switch to gunicorn

Dockerfile

@@ -1,15 +1,14 @@
 # See https://www.digitalocean.com/community/tutorials/how-to-build-and-deploy-a-flask-application-using-docker-on-ubuntu-18-04
-FROM tiangolo/uwsgi-nginx-flask:python3.7
+FROM tiangolo/meinheld-gunicorn-flask:python3.7
 
-ARG AIIDA_VERSION=1.2.1
+ARG AIIDA_VERSION=1.3.1
 
 # Install AiiDA
 RUN pip install aiida-core[rest,atomic_tools]==$AIIDA_VERSION
 RUN reentry scan -r aiida
 
 # Scripts for REST API
 COPY main.py /app
-COPY uwsgi.ini /app
 
 # Container vars
 ENV AIIDA_PATH /app
@@ -25,5 +24,8 @@ ENV AIIDADB_PASS ""
 ENV AIIDADB_BACKEND django
 ENV default_user_email info@materialscloud.org
 
-# start AiiDA REST API
-EXPOSE 5000
+# GUNICORN vars 
+# Set number of gunicorn workers to 2 (overriding automatic scaling with #cores)
+# Note: memory footprint of the container scales linearly with the number of workers
+# https://github.com/tiangolo/meinheld-gunicorn-flask-docker#advanced-usage
+ENV WEB_CONCURRENCY 2