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
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
use std::{
fmt,
path::{Path, PathBuf},
time::Duration,
};
use git_tempfile::{AutoRemove, ContainingDirectory};
use quick_error::quick_error;
use crate::{backoff, File, Marker, DOT_LOCK_SUFFIX};
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
pub enum Fail {
Immediately,
AfterDurationWithBackoff(Duration),
}
impl Default for Fail {
fn default() -> Self {
Fail::Immediately
}
}
impl fmt::Display for Fail {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Fail::Immediately => f.write_str("immediately"),
Fail::AfterDurationWithBackoff(duration) => {
write!(f, "after {:.02}s", duration.as_secs_f32())
}
}
}
}
quick_error! {
#[derive(Debug)]
#[allow(missing_docs)]
pub enum Error {
Io(err: std::io::Error) {
display("Another IO error occurred while obtaining the lock")
from()
source(err)
}
PermanentlyLocked { resource_path: PathBuf, mode: Fail, attempts: usize } {
display("The lock for resource '{} could not be obtained {} after {} attempt(s). The lockfile at '{}{}' might need manual deletion.", resource_path.display(), mode, attempts, resource_path.display(), super::DOT_LOCK_SUFFIX)
}
}
}
impl File {
pub fn acquire_to_update_resource(
at_path: impl AsRef<Path>,
mode: Fail,
boundary_directory: Option<PathBuf>,
) -> Result<File, Error> {
let (lock_path, handle) = lock_with_mode(at_path.as_ref(), mode, boundary_directory, |p, d, c| {
git_tempfile::writable_at(p, d, c)
})?;
Ok(File {
inner: handle,
lock_path,
})
}
}
impl Marker {
pub fn acquire_to_hold_resource(
at_path: impl AsRef<Path>,
mode: Fail,
boundary_directory: Option<PathBuf>,
) -> Result<Marker, Error> {
let (lock_path, handle) = lock_with_mode(at_path.as_ref(), mode, boundary_directory, |p, d, c| {
git_tempfile::mark_at(p, d, c)
})?;
Ok(Marker {
created_from_file: false,
inner: handle,
lock_path,
})
}
}
fn dir_cleanup(boundary: Option<PathBuf>) -> (ContainingDirectory, AutoRemove) {
match boundary {
None => (ContainingDirectory::Exists, AutoRemove::Tempfile),
Some(boundary_directory) => (
ContainingDirectory::CreateAllRaceProof(Default::default()),
AutoRemove::TempfileAndEmptyParentDirectoriesUntil { boundary_directory },
),
}
}
fn lock_with_mode<T>(
resource: &Path,
mode: Fail,
boundary_directory: Option<PathBuf>,
try_lock: impl Fn(&Path, ContainingDirectory, AutoRemove) -> std::io::Result<T>,
) -> Result<(PathBuf, T), Error> {
use std::io::ErrorKind::*;
let (directory, cleanup) = dir_cleanup(boundary_directory);
let lock_path = add_lock_suffix(resource);
let mut attempts = 1;
match mode {
Fail::Immediately => try_lock(&lock_path, directory, cleanup),
Fail::AfterDurationWithBackoff(time) => {
for wait in backoff::Exponential::default_with_random().until_no_remaining(time) {
attempts += 1;
match try_lock(&lock_path, directory, cleanup.clone()) {
Ok(v) => return Ok((lock_path, v)),
#[cfg(windows)]
Err(err) if err.kind() == AlreadyExists || err.kind() == PermissionDenied => {
std::thread::sleep(wait);
continue;
}
#[cfg(not(windows))]
Err(err) if err.kind() == AlreadyExists => {
std::thread::sleep(wait);
continue;
}
Err(err) => return Err(Error::from(err)),
}
}
try_lock(&lock_path, directory, cleanup)
}
}
.map(|v| (lock_path, v))
.map_err(|err| match err.kind() {
AlreadyExists => Error::PermanentlyLocked {
resource_path: resource.into(),
mode,
attempts,
},
_ => Error::Io(err),
})
}
fn add_lock_suffix(resource_path: &Path) -> PathBuf {
resource_path.with_extension(resource_path.extension().map_or_else(
|| DOT_LOCK_SUFFIX.chars().skip(1).collect(),
|ext| format!("{}{}", ext.to_string_lossy(), DOT_LOCK_SUFFIX),
))
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn add_lock_suffix_to_file_with_extension() {
assert_eq!(add_lock_suffix(Path::new("hello.ext")), Path::new("hello.ext.lock"));
}
#[test]
fn add_lock_suffix_to_file_without_extension() {
assert_eq!(add_lock_suffix(Path::new("hello")), Path::new("hello.lock"));
}
}