start-command 0.32.0

Gamification of coding, execute any command with ability to auto-report issues on GitHub
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
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220

//! Options for the guarded Docker snapshot resume (issue #224):
//!
//! ```text
//! --snapshot-wait <seconds>          wait for the host snapshot lock
//! --snapshot-disk-wait <seconds>     wait for free disk instead of refusing
//! --remove-original-after <seconds>  remove the original only if the
//!                                    replacement still runs after the delay
//! --snapshot-size-hint <bytes>       skip the `docker inspect --size` walk
//! --snapshot-prepare <command>       `docker exec` a command in the original
//!                                    before it is committed
//! ```
//!
//! They only apply to `--resume`. The two waits also read
//! START_SNAPSHOT_LOCK_WAIT and START_SNAPSHOT_DISK_WAIT when the flags are
//! absent, so a supervisor can set them once for every resume it runs.

use crate::args_parser::WrapperOptions;
use serde_json::{json, Value};

/// Parsed snapshot resume options; `None` when the flag was not given.
#[derive(Debug, Clone, Default, PartialEq)]
pub struct SnapshotResumeOptions {
    pub wait: Option<f64>,
    pub disk_wait: Option<f64>,
    pub remove_original_after: Option<f64>,
    pub size_hint: Option<u64>,
    pub prepare: Option<String>,
}

const FLAGS: [&str; 5] = [
    "--snapshot-wait",
    "--snapshot-disk-wait",
    "--remove-original-after",
    "--snapshot-size-hint",
    "--snapshot-prepare",
];

/// JavaScript's `Number.MAX_SAFE_INTEGER`, so both editions accept the same hints.
const MAX_SAFE_INTEGER: u64 = (1 << 53) - 1;

/// Parse a non-negative number of seconds; fractions are allowed.
pub fn parse_seconds(value: &str, name: &str) -> Result<f64, String> {
    let text = value.trim();
    let (whole, fraction) = text.split_once('.').unwrap_or((text, "0"));
    let digits = |s: &str| !s.is_empty() && s.chars().all(|c| c.is_ascii_digit());
    match text.parse::<f64>() {
        Ok(seconds) if digits(whole) && digits(fraction) && seconds.is_finite() => Ok(seconds),
        _ => Err(format!(
            "Invalid {} value: \"{}\". Expected a non-negative number of seconds.",
            name, value
        )),
    }
}

/// Parse a size in bytes; k, m, g and t suffixes are 1024-based.
pub fn parse_size_hint(value: &str) -> Result<u64, String> {
    let text = value.trim().to_lowercase();
    let (number, unit) = match text.char_indices().last() {
        Some((index, suffix)) if "bkmgt".contains(suffix) => (&text[..index], Some(suffix)),
        _ => (text.as_str(), None),
    };
    let multiplier: u64 = match unit {
        None | Some('b') => 1,
        Some('k') => 1 << 10,
        Some('m') => 1 << 20,
        Some('g') => 1 << 30,
        _ => 1 << 40,
    };
    number
        .parse::<u64>()
        .ok()
        .filter(|_| !number.is_empty() && number.chars().all(|c| c.is_ascii_digit()))
        .and_then(|n| n.checked_mul(multiplier))
        .filter(|bytes| *bytes <= MAX_SAFE_INTEGER)
        .ok_or_else(|| {
            format!(
                "Invalid --snapshot-size-hint value: \"{}\". Expected a number of bytes (k, m, g, t suffixes allowed).",
                value
            )
        })
}

fn store(flag: &str, value: &str, options: &mut SnapshotResumeOptions) -> Result<(), String> {
    match flag {
        "--snapshot-size-hint" => options.size_hint = Some(parse_size_hint(value)?),
        "--snapshot-prepare" => {
            if value.trim().is_empty() {
                return Err("--snapshot-prepare requires a non-empty command".to_string());
            }
            options.prepare = Some(value.to_string());
        }
        "--snapshot-wait" => options.wait = Some(parse_seconds(value, flag)?),
        "--snapshot-disk-wait" => options.disk_wait = Some(parse_seconds(value, flag)?),
        _ => options.remove_original_after = Some(parse_seconds(value, flag)?),
    }
    Ok(())
}

