imp(timer): kqueue timer implementation

Author: omarabid

src/timer/kqueue.rs

@@ -4,6 +4,7 @@
 // https://www.apache.org/licenses/LICENSE-2.0>. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use crate::utils::check_err;
 use crate::Result;
 
 use std::sync::{mpsc::Sender, Arc, Mutex};
@@ -20,7 +21,43 @@ pub struct Timer {
 
 impl Timer {
     pub fn initialize(self) -> Result<Self> {
-        Ok(self)
+        let txs = Arc::clone(&self.txs);
+
+        let kqueue = kqueue()?;
+
+        let handle = Some(thread::spawn(move || {
+            // Wait for initial expiration
+            let initial_event = Timer::register_initial_expiration(kqueue)?;
+            Timer::wait_event(kqueue, [initial_event].as_mut_ptr())?;
+
+            // Register loop event
+            let loop_event = Timer::register_loop_expiration(kqueue)?;
+
+            // Loop 10s
+            loop {
+                // Exit thread if there are no listeners
+                if txs.lock()?.len() == 0 {
+                    // TODO: should close file descriptors?
+                    return Ok(());
+                }
+
+                // Get current time
+                let current = std::time::SystemTime::now()
+                    .duration_since(std::time::UNIX_EPOCH)?
+                    .as_secs();
+
+                // Iterate through Senders
+                txs.lock()?.iter().for_each(|tx| {
+                    // Send event to attached Sender
+                    tx.send(current).unwrap();
+                });
+
+                // Wait 10s
+                Timer::wait_event(kqueue, [loop_event].as_mut_ptr())?;
+            }
+        }));
+
+        Ok(Self { handle, ..self })
     }
 
     /// Attach an mpsc::Sender to Timer
@@ -42,4 +79,72 @@ impl Timer {
 
         Ok(())
     }
+
+    fn wait_event(kqueue: i32, events: *mut libc::kevent) -> Result<()> {
+        kevent(kqueue, [].as_mut_ptr(), 0, events, 1, std::ptr::null())?;
+        Ok(())
+    }
+    fn register_initial_expiration(kqueue: i32) -> Result<libc::kevent> {
+        // Get the next event time
+        let now = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)?
+            .as_secs();
+        let rem = 10u64.checked_sub(now.checked_rem(10).unwrap()).unwrap();
+        let first_fire = now + rem;
+
+        let initial_event = libc::kevent {
+            ident: 1,
+            filter: libc::EVFILT_TIMER,
+            flags: libc::EV_ADD | libc::EV_ENABLE | libc::EV_ONESHOT,
+            fflags: libc::NOTE_ABSOLUTE | libc::NOTE_SECONDS,
+            data: first_fire as isize,
+            udata: 0 as *mut libc::c_void,
+        };
+
+        // add first event
+        kevent(
+            kqueue,
+            [initial_event].as_ptr() as *const libc::kevent,
+            1,
+            [].as_mut_ptr(),
+            0,
+            std::ptr::null(),
+        )?;
+
+        Ok(initial_event)
+    }
+    fn register_loop_expiration(kqueue: i32) -> Result<libc::kevent> {
+        let loop_event = libc::kevent {
+            ident: 1,
+            filter: libc::EVFILT_TIMER,
+            flags: libc::EV_ADD | libc::EV_ENABLE,
+            fflags: 0,
+            data: 10000,
+            udata: 0 as *mut libc::c_void,
+        };
+
+        // add loop event
+        let ke = kevent(
+            kqueue,
+            [loop_event].as_ptr() as *const libc::kevent,
+            1,
+            [].as_mut_ptr(),
+            0,
+            std::ptr::null(),
+        )?;
+
+        Ok(loop_event)
+    }
+}
+
+fn kqueue() -> Result<i32> {
+    check_err(unsafe { libc::kqueue() }).map(|kq| kq as i32)
+}
+
+fn kevent(
+    kqueue: i32, change: *const libc::kevent, c_count: libc::c_int, events: *mut libc::kevent,
+    e_count: libc::c_int, timeout: *const libc::timespec,
+) -> Result<()> {
+    check_err(unsafe { libc::kevent(kqueue, change, c_count, events, e_count, timeout) })?;
+    Ok(())
 }

src/utils.rs

@@ -5,6 +5,7 @@
 // except according to those terms.
 
 use crate::error::Result;
+use crate::PyroscopeError;
 
 use std::collections::HashMap;
 
@@ -35,6 +36,7 @@ mod tests {
     use crate::utils::merge_tags_with_app_name;
 
     #[test]
+
     fn merge_tags_with_app_name_with_tags() {
         let mut tags = HashMap::new();
         tags.insert("env".to_string(), "staging".to_string());
@@ -54,3 +56,10 @@ mod tests {
         )
     }
 }
+/// Error Wrapper for libc return. Only check for errors.
+pub fn check_err<T: Ord + Default>(num: T) -> Result<T> {
+    if num < T::default() {
+        return Err(PyroscopeError::from(std::io::Error::last_os_error()));
+    }
+    Ok(num)
+}