async: Log every esplora request

Log every request, so we know

1) which endpoints we're calling,
2) how many requests we're making, and
3) which services these requests are sent to.

TODO(max): Eventually this should be done with metrics, not logs.

License: PolyForm Noncommercial License 1.0.0

Author: MaxFangX

src/async.rs

@@ -263,6 +263,7 @@ impl<S: Sleeper> AsyncClient<S> {
         let url = format!("{}{}", self.url, path);
         let body = serialize::<T>(&body).to_lower_hex_string();
 
+        self.log_request(&url, "POST");
         let response = self.client.post(url).body(body).send().await?;
 
         if !response.status().is_success() {
@@ -466,6 +467,7 @@ impl<S: Sleeper> AsyncClient<S> {
         let mut attempts = 0;
 
         loop {
+            self.log_request(url, "GET");
             match self.client.get(url).send().await? {
                 resp if attempts < self.max_retries && is_status_retryable(resp.status()) => {
                     S::sleep(delay).await;
@@ -476,6 +478,40 @@ impl<S: Sleeper> AsyncClient<S> {
             }
         }
     }
+
+    /// Lexe patch: Log every request, so we know
+    ///
+    /// 1) which endpoints we're calling,
+    /// 2) how many requests we're making, and
+    /// 3) which services these requests are sent to.
+    ///
+    /// TODO(max): Eventually this should be done with metrics, not logs.
+    fn log_request(&self, url: &str, method: &str) {
+        let base_url = &self.url;
+
+        // For user privacy, log only the part of the path up to the first `/`.
+        let path_prefix = path_prefix(&self.url, url);
+
+        // "Esplora request: GET https://blockstream.info/api/address"
+        // "Esplora request: POST https://mempool.space/api/tx"
+        debug!("Esplora request: {method} {base_url}/{path_prefix}");
+    }
+}
+
+/// `base_url`: "https://mempool.space/api"
+/// `url`: "/tx/foo"
+/// => `path_prefix`: "/tx"
+fn path_prefix<'a>(base_url: &str, url: &'a str) -> &'a str {
+    if url.len() <= base_url.len() + 1 {
+        return url;
+    }
+
+    let path = &url[base_url.len() + 1..];
+    if let Some(slash_idx) = path.find('/') {
+        &url[..base_url.len() + 1 + slash_idx]
+    } else {
+        url
+    }
 }
 
 fn is_status_retryable(status: reqwest::StatusCode) -> bool {
@@ -498,3 +534,34 @@ impl Sleeper for DefaultSleeper {
         tokio::time::sleep(dur)
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    /// $ cargo test test_sanitize -- --show-output
+    #[test]
+    fn test_path_prefix() {
+        let base_url = "https://mempool.space/api";
+        let test_cases = [
+            ["https://mempool.space", "https://mempool.space"],
+            ["https://mempool.space/api/", "https://mempool.space/api/"],
+            [
+                "https://mempool.space/api/tx",
+                "https://mempool.space/api/tx",
+            ],
+            [
+                "https://mempool.space/api/tx/foo",
+                "https://mempool.space/api/tx",
+            ],
+        ];
+
+        for [url, expected] in test_cases {
+            let sanitized = path_prefix(base_url, url);
+            assert_eq!(sanitized, expected);
+            println!("Original URL: {url}");
+            println!("Sanitized: {sanitized}");
+            println!("---");
+        }
+    }
+}