when metrics is disabled, metrics still try to gather

[jon-nfc]

within settings METRICS_ENABLED attribute exists. its purpose is to disable metrics.

Details

When metrics is enabled, collection of metrics is possible. prior to it being possible, the host must be setup. this is done by ensuring that the metrics directory exists so that ALL processors can save their metrics for the metrics endpoint.

However, if metrics are disabled via METRICS_ENABLED=False, the installed metrics app still tries to gather. This causes a crash as the metrics directory does not exist.

Confirmed by deploying 39a1183 which has the bug. the gunicorn service keeps crashing. simply running mkdir -p /tmp/prometheus and restarting gunicorn and the issue disappears.

Tasks

• when METRICS_ENABLED=False, dont add the middleware
• when METRICS_ENABLED=False, dont add the installed app
• Test