Update Readme (#7)

* Update Readme

* change migration path in the readme

README.md

@@ -6,8 +6,6 @@
 
 Background job processing library for Rust.
 
-Currently, it uses Postgres to store state. But in the future, more backends will be supported.
-
 Note that the README follows the master branch, to see instructions for the latest published version, check [crates.io](https://crates.io/crates/fang).
 
 ## Installation
@@ -17,7 +15,7 @@ Note that the README follows the master branch, to see instructions for the late
 
 ```toml
 [dependencies]
-fang = "0.3.1"
+fang = "0.3.2"
 ```
 
 2. Create `fang_tasks` table in the Postgres database. The migration can be found in [the migrations directory](https://github.com/ayrat555/fang/blob/master/migrations/2021-06-05-112912_create_fang_tasks/up.sql).
@@ -183,11 +181,35 @@ worker_params.set_sleep_params(sleep_params);
 WorkerPool::new_with_params(10, worker_params).start();
 ```
 
-## Potential/future features
+## Periodic Tasks
+
+Fang can add tasks to `fang_tasks` periodically. To use this feature first run [the migration with `fang_periodic_tasks` table](https://github.com/ayrat555/fang/tree/master/migrations/2021-07-24-050243_create_fang_periodic_tasks/up.sql).
+
+Usage example:
+
+```rust
+use fang::Scheduler;
+use fang::Postgres;
+
+let postgres = Postgres::new();
+
+postgres
+     .push_periodic_task(&SyncJob::default(), 120)
+     .unwrap();
+
+postgres
+     .push_periodic_task(&DeliverJob::default(), 60)
+     .unwrap();
+
+Scheduler::start(10, 5);
+```
+
+In the example above, `push_periodic_task` is used to save the specified task to the `fang_periodic_tasks` table which will be enqueued (saved to `fang_tasks` table) every specied number of seconds.
+
+`Scheduler::start(10, 5)` starts scheduler. It accepts two parameters:
+- Db check period in seconds
+- Acceptable error limit in seconds - |current_time - scheduled_time| < error
 
-  * Retries
-  * Scheduled tasks
-  * Extendable/new backends
 
 ## Contributing
 

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

@@ -1,4 +1,2 @@
 DROP TABLE fang_tasks;
 DROP TYPE fang_task_state;
-
-DROP TABLE fang_periodic_tasks;

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

@@ -16,15 +16,3 @@ CREATE INDEX fang_tasks_state_index ON fang_tasks(state);
 CREATE INDEX fang_tasks_type_index ON fang_tasks(task_type);
 CREATE INDEX fang_tasks_created_at_index ON fang_tasks(created_at);
 CREATE INDEX fang_tasks_metadata_index ON fang_tasks(metadata);
-
-CREATE TABLE fang_periodic_tasks (
-  id uuid PRIMARY KEY DEFAULT uuid_generate_v4(),
-  metadata jsonb NOT NULL,
-  period_in_seconds INTEGER NOT NULL,
-  scheduled_at TIMESTAMP WITH TIME ZONE,
-  created_at TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT NOW(),
-  updated_at TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT NOW()
-);
-
-CREATE INDEX fang_periodic_tasks_scheduled_at_index ON fang_periodic_tasks(scheduled_at);
-CREATE INDEX fang_periodic_tasks_metadata_index ON fang_periodic_tasks(metadata);

migrations/2021-07-24-050243_create_fang_periodic_tasks/down.sql

@@ -0,0 +1 @@
+DROP TABLE fang_periodic_tasks;

migrations/2021-07-24-050243_create_fang_periodic_tasks/up.sql

@@ -0,0 +1,11 @@
+CREATE TABLE fang_periodic_tasks (
+  id uuid PRIMARY KEY DEFAULT uuid_generate_v4(),
+  metadata jsonb NOT NULL,
+  period_in_seconds INTEGER NOT NULL,
+  scheduled_at TIMESTAMP WITH TIME ZONE,
+  created_at TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT NOW(),
+  updated_at TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT NOW()
+);
+
+CREATE INDEX fang_periodic_tasks_scheduled_at_index ON fang_periodic_tasks(scheduled_at);
+CREATE INDEX fang_periodic_tasks_metadata_index ON fang_periodic_tasks(metadata);

src/lib.rs

@@ -15,6 +15,7 @@ pub mod worker_pool;
 
 pub use executor::*;
 pub use postgres::*;
+pub use scheduler::*;
 pub use worker_pool::*;
 
 #[doc(hidden)]

src/scheduler.rs

@@ -12,16 +12,13 @@ pub struct Scheduler {
 
 impl Drop for Scheduler {
     fn drop(&mut self) {
-        Scheduler::start(
-            self.check_period,
-            self.error_margin_seconds,
-            Postgres::new(),
-        )
+        Scheduler::start(self.check_period, self.error_margin_seconds)
     }
 }
 
 impl Scheduler {
-    pub fn start(check_period: u64, error_margin_seconds: u64, postgres: Postgres) {
+    pub fn start(check_period: u64, error_margin_seconds: u64) {
+        let postgres = Postgres::new();
         let builder = thread::Builder::new().name("scheduler".to_string());
 
         builder
@@ -114,7 +111,7 @@ mod job_scheduler_tests {
         let postgres = Postgres::new();
 
         postgres.push_periodic_task(&ScheduledJob {}, 10).unwrap();
-        Scheduler::start(1, 2, Postgres::new());
+        Scheduler::start(1, 2);
 
         let sleep_duration = Duration::from_secs(15);
         thread::sleep(sleep_duration);