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use std::os::fd::{AsFd, AsRawFd, OwnedFd};
use std::path::Path;
use std::sync::Arc;
use tokio::io::unix::AsyncFd;
use crate::fid_parser::read_fid_events_cached;
use super::Monitor;
use super::channel::EventSender;
// ---- Reader supervision ----
/// Per-reader-task restart tracking for exponential backoff.
/// Restarts are capped at MAX_RESTARTS within BACKOFF_WINDOW.
pub(crate) struct ReaderState {
pub(crate) restart_count: u32,
pub(crate) last_restart: std::time::Instant,
/// Set when restart_reader gives up (backoff exhausted within window).
/// Reset when spawn_fd_reader attempts a new spawn (even if it later fails).
/// Used by health() for reliable alive/dead reporting.
pub(crate) gave_up: bool,
}
pub(crate) const MAX_RESTARTS: u32 = 3;
pub(crate) const BACKOFF_WINDOW: std::time::Duration = std::time::Duration::from_secs(60);
impl Monitor {
/// Duplicate a file descriptor, returning an owned fd.
/// The returned `OwnedFd` has independent lifetime from the source
/// and will be closed on drop.
pub(crate) fn dup_fd(fd: &impl AsFd) -> std::io::Result<OwnedFd> {
nix::unistd::dup(fd).map_err(std::io::Error::other)
}
/// Open a directory and return an owned fd.
/// The returned `OwnedFd` has the directory open and will be
/// closed on drop.
pub(crate) fn open_dir(path: &Path) -> std::io::Result<OwnedFd> {
nix::fcntl::open(
path,
nix::fcntl::OFlag::O_DIRECTORY,
nix::sys::stat::Mode::empty(),
)
.map_err(std::io::Error::other)
}
/// Spawn a tokio reader task for `group_key` in `fs_groups`.
/// Both the fanotify fd and mount fd are duplicated so the reader task
/// owns independent copies, avoiding double-close with Monitor's OwnedFd.
pub(crate) fn spawn_fd_reader(&mut self, group_key: super::FsGroupKey) {
let tx = match self.event_tx.as_ref() {
Some(t) => t.clone(),
None => {
eprintln!("[ERROR] Cannot spawn reader: event_tx not initialized");
return;
}
};
let dc = match &self.shared_dir_cache {
Some(d) => d.clone(),
None => {
eprintln!("[ERROR] Cannot spawn reader: shared_dir_cache not initialized");
return;
}
};
let death_tx = self.reader_death_tx.clone();
let buf_size = self.buffer_size;
let debug = self.debug;
let group = &self.fs_groups[group_key];
// Duplicate fds so the reader task owns independent copies
let owned_fan_fd = match Self::dup_fd(&group.fan_fd) {
Ok(fd) => fd,
Err(e) => {
eprintln!(
"[ERROR] Failed to dup fanotify fd {}: {}",
group.fan_fd.as_raw_fd(),
e
);
return;
}
};
let owned_mount_fd = match Self::dup_fd(&group.mount_fd) {
Ok(fd) => fd,
Err(e) => {
eprintln!(
"[ERROR] Failed to dup mount fd {}: {}",
group.mount_fd.as_raw_fd(),
e
);
// owned_fan_fd drops here, closing the dup'd fan fd
return;
}
};
let raw_fd = owned_fan_fd.as_raw_fd();
let mfds = Arc::new(vec![owned_mount_fd]);
if debug {
eprintln!(
"[DEBUG] spawning reader for group {:?} (fd {})",
group_key, raw_fd
);
}
tokio::spawn(async move {
if debug {
eprintln!(
"[DEBUG] reader task spawned for group {:?} (fd {})",
group_key, raw_fd
);
}
let afd = match AsyncFd::new(owned_fan_fd) {
Ok(a) => {
if debug {
eprintln!("[DEBUG] reader {} AsyncFd created, entering loop", raw_fd);
}
a
}
Err(e) => {
eprintln!("[ERROR] AsyncFd for fd {}: {}", raw_fd, e);
let _ = death_tx.send(group_key);
return;
}
};
let mut buf = vec![0u8; buf_size];
loop {
let result = afd.readable().await;
let mut guard = match result {
Ok(g) => g,
Err(e) => {
eprintln!("[ERROR] fd {} readable: {}", raw_fd, e);
break;
}
};
let events = read_fid_events_cached(afd.get_ref(), &mfds, &dc, &mut buf);
if debug {
eprintln!(
"[DEBUG] fd {} reader: got {} event(s)",
raw_fd,
events.len()
);
}
if !events.is_empty() {
let send_err = match &tx {
EventSender::Unbounded(tx) => tx.send(events).is_err(),
EventSender::Bounded(tx) => tx.send(events).await.is_err(),
};
if send_err {
break;
}
// Edge-triggered epoll: retain readiness so the next
// readable().await resolves immediately if more events
// are still queued (e.g. DELETE → DELETE_SELF batch).
guard.retain_ready();
if debug {
eprintln!("[DEBUG] fd {} reader: retain_ready, looping", raw_fd);
}
} else {
if debug {
eprintln!("[DEBUG] fd {} reader: empty read, clear_ready", raw_fd);
}
guard.clear_ready();
}
}
if debug {
eprintln!(
"[DEBUG] Reader task for group {:?} (fd {}) exited",
group_key, raw_fd
);
}
let _ = death_tx.send(group_key);
});
// Track reader state for restart backoff
if let Some(state) = self.reader_states.get_mut(&group_key) {
state.restart_count += 1;
state.last_restart = std::time::Instant::now();
state.gave_up = false;
} else {
self.reader_states.insert(
group_key,
ReaderState {
restart_count: 1,
last_restart: std::time::Instant::now(),
gave_up: false,
},
);
}
self.metrics.set_reader_groups(self.fs_groups.len() as i64);
}
/// Restart a reader task that has died.
///
/// Applies exponential backoff: up to MAX_RESTARTS within BACKOFF_WINDOW.
/// If the backoff limit is exceeded, logs a warning and gives up.
/// On success, the dead task's fds are re-duplicated from FsGroup and
/// a new reader is spawned.
pub(crate) fn restart_reader(&mut self, group_key: super::FsGroupKey) {
// Check backoff limits
let now = std::time::Instant::now();
let state = self.reader_states.get(&group_key);
if let Some(s) = state {
let in_window = now.duration_since(s.last_restart) < BACKOFF_WINDOW;
if in_window && s.restart_count >= MAX_RESTARTS {
eprintln!(
"[ERROR] Reader task for group {:?} has crashed {} times in \
the last {}s — giving up. fsmon daemon restart required.",
group_key,
MAX_RESTARTS,
BACKOFF_WINDOW.as_secs(),
);
// Mark gave_up so health() reports accurate alive/dead status.
// This will be reset when spawn_fd_reader is called again.
if let Some(s) = self.reader_states.get_mut(&group_key) {
s.gave_up = true;
}
return;
}
}
// Verify the FsGroup still exists (may have been removed during shutdown)
if !self.fs_groups.contains_key(group_key) {
eprintln!(
"[WARNING] Cannot restart reader for group {:?}: group no longer exists",
group_key
);
return;
}
let dev_id = self.fs_groups[group_key].dev_id;
eprintln!(
"[INFO] Restarting reader task for group {:?} (dev_id={})...",
group_key, dev_id
);
self.spawn_fd_reader(group_key);
}
}