add job pool

Cargo.toml

@@ -16,4 +16,6 @@ uuid = { version = "0.8", features = ["v4"] }
 chrono = "0.4"
 serde_json = "1.0"
 typetag = "0.1"
+log = "0.4.0"
+env_logger = "0.8.4"
 serde = { version = "1.0", features = ["derive"] }

src/executor.rs

@@ -1,8 +1,14 @@
 use crate::postgres::Postgres;
 use crate::postgres::Task;
+use std::thread;
+use std::time::Duration;
 
 pub struct Executor {
     pub storage: Postgres,
+    pub sleep_period: u64,
+    pub max_sleep_period: u64,
+    pub min_sleep_period: u64,
+    pub sleep_step: u64,
 }
 
 #[derive(Debug)]
@@ -17,7 +23,13 @@ pub trait Runnable {
 
 impl Executor {
     pub fn new(storage: Postgres) -> Self {
-        Self { storage }
+        Self {
+            storage,
+            sleep_period: 5,
+            max_sleep_period: 15,
+            min_sleep_period: 5,
+            sleep_step: 5,
+        }
     }
 
     pub fn run(&self, task: &Task) {
@@ -29,11 +41,37 @@ impl Executor {
         };
     }
 
-    pub fn run_tasks(&self) {
-        while let Ok(Some(task)) = self.storage.fetch_and_touch() {
-            self.run(&task)
+    pub fn run_tasks(&mut self) {
+        match self.storage.fetch_and_touch() {
+            Ok(Some(task)) => {
+                self.maybe_reset_sleep_period();
+                self.run(&task);
+            }
+            Ok(None) => {
+                self.sleep();
+            }
+
+            Err(error) => {
+                error!("Failed to fetch a task {:?}", error);
+
+                self.sleep();
+            }
+        };
+    }
+
+    pub fn maybe_reset_sleep_period(&mut self) {
+        if self.sleep_period != self.min_sleep_period {
+            self.sleep_period = self.min_sleep_period;
         }
     }
+
+    pub fn sleep(&mut self) {
+        if self.sleep_period < self.max_sleep_period {
+            self.sleep_period = self.sleep_period + self.sleep_step;
+        }
+
+        thread::sleep(Duration::from_secs(self.sleep_period));
+    }
 }
 
 #[cfg(test)]

src/job_pool.rs

@@ -0,0 +1,57 @@
+use crate::executor::Executor;
+use crate::postgres::Postgres;
+use std::thread;
+
+struct JobPool {
+    pub number_of_workers: u16,
+    pub name: String,
+}
+
+struct JobThread {
+    pub name: String,
+}
+
+impl JobPool {
+    pub fn new(number_of_workers: u16, name: String) -> Self {
+        Self {
+            number_of_workers,
+            name,
+        }
+    }
+
+    pub fn start(&self) {
+        for idx in 1..self.number_of_workers {
+            let name = format!("{}{}", self.name, idx);
+
+            spawn_in_pool(name)
+        }
+    }
+}
+
+impl JobThread {
+    pub fn new(name: String) -> Self {
+        Self { name }
+    }
+}
+
+impl Drop for JobThread {
+    fn drop(&mut self) {
+        spawn_in_pool(self.name.clone())
+    }
+}
+
+fn spawn_in_pool(name: String) {
+    let mut builder = thread::Builder::new().name(name.clone());
+    builder = builder;
+
+    builder
+        .spawn(move || {
+            // when _job is dropped, it will be restarted (see Drop trait impl)
+            let _job = JobThread::new(name);
+
+            let postgres = Postgres::new(None);
+
+            Executor::new(postgres).run_tasks()
+        })
+        .unwrap();
+}

src/lib.rs

@@ -1,29 +1,10 @@
 #[macro_use]
 extern crate diesel;
 
-// pub trait JobQueue {
-//     type Job;
-//     type Error;
-
-//     fn push(job: Self::Job) -> Result<(), Self::Error> {
-
-//     }
-//     fn pop(job: Self::Job) -> Result<(), Self::Error>;
-// }
-
-// pub trait Storage {
-//     fn save() ->
-// }
+#[macro_use]
+extern crate log;
 
 pub mod executor;
+pub mod job_pool;
 pub mod postgres;
-pub mod scheduler;
 mod schema;
-
-#[cfg(test)]
-mod tests {
-    #[test]
-    fn it_works() {
-        assert_eq!(2 + 2, 4);
-    }
-}

src/scheduler.rs

@@ -1,34 +0,0 @@
-use crate::executor::Executor;
-use crate::postgres::Postgres;
-use std::thread;
-use std::thread::JoinHandle;
-
-struct Scheduler {
-    pub number_of_workers: u16,
-    pub handles: Option<Vec<JoinHandle<()>>>,
-}
-
-impl Scheduler {
-    pub fn new(number_of_workers: u16) -> Self {
-        Self {
-            number_of_workers,
-            handles: None,
-        }
-    }
-
-    pub fn start(&mut self) {
-        let mut handles: Vec<JoinHandle<()>> = vec![];
-
-        for _ in 1..self.number_of_workers {
-            let handle = thread::spawn(|| {
-                let postgres = Postgres::new(None);
-
-                Executor::new(postgres).run_tasks()
-            });
-
-            handles.push(handle);
-        }
-
-        self.handles = Some(handles);
-    }
-}