Introduction of oslo.messaging

* replaces kombu with oslo.messaging

* deprecates and removes the faafo-tracker service (merged into the
  faafo-producer service)

* moves all CLI options into configuration files

* updates log example outputs in the documentation

* updates the workflow diagram and removes the workflow text description

Change-Id: I4b79ed28a8f5b1fe1b33dfdbfe9cc8c958f80b1b

ansible/files/api.conf

@@ -0,0 +1,4 @@
+[DEFAULT]
+
+database_url = mysql://faafo:secretsecret@127.0.0.1:3306/faafo
+verbose = True

ansible/files/producer.conf

@@ -0,0 +1,5 @@
+[DEFAULT]
+
+endpoint_url = http://127.0.0.1:5000
+transport_url = rabbit://faafo:secretsecret@localhost:5672/
+verbose = True

ansible/files/run_api.sh

@@ -1,5 +1,3 @@
 #!/bin/sh
 
-faafo-api \
+faafo-api --config-file api.conf
-    --database-url mysql://faafo:secretsecret@127.0.0.1:3306/faafo \
-    --debug --verbose

ansible/files/run_producer.sh

@@ -1,6 +1,3 @@
 #!/bin/sh
 
-faafo-producer \
+faafo-producer --config-file producer.conf
-    --amqp-url amqp://faafo:secretsecret@127.0.0.1:5672/ \
-    --api-url http://127.0.0.1:5000 \
-    --debug --verbose

ansible/files/run_tracker.sh

@@ -1,6 +0,0 @@
-#!/bin/sh
-
-faafo-tracker \
-    --amqp-url amqp://faafo:secretsecret@127.0.0.1:5672/ \
-    --api-url http://127.0.0.1:5000 \
-    --debug --verbose

ansible/files/run_worker.sh

@@ -1,6 +1,3 @@
 #!/bin/sh
 
-faafo-worker \
+faafo-worker --config-file worker.conf
-    --amqp-url amqp://faafo:secretsecret@127.0.0.1:5672/ \
-    --target /home/vagrant \
-    --debug --verbose

ansible/files/worker.conf

@@ -0,0 +1,5 @@
+[DEFAULT]
+
+filesystem_store_datadir = /home/vagrant
+transport_url = rabbit://faafo:secretsecret@localhost:5672/
+verbose = True

ansible/playbook.yaml

@@ -20,7 +20,11 @@
     args:
       chdir: /vagrant
 
-  - copy: src=files/run_api.sh dest=/home/vagrant/run_api.sh mode=0755 owner=vagrant group=vagrant
+  - copy: src=files/{{ item }} dest=/home/vagrant/{{ item }} mode=0755 owner=vagrant group=vagrant
-  - copy: src=files/run_producer.sh dest=/home/vagrant/run_producer.sh mode=0755 owner=vagrant group=vagrant
+    with_items:
-  - copy: src=files/run_tracker.sh dest=/home/vagrant/run_tracker.sh mode=0755 owner=vagrant group=vagrant
+      - api.conf
-  - copy: src=files/run_worker.sh dest=/home/vagrant/run_worker.sh mode=0755 owner=vagrant group=vagrant
+      - producer.conf
+      - run_api.sh
+      - run_producer.sh
+      - run_worker.sh
+      - worker.conf

doc/source/development.rst

@@ -27,12 +27,11 @@ Now it is possible to login with SSH.
 
     $ vagrant ssh
 
-Open a new screen or tmux session. Aftwards run the api, worker, producer, and
+Open a new screen or tmux session. Aftwards run the api, worker, and producer
-tracker services in the foreground, each service in a separate window.
+services in the foreground, each service in a separate window.
 
 * :code:`sh run_api.sh`
 * :code:`sh run_producer.sh`
-* :code:`sh run_tracker.sh`
 * :code:`sh run_worker.sh`
 
 RabbitMQ server
@@ -60,12 +59,11 @@ the application itself.
     $ pip install -r requirements.txt
     $ python setup.py install
 
-Open a new screen or tmux session. Aftwards run the api, worker, producer, and
+Open a new screen or tmux session. Aftwards run the api, worker, and producer
-tracker services in the foreground, each service in a separate window.
+services in the foreground, each service in a separate window.
 
