Re-write simple sample app using connexion

[c-w]

Resolves #293

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This change is 

[cicorias]

Reviewed 14 of 14 files at r1.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @c-w, @fnocera, and @sayar)

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agogosml_cli/cli/templates/apps/simple/{{cookiecutter.PROJECT_NAME_SLUG}}/Dockerfile.{{cookiecutter.PROJECT_NAME_SLUG}}, line 36 at r1 (raw file):

EXPOSE $PORT

CMD gunicorn --log-level="$LOG_LEVEL" --bind="$HOST:$PORT" --workers="$WORKERS" "main:build_app(wsgi=True)"

should this be the exec form? this is shell form - ie. ['gunicorn', '--log......]

https://docs.docker.com/engine/reference/builder/#cmd

any reason this isn't an ENTRYPOINT?

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agogosml_cli/cli/templates/apps/simple/{{cookiecutter.PROJECT_NAME_SLUG}}/main.py, line 33 at r1 (raw file):

    PORT = getenv('PORT', '8888')
    HOST = getenv('HOST', '127.0.0.1')

any reason dotenv isn't used and these defaults are in settings.py ?

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agogosml_cli/cli/templates/apps/simple/{{cookiecutter.PROJECT_NAME_SLUG}}/requirements.txt, line 1 at r1 (raw file):

connexion[swagger-ui]

imho using swagger is a very opinionated approach for an example application. I don't think it's necessary unless i'm missing something.

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agogosml_cli/cli/templates/apps/simple/{{cookiecutter.PROJECT_NAME_SLUG}}/requirements-dev.txt, line 1 at r1 (raw file):

flake8

have we really reduced all the dependencies that both these requirements.txt files are only used in the sample app?

[cicorias]

#293
again, imho swagger is an opinionated approach.

Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @c-w, @fnocera, and @sayar)

[c-w]

See reply on requirements.txt below.

Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @cicorias, @fnocera, and @sayar)

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agogosml_cli/cli/templates/apps/simple/{{cookiecutter.PROJECT_NAME_SLUG}}/Dockerfile.{{cookiecutter.PROJECT_NAME_SLUG}}, line 36 at r1 (raw file):

Previously, cicorias (Shawn Cicoria) wrote…

should this be the exec form? this is shell form - ie. ['gunicorn', '--log......]

https://docs.docker.com/engine/reference/builder/#cmd

any reason this isn't an ENTRYPOINT?

The exec form doesn't dereference environment variables.

Exec form:

Sh form:

What would be the value of setting gunicorn as the entrypoint instead of the cmd? To my understanding, we want to set the entrypoint if we have multiple valid sets of arguments that could be passed to the container. Here, we really only have one valid set of arguments (running gunicorn) so I'm not sure what setting the entypoint buys us. Could you clarify? One advantage of not setting the entrypoint is that we can more easily exec into the container, e.g. to run bash to debug something. docker run foo cat /etc/hosts is less of a pain to type/remember than docker run --entrypoint=cat /etc/hosts.

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agogosml_cli/cli/templates/apps/simple/{{cookiecutter.PROJECT_NAME_SLUG}}/main.py, line 33 at r1 (raw file):

Previously, cicorias (Shawn Cicoria) wrote…

any reason dotenv isn't used and these defaults are in settings.py ?

We can move the configuration to a different file if you wish. My intent here was to keep the amount of code that the developer has to view to a minimum (it's supposed to be a simple app after all) and contain all the "framework code" in main.py.

Adding dotenv pulls in an additional dependency and we're not currently generating a .env file for the user anyways. Happy to do so, but this was omitted to keep the simple app minimal. Let me know what you prefer.

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agogosml_cli/cli/templates/apps/simple/{{cookiecutter.PROJECT_NAME_SLUG}}/requirements.txt, line 1 at r1 (raw file):

Previously, cicorias (Shawn Cicoria) wrote…

imho using swagger is a very opinionated approach for an example application. I don't think it's necessary unless i'm missing something.

To my understanding, the purpose of this simple application template is to give the developer as little to worry about in terms of framework as possible in order to increase productivity.

Using connexion gives us a lot of stuff for free: routing, request post body validation, serialization, etc. The developer really only has to implement a pure Python function to do the data transformation/model prediction. If we use the previous "standard-library only" approach of making a web server, all of this is code that a developer otherwise would have to read/maintain which is not desirable in my opinion.

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agogosml_cli/cli/templates/apps/simple/{{cookiecutter.PROJECT_NAME_SLUG}}/requirements-dev.txt, line 1 at r1 (raw file):

Previously, cicorias (Shawn Cicoria) wrote…

have we really reduced all the dependencies that both these requirements.txt files are only used in the sample app?

Yes we have. For testing, the simple app now uses doctest (built into Python). Pydocstyle and flake8 are the only remaining development dependencies for linting. You can confirm this in the multi-stage dockerfile on lines 16-18.

[sayar]

@c-w Let's press pause on this PR and discuss offline (related to upcoming changes to CLI).