run tasks in threads

migrations/2021-06-05-112912_create_fang_tasks/up.sql

@@ -11,4 +11,5 @@ CREATE TABLE fang_tasks (
      updated_at TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT NOW()
 );
 
+CREATE INDEX fang_tasks_state_index ON fang_tasks(state);
 CREATE INDEX fang_tasks_created_at_index ON fang_tasks(created_at);

src/executor.rs

@@ -42,21 +42,23 @@ impl Executor {
     }
 
     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();
-            }
+        loop {
+            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);
+                Err(error) => {
+                    error!("Failed to fetch a task {:?}", error);
 
-                self.sleep();
-            }
-        };
+                    self.sleep();
+                }
+            };
+        }
     }
 
     pub fn maybe_reset_sleep_period(&mut self) {

src/job_pool.rs

@@ -1,57 +0,0 @@
-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

@@ -5,6 +5,6 @@ extern crate diesel;
 extern crate log;
 
 pub mod executor;
-pub mod job_pool;
 pub mod postgres;
 mod schema;
+pub mod worker_pool;

src/postgres.rs

@@ -1,3 +1,4 @@
+use crate::executor::Runnable;
 use crate::schema::fang_tasks;
 use crate::schema::FangTaskState;
 use chrono::{DateTime, Utc};
@@ -8,7 +9,7 @@ use dotenv::dotenv;
 use std::env;
 use uuid::Uuid;
 
-#[derive(Queryable, Identifiable, Debug, Eq, PartialEq)]
+#[derive(Queryable, Identifiable, Debug, Eq, PartialEq, Clone)]
 #[table_name = "fang_tasks"]
 pub struct Task {
     pub id: Uuid,
@@ -52,6 +53,14 @@ impl Postgres {
         }
     }
 
+    pub fn push_task(&self, job: &dyn Runnable) -> Result<Task, Error> {
+        let json_job = serde_json::to_value(job).unwrap();
+
+        let new_task = NewTask { metadata: json_job };
+
+        self.insert(&new_task)
+    }
+
     pub fn insert(&self, params: &NewTask) -> Result<Task, Error> {
         diesel::insert_into(fang_tasks::table)
             .values(params)
@@ -62,6 +71,7 @@ impl Postgres {
         match fang_tasks::table
             .order(fang_tasks::created_at.asc())
             .limit(1)
+            .filter(fang_tasks::state.eq(FangTaskState::New))
             .for_update()
             .skip_locked()
             .get_result::<Task>(&self.connection)
@@ -134,12 +144,15 @@ mod postgres_tests {
     use super::NewTask;
     use super::Postgres;
     use super::Task;
+    use crate::executor::Error as ExecutorError;
+    use crate::executor::Runnable;
     use crate::schema::fang_tasks;
     use crate::schema::FangTaskState;
     use chrono::{DateTime, Duration, Utc};
     use diesel::connection::Connection;
     use diesel::prelude::*;
     use diesel::result::Error;
+    use serde::{Deserialize, Serialize};
 
     #[test]
     fn insert_inserts_task() {
@@ -238,6 +251,30 @@ mod postgres_tests {
         });
     }
 
+    #[test]
+    fn push_task_serializes_and_inserts_task() {
+        let postgres = Postgres::new(None);
+
+        postgres.connection.test_transaction::<(), Error, _>(|| {
+            let job = Job { number: 10 };
+            let task = postgres.push_task(&job).unwrap();
+
+            let mut m = serde_json::value::Map::new();
+            m.insert(
+                "number".to_string(),
+                serde_json::value::Value::Number(10.into()),
+            );
+            m.insert(
+                "type".to_string(),
+                serde_json::value::Value::String("Job".to_string()),
+            );
+
+            assert_eq!(task.metadata, serde_json::value::Value::Object(m));
+
+            Ok(())
+        });
+    }
+
     // this test is ignored because it commits data to the db
     #[test]
     #[ignore]
@@ -282,6 +319,20 @@ mod postgres_tests {
         assert_eq!(found_task.id, task1_id);
     }
 
+    #[derive(Serialize, Deserialize)]
+    struct Job {
+        pub number: u16,
+    }
+
+    #[typetag::serde]
+    impl Runnable for Job {
+        fn run(&self) -> Result<(), ExecutorError> {
+            println!("the number is {}", self.number);
+
+            Ok(())
+        }
+    }
+
     fn insert_job(
         metadata: serde_json::Value,
         timestamp: DateTime<Utc>,

src/schema.rs

@@ -1,6 +1,6 @@
 use diesel_derive_enum::DbEnum;
 
