From 111177675446ab45bc6ebfc7a66080a96fe16115 Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonyg@leastfixedpoint.com>
Date: Wed, 26 Jan 2022 22:30:47 +0100
Subject: [PATCH] Eliminate need for awkward boot_fn transmission subprotocol

---
 syndicate/src/supervise.rs | 73 ++++++++++----------------------------
 1 file changed, 19 insertions(+), 54 deletions(-)

diff --git a/syndicate/src/supervise.rs b/syndicate/src/supervise.rs
index ca242f5..5138044 100644
--- a/syndicate/src/supervise.rs
+++ b/syndicate/src/supervise.rs
@@ -5,6 +5,7 @@ use preserves::value::NestedValue;
 
 use std::collections::VecDeque;
 use std::sync::Arc;
+use std::sync::Mutex;
 use std::time::Duration;
 
 use tokio::time::Instant;
@@ -12,11 +13,11 @@ use tokio::time::Instant;
 use crate::actor::*;
 use crate::schemas::service::State;
 
-pub type Boot = Box<dyn Send + FnMut(&mut Activation) -> ActorResult>;
+pub type Boot = Arc<Mutex<Box<dyn Send + FnMut(&mut Activation) -> ActorResult>>>;
 
+#[derive(Debug)]
 enum Protocol {
     SuperviseeStarted, // assertion
-    BootFunction(Boot), // message
     Retry, // message
 }
 
@@ -40,22 +41,12 @@ pub struct Supervisor {
     my_name: Name,
     child_name: Name,
     config: SupervisorConfiguration,
-    boot_fn: Option<Boot>,
+    boot_fn: Boot,
     restarts: VecDeque<Instant>,
     state: Arc<Field<State>>,
     ac_ref: Option<ActorRef>,
 }
 
-impl std::fmt::Debug for Protocol {
-    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
-        match self {
-            Protocol::SuperviseeStarted => write!(f, "Protocol::SuperviseeStarted"),
-            Protocol::BootFunction(_) => write!(f, "Protocol::BootFunction(_)"),
-            Protocol::Retry => write!(f, "Protocol::Retry"),
-        }
-    }
-}
-
 impl Default for SupervisorConfiguration {
     fn default() -> Self {
         Self {
@@ -133,12 +124,8 @@ impl Entity<Protocol> for Supervisor
 
     fn message(&mut self, t: &mut Activation, m: Protocol) -> ActorResult {
         match m {
-            Protocol::BootFunction(b) => {
-                self.boot_fn = Some(b);
-                Ok(())
-            }
             Protocol::Retry => {
-                self.ensure_started(t)
+                self.start_now(t)
             }
             _ => Ok(())
         }
@@ -172,13 +159,13 @@ impl Supervisor {
             my_name: my_name.clone(),
             child_name: name,
             config,
-            boot_fn: Some(Box::new(boot_fn)),
+            boot_fn: Arc::new(Mutex::new(Box::new(boot_fn))),
             restarts: VecDeque::new(),
             state: Arc::clone(&state_field),
             ac_ref: None,
         };
         tracing::info!(self_ref = ?supervisor.self_ref, "Supervisor starting");
-        supervisor.ensure_started(t)?;
+        supervisor.start_now(t)?;
         t.dataflow(move |t| {
             let state = t.get(&state_field).clone();
             tracing::debug!(name = ?my_name, ?state);
@@ -189,40 +176,18 @@ impl Supervisor {
         Ok(())
     }
 
-    fn ensure_started(&mut self, t: &mut Activation) -> ActorResult {
-        match self.boot_fn.take() {
-            None => {
-                t.set(&self.state, State::Failed);
-                tracing::error!(name = ?self.my_name,
-                                "Cannot restart supervisee, because it panicked at startup")
-            }
-            Some(mut boot_fn) => {
-                let self_ref = Arc::clone(&self.self_ref);
-                t.facet(|t: &mut Activation| {
-                    t.assert(&self.self_ref, Protocol::SuperviseeStarted);
-                    self.ac_ref = Some(t.spawn_link(
-                        self.child_name.clone(),
-                        move |t| {
-                            match boot_fn(t) {
-                                Ok(()) => {
-                                    t.message(&self_ref, Protocol::BootFunction(boot_fn));
-                                    Ok(())
-                                }
-                                Err(e) => {
-                                    t.clear();
-                                    t.message(&self_ref, Protocol::BootFunction(boot_fn));
-                                    t.deliver();
-                                    Err(e)
-                                }
-                            }
-                        }));
-                    tracing::debug!(self_ref = ?self.self_ref,
-                                    supervisee = ?self.ac_ref,
-                                    "Supervisee started");
-                    Ok(())
-                })?;
-            }
-        }
+    fn start_now(&mut self, t: &mut Activation) -> ActorResult {
+        let boot_cell = Arc::clone(&self.boot_fn);
+        t.facet(|t: &mut Activation| {
+            t.assert(&self.self_ref, Protocol::SuperviseeStarted);
+            self.ac_ref = Some(t.spawn_link(
+                self.child_name.clone(),
+                move |t| boot_cell.lock().expect("Unpoisoned boot_fn mutex")(t)));
+            tracing::debug!(self_ref = ?self.self_ref,
+                            supervisee = ?self.ac_ref,
+                            "Supervisee started");
+            Ok(())
+        })?;
         Ok(())
     }
 }