add multi-channels example

examples/livecoding_channel.rs

@@ -0,0 +1,82 @@
+use scraper::{Html,Selector};
+use url::Url;
+use tokio::sync::mpsc::{self, Sender}; //, Receiver};
+
+const WORKERS : usize = 8;
+
+type SiteStat = (Url, Vec<Url>);
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let addr = std::env::args().nth(1)
+	.unwrap_or_else(|| "https://www.tmplab.org".to_string());
+
+    let links = get_links(addr.as_ref()).await?;
+    let addr = Url::parse(addr.as_ref())?;
+    let mut links : Vec<Url> = links.into_iter()
+	.filter(| url | url.host() != addr.host())
+	.collect();
+
+    let mut to_fetch = links.len();    
+    let (tx, mut rx) = mpsc::channel(32);
+    // spawn a pool of workers to get the things started...
+    for _ in 0..WORKERS {
+	if let Some(addr) = links.pop() {
+	    spawn_worker(addr, tx.clone());
+	}
+    }
+    
+    let mut results = vec![];
+    // gets the results back from the workers through the channel
+    while let Some(res) = rx.recv().await {
+	to_fetch -= 1;
+	let Some(site) = res else {
+	    continue
+	};
+	results.push(site);
+	// if there are still urls to fetch, pop one and spawn a new worker
+	// otherwise we want to break this loop if all the urls
+	// have been fetched...
+	if let Some(addr) = links.pop() {
+	    spawn_worker(addr, tx.clone());	    
+	} else if to_fetch == 0 {
+	    break;
+	}
+    }
+    
+    for (url, links) in results {
+	println!("{url} : {} links", links.len())
+    }
+    
+    Ok(())
+}
+
+// interestingly, this function must not be async...
+//a worker fetch one url, send it's result back in the channel, and terminates.
+fn spawn_worker(url: Url, tx: Sender<Option<SiteStat>>) { 
+    println!("Start fetching {url}");
+    tokio::spawn(async move {
+	let res = get_links(url.as_ref()).await
+	    .ok()
+	    .map(| v | (url.clone(), v));
+	println!("Got {url}");	
+	tx.send(res).await.unwrap()
+    });
+}
+
+async fn get_links(
+    url: &str
+) -> Result<Vec<Url>, reqwest::Error> {
+    let a_selector = Selector::parse("a[href]").unwrap();
+    
+    let body = reqwest::get(url)
+	.await?
+	.text()
+	.await?;
+
+    Ok(Html::parse_document(&body)
+       .select(&a_selector)
+       .filter_map(| link | link.value().attr("href")
+		   .and_then(| href | Url::parse(href).ok()))
+       .collect())
+}

examples/livecoding_channels.rs

@@ -10,58 +10,68 @@ type SiteStat = (Url, Vec<Url>);
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
     let addr = std::env::args().nth(1)
 	.unwrap_or_else(|| "https://www.tmplab.org".to_string());
-
     let links = get_links(addr.as_ref()).await?;
     let addr = Url::parse(addr.as_ref())?;
     let mut links : Vec<Url> = links.into_iter()
 	.filter(| url | url.host() != addr.host())
 	.collect();
 
-    let mut to_fetch = links.len();    
     let (tx, mut rx) = mpsc::channel(32);
-    // spawn a pool of workers to get the things started...
-    for _ in 0..WORKERS {
-	if let Some(addr) = links.pop() {
-	    spawn_worker(addr, tx.clone());
-	}
-    }
     
