rust-tokio-supervisor 0.1.2

A Rust tokio supervisor with declarative task supervision, restart policy, shutdown coordination, and observability.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141

//! Minimal child runner.
//!
//! This module starts one child attempt, advances readiness state, and records
//! the resulting task exit.

use crate::child_runner::attempt::TaskExit;
use crate::error::types::SupervisorError;
use crate::readiness::signal::{ReadinessPolicy, ReadySignal};
use crate::registry::entry::{ChildRuntime, ChildRuntimeStatus};
use crate::task::context::TaskContext;
use tokio::sync::watch;

/// Result of running one child attempt.
#[derive(Debug, Clone)]
pub struct ChildRunReport {
    /// Runtime record after the attempt.
    pub runtime: ChildRuntime,
    /// Final task exit classification.
    pub exit: TaskExit,
    /// Whether the task became ready during the attempt.
    pub became_ready: bool,
}

/// Runner that executes one child attempt.
#[derive(Debug, Clone, Default)]
pub struct ChildRunner;

impl ChildRunner {
    /// Creates a child runner.
    ///
    /// # Arguments
    ///
    /// This function has no arguments.
    ///
    /// # Returns
    ///
    /// Returns a [`ChildRunner`].
    ///
    /// # Examples
    ///
    /// ```
    /// let _runner = rust_supervisor::child_runner::runner::ChildRunner::new();
    /// ```
    pub fn new() -> Self {
        Self
    }

    /// Runs one child attempt.
    ///
    /// # Arguments
    ///
    /// - `runtime`: Runtime record for the child attempt.
    ///
    /// # Returns
    ///
    /// Returns a [`ChildRunReport`] when the child owns a task factory.
    pub async fn run_once(
        &self,
        mut runtime: ChildRuntime,
    ) -> Result<ChildRunReport, SupervisorError> {
        let factory =
            runtime.spec.factory.clone().ok_or_else(|| {
                SupervisorError::fatal_config("worker child requires a task factory")
            })?;
        runtime.status = ChildRuntimeStatus::Starting;
        let (ready_signal, ready_receiver) = ReadySignal::new();
        let (ctx, _heartbeat_receiver) = TaskContext::with_ready_signal(
            runtime.id.clone(),
            runtime.path.clone(),
            runtime.generation,
            runtime.attempt,
            ready_signal,
        );
        mark_immediate_ready(runtime.spec.readiness_policy, &ctx, &mut runtime);
        runtime.status = ChildRuntimeStatus::Running;
        let exit = run_factory(factory, ctx).await;
        let became_ready = observe_ready(ready_receiver);
        if became_ready {
            runtime.status = ChildRuntimeStatus::Ready;
        }
        runtime.last_exit = Some(exit.clone());
        Ok(ChildRunReport {
            runtime,
            exit,
            became_ready,
        })
    }
}

/// Marks a runtime ready when policy requires immediate readiness.
///
/// # Arguments
///
/// - `policy`: Readiness policy attached to the child.
/// - `ctx`: Task context that owns the readiness sender.
/// - `runtime`: Runtime record whose status should advance.
///
/// # Returns
///
/// This function does not return a value.
fn mark_immediate_ready(policy: ReadinessPolicy, ctx: &TaskContext, runtime: &mut ChildRuntime) {
    if policy.is_immediate() {
        ctx.mark_ready();
        runtime.status = ChildRuntimeStatus::Ready;
    }
}

/// Runs a factory and classifies the result.
///
/// # Arguments
///
/// - `factory`: Task factory for this child.
/// - `ctx`: Per-attempt task context.
///
/// # Returns
///
/// Returns the classified task exit.
async fn run_factory(
    factory: std::sync::Arc<dyn crate::task::factory::TaskFactory>,
    ctx: TaskContext,
) -> TaskExit {
    let task = tokio::spawn(factory.build(ctx));
    match task.await {
        Ok(result) => TaskExit::from_task_result(result),
        Err(error) if error.is_panic() => TaskExit::Panicked(String::from("task panicked")),
        Err(_error) => TaskExit::Cancelled,
    }
}

/// Observes whether readiness was reported.
///
/// # Arguments
///
/// - `ready_receiver`: Receiver that stores the latest readiness value.
///
/// # Returns
///
/// Returns `true` when the receiver observed readiness.
fn observe_ready(ready_receiver: watch::Receiver<bool>) -> bool {
    *ready_receiver.borrow()
}