allow gunicorn config to be passed to airflow webserver

[dimberman]

Ticket was created 14/Oct/16 22:48

Description

I have run into an issue when running airflow webserver behind a load balancer where redirects result in https requests forwarded to http. I ran into a similar issue with Caravel which also uses gunicorn. apache/superset#978 From that issue:

When gunicorn is run on a different machine from the load balancer (nginx or ELB), it needs to be told explicitly to trust the X-Forwarded-* headers sent. gunicorn takes an option --forwarded-allow-ips which can either be a comma separated list of ip addresses, or "*" to trust all.

I don't see a simple way to inject custom arguments to the gunicorn call in webserver(). Rather than making a special case to set --forwarded-allow-ips, it would be nice if the caller of airflow webserver could pass an additional gunicorn config file.

The call to gunicorn is already including a -c and I'm not sure gunicorn will take multiple configs, so maybe we have to parse the config and include each name=value on the gunicorn command line. Any suggestions on how best to allow this?

Use case / motivation

Related Issues

Moved here from https://issues.apache.org/jira/browse/AIRFLOW-571