[enh] implement workers, move to a dispatcher pattern

models.py

@@ -33,8 +33,15 @@ class BuildTask(peewee.Model):
         database = db
 
 
+class Worker(peewee.Model):
+    state = peewee.CharField(choices=(
+        ('available', 'Available'),
+        ('busy', 'Busy'),
+    ))
+
+
 # peewee is a bit stupid and will crash if the table already exists
-for i in [Repo, BuildTask]:
+for i in [Repo, BuildTask, Worker]:
     try:
         i.create_table()
     except:

run.py

@@ -19,7 +19,7 @@ from sanic import Sanic, response
 
 from playhouse.shortcuts import model_to_dict, dict_to_model
 
-from models import Repo, BuildTask, db
+from models import Repo, BuildTask, db, Worker
 
 app = Sanic()
 
@@ -65,58 +65,79 @@ async def initialize_app_list():
                     state="scheduled",
                 )
 
-    asyncio.ensure_future(run_jobs())
 
+async def tasks_dispatcher():
+    if Worker.select().count() == 0:
+        for i in range(5):
+            Worker.create(state="available")
 
-async def run_jobs():
-    print("Run jobs...")
     while True:
-        with db.atomic():
-            build_task = BuildTask.select().where(BuildTask.state == "scheduled").limit(1)
+        workers = Worker.select().where(Worker.state == "available")
 
-            if not build_task.count():
+        # no available workers, wait
+        if workers.count() == 0:
+            await asyncio.sleep(3)
+            continue
+
+        with db.atomic('IMMEDIATE'):
+            build_tasks = BuildTask.select().where(BuildTask.state == "scheduled")
+
+            # no task to process, wait
+            if build_tasks.count() == 0:
                 await asyncio.sleep(3)
                 continue
 
-            build_task = build_task[0]
+            for i in range(min(workers.count(), build_tasks.count())):
+                build_task = build_tasks[i]
+                worker = workers[i]
 
-            build_task.state = "running"
-            build_task.started_time = datetime.now()
-            print(build_task)
-            build_task.save()
+                build_task.state = "running"
+                build_task.started_time = datetime.now()
+                print(build_task)
+                build_task.save()
 
-        await broadcast({
-                "target": "build_task",
-                "id": build_task.id,
-                "data": model_to_dict(build_task),
-            }, "build_tasks")
+                worker.state = "busy"
+                worker.save()
 
-        # fake stupid command, whould run CI instead
-        print(f"Starting job for {build_task.repo.name}...")
-        command = await asyncio.create_subprocess_shell("/usr/bin/tail /var/log/auth.log",
-                                                       stdout=asyncio.subprocess.PIPE,
-                                                       stderr=asyncio.subprocess.PIPE)
+                asyncio.ensure_future(run_task(worker, build_task))
 
-        while not command.stdout.at_eof():
-            data = await command.stdout.readline()
-            line = data.decode().rstrip()
-            print(f">> {line}")
 
-        # XXX stupid crap to stimulate long jobs
-        # await asyncio.sleep(random.randint(30, 120))
-        # await asyncio.sleep(5)
-        print(f"Finished task for {build_task.repo.name}")
+async def run_task(worker, build_task):
+    await broadcast({
+            "target": "build_task",
+            "id": build_task.id,
+            "data": model_to_dict(build_task),
+        }, "build_tasks")
 
-        await command.wait()
-        build_task.end_time = datetime.now()
-        build_task.state = "done"
-        build_task.save()
+    # fake stupid command, whould run CI instead
+    print(f"Starting job for {build_task.repo.name}...")
+    command = await asyncio.create_subprocess_shell("/usr/bin/tail /var/log/auth.log",
+                                                   stdout=asyncio.subprocess.PIPE,
+                                                   stderr=asyncio.subprocess.PIPE)
 
-        await broadcast({
-                "target": "build_task",
-                "id": build_task.id,
-                "data": model_to_dict(build_task),
-            }, "build_tasks")
+    while not command.stdout.at_eof():
+        data = await command.stdout.readline()
+        line = data.decode().rstrip()
+        print(f">> {line}")
+
+    # XXX stupid crap to stimulate long jobs
+    await asyncio.sleep(random.randint(1, 15))
+    # await asyncio.sleep(5)
+    print(f"Finished task for {build_task.repo.name}")
+
+    await command.wait()
+    build_task.end_time = datetime.now()
+    build_task.state = "done"
+    build_task.save()
+
+    worker.state = "available"
+    worker.save()
+
+    await broadcast({
+            "target": "build_task",
+            "id": build_task.id,
+            "data": model_to_dict(build_task),
+        }, "build_tasks")
 
 
 async def broadcast(message, channel):
@@ -162,4 +183,5 @@ if __name__ == "__main__":
     subscriptions = defaultdict(list)
 
     app.add_task(initialize_app_list())
+    app.add_task(tasks_dispatcher())
     app.run('localhost', port=5000, debug=True)