title: Airflow webserver suddenly stopped starting
body: <p>My airflow webserver suddenly stopped starting. When I try to start webserver it does not come up with UI. </p>
  
  <p>I tried reseting db as <code>airflow resetdb</code> and <code>airflow initdb</code> restarting all the services. Downgrading Gunicorn and upgrading it again. Restarting my linux machine, however, nothing has changed.</p>
  
  <p>Logs of webserver is following:  </p>
  
  <pre><code>[2019-05-17 08:08:00 +0000] [14978] [INFO] Starting gunicorn 19.9.0
  [2019-05-17 08:08:00 +0000] [14978] [INFO] Listening at: http://0.0.0.0:8081 (14978)
  [2019-05-17 08:08:00 +0000] [14978] [INFO] Using worker: sync
  [2019-05-17 08:08:00 +0000] [14983] [INFO] Booting worker with pid: 14983
  [2019-05-17 08:08:00 +0000] [14984] [INFO] Booting worker with pid: 14984
  [2019-05-17 08:08:00 +0000] [14985] [INFO] Booting worker with pid: 14985
  [2019-05-17 08:08:00 +0000] [14986] [INFO] Booting worker with pid: 14986
  [2019-05-17 08:08:02,179] {__init__.py:51} INFO - Using executor LocalExecutor
  [2019-05-17 08:08:02,279] {__init__.py:51} INFO - Using executor LocalExecutor
  [2019-05-17 08:08:02,324] {__init__.py:51} INFO - Using executor LocalExecutor
  [2019-05-17 08:08:02,342] {models.py:273} INFO - Filling up the DagBag from /root/airflow/dags
  [2019-05-17 08:08:02,376] {__init__.py:51} INFO - Using executor LocalExecutor
  [2019-05-17 08:08:02,435] {models.py:273} INFO - Filling up the DagBag from /root/airflow/dags
  [2019-05-17 08:08:02,521] {models.py:273} INFO - Filling up the DagBag from /root/airflow/dags
  [2019-05-17 08:08:02,524] {models.py:273} INFO - Filling up the DagBag from /root/airflow/dags
  [2019-05-17 08:10:00 +0000] [14978] [CRITICAL] WORKER TIMEOUT (pid:14984)
  [2019-05-17 08:10:00 +0000] [14978] [CRITICAL] WORKER TIMEOUT (pid:14985)
  [2019-05-17 08:10:00 +0000] [14978] [CRITICAL] WORKER TIMEOUT (pid:14986)
  [2019-05-17 08:10:00 +0000] [14978] [CRITICAL] WORKER TIMEOUT (pid:14983)
  [2019-05-17 08:10:01 +0000] [15161] [INFO] Booting worker with pid: 15161
  [2019-05-17 08:10:01 +0000] [15164] [INFO] Booting worker with pid: 15164
  [2019-05-17 08:10:01 +0000] [15167] [INFO] Booting worker with pid: 15167
  [2019-05-17 08:10:01 +0000] [15168] [INFO] Booting worker with pid: 15168
  [2019-05-17 08:10:03,953] {__init__.py:51} INFO - Using executor LocalExecutor
  [2019-05-17 08:10:04,007] {__init__.py:51} INFO - Using executor LocalExecutor
  [2019-05-17 08:10:04,020] {__init__.py:51} INFO - Using executor LocalExecutor
  [2019-05-17 08:10:04,036] {__init__.py:51} INFO - Using executor LocalExecutor
  </code></pre>
  
  <p>Is there anyone who encountered same problem? or Do you have any suggestions?</p>