fastpool 1.1.0

This crates implements a fast object pool for Async Rust.
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

// Copyright 2025 FastLabs Developers
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use std::future::Future;
use std::time::Instant;

/// Statistics regarding an object returned by the pool.
#[derive(Debug, Clone, Copy)]
pub struct ObjectStatus {
    created: Instant,
    pub(crate) recycled: Option<Instant>,
    pub(crate) recycle_count: usize,
}

impl Default for ObjectStatus {
    fn default() -> Self {
        Self {
            created: Instant::now(),
            recycled: None,
            recycle_count: 0,
        }
    }
}

impl ObjectStatus {
    /// Returns the instant when this object was created.
    pub fn created(&self) -> Instant {
        self.created
    }

    /// Returns the instant when this object was last used.
    pub fn last_used(&self) -> Instant {
        self.recycled.unwrap_or(self.created)
    }

    /// Returns the number of times the object was recycled.
    pub fn recycle_count(&self) -> usize {
        self.recycle_count
    }
}

/// A trait whose instance creates new objects and recycles existing ones.
pub trait ManageObject: Send + Sync {
    /// The type of objects that this instance creates and recycles.
    type Object: Send;

    /// The type of errors that this instance can return.
    type Error: Send;

    /// Creates a new object.
    fn create(&self) -> impl Future<Output = Result<Self::Object, Self::Error>> + Send;

    /// Whether the object `o` is recyclable.
    ///
    /// Returns `Ok(())` if the object is recyclable; otherwise, returns an error.
    fn is_recyclable(
        &self,
        o: &mut Self::Object,
        status: &ObjectStatus,
    ) -> impl Future<Output = Result<(), Self::Error>> + Send;

    /// A callback invoked when an object is detached from the pool.
    ///
    /// If this instance does not hold any references to the object, then the default
    /// implementation can be used which does nothing.
    fn on_detached(&self, _o: &mut Self::Object) {}
}

/// Queue strategy when deque objects from the object pool.
#[derive(Debug, Default, Clone, Copy)]
pub enum QueueStrategy {
    /// First in first out.
    ///
    /// This strategy behaves like a queue.
    #[default]
    Fifo,
    /// Last in first out.
    ///
    /// This strategy behaves like a stack.
    Lifo,
}

/// Strategy when recycling object has been cancelled.
///
/// This enum controls the behavior when the recycling process (specifically the
/// [`ManageObject::is_recyclable`] check) is cancelled; for example, when the
/// `get()` future is dropped.
#[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
pub enum RecycleCancelledStrategy {
    /// Detach the object from the pool.
    ///
    /// This is the safest option. If the recycling check is cancelled, we assume the object might
    /// be in an unknown state or that the check was taking too long for a reason. The object will
    /// detach from the pool.
    #[default]
    Detach,

    /// Return the object to the pool for potential reuse.
    ///
    /// This assumes that interrupting the check does not invalidate the object. The object is put
    /// back into the pool.
    ReturnToPool,
}