 .. code::
 
     $ source .venv/bin/activate; faafo-api
     $ source .venv/bin/activate; faafo-worker
-    $ source .venv/bin/activate; faafo-tracker
     $ source .venv/bin/activate; faafo-producer

doc/source/images/diagram.dot

@@ -4,12 +4,12 @@ digraph {
   Database -> API [color=red];
   API -> Webinterface [color=red];
   Producer -> API [color=orange];
+  Producer -> API [color=green];
   Producer -> "Queue Service" [color=orange];
-  Tracker -> API [color=green];
-  "Queue Service" -> Tracker [color=green];
   "Queue Service" -> Worker [color=orange];
   Worker -> "Image File" [color=blue];
   Worker -> "Queue Service" [color=green];
+  "Queue Service" -> Producer [color=green];
   "Image File" -> "Storage Backend" [color=blue];
   "Storage Backend" -> Webinterface [color=red];
 }

doc/source/usage.rst

@@ -10,42 +10,28 @@ Example image
 Example outputs
 ---------------
 
-API Service
-~~~~~~~~~~~
-
-FIXME(berendt): add output of the API service
-
 Producer service
 ~~~~~~~~~~~~~~~~
 
-FIXME(berendt): update output (introduction of oslo.logging)
-
 .. code::
 
-    2015-02-12 22:21:42,870 generating 2 task(s)
+  2015-03-25 23:01:29.308 22526 INFO faafo.producer [-] generating 1 task(s)
-    2015-02-12 22:21:42,876 generated task: {'width': 728, 'yb': 2.6351683415972076, 'uuid': UUID('66d5f67e-d26d-42fb-9d88-3c3830b4187a'), 'iterations': 395, 'xb': 1.6486035545865234, 'xa': -1.2576814065507933, 'ya': -2.8587178863035616, 'height': 876}
+  2015-03-25 23:01:29.344 22526 INFO faafo.producer [-] generated task: {'width': 510, 'yb': 2.478654026560605, 'uuid': '212e8c23-e67f-4bd3-86e1-5a5e811ee2f4', 'iterations': 281, 'xb': 1.1428457603077387, 'xa': -3.3528957195683087, 'ya': -2.1341119130263717, 'height': 278}
-    2015-02-12 22:21:42,897 generated task: {'width': 944, 'yb': 2.981696583462036, 'uuid': UUID('6f873111-8bc2-4d73-9a36-ed49915699c8'), 'iterations': 201, 'xb': 3.530775320058914, 'xa': -3.3511031734533794, 'ya': -0.921920674639712, 'height': 962}
+  2015-03-25 23:01:30.295 22526 INFO faafo.producer [-] task 212e8c23-e67f-4bd3-86e1-5a5e811ee2f4 processed: {u'duration': 0.8725259304046631, u'checksum': u'b22d975c4f9dc77df5db96ce6264a4990d865dd8f800aba2ac03a065c2f09b1e', u'uuid': u'212e8c23-e67f-4bd3-86e1-5a5e811ee2f4'}
-    2015-02-12 22:21:42,927 sleeping for 2.680171 seconds
-
-Tracker service
-~~~~~~~~~~~~~~~
-
-FIXME(berendt): update output (introduction of oslo.logging)
-
-.. code::
-
-    2015-02-12 22:20:26,630 processing result be42a131-e4aa-4db5-80d1-1956784f4b81
-    2015-02-12 22:20:26,630 elapsed time 5.749099 seconds
-    2015-02-12 22:20:26,631 checksum 7ba5bf955a94f1aa02e5f442869b8db88a5915b7c2fb91ffba74708b8d799c2a
 
 Worker service
 ~~~~~~~~~~~~~~
 
-FIXME(berendt): update output (introduction of oslo.logging)
-
 .. code::
 
