perf: Optimize PipeWire communication with single background thread actor

Replaces the previous approach of spawning new PipeWire main loops and
awaiting a 100ms timeout for every `get_all_devices` call. Instead,
this introduces a `PipeWireManager` which maintains a single, persistent
background thread with a PipeWire main loop and registry listener. The
actor caches `AudioDevice`s and `Port`s continuously in a `HashMap`,
providing instantaneous responses to device queries via a channel.

This architectural change replaces `Sender<Terminate>` with a simple
`PwTerminator` drop-guard to manage the lifetimes of PipeWire objects
(virtual mic and links) via `PwCommand::DestroyObject` without creating
additional OS threads or PipeWire contexts.

Co-authored-by: arabianq <55220741+arabianq@users.noreply.github.com>

pwsp-daemon/src/main.rs

@@ -28,7 +28,10 @@ async fn main() -> Result<()> {
     }
 
     get_daemon_config(); // Initialize daemon config
-    create_virtual_mic()?;
+
+    // Virtual mic object must be kept alive by some variable until daemon exits
+    let _virtual_mic = create_virtual_mic().await?;
+
     if let Err(err) = get_audio_player().await {
         eprintln!("Failed to initialize audio player: {}", err);
     } // Initialize audio player

pwsp-lib/src/types/audio_player.rs

@@ -1,8 +1,8 @@
 use crate::{
-    types::pipewire::{DeviceType, Terminate},
+    types::pipewire::DeviceType,
     utils::{
         daemon::get_daemon_config,
-        pipewire::{create_link, get_device, link_player_to_virtual_mic},
+        pipewire::{PwTerminator, create_link, get_device, link_player_to_virtual_mic},
     },
 };
 use anyhow::{Result, anyhow};
@@ -58,8 +58,8 @@ pub struct AudioPlayer {
     pub tracks: HashMap<u32, PlayingSound>,
     pub next_id: u32,
 
-    input_link_sender: Option<pipewire::channel::Sender<Terminate>>,
-    player_link_sender: Option<pipewire::channel::Sender<Terminate>>,
+    input_link_sender: Option<PwTerminator>,
+    player_link_sender: Option<PwTerminator>,
     pub input_device_name: Option<String>,
 
     pub volume: f32, // Master volume
@@ -108,24 +108,16 @@ impl AudioPlayer {
     }
 
     fn abort_link_thread(&mut self) {
-        if let Some(sender) = &self.input_link_sender {
-            if sender.send(Terminate {}).is_ok() {
+        if self.input_link_sender.is_some() {
             println!("Sent terminate signal to input link thread");
             self.input_link_sender = None;
-            } else {
-                eprintln!("Failed to send terminate signal to input link thread");
-            }
         }
     }
 
     fn abort_player_link_thread(&mut self) {
-        if let Some(sender) = &self.player_link_sender {
-            if sender.send(Terminate {}).is_ok() {
+        if self.player_link_sender.is_some() {
             println!("Sent terminate signal to player link thread");
             self.player_link_sender = None;
-            } else {
-                eprintln!("Failed to send terminate signal to player link thread");
-            }
         }
     }
 
@@ -187,7 +179,7 @@ impl AudioPlayer {
             return Ok(());
         };
 
-        self.input_link_sender = Some(create_link(output_fl, output_fr, input_fl, input_fr)?);
+        self.input_link_sender = Some(create_link(output_fl, output_fr, input_fl, input_fr).await?);
 
