Use APScheduler to handle job execution.

app/__init__.py

@@ -3,12 +3,14 @@ from flask import Flask
 from flask_login import LoginManager
 from flask_mail import Mail
 from flask_sqlalchemy import SQLAlchemy
+from .scheduler import Scheduler
 from .swarm import Swarm
 
 db = SQLAlchemy()
 login_manager = LoginManager()
 login_manager.login_view = 'auth.login'
 mail = Mail()
+scheduler = Scheduler()
 swarm = Swarm()
 
 
@@ -20,6 +22,7 @@ def create_app(config_name):
     db.init_app(app)
     login_manager.init_app(app)
     mail.init_app(app)
+    scheduler.init_app(app)
     swarm.init_app(app)
 
     from .auth import auth as auth_blueprint

app/scheduler.py

@@ -0,0 +1,47 @@
+from apscheduler.schedulers.background import BackgroundScheduler
+from datetime import datetime
+from sqlalchemy import create_engine
+from sqlalchemy.orm import scoped_session, sessionmaker
+import os
+
+
+class Scheduler(BackgroundScheduler):
+    def __init__(self, app=None):
+        super().__init__()
+        self.app = app
+        if app is not None:
+            self.init_app(app)
+
+    def init_app(self, app):
+        engine = create_engine(app.config['SQLALCHEMY_DATABASE_URI'])
+        self.session_factory = sessionmaker(bind=engine)
+        self.Session = scoped_session(self.session_factory)
+        if not app.debug or os.environ.get('WERKZEUG_RUN_MAIN') == 'true':
+            self.add_job(self.check_jobs, id='jobs', seconds=10, trigger='interval')
+            self.start()
+
+    def check_jobs(self):
+        from .models import Job
+        from . import swarm
+
+        Session = scoped_session(self.session_factory)
+        session = Session()
+        jobs = session.query(Job)
+        submitted_jobs = jobs.filter_by(status='submitted').all()
+        foo_jobs = jobs.filter(Job.status != 'complete',
+                               Job.status != 'failed',
+                               Job.status != 'submitted').all()
+        for job in submitted_jobs:
+            swarm.run(job.id)
+            job.status = 'scheduled'
+        for job in foo_jobs:
+            '''
+            ' TODO: Handle service not found error.
+            '''
+            service = swarm.docker.services.get(str(job.id))
+            job.status = service.tasks()[0].get('Status').get('State')
+            if job.status == 'complete' or job.status == 'failed':
+                job.end_date = datetime.utcnow()
+                service.remove()
+        session.commit()
+        Session.remove()

app/services/views.py

@@ -22,7 +22,7 @@ def nlp():
                       service='nlp',
                       service_args=json.dumps(['-l {}'.format(new_nlp_job_form.language.data)]),
                       service_version=new_nlp_job_form.version.data,
-                      status='submitted',
+                      status='preparing',
                       title=new_nlp_job_form.title.data)
 
         db.session.add(nlp_job)
@@ -48,8 +48,8 @@ def nlp():
             ' NOTE: Using self created threads is just for testing purpose as
             '       there is no scheduler available.
             '''
-            thread = Thread(target=swarm.run, args=(nlp_job.id,))
-            thread.start()
+            nlp_job.status = 'submitted'
+            db.session.commit()
             flash('Job created!')
         return redirect(url_for('services.nlp'))
 
@@ -74,7 +74,7 @@ def ocr():
                         '-l {}'.format(new_ocr_job_form.language.data),
                         '--skip-binarisation']),
                       service_version=new_ocr_job_form.version.data,
-                      status='submitted',
+                      status='preparing',
                       title=new_ocr_job_form.title.data)
 
         db.session.add(ocr_job)
@@ -94,14 +94,8 @@ def ocr():
         else:
             for file in new_ocr_job_form.files.data:
                 file.save(os.path.join(dir, file.filename))
-            '''
-            ' TODO: Let the scheduler run this job in the background.
-            '
-            ' NOTE: Using self created threads is just for testing purpose as
-            '       there is no scheduler available.
-            '''
-            thread = Thread(target=swarm.run, args=(ocr_job.id,))
-            thread.start()
+            ocr_job.status = 'submitted'
+            db.session.commit()
             flash('Job created!')
         return redirect(url_for('services.ocr'))
 

app/swarm.py

@@ -1,8 +1,6 @@
-from datetime import datetime
 from sqlalchemy import create_engine
 from sqlalchemy.orm import sessionmaker
 import docker
-import time
 import json
 import os
 
@@ -92,33 +90,5 @@ class Swarm:
             resources=_resources,
             restart_policy=_restart_policy
         )
-        '''
-        ' Because it takes some time until all data in the service object is
-        ' initialized (especcially the task list returned by the service.tasks
-        ' method), a poll loop checks if the task list is empty.
-        '''
-        while not service.tasks():
-            time.sleep(1)
-            service.reload()
-        '''
-        ' The following is scheduler work.
-        ' Poll the service until the job is completly executed.
-        '''
-        session.add(job)
-        job.status = 'running'
-        session.commit()
-        current_state = None
-        while True:
-            current_state = service.tasks()[0].get('Status').get('State')
-            if current_state == 'complete' or current_state == 'failed':
-                break
-            time.sleep(1)
-            service.reload()
-        job.end_date = datetime.utcnow()
-        job.status = current_state
-        session.commit()
-        session.close()
-        # Remove the service from the swarm.
-        service.remove()
 
-        return
+        return service

app/templates/main/dashboard.html.j2

@@ -45,6 +45,10 @@
     pagination: true
   };
   corpusList = new List("corpus-list", corpusListOptions);
+  /*
+   * TODO: Hide Pagination if there is only on page
+   * corpusListPagination = document.querySelector("#corpus-list .pagination");
+   */
 </script>
 
 <div class="col s12">

requirements.txt

@@ -1,6 +1,6 @@
+APScheduler==3.6.1 
 docker==4.0.2
 Flask==1.0.3
-Flask-APScheduler==1.11.0
 Flask-Login==0.4.1
 Flask-Mail==0.9.1
 Flask-Migrate==2.5.2