import threading import time from typing import Any, Callable, Dict, List, Optional, cast from kubernetes import client, config, watch from kubernetes.client.rest import ApiException from overrides import EnforceOverrides, override from chromadb.config import RoutingMode, System from chromadb.segment.distributed import ( Member, Memberlist, MemberlistProvider, SegmentDirectory, ) from chromadb.telemetry.opentelemetry import ( OpenTelemetryGranularity, add_attributes_to_current_span, trace_method, ) from chromadb.types import Segment 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" HEADLESS_SERVICE = "svc.cluster.local" class MockMemberlistProvider(MemberlistProvider, EnforceOverrides): """A mock memberlist provider for testing""" _memberlist: Memberlist def __init__(self, system: System): super().__init__(system) self._memberlist = [ Member(id="a", ip="10.0.0.1", node="node1"), Member(id="b", ip="10.0.0.2", node="node2"), Member(id="c", ip="10.0.0.3", node="node3"), ] @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 _done_waiting_for_reset: 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() self._done_waiting_for_reset = 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._done_waiting_for_reset.clear() 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() self._done_waiting_for_reset.clear() return super().stop() @override def reset_state(self) -> None: # Reset the memberlist in kubernetes, and wait for it to # get propagated back again # Note that the component must be running in order to reset the state 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._done_waiting_for_reset.clear() 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": []}, }, ) self._done_waiting_for_reset.wait(5.0) # TODO: For some reason the above can flake and the memberlist won't be populated # Given that this is a test harness, just sleep for an additional 500ms for now # We should understand why this flaps time.sleep(0.5) @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) if ( self._system.settings.require("allow_reset") and not self._done_waiting_for_reset.is_set() and len(self._curr_memberlist) > 0 ): self._done_waiting_for_reset.set() # 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 [] parsed = [] for m in api_response_spec["members"]: id = m["member_id"] ip = m["member_ip"] if "member_ip" in m else "" node = m["member_node_name"] if "member_node_name" in m else "" parsed.append(Member(id=id, ip=ip, node=node)) return parsed 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] _routing_mode: RoutingMode 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._routing_mode = system.settings.require( "chroma_segment_directory_routing_mode" ) 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_endpoints(self, segment: Segment, n: int) -> List[str]: if self._curr_memberlist is None or len(self._curr_memberlist) == 0: raise ValueError("Memberlist is not initialized") # assign() will throw an error if n is greater than the number of members # clamp n to the number of members to align with the contract of this method # which is to return at most n endpoints n = min(n, len(self._curr_memberlist)) # Check if all members in the memberlist have a node set, # if so, route using the node # NOTE(@hammadb) 1/8/2024: This is to handle the migration between routing # using the member id and routing using the node name # We want to route using the node name over the member id # because the node may have a disk cache that we want a # stable identifier for over deploys. can_use_node_routing = ( all([m.node != "" and len(m.node) != 0 for m in self._curr_memberlist]) and self._routing_mode == RoutingMode.NODE ) if can_use_node_routing: # If we are using node routing and the segments assignments = assign( segment["collection"].hex, [m.node for m in self._curr_memberlist], murmur3hasher, n, ) else: # Query to the same collection should end up on the same endpoint assignments = assign( segment["collection"].hex, [m.id for m in self._curr_memberlist], murmur3hasher, n, ) assignments_set = set(assignments) out_endpoints = [] for member in self._curr_memberlist: is_chosen_with_node_routing = ( can_use_node_routing and member.node in assignments_set ) is_chosen_with_id_routing = ( not can_use_node_routing and member.id in assignments_set ) if is_chosen_with_node_routing or is_chosen_with_id_routing: # If the memberlist has an ip, use it, otherwise use the member id with the headless service # this is for backwards compatibility with the old memberlist which only had ids if member.ip is not None and member.ip != "": endpoint = f"{member.ip}:50051" out_endpoints.append(endpoint) else: service_name = self.extract_service_name(member.id) endpoint = f"{member.id}.{service_name}.{KUBERNETES_NAMESPACE}.{HEADLESS_SERVICE}:50051" out_endpoints.append(endpoint) return out_endpoints @override def register_updated_segment_callback( self, callback: Callable[[Segment], None] ) -> None: raise NotImplementedError() @trace_method( "RendezvousHashSegmentDirectory._update_memberlist", OpenTelemetryGranularity.ALL, ) def _update_memberlist(self, memberlist: Memberlist) -> None: with self._curr_memberlist_mutex: add_attributes_to_current_span( {"new_memberlist": [m.id for m in memberlist]} ) self._curr_memberlist = memberlist def extract_service_name(self, pod_name: str) -> Optional[str]: # Split the pod name by the hyphen parts = pod_name.split("-") # The service name is expected to be the prefix before the last hyphen if len(parts) > 1: return "-".join(parts[:-1]) return None