refactor: use futures instead of tokio for media upload

src/lib.rs

@@ -25,12 +25,11 @@ use rusqlite::Connection;
 use std::sync::Arc;
 use tokio::{spawn, sync::Mutex};
 
+use futures::StreamExt;
+
 /// This is where the magic happens
 #[tokio::main]
 pub async fn run(config: Config) {
-    // create the task vector for handling multiple accounts
-    let mut mtask = vec![];
-
     // open the SQLite connection
     let conn = Arc::new(Mutex::new(
         Connection::open(&config.scootaloo.db_path).unwrap_or_else(|e| {
@@ -41,13 +40,14 @@ pub async fn run(config: Config) {
         }),
     ));
 
-    for mastodon_config in config.mastodon.into_values() {
+    let mut stream = futures::stream::iter(config.mastodon.into_values())
+        .map(|mastodon_config| {
         // create temporary value for each task
         let scootaloo_cache_path = config.scootaloo.cache_path.clone();
         let token = get_oauth2_token(&config.twitter);
         let task_conn = conn.clone();
 
-        let task = spawn(async move {
+        spawn(async move {
             info!("Starting treating {}", &mastodon_config.twitter_screen_name);
 
             // retrieve the last tweet ID for the username
@@ -138,14 +138,11 @@ pub async fn run(config: Config) {
             }
             Ok::<(), ScootalooError>(())
         });
-
-        // push each task into the vec task
-        mtask.push(task);
-    }
+    }).buffer_unordered(4);
 
     // launch and wait for every handle
-    for handle in mtask {
-        match handle.await {
+    while let Some(result) = stream.next().await {
+        match result {
             Ok(Err(e)) => eprintln!("Error within thread: {}", e),
             Err(e) => eprintln!("Error with thread: {}", e),
             _ => (),

src/util.rs

@@ -15,6 +15,8 @@ use tokio::{
     io::copy,
 };
 
+use futures::{stream, stream::StreamExt};
+
 /// Generate associative table between media ids and tweet extended entities
 pub async fn generate_media_ids(
     tweet: &Tweet,
@@ -25,45 +27,40 @@ pub async fn generate_media_ids(
     let mut media_ids: Vec<String> = vec![];
 
     if let Some(m) = &tweet.extended_entities {
-        // create tasks list
-        let mut tasks = vec![];
-
-        // size of media_ids vector, should be equal to the media vector
-        media_ids.resize(m.media.len(), String::new());
-
         info!("{} medias in tweet", m.media.len());
 
-        for (i, media) in m.media.iter().enumerate() {
-            // attribute media url
-            media_url = media.url.clone();
+        let medias = m.media.clone();
 
-            // clone everything we need
-            let cache_path = String::from(cache_path);
-            let media = media.clone();
-            let mastodon = mastodon.clone();
+        let mut stream = stream::iter(medias)
+            .map(|media| {
+                // attribute media url
+                media_url = media.url.clone();
 
-            let task = tokio::task::spawn(async move {
-                info!("Start treating {}", media.media_url_https);
-                // get the tweet embedded media
-                let local_tweet_media_path = get_tweet_media(&media, &cache_path).await?;
+                // clone everything we need
+                let cache_path = String::from(cache_path);
+                let mastodon = mastodon.clone();
 
-                // upload media to Mastodon
-                let mastodon_media =
-                    mastodon.media(Cow::from(local_tweet_media_path.to_owned()))?;
-                // at this point, we can safely erase the original file
-                // it doesn’t matter if we can’t remove, cache_media fn is idempotent
-                remove_file(&local_tweet_media_path).await.ok();
+                tokio::task::spawn(async move {
+                    info!("Start treating {}", media.media_url_https);
+                    // get the tweet embedded media
+                    let local_tweet_media_path = get_tweet_media(&media, &cache_path).await?;
 
-                Ok::<(usize, String), ScootalooError>((i, mastodon_media.id))
-            });
+                    // upload media to Mastodon
+                    let mastodon_media =
+                        mastodon.media(Cow::from(local_tweet_media_path.to_owned()))?;
+                    // at this point, we can safely erase the original file
+                    // it doesn’t matter if we can’t remove, cache_media fn is idempotent
+                    remove_file(&local_tweet_media_path).await.ok();
 
-            tasks.push(task);
-        }
+                    Ok::<String, ScootalooError>(mastodon_media.id)
+                })
+            })
+            .buffered(4); // there are max four medias per tweet and they need to be treated in
+                          // order
 
-        for task in tasks {
-            match task.await {
-                // insert the media at the right place
-                Ok(Ok((i, v))) => media_ids[i] = v,
+        while let Some(result) = stream.next().await {
+            match result {
+                Ok(Ok(v)) => media_ids.push(v),
                 Ok(Err(e)) => warn!("Cannot treat media: {}", e),
                 Err(e) => error!("Something went wrong when joining the main thread: {}", e),
             }