Airflow webserver not starting - airflow

Question

I have installed airflow via github source. I have configured airflow with mysql metadb with local executer. When I tried to start my webserver it couldn't able to start.
install.sh
mkdir -p ~/home
export AIRFLOW_HOME=~/airflow
cd $AIRFLOW_HOME
virtualenv env
source env/bin/activate
mkdir -p /usr/local/src/
cd /usr/local/src/
git clone https://github.com/apache/incubator-airflow.git
cd incubator-airflow
git checkout tags/1.8.2
pip install -e .
pip install -e .[hive]
pip install -e .[gcp_api]
pip install -e .[mysql]
pip install -e .[password]
pip install -e .[celery]
airflow.cfg:
[core]
# The home folder for airflow, default is ~/airflow
airflow_home = /root/airflow
dags_folder = /root/airflow/dags
base_log_folder = /root/airflow/logs
encrypt_s3_logs = False
executor = LocalExecutor
sql_alchemy_conn = mysql://root:*****#localhost/airflow
when I tried to start my webserver using it shows ttou signal handling and existing worker.
airflow webserver -p 8080
[2017-11-20 04:05:30,642] {__init__.py:57} INFO - Using executor LocalExecutor
[2017-11-20 04:05:30,723] {driver.py:120} INFO - Generating grammar tables from /usr/lib/python2.7/lib2to3/Grammar.txt
[2017-11-20 04:05:30,756] {driver.py:120} INFO - Generating grammar tables from /usr/lib/python2.7/lib2to3/PatternGrammar.txt
____________ _____________
____ |__( )_________ __/__ /________ __
____ /| |_ /__ ___/_ /_ __ /_ __ \_ | /| / /
___ ___ | / _ / _ __/ _ / / /_/ /_ |/ |/ /
_/_/ |_/_/ /_/ /_/ /_/ \____/____/|__/
/root/env/local/lib/python2.7/site-packages/flask/exthook.py:71: ExtDeprecationWarning: Importing flask.ext.cache is deprecated, use flask_cache instead.
.format(x=modname), ExtDeprecationWarning
[2017-11-20 04:05:31,437] [3079] {models.py:167} INFO - Filling up the DagBag from /root/airflow/dags
Running the Gunicorn Server with:
Workers: 8 sync
Host: 0.0.0.0:8080
Timeout: 120
Logfiles: - -
=================================================================
[2017-11-20 04:05:32,074] {__init__.py:57} INFO - Using executor LocalExecutor
[2017-11-20 04:05:32,153] {driver.py:120} INFO - Generating grammar tables from /usr/lib/python2.7/lib2to3/Grammar.txt
[2017-11-20 04:05:32,184] {driver.py:120} INFO - Generating grammar tables from /usr/lib/python2.7/lib2to3/PatternGrammar.txt
[2017-11-20 04:05:32 +0000] [3087] [INFO] Starting gunicorn 19.3.0
[2017-11-20 04:05:32 +0000] [3087] [INFO] Listening at: http://0.0.0.0:8080 (3087)
[2017-11-20 04:05:32 +0000] [3087] [INFO] Using worker: sync
[2017-11-20 04:05:32 +0000] [3098] [INFO] Booting worker with pid: 3098
[2017-11-20 04:05:32 +0000] [3099] [INFO] Booting worker with pid: 3099
/root/env/local/lib/python2.7/site-packages/flask/exthook.py:71: ExtDeprecationWarning: Importing flask.ext.cache is deprecated, use flask_cache instead.
.format(x=modname), ExtDeprecationWarning
/root/env/local/lib/python2.7/site-packages/flask/exthook.py:71: ExtDeprecationWarning: Importing flask.ext.cache is deprecated, use flask_cache instead.
.format(x=modname), ExtDeprecationWarning
[2017-11-20 04:05:32 +0000] [3100] [INFO] Booting worker with pid: 3100
[2017-11-20 04:05:32 +0000] [3101] [INFO] Booting worker with pid: 3101
/root/env/local/lib/python2.7/site-packages/flask/exthook.py:71: ExtDeprecationWarning: Importing flask.ext.cache is deprecated, use flask_cache instead.
.format(x=modname), ExtDeprecationWarning
[2017-11-20 04:05:32 +0000] [3102] [INFO] Booting worker with pid: 3102
[2017-11-20 04:05:32 +0000] [3103] [INFO] Booting worker with pid: 3103
