minigh 0.2.0

Minimal and opinionated GitHub REST API client
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
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304

use super::{Method, RequestError, StatusError};
use mime::{JSON, Mime};
use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
use ureq::{
    Body,
    http::{
        header::{CONTENT_TYPE, HeaderName, LINK, RETRY_AFTER},
        response::{Parts, Response},
        status::StatusCode,
    },
};
use url::Url;

/// Maximum number of times to retry a request
const RETRIES: i32 = 10;

/// Multiplier for exponential backoff delays
const BACKOFF_FACTOR: f64 = 1.0;

/// Base value for exponential backoff delays
const BACKOFF_BASE: f64 = 1.25;

/// Maximum value of exponential backoff delays
const BACKOFF_MAX: f64 = 120.0;

/// Maximum amount of time to spend retrying a request
const TOTAL_WAIT: Duration = Duration::from_secs(300);

/// The name of the `X-Ratelimit-Remaining` header
const RATELIMIT_REMAINING_HEADER: HeaderName = HeaderName::from_static("x-ratelimit-remaining");

/// The name of the `X-Ratelimit-Reset` header
const RATELIMIT_RESET_HEADER: HeaderName = HeaderName::from_static("x-ratelimit-reset");

/// A struct for determining retries for a single request
#[derive(Clone, Debug, Eq, PartialEq)]
pub(super) struct Retrier {
    /// The HTTP method of the request
    method: Method,

    /// The URL to which the request is being sent
    url: Url,

    /// Which retry we're currently on
    attempts: i32,

    /// Timestamp beyond which we should stop retrying
    stop_time: Instant,
}

impl Retrier {
    pub(super) fn new(method: Method, url: Url) -> Retrier {
        Retrier {
            method,
            url,
            attempts: 0,
            stop_time: Instant::now() + TOTAL_WAIT,
        }
    }

    /// Takes the return value of a call to
    /// [`ureq::RequestBuilder::send_json()`] or similar and decides whether or
    /// not to retry the request.
    ///
    /// - If the request was successful (status code and everything), returns
    ///   `Ok(RetryDecision::Success(response))`.
    ///
    /// - If the request should be retried, returns
    ///   `Ok(RetryDecision::Retry(delay))`.
    ///
    /// - If the request was a failure (possibly due to status code) and should
    ///   not be retried (possibly due to all retries having been exhausted),
    ///   returns an `Err` to return to the caller.
    pub(super) fn handle(
        &mut self,
        resp: Result<Response<Body>, ureq::Error>,
    ) -> Result<RetryDecision, RequestError> {
        self.attempts += 1;
        if self.attempts > RETRIES {
            log::debug!("Retries exhausted");
            return self.finalize(resp);
        }
        let now = Instant::now();
        let time_left = self.stop_time.saturating_duration_since(now);
        if time_left == Duration::ZERO {
            log::debug!("Maximum total retry wait time exceeded");
            return self.finalize(resp);
        }
        let backoff = if self.attempts < 2 {
            // urllib3 says "most errors are resolved immediately by a second
            // try without a delay" and thus doesn't sleep on the first retry,
            // but that seems irresponsible
            BACKOFF_FACTOR * 0.1
        } else {
            (BACKOFF_FACTOR * BACKOFF_BASE.powi(self.attempts - 1)).clamp(0.0, BACKOFF_MAX)
        };
        let backoff = Duration::from_secs_f64(backoff);
        let delay = match resp {
            Ok(r) if r.status() == StatusCode::FORBIDDEN => {
                let mut rr = ReadableResponse::new(self.method, self.url.clone(), r);
                if let Some(v) = rr.header(RETRY_AFTER) {
                    let secs = v.parse::<u64>().ok().map(|n| n + 1);
                    if let Some(delay) = secs {
                        log::debug!("Server responded with 403 and Retry-After header");
                        if time_left < Duration::from_secs(delay) {
                            log::debug!(
                                "Retrying after Retry-After would exceed maximum total retry wait time; not retrying"
                            );
                            return Err(RequestError::Status(StatusError::from(rr)));
                        }
                    }
                    Duration::from_secs(secs.unwrap_or_default())
                } else if rr.body().is_some_and(|s| s.contains("rate limit")) {
                    if rr
                        .header(RATELIMIT_REMAINING_HEADER)
                        .is_some_and(|v| v == "0")
                    {
                        if let Some(reset) = rr
                            .header(RATELIMIT_RESET_HEADER)
                            .and_then(|s| s.parse::<u64>().ok())
                        {
                            let delay = time_till_timestamp(reset).unwrap_or_default()
                                + Duration::from_secs(1);
                            if time_left < delay {
                                log::debug!(
                                    "Primary rate limit exceeded; waiting for reset would exceed maximum total retry wait time; not retrying"
                                );
                                return Err(RequestError::Status(StatusError::from(rr)));
                            } else {
                                log::debug!("Primary rate limit exceeded; waiting for reset");
                            }
                            delay
                        } else {
                            Duration::ZERO
                        }
                    } else {
                        log::debug!("Secondary rate limit triggered");
                        backoff
                    }
                } else {
                    return Err(RequestError::Status(StatusError::from(rr)));
                }
            }
            Ok(r) if r.status().is_server_error() => backoff,
            Ok(ref r) if r.status().is_client_error() => return self.finalize(resp),
            Err(_) => backoff,
            Ok(_) => return self.finalize(resp),
        };
        Ok(RetryDecision::Retry(delay.min(time_left)))
    }