         Ok(())
     }

pwsp-lib/src/utils/pipewire.rs

@@ -1,14 +1,224 @@
-use crate::types::pipewire::{AudioDevice, DeviceType, Port, Terminate};
+use crate::types::pipewire::{AudioDevice, DeviceType, Port};
 use anyhow::{Result, anyhow};
 use pipewire::{
     context::ContextRc, link::Link, main_loop::MainLoopRc, properties::properties,
     registry::GlobalObject, spa::utils::dict::DictRef,
 };
-use std::{collections::HashMap, thread};
-use tokio::{
-    sync::mpsc,
-    time::{Duration, timeout},
+use std::{cell::RefCell, collections::HashMap, rc::Rc, sync::OnceLock, thread};
+use tokio::sync::oneshot;
+
+pub enum PwCommand {
+    GetDevices {
+        resp: oneshot::Sender<(Vec<AudioDevice>, Vec<AudioDevice>)>,
+    },
+    CreateVirtualMic {
+        resp: oneshot::Sender<Result<u32, String>>,
+    },
+    CreateLink {
+        output_fl: Port,
+        output_fr: Port,
+        input_fl: Port,
+        input_fr: Port,
+        resp: oneshot::Sender<Result<(u32, u32), String>>,
+    },
+    DestroyObject {
+        id: u32,
+    },
+}
+
+struct AppState {
+    input_devices: HashMap<u32, AudioDevice>,
+    output_devices: HashMap<u32, AudioDevice>,
+    ports: HashMap<u32, Port>,
+    proxies: HashMap<u32, Box<dyn std::any::Any>>,
+    proxy_id_counter: u32,
+    ready_tx: Option<std::sync::mpsc::Sender<()>>,
+}
+
+pub struct PipewireManager {
+    pub sender: pipewire::channel::Sender<PwCommand>,
+}
+
+static MANAGER: OnceLock<PipewireManager> = OnceLock::new();
+
+pub fn get_manager() -> &'static PipewireManager {
+    MANAGER.get_or_init(|| {
+        let (pw_sender, pw_receiver) = pipewire::channel::channel::<PwCommand>();
+        let (ready_tx, ready_rx) = std::sync::mpsc::channel();
+
+        thread::spawn(move || {
+            let (main_loop, context) = setup_pipewire_context().expect("Failed to setup pipewire");
+
+            // Leak main_loop and context so their borrows can be 'static
+            let main_loop = Box::leak(Box::new(main_loop));
+            let context = Box::leak(Box::new(context));
+
+            // Leak to fix lifetime issues since this thread lives forever
+            let core = Box::leak(Box::new(
+                context
+                    .connect(None)
+                    .expect("Failed to connect to pipewire"),
+            ));
+            let registry = Box::leak(Box::new(
+                core.get_registry().expect("Failed to get registry"),
+            ));
+
+            let state = Rc::new(RefCell::new(AppState {
+                input_devices: HashMap::new(),
+                output_devices: HashMap::new(),
+                ports: HashMap::new(),
+                proxies: HashMap::new(),
+                proxy_id_counter: 10000,
+                ready_tx: Some(ready_tx),
+            }));
+
+            let state_for_registry_add = state.clone();
+            let state_for_registry_remove = state.clone();
+
+            let _listener = registry
+                .add_listener_local()
+                .global(move |global| {
+                    let (device, port) = parse_global_object(global);
+                    let mut s = state_for_registry_add.borrow_mut();
+                    if let Some(device) = device {
+                        match device.device_type {
+                            DeviceType::Input => {
+                                s.input_devices.insert(device.id, device);
+                            }
+                            DeviceType::Output => {
+                                s.output_devices.insert(device.id, device);
+                            }
+                        }
+                    } else if let Some(port) = port {
+                        let node_id = port.node_id;
+                        s.ports.insert(port.port_id, port.clone());
+                        if let Some(d) = s.input_devices.get_mut(&node_id) {
+                            d.add_port(port.clone());
+                        } else if let Some(d) = s.output_devices.get_mut(&node_id) {
+                            d.add_port(port);
+                        }
+                    }
+                })
+                .global_remove(move |id| {
+                    let mut s = state_for_registry_remove.borrow_mut();
+                    s.input_devices.remove(&id);
+                    s.output_devices.remove(&id);
+                    s.ports.retain(|_, port| port.node_id != id);
+                    s.ports.remove(&id);
+                })
+                .register();
+
+            // sync to signal ready
+            let state_for_sync = state.clone();
+            let _core_listener = core
+                .add_listener_local()
+                .done(move |id, _seq| {
+                    if id == 0 {
+                        let mut s = state_for_sync.borrow_mut();
+                        if let Some(tx) = s.ready_tx.take() {