[2017-11-20 04:05:32 +0000] [3104] [INFO] Booting worker with pid: 3104
/root/env/local/lib/python2.7/site-packages/flask/exthook.py:71: ExtDeprecationWarning: Importing flask.ext.cache is deprecated, use flask_cache instead.
.format(x=modname), ExtDeprecationWarning
[2017-11-20 04:05:32 +0000] [3105] [INFO] Booting worker with pid: 3105
/root/env/local/lib/python2.7/site-packages/flask/exthook.py:71: ExtDeprecationWarning: Importing flask.ext.cache is deprecated, use flask_cache instead.
.format(x=modname), ExtDeprecationWarning
/root/env/local/lib/python2.7/site-packages/flask/exthook.py:71: ExtDeprecationWarning: Importing flask.ext.cache is deprecated, use flask_cache instead.
.format(x=modname), ExtDeprecationWarning
/root/env/local/lib/python2.7/site-packages/flask/exthook.py:71: ExtDeprecationWarning: Importing flask.ext.cache is deprecated, use flask_cache instead.
.format(x=modname), ExtDeprecationWarning
/root/env/local/lib/python2.7/site-packages/flask/exthook.py:71: ExtDeprecationWarning: Importing flask.ext.cache is deprecated, use flask_cache instead.
.format(x=modname), ExtDeprecationWarning
[2017-11-20 04:05:33,198] [3099] {models.py:167} INFO - Filling up the DagBag from /root/airflow/dags
[2017-11-20 04:05:33,312] [3098] {models.py:167} INFO - Filling up the DagBag from /root/airflow/dags
[2017-11-20 04:05:33,538] [3100] {models.py:167} INFO - Filling up the DagBag from /root/airflow/dags
[2017-11-20 04:05:33,863] [3101] {models.py:167} INFO - Filling up the DagBag from /root/airflow/dags
[2017-11-20 04:05:33,963] [3102] {models.py:167} INFO - Filling up the DagBag from /root/airflow/dags
[2017-11-20 04:05:33,987] [3104] {models.py:167} INFO - Filling up the DagBag from /root/airflow/dags
[2017-11-20 04:05:34,062] [3105] {models.py:167} INFO - Filling up the DagBag from /root/airflow/dags
[2017-11-20 04:05:34,162] [3103] {models.py:167} INFO - Filling up the DagBag from /root/airflow/dags
[2017-11-20 04:06:05 +0000] [3087] [INFO] Handling signal: ttin
[2017-11-20 04:06:05 +0000] [3121] [INFO] Booting worker with pid: 3121
/root/env/local/lib/python2.7/site-packages/flask/exthook.py:71: ExtDeprecationWarning: Importing flask.ext.cache is deprecated, use flask_cache instead.
.format(x=modname), ExtDeprecationWarning
[2017-11-20 04:06:05,426] [3121] {models.py:167} INFO - Filling up the DagBag from /root/airflow/dags
[2017-11-20 04:06:06 +0000] [3087] [INFO] Handling signal: ttou
[2017-11-20 04:06:06 +0000] [3098] [INFO] Worker exiting (pid: 3098)
[2017-11-20 04:06:36 +0000] [3087] [INFO] Handling signal: ttin
[2017-11-20 04:06:36 +0000] [3136] [INFO] Booting worker with pid: 3136
/root/env/local/lib/python2.7/site-packages/flask/exthook.py:71: ExtDeprecationWarning: Importing flask.ext.cache is deprecated, use flask_cache instead.
.format(x=modname), ExtDeprecationWarning
[2017-11-20 04:06:36,818] [3136] {models.py:167} INFO - Filling up the DagBag from /root/airflow/dags
[2017-11-20 04:06:37 +0000] [3087] [INFO] Handling signal: ttou
[2017-11-20 04:06:37 +0000] [3099] [INFO] Worker exiting (pid: 3099)
[2017-11-20 04:07:07 +0000] [3087] [INFO] Handling signal: ttin
[2017-11-20 04:07:07 +0000] [3144] [INFO] Booting worker with pid: 3144

Answer 1

Your webserver is running fine. Workers are regularly "refreshed" at an interval set by worker_refresh_interval so that they pickup on new or updated DAGs. When this happens, you'll see the signal ttin (increase processes by one) always followed byttou (decrease processes by one), where a new worker is added before the oldest worker is removed.