    fn finalize(
        &self,
        resp: Result<Response<Body>, ureq::Error>,
    ) -> Result<RetryDecision, RequestError> {
        match resp {
            Ok(r) if r.status().is_client_error() || r.status().is_server_error() => {
                Err(RequestError::Status(StatusError::from(
                    ReadableResponse::new(self.method, self.url.clone(), r),
                )))
            }
            Ok(r) => Ok(RetryDecision::Success(r)),
            Err(source) => Err(RequestError::Send {
                method: self.method,
                url: self.url.clone(),
                source: Box::new(source),
            }),
        }
    }
}

/// Return type of [`Retrier::handle()`]
#[derive(Debug)]
#[allow(clippy::large_enum_variant)]
pub(super) enum RetryDecision {
    /// Return the given response without retrying
    Success(Response<Body>),

    /// Sleep for the given duration and then retry the request
    Retry(Duration),
}

/// A decomposed HTTP response that can read & store the response body.
#[derive(Debug)]
pub(super) struct ReadableResponse {
    /// The HTTP method of the corresponding request
    method: Method,

    /// The URL to which the corresponding request was made
    url: Url,

    /// The [`http::response::Parts`] of the response
    parts: Parts,

    /// The response body
    body: ReadableBody,
}

impl ReadableResponse {
    fn new(method: Method, url: Url, resp: Response<Body>) -> Self {
        let (parts, body) = resp.into_parts();
        ReadableResponse {
            method,
            url,
            parts,
            body: ReadableBody::Unread(body),
        }
    }

    /// Returns the value of the given header as a string, if set and UTF-8
    fn header(&self, key: HeaderName) -> Option<&str> {
        let v = self.parts.headers.get(&key)?;
        v.to_str().ok()
    }

    /// Returns the response body if it can be successfully read as a string
    fn body(&mut self) -> Option<&str> {
        self.body.as_str()
    }

    /// Returns the response body if it can be successfully read as a string.
    /// If the response's headers indicate the body is JSON, the body is
    /// pretty-printed.
    fn pretty_body(&mut self) -> Option<String> {
        if self.header(CONTENT_TYPE).is_some_and(is_json_content_type) {
            self.body
                .as_str()
                .and_then(|s| serde_json::from_str::<serde_json::Value>(s).ok())
                .map(|v| {
                    serde_json::to_string_pretty(&v)
                        .expect("Re-JSONifying a JSON response should not fail")
                })
        } else {
            self.body
                .as_str()
                .filter(|s| !s.is_empty())
                .map(ToOwned::to_owned)
        }
    }
}

impl From<ReadableResponse> for StatusError {
    fn from(mut value: ReadableResponse) -> StatusError {
        let body = value.pretty_body();
        StatusError {
            method: value.method,
            url: value.url,
            status: value.parts.status,
            body,
        }
    }
}

/// A response body that may or may not have been read yet
#[derive(Debug)]
#[allow(clippy::large_enum_variant)]
enum ReadableBody {
    /// A body that has not yet been read
    Unread(Body),

    /// A body that has been read.  If the body was successfully read as a
    /// string, this variant contains the string; otherwise, it contains
    /// `None`.
    Read(Option<String>),
}

impl ReadableBody {
    /// If the body has not been read yet, read & store it as a string.
    /// Returns the read body.
    fn as_str(&mut self) -> Option<&str> {
        if let ReadableBody::Unread(body) = self {
            *self = ReadableBody::Read(body.read_to_string().ok());
        }
        let &mut ReadableBody::Read(ref s) = self else {
            unreachable!("ReadableBody should be Read after reading");
        };
        s.as_deref()
    }
}

/// Return the `rel="next"` URL, if any, from the response's "Link" header
pub(super) fn get_next_link(r: &Response<Body>) -> Option<Url> {
    let header_value = r.headers().get(LINK)?.to_str().ok()?;
    parse_link_header::parse_with_rel(header_value)
        .ok()?
        .get("next")
        .map(|link| link.uri.clone())
}

/// Given the value of a `Content-Type` header, returns `true` if the value
/// is for a JSON payload
fn is_json_content_type(ct_value: &str) -> bool {
    ct_value.parse::<Mime>().ok().is_some_and(|ct| {
        ct.type_() == "application" && (ct.subtype() == "json" || ct.suffix() == Some(JSON))
    })
}

/// Calculate the [`Duration`] until the system time is at the given number of
/// seconds since the Unix epoch
fn time_till_timestamp(ts: u64) -> Option<Duration> {
    (UNIX_EPOCH + Duration::from_secs(ts))
        .duration_since(SystemTime::now())
        .ok()
}