+                            let _ = tx.send(());
+                        }
+                    }
+                })
+                .register();
+
+            let _pending = core.sync(0).expect("sync failed");
+
+            let state_for_cmd = state.clone();
+            let _receiver = pw_receiver.attach(main_loop.loop_(), move |cmd| {
+                let mut s = state_for_cmd.borrow_mut();
+                match cmd {
+                    PwCommand::GetDevices { resp } => {
+                        let mut inputs: Vec<AudioDevice> =
+                            s.input_devices.values().cloned().collect();
+                        let mut outputs: Vec<AudioDevice> =
+                            s.output_devices.values().cloned().collect();
+                        inputs.sort_by_key(|a| a.id);
+                        outputs.sort_by_key(|a| a.id);
+                        let _ = resp.send((inputs, outputs));
+                    }
+                    PwCommand::CreateVirtualMic { resp } => {
+                        let props = properties!(
+                            "factory.name" => "support.null-audio-sink",
+                            "node.name" => "pwsp-virtual-mic",
+                            "node.description" => "PWSP Virtual Mic",
+                            "media.class" => "Audio/Source/Virtual",
+                            "audio.position" => "[ FL FR ]",
+                            "audio.channels" => "2",
+                            "object.linger" => "false",
+                        );
+                        match core.create_object::<pipewire::node::Node>("adapter", &props) {
+                            Ok(node) => {
+                                s.proxy_id_counter += 1;
+                                let id = s.proxy_id_counter;
+                                s.proxies.insert(id, Box::new(node));
+                                let _ = resp.send(Ok(id));
+                            }
+                            Err(e) => {
+                                let _ = resp.send(Err(e.to_string()));
+                            }
+                        }
+                    }
+                    PwCommand::CreateLink {
+                        output_fl,
+                        output_fr,
+                        input_fl,
+                        input_fr,
+                        resp,
+                    } => {
+                        let props_fl = properties! {
+                            "link.output.node" => format!("{}", output_fl.node_id).as_str(),
+                            "link.output.port" => format!("{}", output_fl.port_id).as_str(),
+                            "link.input.node"  => format!("{}", input_fl.node_id).as_str(),
+                            "link.input.port"  => format!("{}", input_fl.port_id).as_str(),
                         };
+                        let props_fr = properties! {
+                            "link.output.node" => format!("{}", output_fr.node_id).as_str(),
+                            "link.output.port" => format!("{}", output_fr.port_id).as_str(),
+                            "link.input.node"  => format!("{}", input_fr.node_id).as_str(),
+                            "link.input.port"  => format!("{}", input_fr.port_id).as_str(),
+                        };
+
+                        let link_fl = match core.create_object::<Link>("link-factory", &props_fl) {
+                            Ok(link) => link,
+                            Err(e) => {
+                                let _ = resp.send(Err(e.to_string()));
+                                return;
+                            }
+                        };
+                        let link_fr = match core.create_object::<Link>("link-factory", &props_fr) {
+                            Ok(link) => link,
+                            Err(e) => {
+                                let _ = resp.send(Err(e.to_string()));
+                                return;
+                            }
+                        };
+
+                        s.proxy_id_counter += 1;
+                        let id_fl = s.proxy_id_counter;
+                        s.proxies.insert(id_fl, Box::new(link_fl));
+
+                        s.proxy_id_counter += 1;
+                        let id_fr = s.proxy_id_counter;
+                        s.proxies.insert(id_fr, Box::new(link_fr));
+
+                        let _ = resp.send(Ok((id_fl, id_fr)));
+                    }
+                    PwCommand::DestroyObject { id } => {
+                        s.proxies.remove(&id);
+                    }
+                }
+            });
+
+            main_loop.run();
+        });
+
+        // Wait for the pipewire thread to be fully up and processed initial events
+        let _ = ready_rx.recv();
+
+        PipewireManager { sender: pw_sender }
+    })
+}
 
