{"id":2920,"date":"2018-12-08T18:43:10","date_gmt":"2018-12-08T23:43:10","guid":{"rendered":"http:\/\/osric.com\/chris\/accidental-developer\/?p=2920"},"modified":"2018-12-08T19:55:51","modified_gmt":"2018-12-09T00:55:51","slug":"running-a-python-flask-application-in-a-docker-container","status":"publish","type":"post","link":"https:\/\/osric.com\/chris\/accidental-developer\/2018\/12\/running-a-python-flask-application-in-a-docker-container\/","title":{"rendered":"Running a Python Flask application in a Docker container"},"content":{"rendered":"

I’ve played with Docker containers but haven’t really done anything, useful or otherwise, with them. I decided to create a Docker image that includes a web-based chatbot. You can find the Git repository for this (including the finished Dockerfile<\/code>) at https:\/\/github.com\/cherdt\/docker-nltk-chatbot<\/a><\/p>\n

<\/p>\n

I’ve worked with this particular chatbot before, which is based on the nltk.chat.eliza<\/a> module. I turned it into a web application by wrapping it in a Flask app. And because Flask warns you not to run Flask directly in production, I call the Flask app via uWSGI.<\/p>\n

I started by creating a Dockerfile<\/code>:<\/p>\n

# mkdir chatbot\r\n# cd chatbot\r\n# vi Dockerfile<\/code><\/pre>\n
I needed to start with a base image, so I picked CentOS 7:<\/p>\n
FROM centos:centos7<\/code><\/pre>\n
I knew I would need several packages installed to satisfy the dependencies for Flask and uWSGI (although it took me a couple tries before I determined that I would need gcc and python-devel in order to install uWSGI):<\/p>\n
RUN \/usr\/bin\/yum --assumeyes install epel-release gcc\r\nRUN \/usr\/bin\/yum --assumeyes install python python-devel python-pip<\/code><\/pre>\n
Then to install Flask and dependencies, uWSGI, and the Python NLTK (Natural Language ToolKit):<\/p>\n
RUN \/usr\/bin\/pip install Flask flask-cors nltk requests uwsgi<\/code><\/pre>\n
The Python file for the Flask app and the HTML template file needed to be copied into the container:<\/p>\n
COPY chatbot.py .\/\r\nCOPY chat.html .\/<\/code><\/pre>\n
Finally, the command that will run uWSGI and point it at the Flask app:<\/p>\n
CMD [\"\/usr\/bin\/uwsgi\", \"--http\", \":9500\", \"--manage-script-name\", \"--mount\", \"\/=chatbot:app\"]<\/code><\/pre>\n
Note that CMD does not like spaces: each item needs to be a separate array element.<\/p>\n
Now to build the image:<\/p>\n
# docker build --tag chatbot .\r\n...[some other output]...\r\nSuccessfully built ab3a32938f0e\r\nSuccessfully tagged chatbot:latest\r\n\r\n# docker images\r\nREPOSITORY          TAG                 IMAGE ID            CREATED              SIZE\r\nchatbot             latest              ab3a32938f0e        5 seconds ago        486MB<\/code><\/pre>\n
To run a container based on this image, I wanted to do several things:<\/p>\n