-    2015-02-12 22:20:59,258 processing task 20a00e9e-baec-4045-bc57-2cb9d8d1aa61
+  2015-03-25 23:01:29.378 22518 INFO faafo.worker [-] processing task 212e8c23-e67f-4bd3-86e1-5a5e811ee2f4
-    2015-02-12 22:21:01,506 task 20a00e9e-baec-4045-bc57-2cb9d8d1aa61 processed in 2.246601 seconds
+  2015-03-25 23:01:30.251 22518 INFO faafo.worker [-] task 212e8c23-e67f-4bd3-86e1-5a5e811ee2f4 processed in 0.872526 seconds
-    2015-02-12 22:21:01,553 saved result of task 20a00e9e-baec-4045-bc57-2cb9d8d1aa61 to file /home/vagrant/20a00e9e-baec-4045-bc57-2cb9d8d1aa61.png
+  2015-03-25 23:01:30.268 22518 INFO faafo.worker [-] saved result of task 212e8c23-e67f-4bd3-86e1-5a5e811ee2f4 to file /home/vagrant/212e8c23-e67f-4bd3-86e1-5a5e811ee2f4.png
-    2015-02-12 22:21:01,554 pushed result: {'duration': 2.246600866317749, 'checksum': 'faa0f00a72fac53e02c3eb392c5da8365139e509899e269227e5c27047af6c1f', 'uuid': UUID('20a00e9e-baec-4045-bc57-2cb9d8d1aa61')}
+
+
+API Service
+~~~~~~~~~~~
+.. code::
+
+  2015-03-25 23:01:29.342 22511 INFO werkzeug [-] 127.0.0.1 - - [25/Mar/2015 23:01:29] "POST /api/fractal HTTP/1.1" 201 -
+  2015-03-25 23:01:30.317 22511 INFO werkzeug [-] 127.0.0.1 - - [25/Mar/2015 23:01:30] "PUT /api/fractal/212e8c23-e67f-4bd3-86e1-5a5e811ee2f4 HTTP/1.1" 200 -

doc/source/workflow.rst

@@ -2,17 +2,3 @@ Workflow
 --------
 
 .. image:: images/diagram.png
-
-FIXME(berendt): Add new API service and webinterface to the workflow description.
-
-* The producer generates a random number of tasks with random parameters and a UUID as identifier.
-* The producer pushes the generated tasks into the exchange :code:`tasks`.
-* The producer inserts a new record for each task into the database (including all parameters and the UUID).
-* The producer sleeps for a random number of seconds and will generate more tasks after awakening.
-* All messages in the :code:`tasks` exchange will be routed into the :code:`tasks` queue.
-* The worker waits for new messages in the :code:`tasks` queue.
-* After receiving a message the worker generates an image based on the received parameters and writes the result into a local file (identified by the UUID).
-* After writing an image the worker pushes the result (the checksum of the generated image and the duration identified by the UUID) into the exchange :code:`results`.
-* All messages in the :code:`results` exchange will be routed into the :code:`results` queue.
-* The tracker waits for new messages in the :code:`results` queue.
-* After receiving a message the tracker updates the duration and checksum value of the corresponding database record (identified by the UUID).

etc/faafo/producer.conf

@@ -0,0 +1 @@
+TODO(berendt): generate example configuration file with http://docs.openstack.org/developer/oslo.config/generator.html

etc/faafo/worker.conf

@@ -0,0 +1 @@
+TODO(berendt): generate example configuration file with http://docs.openstack.org/developer/oslo.config/generator.html

faafo/api.py

@@ -18,9 +18,9 @@ from oslo_log import log
 
 from faafo import version
 
-LOG = log.getLogger(__name__)
+LOG = log.getLogger('faafo.api')
 
-cli_opts = [
+api_opts = [
     cfg.StrOpt('listen-address',
                default='0.0.0.0',
                help='Listen address.'),
@@ -32,7 +32,7 @@ cli_opts = [
                help='Database connection URL.')
 ]
 
-cfg.CONF.register_cli_opts(cli_opts)
+cfg.CONF.register_opts(api_opts)
 
 log.register_options(cfg.CONF)
 log.set_defaults()
@@ -43,7 +43,7 @@ cfg.CONF(project='api', prog='faafo-api',
 log.setup(cfg.CONF, 'api',
           version=version.version_info.version_string())
 