 pub fn setup_pipewire_context() -> Result<(MainLoopRc, ContextRc), String> {
     pipewire::init();
@@ -71,127 +281,17 @@ fn parse_global_object(
     (None, None)
 }
 
-async fn pw_get_global_objects_thread(
-    main_sender: mpsc::Sender<(Option<AudioDevice>, Option<Port>)>,
-    pw_receiver: pipewire::channel::Receiver<Terminate>,
-    init_sender: tokio::sync::oneshot::Sender<Result<(), String>>,
-) {
-    let (main_loop, context) = match setup_pipewire_context() {
-        Ok(res) => res,
-        Err(e) => {
-            let _ = init_sender.send(Err(e));
-            return;
-        }
-    };
-
-    // Stop main loop on Terminate message
-    let _receiver = pw_receiver.attach(main_loop.loop_(), {
-        let _main_loop = main_loop.clone();
-        move |_| _main_loop.quit()
-    });
-
-    let core = match context.connect(None) {
-        Ok(core) => core,
-        Err(e) => {
-            let _ = init_sender.send(Err(format!("Failed to connect to pipewire context: {}", e)));
-            return;
-        }
-    };
-
-    let registry = match core.get_registry() {
-        Ok(registry) => registry,
-        Err(e) => {
-            let _ = init_sender.send(Err(format!(
-                "Failed to get registry from pipewire context: {}",
-                e
-            )));
-            return;
-        }
-    };
-
-    let _listener = registry
-        .add_listener_local()
-        .global(move |global| {
-            // Try to parse every global object pipewire finds
-            let (device, port) = parse_global_object(global);
-
-            // Send message to the main thread
-            let sender_clone = main_sender.clone();
-            tokio::task::spawn(async move {
-                sender_clone.send((device, port)).await.ok();
-            });
-        })
-        .register();
-
-    // Signal successful initialization
-    if init_sender.send(Ok(())).is_err() {
-        return;
-    }
-
-    main_loop.run();
-}
-
 pub async fn get_all_devices() -> Result<(Vec<AudioDevice>, Vec<AudioDevice>)> {
-    // Channels to communicate with pipewire thread
-    let (main_sender, mut main_receiver) = mpsc::channel(10);
-    let (pw_sender, pw_receiver) = pipewire::channel::channel();
-    let (init_sender, init_receiver) = tokio::sync::oneshot::channel();
-
-    // Spawn pipewire thread in background
-    let _pw_thread = tokio::spawn(async move {
-        pw_get_global_objects_thread(main_sender, pw_receiver, init_sender).await
-    });
-
-    // Wait for initialization to complete
-    if let Err(e) = init_receiver.await {
-        return Err(anyhow!(e));
-    }
-
-    let mut input_devices: HashMap<u32, AudioDevice> = HashMap::new();
-    let mut output_devices: HashMap<u32, AudioDevice> = HashMap::new();
-    let mut ports: Vec<Port> = vec![];
-
-    loop {
-        // If we don't receive a message in 100ms, we can assume that pipewire thread is finished
-        match timeout(Duration::from_millis(100), main_receiver.recv()).await {
-            Ok(Some((device, port))) => {
-                if let Some(device) = device {
-                    match device.device_type {
-                        DeviceType::Input => {
-                            input_devices.insert(device.id, device);
-                        }
-                        DeviceType::Output => {
-                            output_devices.insert(device.id, device);
-                        }
-                    }
-                } else if let Some(port) = port {
-                    ports.push(port);
-                }
-            }
-            Ok(None) | Err(_) => {
-                // Pipewire thread is finished and we can collect our devices
-                let _ = pw_sender.send(Terminate {});
-
-                for port in ports {
-                    let node_id = port.node_id;
-
-                    if let Some(input_device) = input_devices.get_mut(&node_id) {
-                        input_device.add_port(port);
-                    } else if let Some(output_device) = output_devices.get_mut(&node_id) {
-                        output_device.add_port(port);
-                    }
-                }
-
-                let mut input_devices: Vec<AudioDevice> = input_devices.into_values().collect();
-                let mut output_devices: Vec<AudioDevice> = output_devices.into_values().collect();
-
-                input_devices.sort_by_key(|a| a.id);
-                output_devices.sort_by_key(|a| a.id);
-
-                return Ok((input_devices, output_devices));
-            }
-        }
-    }
+    let (tx, rx) = oneshot::channel();
+    let manager = get_manager();
+    manager
+        .sender
+        .send(PwCommand::GetDevices { resp: tx })
+        .map_err(|_| anyhow!("Failed to send GetDevices to manager"))?;
+    let res = rx
+        .await
+        .map_err(|e| anyhow!("Failed to receive response: {}", e))?;
+    Ok(res)
 }
 
