static-web-server 2.42.0

A cross-platform, high-performance and asynchronous web server for static files-serving.
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
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351

// SPDX-License-Identifier: MIT OR Apache-2.0
// This file is part of Static Web Server.
// See https://static-web-server.net/ for more information
// Copyright (C) 2019-present Jose Quintana <joseluisq.net>

//! Module providing the metrics endpoint and HTTP-level instrumentation.
//!

use std::sync::LazyLock;

use headers::{ContentType, HeaderMapExt};
use hyper::{Body, Request, Response, StatusCode};
use prometheus::{
    Encoder, HistogramOpts, HistogramVec, IntCounterVec, IntGauge, Opts, TextEncoder,
    default_registry,
};

use crate::{Error, handler::RequestHandlerOpts, http_ext::MethodExt};

// Histogram buckets tuned for static file serving (50µs to 10s).
// Sub-millisecond range captures cache hits and small in-memory responses.
const LATENCY_BUCKETS: &[f64] = &[
    0.00005, 0.0001, 0.00025, 0.0005, 0.001, 0.0025, 0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1.0,
    2.5, 5.0, 10.0,
];

static HTTP_REQUESTS_TOTAL: LazyLock<IntCounterVec> = LazyLock::new(|| {
    IntCounterVec::new(
        Opts::new(
            "sws_http_requests_total",
            "Total HTTP requests by method, status class, and host.",
        ),
        &["method", "status", "host"],
    )
    .unwrap()
});

static HTTP_REQUEST_DURATION_SECONDS: LazyLock<HistogramVec> = LazyLock::new(|| {
    HistogramVec::new(
        HistogramOpts::new(
            "sws_http_request_duration_seconds",
            "HTTP request duration in seconds by method, status class, and host.",
        )
        .buckets(LATENCY_BUCKETS.to_vec()),
        &["method", "status", "host"],
    )
    .unwrap()
});

static HTTP_RESPONSE_BYTES_TOTAL: LazyLock<IntCounterVec> = LazyLock::new(|| {
    IntCounterVec::new(
        Opts::new(
            "sws_http_response_bytes_total",
            "Total HTTP response bytes (Content-Length) by method, status class, and host.",
        ),
        &["method", "status", "host"],
    )
    .unwrap()
});

static HTTP_REQUESTS_INFLIGHT: LazyLock<IntGauge> = LazyLock::new(|| {
    IntGauge::new(
        "sws_http_requests_inflight",
        "Number of HTTP requests currently being processed.",
    )
    .unwrap()
});

static HTTP_CONNECTIONS_ACTIVE: LazyLock<IntGauge> = LazyLock::new(|| {
    IntGauge::new(
        "sws_http_connections_active",
        "Number of currently active HTTP connections.",
    )
    .unwrap()
});

/// Initializes the metrics endpoint and registers HTTP-level collectors.
/// Tokio runtime metrics are additionally registered when the `experimental`
/// feature is enabled and built with `RUSTFLAGS="--cfg tokio_unstable"`.
pub fn init(enabled: bool, handler_opts: &mut RequestHandlerOpts) {
    handler_opts.metrics_enabled = enabled;
    tracing::info!("metrics endpoint: enabled={enabled}");

    if enabled {
        let registry = default_registry();

        // Tokio runtime metrics (experimental, unix-only, requires tokio_unstable)
        #[cfg(all(unix, feature = "experimental"))]
        {
            registry
                .register(Box::new(
                    tokio_metrics_collector::default_runtime_collector(),
                ))
                .unwrap();
            tracing::info!("tokio runtime metrics: enabled");
        }

        // HTTP-level metrics
        registry
            .register(Box::new(HTTP_REQUESTS_TOTAL.clone()))
            .unwrap();
        registry
            .register(Box::new(HTTP_REQUEST_DURATION_SECONDS.clone()))
            .unwrap();
        registry
            .register(Box::new(HTTP_RESPONSE_BYTES_TOTAL.clone()))
            .unwrap();
        registry
            .register(Box::new(HTTP_REQUESTS_INFLIGHT.clone()))
            .unwrap();
        registry
            .register(Box::new(HTTP_CONNECTIONS_ACTIVE.clone()))
            .unwrap();
    }
}

/// Handles metrics requests.
pub fn pre_process<T>(
    opts: &RequestHandlerOpts,
    req: &Request<T>,
) -> Option<Result<Response<Body>, Error>> {
    if !opts.metrics_enabled {
        return None;
    }

    let uri = req.uri();
    if uri.path() != "/metrics" {
        return None;
    }

    let method = req.method();
    if !method.is_get() && !method.is_head() {
        return None;
    }

    let body = if method.is_get() {
        let encoder = TextEncoder::new();
        let mut buffer = Vec::new();
        encoder
            .encode(&default_registry().gather(), &mut buffer)
            .unwrap();
        let data = String::from_utf8(buffer).unwrap();
        Body::from(data)
    } else {
        Body::empty()
    };
    let mut resp = Response::new(body);
    resp.headers_mut()
        .typed_insert(ContentType::from(mime_guess::mime::TEXT_PLAIN_UTF_8));
    Some(Ok(resp))
}