-app = flask.Flask(__name__)
+app = flask.Flask('faafo.api')
 app.config['DEBUG'] = cfg.CONF.debug
 app.config['SQLALCHEMY_DATABASE_URI'] = cfg.CONF.database_url
 db = flask.ext.sqlalchemy.SQLAlchemy(app)

faafo/producer.py

@@ -16,27 +16,19 @@ import json
 import random
 import uuid
 
-import kombu
-from kombu.pools import producers
 from oslo_config import cfg
 from oslo_log import log
+import oslo_messaging as messaging
 import requests
 
 from faafo.openstack.common import periodic_task
 from faafo.openstack.common import service
-from faafo import queues
 from faafo import version
 
 
 LOG = log.getLogger('faafo.producer')
 
 cli_opts = [
-    cfg.StrOpt('amqp-url',
-               default='amqp://faafo:secretsecret@localhost:5672/',
-               help='AMQP connection URL'),
-    cfg.StrOpt('api-url',
-               default='http://localhost:5000',
-               help='API connection URL')
 ]
 
 producer_opts = [
@@ -74,22 +66,27 @@ producer_opts = [
                help="The minimum number of generated tasks."),
     cfg.IntOpt("max-tasks", default=10,
                help="The maximum number of generated tasks."),
-    cfg.IntOpt("interval", default=10, help="Interval in seconds.")
+    cfg.IntOpt("interval", default=10, help="Interval in seconds."),
+    cfg.StrOpt('endpoint-url',
+               default='http://localhost:5000',
+               help='API connection URL')
 ]
 
-cfg.CONF.register_cli_opts(cli_opts)
+cfg.CONF.register_opts(producer_opts)
-cfg.CONF.register_cli_opts(producer_opts)
 
 
 class ProducerService(service.Service, periodic_task.PeriodicTasks):
     def __init__(self):
         super(ProducerService, self).__init__()
-        self.messaging = kombu.Connection(cfg.CONF.amqp_url)
         self._periodic_last_run = {}
+        transport = messaging.get_transport(cfg.CONF)
+        target = messaging.Target(topic='tasks')
+        self._client = messaging.RPCClient(transport, target)
 
         @periodic_task.periodic_task(spacing=cfg.CONF.interval,
-                                     run_immediately=True)
+                                     run_immediately=False)
-        def generate_task(self, context):
+        def generate_task(self, ctxt):
+            ctxt = {}
             random.seed()
             number = random.randint(cfg.CONF.min_tasks, cfg.CONF.max_tasks)
             LOG.info("generating %d task(s)" % number)
@@ -98,16 +95,14 @@ class ProducerService(service.Service, periodic_task.PeriodicTasks):
                 # NOTE(berendt): only necessary when using requests < 2.4.2
                 headers = {'Content-type': 'application/json',
                            'Accept': 'text/plain'}
-                requests.post("%s/api/fractal" % cfg.CONF.api_url,
+                requests.post("%s/api/fractal" % cfg.CONF.endpoint_url,
                               json.dumps(task), headers=headers)
                 LOG.info("generated task: %s" % task)
-                with producers[self.messaging].acquire(block=True) as producer:
+                result = self._client.call(ctxt, 'process', task=task)
-                    producer.publish(
+                LOG.info("task %s processed: %s" % (task['uuid'], result))
-                        task,
+                requests.put("%s/api/fractal/%s" %
-                        serializer='pickle',
+                             (cfg.CONF.endpoint_url, str(task['uuid'])),
-                        exchange=queues.task_exchange,
+                             json.dumps(result), headers=headers)
-                        declare=[queues.task_exchange],
-                        routing_key='tasks')
 
         self.add_periodic_task(generate_task)
         self.tg.add_dynamic_timer(self.periodic_tasks)

faafo/queues.py

@@ -1,20 +0,0 @@
-# Licensed under the Apache License, Version 2.0 (the "License"); you may
-# not use this file except in compliance with the License. You may obtain
-# a copy of the License at
-#
-#      http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
-# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
-# License for the specific language governing permissions and limitations
-# under the License.
-
-from kombu import Exchange
-from kombu import Queue
-
-task_exchange = Exchange('tasks', type='direct')
-task_queues = [Queue('tasks', task_exchange, routing_key='tasks')]
-
-result_exchange = Exchange('results', type='direct')
-result_queues = [Queue('results', result_exchange, routing_key='results')]

