feat(run): Add timeout comment to Dockerfiles (GoogleCloudPlatform#5375)

## Description

Fixes #<ISSUE-NUMBER>

Note: It's a good idea to open an issue first for discussion.

## Checklist
- [ ] I have followed [Sample Guidelines from AUTHORING_GUIDE.MD](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/AUTHORING_GUIDE.md)
- [ ] README is updated to include [all relevant information](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/AUTHORING_GUIDE.md#readme-file)
- [ ] **Tests** pass:   `nox -s py-3.6` (see [Test Environment Setup](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/AUTHORING_GUIDE.md#test-environment-setup))
- [ ] **Lint** pass:   `nox -s lint` (see [Test Environment Setup](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/AUTHORING_GUIDE.md#test-environment-setup))
- [ ] These samples need a new **API enabled** in testing projects to pass (let us know which ones)
- [ ] These samples need a new/updated **env vars** in testing projects set to pass (let us know which ones)
- [ ] Please **merge** this PR for me once it is approved.
- [ ] This sample adds a new sample directory, and I updated the [CODEOWNERS file](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/.github/CODEOWNERS) with the codeowners for this sample

Author: averikitsch

run/django/Dockerfile

@@ -24,7 +24,7 @@ ENV PYTHONUNBUFFERED 1
 
 # Install dependencies
 COPY requirements.txt .
-RUN pip install --no-cache-dir -r requirements.txt 
+RUN pip install --no-cache-dir -r requirements.txt
 
 # Copy local code to the container image.
 COPY . .
@@ -33,4 +33,5 @@ COPY . .
 # webserver, with one worker process and 8 threads.
 # For environments with multiple CPU cores, increase the number of workers
 # to be equal to the cores available.
+# Timeout is set to 0 to disable the timeouts of the workers to allow Cloud Run to handle instance scaling.
 CMD exec gunicorn --bind 0.0.0.0:$PORT --workers 1 --threads 8 --timeout 0 mysite.wsgi:application

run/hello-broken/Dockerfile

@@ -38,6 +38,7 @@ COPY . ./
 # Use gunicorn webserver with one worker process and 8 threads.
 # For environments with multiple CPU cores, increase the number of workers
 # to be equal to the cores available.
+# Timeout is set to 0 to disable the timeouts of the workers to allow Cloud Run to handle instance scaling.
 CMD exec gunicorn --bind :$PORT --workers 1 --threads 8 --timeout 0 main:app
 
 # [END run_broken_dockerfile]

run/helloworld/Dockerfile

@@ -34,6 +34,7 @@ RUN pip install Flask gunicorn
 # webserver, with one worker process and 8 threads.
 # For environments with multiple CPU cores, increase the number of workers
 # to be equal to the cores available.
+# Timeout is set to 0 to disable the timeouts of the workers to allow Cloud Run to handle instance scaling.
 CMD exec gunicorn --bind :$PORT --workers 1 --threads 8 --timeout 0 main:app
 
 # [END run_helloworld_dockerfile]

run/image-processing/Dockerfile

@@ -47,4 +47,5 @@ COPY . ./
 # Use gunicorn webserver with one worker process and 8 threads.
 # For environments with multiple CPU cores, increase the number of workers
 # to be equal to the cores available.
+# Timeout is set to 0 to disable the timeouts of the workers to allow Cloud Run to handle instance scaling.
 CMD exec gunicorn --bind :$PORT --workers 1 --threads 8 --timeout 0 main:app

run/logging-manual/Dockerfile

@@ -31,8 +31,9 @@ ENV APP_HOME /app
 WORKDIR $APP_HOME
 COPY . ./
 
-# Run the web service on container startup. 
+# Run the web service on container startup.
 # Use gunicorn webserver with one worker process and 8 threads.
 # For environments with multiple CPU cores, increase the number of workers
 # to be equal to the cores available.
+# Timeout is set to 0 to disable the timeouts of the workers to allow Cloud Run to handle instance scaling.
 CMD exec gunicorn --bind :$PORT --workers 1 --threads 8 --timeout 0 main:app

run/markdown-preview/editor/Dockerfile

@@ -31,8 +31,9 @@ ENV APP_HOME /app
 WORKDIR $APP_HOME
 COPY . ./
 
-# Run the web service on container startup. 
+# Run the web service on container startup.
 # Use gunicorn webserver with one worker process and 8 threads.
 # For environments with multiple CPU cores, increase the number of workers
 # to be equal to the cores available.
+# Timeout is set to 0 to disable the timeouts of the workers to allow Cloud Run to handle instance scaling.
 CMD exec gunicorn --bind :$PORT --workers 1 --threads 8 --timeout 0 main:app

run/markdown-preview/renderer/Dockerfile

@@ -31,8 +31,9 @@ ENV APP_HOME /app
 WORKDIR $APP_HOME
 COPY . ./
 
-# Run the web service on container startup. 
+# Run the web service on container startup.
 # Use gunicorn webserver with one worker process and 8 threads.
 # For environments with multiple CPU cores, increase the number of workers
 # to be equal to the cores available.
+# Timeout is set to 0 to disable the timeouts of the workers to allow Cloud Run to handle instance scaling.
 CMD exec gunicorn --bind :$PORT --workers 1 --threads 8 --timeout 0 main:app

run/pubsub/Dockerfile

@@ -38,6 +38,7 @@ COPY . ./
 # Use gunicorn webserver with one worker process and 8 threads.
 # For environments with multiple CPU cores, increase the number of workers
 # to be equal to the cores available.
+# Timeout is set to 0 to disable the timeouts of the workers to allow Cloud Run to handle instance scaling.
 CMD exec gunicorn --bind :$PORT --workers 1 --threads 8 --timeout 0 main:app
 
 # [END run_pubsub_dockerfile]

run/system-package/Dockerfile

@@ -43,4 +43,5 @@ COPY . ./
 # Use gunicorn webserver with one worker process and 8 threads.
 # For environments with multiple CPU cores, increase the number of workers
 # to be equal to the cores available.
+# Timeout is set to 0 to disable the timeouts of the workers to allow Cloud Run to handle instance scaling.
 CMD exec gunicorn --bind :$PORT --workers 1 --threads 8 --timeout 0 main:app