moka/notification/
notifier.rs

1use std::sync::{
2    atomic::{AtomicBool, Ordering},
3    Arc,
4};
5
6use crate::notification::{EvictionListener, RemovalCause};
7
8pub(crate) struct RemovalNotifier<K, V> {
9    listener: EvictionListener<K, V>,
10    is_enabled: AtomicBool,
11    #[cfg(feature = "logging")]
12    cache_name: Option<String>,
13}
14
15impl<K, V> RemovalNotifier<K, V> {
16    pub(crate) fn new(listener: EvictionListener<K, V>, _cache_name: Option<String>) -> Self {
17        Self {
18            listener,
19            is_enabled: AtomicBool::new(true),
20            #[cfg(feature = "logging")]
21            cache_name: _cache_name,
22        }
23    }
24
25    pub(crate) fn notify(&self, key: Arc<K>, value: V, cause: RemovalCause) {
26        use std::panic::{catch_unwind, AssertUnwindSafe};
27
28        if !self.is_enabled.load(Ordering::Acquire) {
29            return;
30        }
31
32        let listener_clo = || (self.listener)(key, value, cause);
33
34        // Safety: It is safe to assert unwind safety here because we will not
35        // call the listener again if it has been panicked.
36        let result = catch_unwind(AssertUnwindSafe(listener_clo));
37        if let Err(_payload) = result {
38            self.is_enabled.store(false, Ordering::Release);
39            #[cfg(feature = "logging")]
40            log_panic(&*_payload, self.cache_name.as_deref());
41        }
42    }
43}
44
45#[cfg(feature = "logging")]
46fn log_panic(payload: &(dyn std::any::Any + Send + 'static), cache_name: Option<&str>) {
47    // Try to downcast the payload into &str or String.
48    //
49    // NOTE: Clippy will complain if we use `if let Some(_)` here.
50    // https://rust-lang.github.io/rust-clippy/master/index.html#manual_map
51    let message: Option<std::borrow::Cow<'_, str>> =
52        (payload.downcast_ref::<&str>().map(|s| (*s).into()))
53            .or_else(|| payload.downcast_ref::<String>().map(Into::into));
54
55    let cn = cache_name
56        .map(|name| format!("[{name}] "))
57        .unwrap_or_default();
58
59    if let Some(m) = message {
60        log::error!("{cn}Disabled the eviction listener because it panicked at '{m}'");
61    } else {
62        log::error!("{cn}Disabled the eviction listener because it panicked");
63    }
64}