feat(extension): Add option to enable async workers in Flask and Django

docs/howto/code/flask-async/requirements.txt

@@ -0,0 +1,2 @@
+Flask
+gevent

docs/tutorial/code/flask-async/task.yaml → docs/howto/code/flask-async/task.yaml

@@ -5,7 +5,7 @@
 # markers for including said instructions
 # as snippets in the docs.
 ###########################################
-summary: Getting started with Flask tutorial
+summary: How to create async Flask Charm
 
 kill-timeout: 90m
 
@@ -22,28 +22,11 @@ execute: |
   unset CHARMCRAFT_REGISTRY_URL
 
   # Add setup instructions
-  # (Ran into issues in prepare section)
-  # snap install rockcraft --channel=latest/edge --classic
-
-  # Install the latest rockcraft snap
-  # (This can be removed after the Rockcraft PR is merged)
-  # The PR: https://github.com/canonical/rockcraft/pull/747
-  snap install snapcraft --channel=latest/edge --classic
-  # Download rockcraft async-workers branch and alithethird fork
-  git clone -b flask-django-extention-async-workers https://github.com/alithethird/rockcraft
-  cd rockcraft
-  snapcraft pack
-  snap install --dangerous --classic rockcraft_*
-
-
-  snap install lxd
-  lxd init --auto
-  # snap refresh charmcraft --channel=latest/edge --amend
+  snap install rockcraft --channel=latest/edge --classic
+
   snap install microk8s --channel=1.31-strict/stable
-  snap install juju --channel=3.5/stable
+  snap install juju --channel=3/stable
 
-  # Juju config setup
-  lxc network set lxdbr0 ipv6.address none
   mkdir -p ~/.local/share
 
   # MicroK8s config setup
@@ -61,7 +44,6 @@ execute: |
   python3 -m venv .venv
   source .venv/bin/activate
   pip install -r requirements.txt
-  pip install Flask
   # [docs:create-venv-end]
 
   flask run -p 8000 &
@@ -84,36 +66,6 @@ execute: |
   sed -i "s/name: .*/name: flask-async-app/g" rockcraft.yaml
   sed -i "s/amd64/$(dpkg --print-architecture)/g" rockcraft.yaml
 
-  # uncomment the parts main section
-  sed -i "s/# parts:/parts:/g" rockcraft.yaml
-  # uncomment the async-dependencies part
-  awk -i inplace -v block_key="flask-framework/async-dependencies" '
-  BEGIN {
-    in_block = 0;
-    comment_pattern = "^#[[:space:]]";
-    uncommented_line = "";
-  }
-
-  /^#[[:space:]]/ {
-    # Check if the line contains the block key
-    if (in_block == 0 && $0 ~ block_key) {
-      in_block = 1;
-    }
-  }
-
-  {
-    # If in_block is active, uncomment lines
-    if (in_block == 1) {
-      uncommented_line = gensub(comment_pattern, "", 1, $0);
-      if (uncommented_line == $0) {
-        in_block = 0;
-      }
-      print uncommented_line;
-    } else {
-      print $0;
-    }
-  }' rockcraft.yaml
-
   # [docs:pack]
   rockcraft pack
   # [docs:pack-end]
@@ -160,7 +112,7 @@ execute: |
   # [docs:deploy-juju-model-end]
 
   # [docs:deploy-nginx]
-  juju deploy nginx-ingress-integrator --channel=latest/edge --revision 122
+  juju deploy nginx-ingress-integrator --channel=latest/edge --base [email protected]
   juju integrate nginx-ingress-integrator flask-async-app
   # [docs:deploy-nginx-end]
 
@@ -181,11 +133,13 @@ execute: |
   juju config flask-async-app webserver-worker-class=gevent
   # [docs:config-async-end]
 
+  juju wait-for application flask-async-app --query='status=="active"' --timeout 10m
+
   # test the async flask service
   NUM_REQUESTS=15
   ASYNC_RESULT='TRUE'
 
-  echo "Firing $NUM_REQUESTS requests to $URL..."
+  echo "Firing $NUM_REQUESTS requests to http://flask-async-app/io..."
 
   overall_start_time=$(date +%s)
 
@@ -221,8 +175,7 @@ execute: |
   deactivate
   rm -rf charm .venv __pycache__
   # delete all the files created during the tutorial
-  rm flask-async-app_0.1_$(dpkg --print-architecture).rock flask-async-app_0.2_$(dpkg --print-architecture).rock \
-    flask-async-app_0.3_$(dpkg --print-architecture).rock rockcraft.yaml app.py \
+  rm flask-async-app_0.1_$(dpkg --print-architecture).rock rockcraft.yaml app.py \
     requirements.txt migrate.py
   # Remove the juju model
   juju destroy-model flask-async-app --destroy-storage --no-prompt --force

docs/howto/flask-async.rst

@@ -0,0 +1,53 @@
+======================================================
+How to write a Kubernetes charm for an Async Flask app
+======================================================
+
+In this how-to guide we will configure a 12-factor Flask
+application to use asynchronous Gunicorn workers to be
+able to serve to multiple users easily.
+
+Make the rock async
+===================
+
+Before packing the rock make sure to put the following in ``requirements.txt``
+file:
+
+.. literalinclude:: code/flask-async/requirements.txt
+
+Configure the async application
+===============================
+
+Now let's enable async Gunicorn workers using a configuration option. We will
+expect this configuration option to be available in the Flask app configuration
+under the keyword ``webserver-worker-class``. Verify that the new configuration
+has been added using
+``juju config flask-async-app | grep -A 6 webserver-worker-class:`` which should
+show the configuration option.
+
+The worker class can be changed using Juju:
+
+.. literalinclude:: code/flask-async/task.yaml
+    :language: bash
+    :start-after: [docs:config-async]
+    :end-before: [docs:config-async-end]
+    :dedent: 2
+
+Now you can run
+``curl --parallel --parallel-immediate --resolve flask-async-app:80:127.0.0.1 \
+http://flask-async-app/io http://flask-async-app/io http://flask-async-app/io \
+http://flask-async-app/io http://flask-async-app/io``
+in they will all return at the same time.
+
+Output will be similar to following:
+
+.. code-block:: bash
+
+   ok
+   ok
+   ok
+   ok
+   ok
+
+.. note::
+
+    It might take a short time for the configuration to take effect.

docs/howto/index.rst

@@ -9,3 +9,4 @@ How-To
    charm-to-poetry
    charm-to-python
    shared-cache
+   flask-async