/// Parse one snapshot option; returns the arguments consumed, 0 when
/// `args[index]` is not one.
pub fn parse(args: &[String], index: usize, options: &mut WrapperOptions) -> Result<usize, String> {
    let arg = args[index].as_str();
    let (flag, inline) = match arg.split_once('=') {
        Some((flag, value)) => (flag, Some(value)),
        None => (arg, None),
    };
    if !FLAGS.contains(&flag) {
        return Ok(0);
    }
    if let Some(value) = inline {
        store(flag, value, &mut options.snapshot)?;
        return Ok(1);
    }
    // A prepare command may itself start with a dash only through `=`.
    let Some(value) = args.get(index + 1).filter(|value| !value.starts_with('-')) else {
        let kind = match flag {
            "--snapshot-size-hint" => "bytes",
            "--snapshot-prepare" => "command",
            _ => "seconds",
        };
        return Err(format!("Option {} requires a {} argument", flag, kind));
    };
    store(flag, value, &mut options.snapshot)?;
    Ok(2)
}

/// Reject snapshot options outside `--resume` and fill the waits from the
/// environment.
pub fn validate(options: &mut WrapperOptions) -> Result<(), String> {
    validate_with_env(options, &|name| std::env::var(name).ok())
}

pub fn validate_with_env(
    options: &mut WrapperOptions,
    env: &dyn Fn(&str) -> Option<String>,
) -> Result<(), String> {
    let snapshot = &mut options.snapshot;
    if options.resume.is_none() {
        let given = [
            snapshot.wait.is_some(),
            snapshot.disk_wait.is_some(),
            snapshot.remove_original_after.is_some(),
            snapshot.size_hint.is_some(),
            snapshot.prepare.is_some(),
        ];
        return match FLAGS.iter().zip(given).find(|(_, given)| *given) {
            Some((flag, _)) => Err(format!("{} is only valid with --resume", flag)),
            None => Ok(()),
        };
    }
    for (field, name, flag) in [
        (
            &mut snapshot.wait,
            "START_SNAPSHOT_LOCK_WAIT",
            "--snapshot-wait",
        ),
        (
            &mut snapshot.disk_wait,
            "START_SNAPSHOT_DISK_WAIT",
            "--snapshot-disk-wait",
        ),
    ] {
        if field.is_none() {
            if let Some(value) = env(name).filter(|value| !value.is_empty()) {
                *field = Some(parse_seconds(&value, &format!("{} ({})", name, flag))?);
            }
        }
    }
    if snapshot.remove_original_after.is_some() {
        options.remove_original = true;
    }
    Ok(())
}

/// Add the options to the resume `overrides` object.
pub fn insert_overrides(options: &SnapshotResumeOptions, overrides: &mut Value) {
    overrides["snapshotWait"] = json!(options.wait);
    overrides["snapshotDiskWait"] = json!(options.disk_wait);
    overrides["removeOriginalAfter"] = json!(options.remove_original_after);
    overrides["snapshotSizeHint"] = json!(options.size_hint);
    overrides["snapshotPrepare"] = json!(options.prepare);
}

/// What a snapshot resume reads from its `overrides`.
#[derive(Debug, Clone, Default, PartialEq)]
pub struct SnapshotSettings {
    pub wait_seconds: f64,
    pub disk_wait_seconds: f64,
    pub size_hint: Option<u64>,
    pub prepare: Option<String>,
    pub remove_original_after: f64,
    /// Lock file instead of START_SNAPSHOT_LOCK (tests).
    pub lock_path: Option<std::path::PathBuf>,
    /// Disk poll interval instead of START_SNAPSHOT_DISK_POLL (tests).
    pub disk_poll_seconds: Option<f64>,
    /// Progress interval instead of START_SNAPSHOT_PROGRESS_INTERVAL (tests).
    pub progress_interval_seconds: Option<f64>,
}

impl SnapshotSettings {
    pub fn from_overrides(overrides: &Value) -> Self {
        let seconds = |key: &str| overrides.get(key).and_then(Value::as_f64);
        Self {
            wait_seconds: seconds("snapshotWait").unwrap_or(0.0),
            disk_wait_seconds: seconds("snapshotDiskWait").unwrap_or(0.0),
            size_hint: overrides.get("snapshotSizeHint").and_then(Value::as_u64),
            prepare: overrides
                .get("snapshotPrepare")
                .and_then(Value::as_str)
                .map(String::from),
            remove_original_after: seconds("removeOriginalAfter").unwrap_or(0.0),
            lock_path: overrides
                .get("snapshotLockPath")
                .and_then(Value::as_str)
                .map(std::path::PathBuf::from),
            disk_poll_seconds: seconds("snapshotDiskPoll"),
            progress_interval_seconds: seconds("snapshotProgressInterval"),
        }
    }
}