behavior/
watching.rs

1//! Pure peer-observation composition over an ordinary monitor actor protocol.
2
3use crate::behavior::{
4    Actions, Address, Become, Behavior, BirthMode, Delivery, Recipient, SendAlgebra, SendProduct,
5    User, UserEvent,
6};
7use crate::deadlined::{TimeEvent, TimeReached};
8use crate::supervising::{ChildEvent, ChildStopped};
9use crate::{Crash, Exit, Step};
10
11#[derive(Debug, Clone, Copy, PartialEq, Eq)]
12pub struct ObservePeer<A> {
13    pub peer: A,
14}
15
16#[derive(Debug, Clone, PartialEq, Eq)]
17pub struct PeerStopped<A: Address> {
18    pub peer: A,
19    pub outcome: Result<Exit<A>, Crash>,
20}
21
22#[derive(Debug, Clone, PartialEq, Eq)]
23pub enum WatchEvent<E, A: Address> {
24    Inner(E),
25    PeerStopped(PeerStopped<A>),
26}
27
28pub trait PeerEvent<A: Address>: Sized {
29    fn peer_stopped(event: PeerStopped<A>) -> Option<Self>;
30}
31
32impl<E, A: Address> PeerEvent<A> for WatchEvent<E, A> {
33    fn peer_stopped(event: PeerStopped<A>) -> Option<Self> {
34        Some(Self::PeerStopped(event))
35    }
36}
37
38impl<E: UserEvent, A: Address> UserEvent for WatchEvent<E, A> {
39    type Addr = E::Addr;
40    type Message = E::Message;
41
42    fn user(from: Self::Addr, message: Self::Message) -> Self {
43        Self::Inner(E::user(from, message))
44    }
45
46    fn into_user(self) -> Result<User<Self::Addr, Self::Message>, Self> {
47        match self {
48            Self::Inner(event) => event.into_user().map_err(Self::Inner),
49            stopped @ Self::PeerStopped(_) => Err(stopped),
50        }
51    }
52}
53
54impl<E: TimeEvent, A: Address> TimeEvent for WatchEvent<E, A> {
55    fn time_reached(event: TimeReached) -> Option<Self> {
56        E::time_reached(event).map(Self::Inner)
57    }
58}
59
60impl<E: ChildEvent<A>, A: Address> ChildEvent<A> for WatchEvent<E, A> {
61    fn child_stopped(event: ChildStopped<A>) -> Option<Self> {
62        E::child_stopped(event).map(Self::Inner)
63    }
64}
65
66pub type LinkReaction<B> = fn(
67    &mut B,
68    <B as Behavior>::Addr,
69    &Result<Exit<<B as Behavior>::Addr>, Crash>,
70) -> Result<Become<<B as Behavior>::Addr>, <B as Behavior>::Error>;
71
72pub type WatchSends<B> = SendProduct<
73    <B as Behavior>::Sends,
74    Vec<Delivery<<B as Behavior>::Addr, ObservePeer<<B as Behavior>::Addr>>>,
75>;
76
77pub type WatchActions<B> =
78    Actions<<B as Behavior>::Addr, <B as Behavior>::Ph, WatchSends<B>, <B as Behavior>::Birth>;
79
80pub struct Watching<B: Behavior> {
81    inner: B,
82    peer: B::Addr,
83    on_stopped: LinkReaction<B>,
84}
85
86impl<B: Behavior> Watching<B> {
87    #[must_use]
88    pub fn new(inner: B, peer: B::Addr, on_stopped: LinkReaction<B>) -> Self {
89        Self {
90            inner,
91            peer,
92            on_stopped,
93        }
94    }
95
96    #[must_use]
97    pub fn inner(&self) -> &B {
98        &self.inner
99    }
100}
101
102impl<B, A, Ph, Sends, Br> Behavior for Watching<B>
103where
104    A: Address + Send,
105    Sends: SendAlgebra,
106    Br: BirthMode,
107    B: Behavior<
108            Addr = A,
109            Ph = Ph,
110            Sends = Sends,
111            Birth = Br,
112            Effect = Actions<A, Ph, Sends, Br>,
113            Done = Exit<A>,
114        > + Send,
115    B::Event: PeerEvent<B::Addr> + Send,
116    B::Msg: Send,
117{
118    type Addr = A;
119    type Msg = B::Msg;
120    type Event = WatchEvent<B::Event, B::Addr>;
121    type Sends = SendProduct<Sends, Vec<Delivery<A, ObservePeer<A>>>>;
122    type Ph = Ph;
123    type Error = B::Error;
124    type Birth = Br;
125    type Effect = Actions<A, Ph, Self::Sends, Br>;
126    type Done = Exit<A>;
127
128    async fn init(&mut self) -> Result<Self::Effect, B::Error> {
129        let actions = self.inner.init().await?;
130        Ok(Self::wrap(
131            actions,
132            vec![Delivery::new(
133                Recipient::service(),
134                ObservePeer { peer: self.peer },
135            )],
136        ))
137    }
138
139    async fn step(&mut self, event: Self::Event) -> Result<Self::Effect, B::Error> {
140        match event {
141            WatchEvent::PeerStopped(event) if event.peer == self.peer => {
142                let become_ = match (self.on_stopped)(&mut self.inner, event.peer, &event.outcome)?
143                {
144                    Step::Continue => Step::Continue,
145                    Step::Goto(never) => match never {},
146                    Step::Stop(exit) => Step::Stop(exit),
147                };
148                Ok(Actions {
149                    sends: Self::Sends::empty(),
150                    creates: Vec::new(),
151                    become_,
152                })
153            }
154            WatchEvent::PeerStopped(event) => match B::Event::peer_stopped(event) {
155                Some(inner) => self
156                    .inner
157                    .step(inner)
158                    .await
159                    .map(|actions| Self::wrap(actions, Vec::new())),
160                None => Ok(Actions::cont()),
161            },
162            WatchEvent::Inner(event) => self
163                .inner
164                .step(event)
165                .await
166                .map(|actions| Self::wrap(actions, Vec::new())),
167        }
168    }
169}
170
171impl<B: Behavior> Watching<B> {
172    fn wrap(
173        actions: Actions<B::Addr, B::Ph, B::Sends, B::Birth>,
174        own: Vec<Delivery<B::Addr, ObservePeer<B::Addr>>>,
175    ) -> WatchActions<B> {
176        Actions {
177            sends: SendProduct {
178                inner: actions.sends,
179                own,
180            },
181            creates: actions.creates,
182            become_: actions.become_,
183        }
184    }
185}
186
187/// Stop when the monitor reports an abnormal outcome.
188///
189/// # Errors
190/// This supplied policy never creates a controlled error.
191pub fn stop_on_abnormal_death<B: Behavior>(
192    _behavior: &mut B,
193    peer: B::Addr,
194    outcome: &Result<Exit<B::Addr>, Crash>,
195) -> Result<Become<B::Addr>, B::Error> {
196    Ok(match outcome {
197        Ok(Exit::Normal | Exit::Collected) => Step::Continue,
198        _ => Step::Stop(Exit::LinkDied(peer)),
199    })
200}
behavior/watching.rs

behavior/
watching.rs
