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= Experimenting with the `flags2*` examples
== Install SSL Certificates (for MacOS)
On Macos, depending on how in installed Python you may need to manually run a command
after Python's installer finishes, to install SSL certificates for HTTPS connections.
Using the Finder, open the `Python 3.X` folder inside `/Applications` folder
and double-click "Install Certificates" or "Install Certificates.command".
Using the terminal, you can type for example:
[source, text]
----
$ open /Applications/Python 3.10/"Install Certificates.command"
----
== Setting up a test server
If you don't already have a local HTTP server for testing,
here are the steps to experiment using only Python ≥ 3.9—no external libraries:
here are the steps to experiment using only Python ≥ 3.9:
. Clone or download the https://github.com/fluentpython/example-code-2e[_Fluent Python 2e_ code repository].
. Open your shell and go to the _20-futures/getflags/_ directory of your local copy of the repository.
. Clone or download the https://github.com/fluentpython/example-code-2e[_Fluent Python 2e_ code repository] (this repo!).
. Open your shell and go to the _20-futures/getflags/_ directory of your local copy of the repository (this directory!)
. Unzip the _flags.zip_ file, creating a _flags_ directory at _20-futures/getflags/flags/_.
. Open a second shell, go to the _20-futures/getflags/_ directory and run `python3 -m http.server`. This will start a `ThreadingHTTPServer` listening to port 8000, serving the local files. If you open the URL http://localhost:8000/flags/[http://localhost:8000/flags/] with your browser, you'll see a long list of directories named with two-letter country codes from `ad/` to `zw/`.
. Now you can go back to the first shell and run the _flags2*.py_ examples with the default `--server LOCAL` option.
. To test with the `--server DELAY` option, go to _20-futures/getflags/_ and run `python3 slow_server.py 8001`. This will add a .5s delay before each response.
. To test with the `--server ERROR` option, go to _20-futures/getflags/_ and run `python3 slow_server.py 8002 --error-rate .25`. Each request will have a 25% probability of getting a https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/418[418 I'm a teapot] response, and all responses will be delayed .5s.
. To test with the `--server DELAY` option, go to _20-futures/getflags/_ and run `python3 slow_server.py`. This bind to port 8001 by default. It will add a .5s delay before each response.
. To test with the `--server ERROR` option, go to _20-futures/getflags/_ and run `python3 slow_server.py 8002 --error-rate .25`.
Each request will have a 25% probability of getting a
https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/418[418 I'm a teapot] response,
and all responses will be delayed .5s.
I wrote _slow_server.py_ reusing code from Python's
https://github.com/python/cpython/blob/917eca700aa341f8544ace43b75d41b477e98b72/Lib/http/server.py[`http.server`] standard library module,
which "is not recommended for production"—according to the
https://docs.python.org/3/library/http.server.html[documentation].
To set up a more reliable testing environment, I recommend configuring
[NOTE]
====
This is a simple testing environment that does nor require any external libraries or
tools—apart from the libraries used in the `flags2*` scripts themselves, as discussed in the book.
For a more robust testing environment, I recommend configuring
https://www.nginx.com/[NGINX] and
https://github.com/shopify/toxiproxy[Toxiproxy] with equivalent parameters.
====
== Running a `flags2*` script