mirror of
https://github.com/aykhans/AzSuicideDataVisualization.git
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272 lines
8.6 KiB
Python
272 lines
8.6 KiB
Python
# Copyright 2018-2022 Streamlit Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import hashlib
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from typing import MutableMapping, Dict, Optional, TYPE_CHECKING, List
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from weakref import WeakKeyDictionary
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from streamlit import config
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from streamlit import util
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from streamlit.logger import get_logger
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from streamlit.proto.ForwardMsg_pb2 import ForwardMsg
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from streamlit.stats import CacheStatsProvider, CacheStat
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if TYPE_CHECKING:
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from streamlit.app_session import AppSession
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LOGGER = get_logger(__name__)
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def populate_hash_if_needed(msg: ForwardMsg) -> str:
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"""Computes and assigns the unique hash for a ForwardMsg.
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If the ForwardMsg already has a hash, this is a no-op.
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Parameters
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----------
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msg : ForwardMsg
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Returns
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-------
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string
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The message's hash, returned here for convenience. (The hash
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will also be assigned to the ForwardMsg; callers do not need
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to do this.)
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"""
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if msg.hash == "":
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# Move the message's metadata aside. It's not part of the
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# hash calculation.
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metadata = msg.metadata
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msg.ClearField("metadata")
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# MD5 is good enough for what we need, which is uniqueness.
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hasher = hashlib.md5()
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hasher.update(msg.SerializeToString())
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msg.hash = hasher.hexdigest()
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# Restore metadata.
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msg.metadata.CopyFrom(metadata)
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return msg.hash
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def create_reference_msg(msg: ForwardMsg) -> ForwardMsg:
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"""Create a ForwardMsg that refers to the given message via its hash.
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The reference message will also get a copy of the source message's
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metadata.
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Parameters
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----------
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msg : ForwardMsg
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The ForwardMsg to create the reference to.
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Returns
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-------
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ForwardMsg
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A new ForwardMsg that "points" to the original message via the
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ref_hash field.
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"""
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ref_msg = ForwardMsg()
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ref_msg.ref_hash = populate_hash_if_needed(msg)
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ref_msg.metadata.CopyFrom(msg.metadata)
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return ref_msg
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class ForwardMsgCache(CacheStatsProvider):
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"""A cache of ForwardMsgs.
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Large ForwardMsgs (e.g. those containing big DataFrame payloads) are
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stored in this cache. The server can choose to send a ForwardMsg's hash,
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rather than the message itself, to a client. Clients can then
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request messages from this cache via another endpoint.
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This cache is *not* thread safe. It's intended to only be accessed by
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the server thread.
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"""
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class Entry:
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"""Cache entry.
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Stores the cached message, and the set of AppSessions
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that we've sent the cached message to.
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"""
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def __init__(self, msg: ForwardMsg):
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self.msg = msg
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self._session_script_run_counts: MutableMapping[
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"AppSession", int
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] = WeakKeyDictionary()
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def __repr__(self) -> str:
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return util.repr_(self)
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def add_session_ref(self, session: "AppSession", script_run_count: int) -> None:
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"""Adds a reference to a AppSession that has referenced
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this Entry's message.
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Parameters
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----------
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session : AppSession
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script_run_count : int
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The session's run count at the time of the call
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"""
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prev_run_count = self._session_script_run_counts.get(session, 0)
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if script_run_count < prev_run_count:
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LOGGER.error(
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"New script_run_count (%s) is < prev_run_count (%s). "
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"This should never happen!" % (script_run_count, prev_run_count)
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)
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script_run_count = prev_run_count
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self._session_script_run_counts[session] = script_run_count
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def has_session_ref(self, session: "AppSession") -> bool:
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return session in self._session_script_run_counts
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def get_session_ref_age(
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self, session: "AppSession", script_run_count: int
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) -> int:
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"""The age of the given session's reference to the Entry,
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given a new script_run_count.
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"""
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return script_run_count - self._session_script_run_counts[session]
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def remove_session_ref(self, session: "AppSession") -> None:
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del self._session_script_run_counts[session]
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def has_refs(self) -> bool:
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"""True if this Entry has references from any AppSession.
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If not, it can be removed from the cache.
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"""
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return len(self._session_script_run_counts) > 0
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def __init__(self):
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self._entries: Dict[str, "ForwardMsgCache.Entry"] = {}
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def __repr__(self) -> str:
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return util.repr_(self)
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def add_message(
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self, msg: ForwardMsg, session: "AppSession", script_run_count: int
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) -> None:
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"""Add a ForwardMsg to the cache.
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The cache will also record a reference to the given AppSession,
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so that it can track which sessions have already received
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each given ForwardMsg.
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Parameters
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----------
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msg : ForwardMsg
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session : AppSession
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script_run_count : int
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The number of times the session's script has run
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"""
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populate_hash_if_needed(msg)
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entry = self._entries.get(msg.hash, None)
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if entry is None:
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entry = ForwardMsgCache.Entry(msg)
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self._entries[msg.hash] = entry
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entry.add_session_ref(session, script_run_count)
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def get_message(self, hash: str) -> Optional[ForwardMsg]:
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"""Return the message with the given ID if it exists in the cache.
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Parameters
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----------
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hash : string
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The id of the message to retrieve.
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Returns
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-------
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ForwardMsg | None
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"""
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entry = self._entries.get(hash, None)
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return entry.msg if entry else None
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def has_message_reference(
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self, msg: ForwardMsg, session: "AppSession", script_run_count: int
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) -> bool:
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"""Return True if a session has a reference to a message."""
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populate_hash_if_needed(msg)
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entry = self._entries.get(msg.hash, None)
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if entry is None or not entry.has_session_ref(session):
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return False
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# Ensure we're not expired
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age = entry.get_session_ref_age(session, script_run_count)
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return age <= int(config.get_option("global.maxCachedMessageAge"))
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def remove_expired_session_entries(
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self, session: "AppSession", script_run_count: int
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) -> None:
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"""Remove any cached messages that have expired from the given session.
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This should be called each time a AppSession finishes executing.
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Parameters
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----------
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session : AppSession
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script_run_count : int
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The number of times the session's script has run
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"""
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max_age = config.get_option("global.maxCachedMessageAge")
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# Operate on a copy of our entries dict.
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# We may be deleting from it.
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for msg_hash, entry in self._entries.copy().items():
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if not entry.has_session_ref(session):
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continue
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age = entry.get_session_ref_age(session, script_run_count)
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if age > max_age:
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LOGGER.debug(
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"Removing expired entry [session=%s, hash=%s, age=%s]",
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id(session),
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msg_hash,
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age,
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)
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entry.remove_session_ref(session)
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if not entry.has_refs():
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# The entry has no more references. Remove it from
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# the cache completely.
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del self._entries[msg_hash]
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def clear(self) -> None:
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"""Remove all entries from the cache"""
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self._entries.clear()
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def get_stats(self) -> List[CacheStat]:
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stats: List[CacheStat] = []
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for entry_hash, entry in self._entries.items():
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stats.append(
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CacheStat(
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category_name="ForwardMessageCache",
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cache_name="",
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byte_length=entry.msg.ByteSize(),
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)
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)
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return stats
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