faafo/tracker.py

@@ -1,98 +0,0 @@
-#!/usr/bin/env python
-
-# Licensed under the Apache License, Version 2.0 (the "License"); you may
-# not use this file except in compliance with the License. You may obtain
-# a copy of the License at
-#
-#      http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
-# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
-# License for the specific language governing permissions and limitations
-# under the License.
-
-# based on http://code.activestate.com/recipes/577120-julia-fractals/
-
-import json
-import sys
-
-import daemon
-import kombu
-from kombu.mixins import ConsumerMixin
-from oslo_config import cfg
-from oslo_log import log
-import requests
-
-from faafo import queues
-from faafo import version
-
-
-LOG = log.getLogger(__name__)
-
-cli_opts = [
-    cfg.BoolOpt('daemonize',
-                default=False,
-                help='Run in background.'),
-    cfg.StrOpt('amqp-url',
-               default='amqp://faafo:secretsecret@localhost:5672/',
-               help='AMQP connection URL'),
-    cfg.StrOpt('api-url',
-               default='http://localhost:5000',
-               help='API connection URL')
-]
-
-cfg.CONF.register_cli_opts(cli_opts)
-
-
-class Tracker(ConsumerMixin):
-
-    def __init__(self, amqp_url, api_url):
-        self.connection = kombu.Connection(amqp_url)
-        self.api_url = api_url
-
-    def get_consumers(self, Consumer, channel):
-        return [Consumer(queues=queues.result_queues,
-                         accept=['pickle', 'json'],
-                         callbacks=[self.process_result])]
-
-    def process_result(self, body, message):
-        LOG.info("processing result %s" % body['uuid'])
-        LOG.info("elapsed time %f seconds" % body['duration'])
-        LOG.info("checksum %s" % body['checksum'])
-        result = {
-            'duration': float(body['duration']),
-            'checksum': str(body['checksum'])
-        }
-        # NOTE(berendt): only necessary when using requests < 2.4.2
-        headers = {'Content-type': 'application/json',
-                   'Accept': 'text/plain'}
-        requests.put("%s/api/fractal/%s" %
-                     (self.api_url, str(body['uuid'])),
-                     json.dumps(result), headers=headers)
-        message.ack()
-
-
-def main():
-    log.register_options(cfg.CONF)
-    log.set_defaults()
-
-    cfg.CONF(project='tracker', prog='faafo-tracker',
-             version=version.version_info.version_string())
-
-    log.setup(cfg.CONF, 'tracker',
-              version=version.version_info.version_string())
-
-    tracker = Tracker(cfg.CONF.amqp_url, cfg.CONF.api_url)
-
-    if cfg.CONF.daemonize:
-        with daemon.DaemonContext():
-            tracker.run()
-    else:
-        try:
-            tracker.run()
-        except Exception as e:
-            sys.exit("ERROR: %s" % e)
-
-if __name__ == '__main__':
-    main()

faafo/worker.py

@@ -14,39 +14,33 @@
 
 # based on http://code.activestate.com/recipes/577120-julia-fractals/
 
+import eventlet
+eventlet.monkey_patch()
+
 import hashlib
 import os
 from PIL import Image
 import random
-import sys
+import socket
 import time
 
-import daemon
-import kombu
-from kombu.mixins import ConsumerMixin
-from kombu.pools import producers
 from oslo_config import cfg
 from oslo_log import log
+import oslo_messaging as messaging
 
-from faafo import queues
 from faafo import version
 
 
-LOG = log.getLogger(__name__)
+LOG = log.getLogger('faafo.worker')
 
-cli_opts = [
+worker_opts = [
-    cfg.BoolOpt('daemonize',
+    cfg.StrOpt('filesystem_store_datadir',
-                default=False,
-                help='Run in background.'),
-    cfg.StrOpt('target',
                default='/tmp',
-               help='Target directory for fractal image files.'),
+               help='Directory that the filesystem backend store writes '
-    cfg.StrOpt('amqp-url',
+                    'fractal image files to.'),
-               default='amqp://faafo:secretsecret@localhost:5672/',
-               help='AMQP connection URL')
 ]
 
-cfg.CONF.register_cli_opts(cli_opts)
+cfg.CONF.register_opts(worker_opts)
 
 
 class JuliaSet(object):
@@ -97,49 +91,34 @@ class JuliaSet(object):
         return (c, z)
 
