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from typing import Any, Callable, Dict, Optional, cast
from overrides import EnforceOverrides, override
from chromadb.config import System
from chromadb.segment.distributed import (
Memberlist,
MemberlistProvider,
SegmentDirectory,
)
from chromadb.types import Segment
from kubernetes import client, config, watch
from kubernetes.client.rest import ApiException
import threading
from chromadb.utils.rendezvous_hash import assign, murmur3hasher
# These could go in config but given that they will rarely change, they are here for now to avoid
# polluting the config file further.
WATCH_TIMEOUT_SECONDS = 60
KUBERNETES_NAMESPACE = "chroma"
KUBERNETES_GROUP = "chroma.cluster"
class MockMemberlistProvider(MemberlistProvider, EnforceOverrides):
"""A mock memberlist provider for testing"""
_memberlist: Memberlist
def __init__(self, system: System):
super().__init__(system)
self._memberlist = ["a", "b", "c"]
@override
def get_memberlist(self) -> Memberlist:
return self._memberlist
@override
def set_memberlist_name(self, memberlist: str) -> None:
pass # The mock provider does not need to set the memberlist name
def update_memberlist(self, memberlist: Memberlist) -> None:
"""Updates the memberlist and calls all registered callbacks. This mocks an update from a k8s CR"""
self._memberlist = memberlist
for callback in self.callbacks:
callback(memberlist)
class CustomResourceMemberlistProvider(MemberlistProvider, EnforceOverrides):
"""A memberlist provider that uses a k8s custom resource to store the memberlist"""
_kubernetes_api: client.CustomObjectsApi
_memberlist_name: Optional[str]
_curr_memberlist: Optional[Memberlist]
_curr_memberlist_mutex: threading.Lock
_watch_thread: Optional[threading.Thread]
_kill_watch_thread: threading.Event
def __init__(self, system: System):
super().__init__(system)
config.load_config()
self._kubernetes_api = client.CustomObjectsApi()
self._watch_thread = None
self._memberlist_name = None
self._curr_memberlist = None
self._curr_memberlist_mutex = threading.Lock()
self._kill_watch_thread = threading.Event()
@override
def start(self) -> None:
if self._memberlist_name is None:
raise ValueError("Memberlist name must be set before starting")
self.get_memberlist()
self._watch_worker_memberlist()
return super().start()
@override
def stop(self) -> None:
self._curr_memberlist = None
self._memberlist_name = None
# Stop the watch thread
self._kill_watch_thread.set()
if self._watch_thread is not None:
self._watch_thread.join()
self._watch_thread = None
self._kill_watch_thread.clear()
return super().stop()
@override
def reset_state(self) -> None:
if not self._system.settings.require("allow_reset"):
raise ValueError(
"Resetting the database is not allowed. Set `allow_reset` to true in the config in tests or other non-production environments where reset should be permitted."
)
if self._memberlist_name:
self._kubernetes_api.patch_namespaced_custom_object(
group=KUBERNETES_GROUP,
version="v1",
namespace=KUBERNETES_NAMESPACE,
plural="memberlists",
name=self._memberlist_name,
body={
"kind": "MemberList",
"spec": {"members": []},
},
)
@override
def get_memberlist(self) -> Memberlist:
if self._curr_memberlist is None:
self._curr_memberlist = self._fetch_memberlist()
return self._curr_memberlist
@override
def set_memberlist_name(self, memberlist: str) -> None:
self._memberlist_name = memberlist
def _fetch_memberlist(self) -> Memberlist:
api_response = self._kubernetes_api.get_namespaced_custom_object(
group=KUBERNETES_GROUP,
version="v1",
namespace=KUBERNETES_NAMESPACE,
plural="memberlists",
name=f"{self._memberlist_name}",
)
api_response = cast(Dict[str, Any], api_response)
if "spec" not in api_response:
return []
response_spec = cast(Dict[str, Any], api_response["spec"])
return self._parse_response_memberlist(response_spec)
def _watch_worker_memberlist(self) -> None:
# TODO: We may want to make this watch function a library function that can be used by other
# components that need to watch k8s custom resources.
def run_watch() -> None:
w = watch.Watch()
def do_watch() -> None:
for event in w.stream(
self._kubernetes_api.list_namespaced_custom_object,
group=KUBERNETES_GROUP,
version="v1",
namespace=KUBERNETES_NAMESPACE,
plural="memberlists",
field_selector=f"metadata.name={self._memberlist_name}",
timeout_seconds=WATCH_TIMEOUT_SECONDS,
):
event = cast(Dict[str, Any], event)
response_spec = event["object"]["spec"]
response_spec = cast(Dict[str, Any], response_spec)
with self._curr_memberlist_mutex:
self._curr_memberlist = self._parse_response_memberlist(
response_spec
)
self._notify(self._curr_memberlist)
# Watch the custom resource for changes
# Watch with a timeout and retry so we can gracefully stop this if needed
while not self._kill_watch_thread.is_set():
try:
do_watch()
except ApiException as e:
# If status code is 410, the watch has expired and we need to start a new one.
if e.status == 410:
pass
return
if self._watch_thread is None:
thread = threading.Thread(target=run_watch, daemon=True)
thread.start()
self._watch_thread = thread
else:
raise Exception("A watch thread is already running.")
def _parse_response_memberlist(
self, api_response_spec: Dict[str, Any]
) -> Memberlist:
if "members" not in api_response_spec:
return []
return [m["url"] for m in api_response_spec["members"]]
def _notify(self, memberlist: Memberlist) -> None:
for callback in self.callbacks:
callback(memberlist)
class RendezvousHashSegmentDirectory(SegmentDirectory, EnforceOverrides):
_memberlist_provider: MemberlistProvider
_curr_memberlist_mutex: threading.Lock
_curr_memberlist: Optional[Memberlist]
def __init__(self, system: System):
super().__init__(system)
self._memberlist_provider = self.require(MemberlistProvider)
memberlist_name = system.settings.require("worker_memberlist_name")
self._memberlist_provider.set_memberlist_name(memberlist_name)
self._curr_memberlist = None
self._curr_memberlist_mutex = threading.Lock()
@override
def start(self) -> None:
self._curr_memberlist = self._memberlist_provider.get_memberlist()
self._memberlist_provider.register_updated_memberlist_callback(
self._update_memberlist
)
return super().start()
@override
def stop(self) -> None:
self._memberlist_provider.unregister_updated_memberlist_callback(
self._update_memberlist
)
return super().stop()
@override
def get_segment_endpoint(self, segment: Segment) -> str:
if self._curr_memberlist is None or len(self._curr_memberlist) == 0:
raise ValueError("Memberlist is not initialized")
assignment = assign(segment["id"].hex, self._curr_memberlist, murmur3hasher)
assignment = f"{assignment}:50051" # TODO: make port configurable
return assignment
@override
def register_updated_segment_callback(
self, callback: Callable[[Segment], None]
) -> None:
raise NotImplementedError()
def _update_memberlist(self, memberlist: Memberlist) -> None:
with self._curr_memberlist_mutex:
self._curr_memberlist = memberlist
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