword arguments.
Parameters
----------
session_id : str
a uuid that identifies a session in the sqlite3 database
**kwargs : str
the key must correspond to a column title in session database,
and the value replaces the current value in the session
with session_id.
"""
await self.get_session(session_id=session_id)
if not kwargs:
# no changes
return
sets = []
for column in kwargs:
if column not in self._columns:
raise TypeError("No such column: %r" % column)
sets.append("%s=?" % column)
query = "UPDATE session SET %s WHERE session_id=?" % (", ".join(sets)) # noqa: S608
self.cursor.execute(query, [*list(kwargs.values()), session_id])
if hasattr(self.kernel_manager, "update_env"):
self.cursor.execute(
"SELECT path, name, kernel_id FROM session WHERE session_id=?", [session_id]
)
path, name, kernel_id = self.cursor.fetchone()
self.kernel_manager.update_env(kernel_id=kernel_id, env=self.get_kernel_env(path, name))
async def kernel_culled(self, kernel_id: str) -> bool:
"""Checks if the kernel is still considered alive and returns true if its not found."""
return kernel_id not in self.kernel_manager
async def row_to_model(self, row, tolerate_culled=False):
"""Takes sqlite database session row and turns it into a dictionary"""
kernel_culled: bool = await ensure_async(self.kernel_culled(row["kernel_id"]))
if kernel_culled:
# The kernel was culled or died without deleting the session.
# We can't use delete_session here because that tries to find
# and shut down the kernel - so we'll delete the row directly.
#
# If caller wishes to tolerate culled kernels, log a warning
# and return None. Otherwise, raise KeyError with a similar
# message.
self.cursor.execute("DELETE FROM session WHERE session_id=?", (row["session_id"],))
msg = (
"Kernel '{kernel_id}' appears to have been culled or died unexpectedly, "
"invalidating session '{session_id}'. The session has been removed.".format(
kernel_id=row["kernel_id"], session_id=row["session_id"]
)
)
if tolerate_culled:
self.log.warning(f"{msg} Continuing...")
return None
raise KeyError(msg)
kernel_model = await ensure_async(self.kernel_manager.kernel_model(row["kernel_id"]))
model = {
"id": row["session_id"],
"path": row["path"],
"name": row["name"],
"type": row["type"],
"kernel": kernel_model,
}
if row["type"] == "notebook":
# Provide the deprecated API.
model["notebook"] = {"path": row["path"], "name": row["name"]}
return model
async def list_sessions(self):
"""Returns a list of dictionaries containing all the information from
the session database"""
c = self.cursor.execute("SELECT * FROM session")
result = []
# We need to use fetchall() here, because row_to_model can delete rows,
# which messes up the cursor if we're iterating over rows.
for row in c.fetchall():
try:
model = await self.row_to_model(row)
result.append(model)
except KeyError:
pass
return result
async def delete_session(self, session_id):
"""Deletes the row in the session database with given session_id"""
record = KernelSessionRecord(session_id=session_id)
self._pending_sessions.update(record)
session = await self.get_session(session_id=session_id)
await ensure_async(self.kernel_manager.shutdown_kernel(session["kernel"]["id"]))
self.cursor.execute("DELETE FROM session WHERE session_id=?", (session_id,))
self._pending_sessions.remove(record)
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