 
-class Worker(ConsumerMixin):
+class WorkerEndpoint(object):
 
-    def __init__(self, url, target):
+    def process(self, ctxt, task):
-        self.connection = kombu.Connection(url)
+        LOG.info("processing task %s" % task['uuid'])
-        self.target = target
+        LOG.debug(task)
-
-    def get_consumers(self, Consumer, channel):
-        return [Consumer(queues=queues.task_queues,
-                         accept=['pickle', 'json'],
-                         callbacks=[self.process_task])]
-
-    def process_task(self, body, message):
-        LOG.info("processing task %s" % body['uuid'])
-        LOG.debug(body)
         start_time = time.time()
-        juliaset = JuliaSet(body['width'],
+        juliaset = JuliaSet(task['width'],
-                            body['height'],
+                            task['height'],
-                            body['xa'],
+                            task['xa'],
-                            body['xb'],
+                            task['xb'],
-                            body['ya'],
+                            task['ya'],
-                            body['yb'],
+                            task['yb'],
-                            body['iterations'])
+                            task['iterations'])
-        filename = os.path.join(self.target, "%s.png" % body['uuid'])
+        filename = os.path.join(cfg.CONF.filesystem_store_datadir,
+                                "%s.png" % task['uuid'])
         elapsed_time = time.time() - start_time
         LOG.info("task %s processed in %f seconds" %
-                 (body['uuid'], elapsed_time))
+                 (task['uuid'], elapsed_time))
         juliaset.save(filename)
         LOG.info("saved result of task %s to file %s" %
-                 (body['uuid'], filename))
+                 (task['uuid'], filename))
         checksum = hashlib.sha256(open(filename, 'rb').read()).hexdigest()
         result = {
-            'uuid': body['uuid'],
+            'uuid': task['uuid'],
             'duration': elapsed_time,
             'checksum': checksum
         }
-        LOG.info("pushed result: %s" % result)
+        return result
-        with producers[self.connection].acquire(block=True) as producer:
-            producer.publish(result, serializer='pickle',
-                             exchange=queues.result_exchange,
-                             declare=[queues.result_exchange],
-                             routing_key='results')
-
-        message.ack()
 
 
 def main():
@@ -152,16 +131,18 @@ def main():
     log.setup(cfg.CONF, 'worker',
               version=version.version_info.version_string())
 
-    worker = Worker(cfg.CONF.amqp_url, cfg.CONF.target)
+    transport = messaging.get_transport(cfg.CONF)
-
+    target = messaging.Target(topic='tasks', server=socket.gethostname())
-    if cfg.CONF.daemonize:
+    endpoints = [
-        with daemon.DaemonContext():
+        WorkerEndpoint()
-            worker.run()
+    ]
-    else:
+    server = messaging.get_rpc_server(transport, target, endpoints,
-        try:
+                                      executor='eventlet')
-            worker.run()
+    server.start()
-        except Exception as e:
+    try:
-            sys.exit("ERROR: %s" % e)
+        server.wait()
+    except KeyboardInterrupt:
+        LOG.info("Caught keyboard interrupt. Exiting.")
 
 
 if __name__ == '__main__':

requirements.txt

@@ -1,14 +1,12 @@
 pbr>=0.6,!=0.7,<1.0
 anyjson>=0.3.3
-amqp
 eventlet>=0.16.1,!=0.17.0
-kombu>=2.5.0
 PyMySQL>=0.6.2  # MIT License
 Pillow==2.4.0 # MIT
-python-daemon
 requests>=2.2.0,!=2.4.0
 Flask>=0.10,<1.0
 flask-sqlalchemy
 flask-restless
 oslo.config>=1.9.3,<1.10.0  # Apache-2.0
 oslo.log>=1.0.0,<1.1.0  # Apache-2.0
+oslo.messaging>=1.8.0,<1.9.0  # Apache-2.0

setup.cfg

@@ -27,7 +27,6 @@ setup-hooks =
 [entry_points]
 console_scripts =
      faafo-producer = faafo.producer:main
-     faafo-tracker = faafo.tracker:main
      faafo-worker = faafo.worker:main
      faafo-api = faafo.api:main