/// Records HTTP request metrics after a response is produced.
pub fn record_request<T>(req: &Request<T>, status: StatusCode, bytes: u64, elapsed: f64) {
    if req.uri().path() == "/metrics" {
        return;
    }
    let m = req.method().as_str();
    let host = req
        .headers()
        .get(hyper::header::HOST)
        .and_then(|v| v.to_str().ok())
        .unwrap_or("");
    let sc = status_class(status.as_u16());
    HTTP_REQUESTS_TOTAL.with_label_values(&[m, sc, host]).inc();
    HTTP_REQUEST_DURATION_SECONDS
        .with_label_values(&[m, sc, host])
        .observe(elapsed);
    if bytes > 0 {
        HTTP_RESPONSE_BYTES_TOTAL
            .with_label_values(&[m, sc, host])
            .inc_by(bytes);
    }
}

/// Increments the inflight requests gauge.
pub fn inc_requests_inflight() {
    HTTP_REQUESTS_INFLIGHT.inc();
}

/// Decrements the inflight requests gauge.
pub fn dec_requests_inflight() {
    HTTP_REQUESTS_INFLIGHT.dec();
}

/// Increments the active connections gauge.
pub fn inc_connections() {
    HTTP_CONNECTIONS_ACTIVE.inc();
}

/// Decrements the active connections gauge.
pub fn dec_connections() {
    HTTP_CONNECTIONS_ACTIVE.dec();
}

fn status_class(code: u16) -> &'static str {
    match code / 100 {
        1 => "1xx",
        2 => "2xx",
        3 => "3xx",
        4 => "4xx",
        _ => "5xx",
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::handler::RequestHandlerOpts;
    use hyper::{Body, Request};

    fn make_request(method: &str, uri: &str) -> Request<Body> {
        Request::builder()
            .method(method)
            .uri(uri)
            .body(Body::empty())
            .unwrap()
    }

    #[test]
    fn test_metrics_disabled() {
        assert!(
            pre_process(
                &RequestHandlerOpts {
                    metrics_enabled: false,
                    ..Default::default()
                },
                &make_request("GET", "/metrics")
            )
            .is_none()
        );
    }

    #[test]
    fn test_wrong_uri() {
        assert!(
            pre_process(
                &RequestHandlerOpts {
                    metrics_enabled: true,
                    ..Default::default()
                },
                &make_request("GET", "/metrics2")
            )
            .is_none()
        );
    }

    #[test]
    fn test_wrong_method() {
        assert!(
            pre_process(
                &RequestHandlerOpts {
                    metrics_enabled: true,
                    ..Default::default()
                },
                &make_request("POST", "/metrics")
            )
            .is_none()
        );
    }

    #[test]
    fn test_correct_request() {
        assert!(
            pre_process(
                &RequestHandlerOpts {
                    metrics_enabled: true,
                    ..Default::default()
                },
                &make_request("GET", "/metrics")
            )
            .is_some()
        );
    }

    #[test]
    fn test_status_class() {
        assert_eq!(status_class(100), "1xx");
        assert_eq!(status_class(200), "2xx");
        assert_eq!(status_class(301), "3xx");
        assert_eq!(status_class(404), "4xx");
        assert_eq!(status_class(500), "5xx");
        assert_eq!(status_class(999), "5xx");
    }

    #[test]
    fn test_record_request() {
        let before = HTTP_REQUESTS_TOTAL
            .with_label_values(&["GET", "2xx", "example.com"])
            .get();
        let bytes_before = HTTP_RESPONSE_BYTES_TOTAL
            .with_label_values(&["GET", "2xx", "example.com"])
            .get();

        let req = Request::builder()
            .method("GET")
            .uri("/index.html")
            .header(hyper::header::HOST, "example.com")
            .body(Body::empty())
            .unwrap();
        record_request(&req, StatusCode::OK, 1024, 0.005);

        assert_eq!(
            HTTP_REQUESTS_TOTAL
                .with_label_values(&["GET", "2xx", "example.com"])
                .get(),
            before + 1
        );
        assert_eq!(
            HTTP_RESPONSE_BYTES_TOTAL
                .with_label_values(&["GET", "2xx", "example.com"])
                .get(),
            bytes_before + 1024
        );
    }

    #[test]
    fn test_record_request_skips_metrics_path() {
        let before = HTTP_REQUESTS_TOTAL
            .with_label_values(&["GET", "2xx", ""])
            .get();

        let req = make_request("GET", "/metrics");
        record_request(&req, StatusCode::OK, 0, 0.001);

        assert_eq!(
            HTTP_REQUESTS_TOTAL
                .with_label_values(&["GET", "2xx", ""])
                .get(),
            before
        );
    }

    #[test]
    fn test_connection_gauge() {
        let before = HTTP_CONNECTIONS_ACTIVE.get();
        inc_connections();
        assert_eq!(HTTP_CONNECTIONS_ACTIVE.get(), before + 1);
        dec_connections();
        assert_eq!(HTTP_CONNECTIONS_ACTIVE.get(), before);
    }

    #[test]
    fn test_inflight_gauge() {
        let before = HTTP_REQUESTS_INFLIGHT.get();
        inc_requests_inflight();
        assert_eq!(HTTP_REQUESTS_INFLIGHT.get(), before + 1);
        dec_requests_inflight();
        assert_eq!(HTTP_REQUESTS_INFLIGHT.get(), before);
    }
}