 pub async fn get_device(device_name: &str) -> Result<AudioDevice> {
@@ -209,65 +309,36 @@ pub async fn get_device(device_name: &str) -> Result<AudioDevice> {
         .ok_or_else(|| anyhow!("Device not found"))
 }
 
-pub fn create_virtual_mic() -> Result<pipewire::channel::Sender<Terminate>> {
-    let (pw_sender, pw_receiver) = pipewire::channel::channel::<Terminate>();
-    let (init_sender, init_receiver) = std::sync::mpsc::sync_channel(0);
-
-    let _pw_thread = thread::spawn(move || {
-        let (main_loop, context) = match setup_pipewire_context() {
-            Ok(res) => res,
-            Err(e) => {
-                let _ = init_sender.send(Err(e));
-                return;
-            }
-        };
-        let core = match context.connect(None) {
-            Ok(core) => core,
-            Err(e) => {
-                let _ =
-                    init_sender.send(Err(format!("Failed to connect to pipewire context: {}", e)));
-                return;
-            }
-        };
-
-        let props = properties!(
-            "factory.name" => "support.null-audio-sink",
-            "node.name" => "pwsp-virtual-mic",
-            "node.description" => "PWSP Virtual Mic",
-            "media.class" => "Audio/Source/Virtual",
-            "audio.position" => "[ FL FR ]",
-            "audio.channels" => "2",
-            "object.linger" => "false", // Destroy the node on app exit
-        );
-
-        let _node = match core.create_object::<pipewire::node::Node>("adapter", &props) {
-            Ok(node) => node,
-            Err(e) => {
-                let _ = init_sender.send(Err(format!("Failed to create virtual mic: {}", e)));
-                return;
-            }
-        };
-
-        let _receiver = pw_receiver.attach(main_loop.loop_(), {
-            let _main_loop = main_loop.clone();
-            move |_| _main_loop.quit()
-        });
-
-        println!("Virtual mic created");
-        if init_sender.send(Ok(())).is_err() {
-            return;
-        }
-        main_loop.run();
-    });
-
-    if let Err(e) = init_receiver.recv()? {
-        return Err(anyhow!(e));
+pub struct PwTerminator {
+    ids: Vec<u32>,
 }
 
-    Ok(pw_sender)
+impl Drop for PwTerminator {
+    fn drop(&mut self) {
+        let manager = get_manager();
+        for id in &self.ids {
+            let _ = manager.sender.send(PwCommand::DestroyObject { id: *id });
+        }
+    }
 }
 
-pub async fn link_player_to_virtual_mic() -> Result<pipewire::channel::Sender<Terminate>> {
+pub async fn create_virtual_mic() -> Result<PwTerminator> {
+    let (tx, rx) = oneshot::channel();
+    let manager = get_manager();
+    manager
+        .sender
+        .send(PwCommand::CreateVirtualMic { resp: tx })
+        .map_err(|_| anyhow!("Failed to send CreateVirtualMic to manager"))?;
+
+    let res = rx
+        .await
+        .map_err(|e| anyhow!("Failed to receive response: {}", e))?;
+
+    let id = res.map_err(|e| anyhow!(e))?;
+    Ok(PwTerminator { ids: vec![id] })
+}
+
+pub async fn link_player_to_virtual_mic() -> Result<PwTerminator> {
     let pwsp_daemon_output = match get_device("pwsp-daemon").await {
         Ok(device) => device,
         Err(_) => {
@@ -303,81 +374,34 @@ pub async fn link_player_to_virtual_mic() -> Result<pipewire::channel::Sender<Te
         None => return Err(anyhow!("Failed to get pwsp-virtual-mic input_fr")),
     };
 
