behavior/
watching.rs

1//! Pure peer-observation composition over an ordinary monitor actor protocol.
2
3use crate::behavior::{
4    Actions, Address, Become, Behavior, BirthMode, SendAlgebra, SendProduct, ServiceSends, User,
5    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> =
73    SendProduct<<B as Behavior>::Sends, ServiceSends<ObservePeer<<B as Behavior>::Addr>>>;
74
75pub type WatchActions<B> =
76    Actions<<B as Behavior>::Addr, <B as Behavior>::Ph, WatchSends<B>, <B as Behavior>::Birth>;
77
78pub struct Watching<B: Behavior> {
79    inner: B,
80    peer: B::Addr,
81    on_stopped: LinkReaction<B>,
82}
83
84impl<B: Behavior> Watching<B> {
85    #[must_use]
86    pub fn new(inner: B, peer: B::Addr, on_stopped: LinkReaction<B>) -> Self {
87        Self {
88            inner,
89            peer,
90            on_stopped,
91        }
92    }
93
94    #[must_use]
95    pub fn inner(&self) -> &B {
96        &self.inner
97    }
98}
99
100impl<B, A, Ph, Sends, Br> Behavior for Watching<B>
101where
102    A: Address + Send,
103    Sends: SendAlgebra,
104    Br: BirthMode,
105    B: Behavior<
106            Addr = A,
107            Ph = Ph,
108            Sends = Sends,
109            Birth = Br,
110            Effect = Actions<A, Ph, Sends, Br>,
111            Done = Exit<A>,
112        > + Send,
113    B::Event: PeerEvent<B::Addr> + Send,
114    B::Msg: Send,
115{
116    type Addr = A;
117    type Msg = B::Msg;
118    type Event = WatchEvent<B::Event, B::Addr>;
119    type Sends = SendProduct<Sends, ServiceSends<ObservePeer<A>>>;
120    type Ph = Ph;
121    type Error = B::Error;
122    type Birth = Br;
123    type Effect = Actions<A, Ph, Self::Sends, Br>;
124    type Done = Exit<A>;
125
126    async fn init(&mut self) -> Result<Self::Effect, B::Error> {
127        let actions = self.inner.init().await?;
128        Ok(Self::wrap(
129            actions,
130            ServiceSends::one(ObservePeer { peer: self.peer }),
131        ))
132    }
133
134    async fn step(&mut self, event: Self::Event) -> Result<Self::Effect, B::Error> {
135        match event {
136            WatchEvent::PeerStopped(event) if event.peer == self.peer => {
137                let become_ = match (self.on_stopped)(&mut self.inner, event.peer, &event.outcome)?
138                {
139                    Step::Continue => Step::Continue,
140                    Step::Goto(never) => match never {},
141                    Step::Stop(exit) => Step::Stop(exit),
142                };
143                Ok(Actions {
144                    sends: Self::Sends::empty(),
145                    creates: Vec::new(),
146                    become_,
147                })
148            }
149            WatchEvent::PeerStopped(event) => match B::Event::peer_stopped(event) {
150                Some(inner) => self
151                    .inner
152                    .step(inner)
153                    .await
154                    .map(|actions| Self::wrap(actions, ServiceSends::empty())),
155                None => Ok(Actions::cont()),
156            },
157            WatchEvent::Inner(event) => self
158                .inner
159                .step(event)
160                .await
161                .map(|actions| Self::wrap(actions, ServiceSends::empty())),
162        }
163    }
164}
165
166impl<B: Behavior> Watching<B> {
167    fn wrap(
168        actions: Actions<B::Addr, B::Ph, B::Sends, B::Birth>,
169        own: ServiceSends<ObservePeer<B::Addr>>,
170    ) -> WatchActions<B> {
171        Actions {
172            sends: SendProduct {
173                inner: actions.sends,
174                own,
175            },
176            creates: actions.creates,
177            become_: actions.become_,
178        }
179    }
180}
181
182/// Stop when the monitor reports an abnormal outcome.
183///
184/// # Errors
185/// This supplied policy never creates a controlled error.
186pub fn stop_on_abnormal_death<B: Behavior>(
187    _behavior: &mut B,
188    peer: B::Addr,
189    outcome: &Result<Exit<B::Addr>, Crash>,
190) -> Result<Become<B::Addr>, B::Error> {
191    Ok(match outcome {
192        Ok(Exit::Normal | Exit::Collected) => Step::Continue,
193        _ => Step::Stop(Exit::LinkDied(peer)),
194    })
195}
behavior/watching.rs

behavior/
watching.rs
