Rewrite the fibonacci example with MessageHanlder

src/bastion/examples/fibonacci_message_handler.rs

@@ -0,0 +1,147 @@
+use bastion::{message::MessageHandler, prelude::*};
+
+use tracing::{error, info};
+
+// This terribly slow implementation
+// will allow us to be rough on the cpu
+fn fib(n: usize) -> usize {
+    if n == 0 || n == 1 {
+        n
+    } else {
+        fib(n - 1) + fib(n - 2)
+    }
+}
+
+// This terrible helper is converting `fib 50` into a tuple ("fib", 50)
+// we might want to use actual serializable / deserializable structures
+// in the real world
+fn deserialize_into_fib_command(message: String) -> (String, usize) {
+    let arguments: Vec<&str> = message.split(' ').collect();
+    let command = arguments.first().map(|s| s.to_string()).unwrap_or_default();
+    let number = usize::from_str_radix(arguments.get(1).unwrap_or(&"0"), 10).unwrap_or(0);
+    (command, number)
+}
+
+// This is the heavylifting.
+// A child will wait for a message, and try to process it.
+async fn fib_child_task(ctx: BastionContext) -> Result<(), ()> {
+    loop {
+        MessageHandler::new(ctx.recv().await?)
+            .on_question(|request: String, sender| {
+                let (command, number) = deserialize_into_fib_command(request);
+                if command == "fib" {
+                    sender
+                        .reply(format!("{}", fib(number)))
+                        .expect("couldn't reply :(");
+                } else {
+                    sender
+                        .reply(format!(
+                            "I'm sorry I didn't understand the task I was supposed to do"
+                        ))
+                        .expect("couldn't reply :(");
+                }
+            })
+            .on_broadcast(|broadcast: &String, _sender_addr| {
+                info!("received broadcast: {:?}", *broadcast);
+            })
+            .on_tell(|message: String, _sender_addr| {
+                info!("someone told me something: {}", message);
+            })
+            .on_fallback(|unknown, _sender_addr| {
+                error!(
+                    "uh oh, I received a message I didn't understand\n {:?}",
+                    unknown
+                );
+            });
+    }
+}
+
+// This little helper allows me to send a request, and get a reply.
+// The types are `String` for this quick example, but there's a way for us to do better.
+// We will see this in other examples.
+async fn request(child: &ChildRef, body: String) -> std::io::Result<String> {
+    let answer = child
+        .ask_anonymously(body)
+        .expect("couldn't perform request");
+
+    Ok(
+        MessageHandler::new(answer.await.expect("couldn't receive answer"))
+            .on_tell(|reply, _sender_addr| reply)
+            .on_fallback(|unknown, _sender_addr| {
+                error!(
+                    "uh oh, I received a message I didn't understand: {:?}",
+                    unknown
+                );
+                "".to_string()
+            }),
+    )
+}
+
+// RUST_LOG=info cargo run --example fibonacci_message_handler
+fn main() {
+    // This will allow us to have nice colored logs when we run the program
+    env_logger::init();
+
+    // We need a bastion in order to run everything
+    Bastion::init();
+    Bastion::start();
+
+    // Spawn 4 children that will execute our fibonacci task
+    let children =
+        Bastion::children(|children| children.with_redundancy(4).with_exec(fib_child_task))
+            .expect("couldn't create children");
+
+    // Broadcasting 1 message to the children
+    // Have a look at the console output
+    // to see 1 log entry for each child!
+    children
+        .broadcast("Hello there :)".to_string())
+        .expect("Couldn't broadcast to the children.");
+
+    let mut fib_to_compute = 35;
+    for child in children.elems() {
+        child
+            .tell_anonymously("shhh here's a message, don't tell anyone.".to_string())
+            .expect("Couldn't whisper to child.");
+
+        let now = std::time::Instant::now();
+        // by using run!, we are blocking.
+        // we could have used spawn! instead,
+        // to run everything in parallel.
+        let fib_reply = run!(request(child, format!("fib {}", fib_to_compute)))
+            .expect("send_command_to_child failed");
+
+        println!(
+            "fib({}) = {} - Computed in {}ms",
+            fib_to_compute,
+            fib_reply,
+            now.elapsed().as_millis()
+        );
+        // Let's not go too far with the fib sequence
+        // Otherwise the computer may take a while!
+        fib_to_compute += 2;
+    }
+    Bastion::stop();
+    Bastion::block_until_stopped();
+}
+
+// Compiling bastion v0.3.5-alpha (/home/ignition/Projects/oss/bastion/src/bastion)
+// Finished dev [unoptimized + debuginfo] target(s) in 1.07s
+//  Running `target/debug/examples/fibonacci`
+// [2020-05-08T14:00:53Z INFO  bastion::system] System: Initializing.
+// [2020-05-08T14:00:53Z INFO  bastion::system] System: Launched.
+// [2020-05-08T14:00:53Z INFO  bastion::system] System: Starting.
+// [2020-05-08T14:00:53Z INFO  bastion::system] System: Launching Supervisor(00000000-0000-0000-0000-000000000000).
+// [2020-05-08T14:00:53Z INFO  fibonacci] someone told me something: shhh here's a message, don't tell anyone.
+// [2020-05-08T14:00:53Z INFO  fibonacci] received broadcast: "Hello there :)"
+// [2020-05-08T14:00:53Z INFO  fibonacci] received broadcast: "Hello there :)"
+// [2020-05-08T14:00:53Z INFO  fibonacci] received broadcast: "Hello there :)"
+// fib(35) = 9227465 - Computed in 78ms
+// [2020-05-08T14:00:53Z INFO  fibonacci] received broadcast: "Hello there :)"
+// [2020-05-08T14:00:53Z INFO  fibonacci] someone told me something: shhh here's a message, don't tell anyone.
+// fib(37) = 24157817 - Computed in 196ms
+// [2020-05-08T14:00:53Z INFO  fibonacci] someone told me something: shhh here's a message, don't tell anyone.
+// fib(39) = 63245986 - Computed in 512ms
+// [2020-05-08T14:00:54Z INFO  fibonacci] someone told me something: shhh here's a message, don't tell anyone.
+// fib(41) = 165580141 - Computed in 1327ms
+// [2020-05-08T14:00:55Z INFO  bastion::system] System: Stopping.