cohost2autost: use exponential backoff for attachment redirects

src/attachments.rs

@@ -2,6 +2,8 @@ use std::{
     fs::{copy, create_dir_all, read_dir, File},
     io::{Read, Write},
     path::Path,
+    thread::sleep,
+    time::Duration,
 };
 
 use jane_eyre::eyre::{self, bail, OptionExt};
@@ -237,7 +239,8 @@ fn cache_cohost_attachment(
         .redirect(Policy::none())
         .build()?;
 
-    let mut retries = 2;
+    let mut retries = 4;
+    let mut wait = Duration::from_secs(4);
     let mut redirect;
     let url = loop {
         let result = client.head(url).send();
@@ -247,6 +250,9 @@ fn cache_cohost_attachment(
                 if retries == 0 {
                     bail!("failed to get attachment redirect (after retries): {url}: {error:?}");
                 } else {
+                    warn!(?wait, url, ?error, "retrying failed request");
+                    sleep(wait);
+                    wait *= 2;
                     retries -= 1;
                     continue;
                 }
@@ -276,6 +282,9 @@ fn cache_cohost_attachment(
                     redirect.status()
                 );
             } else {
+                warn!(?wait, url, status = ?redirect.status(), "retrying failed request");
+                sleep(wait);
+                wait *= 2;
                 retries -= 1;
                 continue;
             }