+    // spawn a pool of workers
+    let mut workers : Vec<Option<Sender<Url>>> = (0..WORKERS)
+	.map(| n | Some(spawn_worker(n, tx.clone())))
+	.collect();
+
+    // send 1 url to each worker to get things started
+    for tx in &workers {
+	if let Some(url) = links.pop() {
+	    tx.as_ref().unwrap().send(url).await.unwrap();
+	}
+    }
+    println!("links: {}", links.len());
     let mut results = vec![];
-    // gets the results back from the workers through the channel
+    // recieve the results and send back new url to the workers
-    while let Some(res) = rx.recv().await {
+    while let Some((idx, res)) = rx.recv().await {
-	to_fetch -= 1;
+	if let Some(res) = res {
-	let Some(site) = res else {
+	    results.push(res);
-	    continue
+	}
-	};
-	results.push(site);
-	// if there are still urls to fetch, pop one and spawn a new worker
-	// otherwise we want to break this loop if all the urls
-	// have been fetched...
 	if let Some(addr) = links.pop() {
-	    spawn_worker(addr, tx.clone());	    
+	    workers[idx].as_ref().unwrap().send(addr).await.unwrap();
-	} else if to_fetch == 0 {
+	} else {
+	    workers[idx].take().unwrap();
+	    if workers.iter().filter(| tx | tx.is_some()).count() == 0 {
 		break;
 	    }
 	}
-    
-    for (url, links) in results {
-	println!("{url} : {} links", links.len())
     }
     
+    for (url, links) in &results {
+	println!("{url} : {} links", links.len())
+    }
+    println!("TOTAL: {}", results.len());    
     Ok(())
 }
 
-// interestingly, this function must not be async...
+fn spawn_worker(
-//a worker fetch one url, send it's result back in the channel, and terminates.
+    id: usize,
-fn spawn_worker(url: Url, tx: Sender<Option<SiteStat>>) { 
+    tx: Sender<(usize,Option<SiteStat>)>
-    println!("Start fetching {url}");
+) -> Sender<Url> { 
+    let (tx1, mut rx) = mpsc::channel::<Url>(16);    
+    
     tokio::spawn(async move {
+	println!("Start worker {id}");	
+	while let Some(url) = rx.recv().await {
+	    println!("Start fetching {url}");
 	    let res = get_links(url.as_ref()).await
-	    .ok()
+		.map(| v | (url.clone(), v)).ok();
-	    .map(| v | (url.clone(), v));
 	    println!("Got {url}");	
-	tx.send(res).await.unwrap()
+	    tx.send((id, res)).await.unwrap()
+	}
+	println!("Terminate worker {id}");		
     });
+
+    tx1
 }
 
 async fn get_links(

examples/livecoding_cleaner.rs

@@ -11,11 +11,11 @@ type SiteStat = (Url, Vec<Url>);
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
     let addr = std::env::args().nth(1)
-	.unwrap_or_else(|| "www.tmplab.org".to_string());
+	.unwrap_or_else(|| "https://www.tmplab.org".to_string());
-    
     let links = get_links(addr.as_ref()).await?;
-    let links : Vec<Url> = links.into_iter()
+    let addr = Url::parse(addr.as_ref())?;
-	.filter(| url | url.host() != Some(Host::Domain(&addr)))
+    let mut links : Vec<Url> = links.into_iter()
+	.filter(| url | url.host() != addr.host())
 	.collect();
 
     let links = Arc::new(Mutex::new(links));
@@ -23,15 +23,16 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     let joins = (0..WORKERS)
 	.map(| n | spawn_worker(n, &links));	
 
-    let results = future::join_all(joins).await
+    let results : Vec<_>= future::join_all(joins).await
 	.into_iter()
 	.filter_map(| r | r.ok())
-	.flatten();
+	.flatten()
+	.collect();
 
-    for (url, links) in results {
+    for (url, links) in &results {
 	println!("{url} : {} links", links.len())
     }
-    
+    println!("TOTAL: {}", results.len());
     Ok(())
 }
 

examples/livecoding_simple.rs

@@ -7,9 +7,9 @@ type SiteStat = (Url, Vec<Url>);
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
     let addr = std::env::args().nth(1)
-	.unwrap_or_else(|| "www.tmplab.org".to_string());
+	.unwrap_or_else(|| "https://tmplab.org".to_string());
     
-    let links = get_links("https://tmplab.org").await?;
+    let links = get_links(addr.as_ref()).await?;
     let links : Vec<Url> = links.into_iter()
 	.filter(| url | url.host() != Some(Host::Domain(&addr)))
 	.collect();

src/main.rs

@@ -9,6 +9,7 @@ Try:
     > cargo run --release --example livecoding
     > cargo run --release --example livecoding_cleaner
     > cargo run --release --example livecoding_simple
+    > cargo run --release --example livecoding_channel
     > cargo run --release --example livecoding_channels
 "#);
 }