Implementation:LMCache LMCache PDBackend Close

Knowledge Sources	LMCache
Domains	Infrastructure, Resource_Management
Last Updated	2026-02-09 00:00 GMT

Overview

Concrete tool for closing the PD backend and releasing NIXL transfer channels and ZMQ resources, provided by the PDBackend class.

Description

The PDBackend.close method sets the running flag to False, joins all background threads (allocation listener, heartbeat), closes the NIXL transfer channel, and terminates the ZMQ context.

Usage

Called during engine shutdown via LMCacheEngineBuilder.destroy() or when the vLLM process terminates.

Code Reference

Source Location

• Repository: LMCache
• File: lmcache/v1/storage_backend/pd_backend.py
• Lines: L596-L604

Signature

def close(self) -> None:
    """Close the storage backend."""
    self.running = False
    for thread in self.running_threads:
        thread.join()
    self.transfer_channel.close()
    self.zmq_context.term()

Import

from lmcache.v1.storage_backend.pd_backend import PDBackend

I/O Contract

Inputs

Name	Type	Required	Description
(none)			Called on self, no parameters

Outputs

Name	Type	Description
(none)	None	All threads joined, NIXL channel closed, ZMQ context terminated

Related Pages

Implements Principle

• Principle:LMCache_LMCache_Disaggregated_Shutdown

Requires Environment

• Environment:LMCache_LMCache_NIXL_Transfer_Library