-#[derive(DbEnum, Debug, Eq, PartialEq)]
+#[derive(DbEnum, Debug, Eq, PartialEq, Clone)]
 pub enum FangTaskState {
     New,
     InProgress,

src/worker_pool.rs

@@ -0,0 +1,158 @@
+use crate::executor::Executor;
+use crate::postgres::Postgres;
+use std::thread;
+
+struct WorkerPool {
+    pub number_of_workers: u16,
+    pub name: String,
+}
+
+struct WorkerThread {
+    pub name: String,
+    pub restarts: u64,
+}
+
+impl WorkerPool {
+    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 + 1 {
+            let name = format!("{}{}", self.name, idx);
+
+            WorkerThread::spawn_in_pool(name, 0)
+        }
+    }
+}
+
+impl WorkerThread {
+    pub fn new(name: String, restarts: u64) -> Self {
+        Self { name, restarts }
+    }
+
+    pub fn spawn_in_pool(name: String, restarts: u64) {
+        let mut builder = thread::Builder::new().name(name.clone());
+        builder = builder;
+
+        info!(
+            "starting a worker thread {}, number of restarts {}",
+            name, restarts
+        );
+
+        builder
+            .spawn(move || {
+                // when _job is dropped, it will be restarted (see Drop trait impl)
+                let _job = WorkerThread::new(name, restarts);
+
+                let postgres = Postgres::new(None);
+
+                Executor::new(postgres).run_tasks()
+            })
+            .unwrap();
+    }
+}
+
+impl Drop for WorkerThread {
+    fn drop(&mut self) {
+        WorkerThread::spawn_in_pool(self.name.clone(), self.restarts + 1)
+    }
+}
+
+#[cfg(test)]
+mod job_pool_tests {
+    use super::WorkerPool;
+    use crate::executor::Error;
+    use crate::executor::Runnable;
+    use crate::postgres::Postgres;
+    use crate::postgres::Task;
+    use crate::schema::fang_tasks;
+    use diesel::pg::PgConnection;
+    use diesel::prelude::*;
+    use serde::{Deserialize, Serialize};
+    use std::thread;
+    use std::time::Duration;
+
+    #[derive(Serialize, Deserialize)]
+    struct MyJob {
+        pub number: u16,
+        pub current_thread_name: String,
+    }
+
+    impl MyJob {
+        pub fn new(number: u16) -> Self {
+            let handle = thread::current();
+            let current_thread_name = handle.name().unwrap().to_string();
+
+            Self {
+                number,
+                current_thread_name,
+            }
+        }
+    }
+
+    fn get_all_tasks(conn: &PgConnection) -> Vec<Task> {
+        fang_tasks::table.get_results::<Task>(conn).unwrap()
+    }
+
+    #[typetag::serde]
+    impl Runnable for MyJob {
+        fn run(&self) -> Result<(), Error> {
+            let postgres = Postgres::new(None);
+
+            thread::sleep(Duration::from_secs(3));
+
+            let new_job = MyJob::new(self.number + 1);
+
+            postgres.push_task(&new_job).unwrap();
+
+            Ok(())
+        }
+    }
+
+    // this test is ignored because it commits data to the db
+    #[test]
+    #[ignore]
+    fn tasks_are_split_between_two_threads() {
+        env_logger::init();
+
+        let postgres = Postgres::new(None);
+        let job_pool = WorkerPool::new(2, "test_worker".to_string());
+
+        postgres.push_task(&MyJob::new(0)).unwrap();
+        postgres.push_task(&MyJob::new(0)).unwrap();
+
+        job_pool.start();
+
+        thread::sleep(Duration::from_secs(100));
+
+        let tasks = get_all_tasks(&postgres.connection);
+
+        assert!(tasks.len() > 40);
+
+        let test_worker1_jobs: Vec<Task> = tasks
+            .clone()
+            .into_iter()
+            .filter(|job| {
+                serde_json::to_string(&job.metadata)
+                    .unwrap()
+                    .contains("test_worker1")
+            })
+            .collect();
+
+        let test_worker2_jobs: Vec<Task> = tasks
+            .into_iter()
+            .filter(|job| {
+                serde_json::to_string(&job.metadata)
+                    .unwrap()
+                    .contains("test_worker2")
+            })
+            .collect();
+
+        assert!(test_worker1_jobs.len() > 20);
+        assert!(test_worker2_jobs.len() > 20);
+    }
+}