aedb 0.2.9

Embedded Rust storage engine with transactional commits, WAL durability, and snapshot-consistent reads
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
142
143
144
145
146
147
148
149
150
151
152
153
154

use crate::error::AedbError;
use crate::snapshot::reader::SnapshotReadView;
use std::collections::{HashMap, HashSet};
use std::time::{Duration, Instant};

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct SnapshotHandle(u64);

#[derive(Debug, Clone)]
pub struct LeakWarning {
    pub handle: SnapshotHandle,
    pub age: Duration,
}

#[derive(Debug, Clone, Default)]
pub struct GcResult {
    pub reclaimed_snapshots: usize,
}

#[derive(Debug)]
struct SnapshotRef {
    view: SnapshotReadView,
    acquired_at: Instant,
    released: bool,
}

#[derive(Debug, Default)]
pub struct SnapshotManager {
    active_snapshots: HashMap<SnapshotHandle, SnapshotRef>,
    next_id: u64,
}

impl SnapshotManager {
    pub fn acquire(&mut self, view: SnapshotReadView) -> SnapshotHandle {
        self.next_id += 1;
        let handle = SnapshotHandle(self.next_id);
        self.active_snapshots.insert(
            handle,
            SnapshotRef {
                view,
                acquired_at: Instant::now(),
                released: false,
            },
        );
        handle
    }

    pub fn acquire_bounded(
        &mut self,
        view: SnapshotReadView,
        max_concurrent_snapshots: usize,
    ) -> Result<SnapshotHandle, AedbError> {
        let active = self
            .active_snapshots
            .values()
            .filter(|s| !s.released)
            .count();
        if active >= max_concurrent_snapshots {
            return Err(AedbError::QueueFull);
        }
        Ok(self.acquire(view))
    }

    pub fn release(&mut self, handle: SnapshotHandle) {
        if let Some(snapshot) = self.active_snapshots.get_mut(&handle) {
            snapshot.released = true;
        }
    }

    pub fn gc(&mut self) -> GcResult {
        let before = self.active_snapshots.len();
        self.active_snapshots.retain(|_, s| !s.released);
        GcResult {
            reclaimed_snapshots: before.saturating_sub(self.active_snapshots.len()),
        }
    }

    pub fn check_leaks(&self, threshold_ms: u64) -> Vec<LeakWarning> {
        let threshold = Duration::from_millis(threshold_ms);
        let now = Instant::now();
        self.active_snapshots
            .iter()
            .filter_map(|(handle, snapshot)| {
                if snapshot.released {
                    return None;
                }
                let age = now.duration_since(snapshot.acquired_at);
                if age >= threshold {
                    Some(LeakWarning {
                        handle: *handle,
                        age,
                    })
                } else {
                    None
                }
            })
            .collect()
    }

    pub fn get(&self, handle: SnapshotHandle) -> Option<&SnapshotReadView> {
        self.active_snapshots.get(&handle).map(|s| &s.view)
    }

    pub fn get_checked(
        &mut self,
        handle: SnapshotHandle,
        max_snapshot_age_ms: u64,
    ) -> Result<&SnapshotReadView, AedbError> {
        let Some(snapshot) = self.active_snapshots.get_mut(&handle) else {
            return Err(AedbError::SnapshotExpired);
        };
        if snapshot.released {
            return Err(AedbError::SnapshotExpired);
        }
        if snapshot.acquired_at.elapsed() > Duration::from_millis(max_snapshot_age_ms) {
            snapshot.released = true;
            return Err(AedbError::SnapshotExpired);
        }
        Ok(&snapshot.view)
    }

    pub fn active_kv_segment_filenames(&self) -> HashSet<String> {
        let mut filenames = HashSet::new();
        for snapshot in self.active_snapshots.values() {
            if snapshot.released {
                continue;
            }
            filenames.extend(snapshot.view.keyspace.kv_segment_filenames());
        }
        filenames
    }

    pub fn eligible_segment_reclaims(
        &self,
        segment_seqs: &[u64],
        checkpointed_through_seq: u64,
        active_segment_seq: u64,
    ) -> Vec<u64> {
        let has_live_snapshots = self.active_snapshots.values().any(|s| !s.released);
        if has_live_snapshots {
            return Vec::new();
        }
        let mut out: Vec<u64> = segment_seqs
            .iter()
            .copied()
            .filter(|seq| *seq <= checkpointed_through_seq && *seq != active_segment_seq)
            .collect();
        out.sort_unstable();
        out
    }
}

#[cfg(test)]
mod tests;