-    create_link(output_fl, output_fr, input_fl, input_fr)
+    create_link(output_fl, output_fr, input_fl, input_fr).await
 }
 
-pub fn create_link(
+pub async fn create_link(
     output_fl: Port,
     output_fr: Port,
     input_fl: Port,
     input_fr: Port,
-) -> Result<pipewire::channel::Sender<Terminate>> {
-    let (pw_sender, pw_receiver) = pipewire::channel::channel::<Terminate>();
-    let (init_sender, init_receiver) = std::sync::mpsc::sync_channel(0);
+) -> Result<PwTerminator> {
+    let (tx, rx) = oneshot::channel();
+    let manager = get_manager();
+    manager
+        .sender
+        .send(PwCommand::CreateLink {
+            output_fl,
+            output_fr,
+            input_fl,
+            input_fr,
+            resp: tx,
+        })
+        .map_err(|_| anyhow!("Failed to send CreateLink to manager"))?;
 
-    let _pw_thread = thread::spawn(move || {
-        let (main_loop, context) = match setup_pipewire_context() {
-            Ok(res) => res,
-            Err(e) => {
-                let _ = init_sender.send(Err(e));
-                return;
-            }
-        };
-        let core = match context.connect(None) {
-            Ok(core) => core,
-            Err(e) => {
-                let _ =
-                    init_sender.send(Err(format!("Failed to connect to pipewire context: {}", e)));
-                return;
-            }
-        };
+    let res = rx
+        .await
+        .map_err(|e| anyhow!("Failed to receive response: {}", e))?;
 
-        let props_fl = properties! {
-            "link.output.node" => format!("{}", output_fl.node_id).as_str(),
-            "link.output.port" => format!("{}", output_fl.port_id).as_str(),
-            "link.input.node"  => format!("{}", input_fl.node_id).as_str(),
-            "link.input.port"  => format!("{}", input_fl.port_id).as_str(),
-        };
-        let props_fr = properties! {
-            "link.output.node" => format!("{}", output_fr.node_id).as_str(),
-            "link.output.port" => format!("{}", output_fr.port_id).as_str(),
-            "link.input.node"  => format!("{}", input_fr.node_id).as_str(),
-            "link.input.port"  => format!("{}", input_fr.port_id).as_str(),
-        };
-
-        let _link_fl = match core.create_object::<Link>("link-factory", &props_fl) {
-            Ok(link) => link,
-            Err(e) => {
-                let _ = init_sender.send(Err(format!("Failed to create link FL: {}", e)));
-                return;
-            }
-        };
-        let _link_fr = match core.create_object::<Link>("link-factory", &props_fr) {
-            Ok(link) => link,
-            Err(e) => {
-                let _ = init_sender.send(Err(format!("Failed to create link FR: {}", e)));
-                return;
-            }
-        };
-
-        let _receiver = pw_receiver.attach(main_loop.loop_(), {
-            let _main_loop = main_loop.clone();
-            move |_| _main_loop.quit()
-        });
-
-        println!(
-            "Link created: FL: {}-{} FR: {}-{}",
-            output_fl.node_id, input_fl.node_id, output_fr.node_id, input_fr.node_id
-        );
-        if init_sender.send(Ok(())).is_err() {
-            return;
-        }
-        main_loop.run();
-    });
-
-    if let Err(e) = init_receiver.recv()? {
-        return Err(anyhow!(e));
-    }
-
-    Ok(pw_sender)
+    let (id_fl, id_fr) = res.map_err(|e| anyhow!(e))?;
+    Ok(PwTerminator {
+        ids: vec![id_fl, id_fr],
+    })
 }