Remove PORT environment variable from helloworld Dockerfiles (#1019)

docs/serving/samples/hello-world/helloworld-csharp/Dockerfile

@@ -14,9 +14,5 @@ COPY . .
 # Build a release artifact.
 RUN dotnet publish -c Release -o out
 
-# Service must listen to $PORT environment variable.
-# This default value facilitates local development.
-ENV PORT 8080
-
 # Run the web service on container startup.
 CMD ["dotnet", "out/helloworld-csharp.dll"]

docs/serving/samples/hello-world/helloworld-csharp/README.md

@@ -78,10 +78,6 @@ recreate the source files from this folder.
    # Build a release artifact.
    RUN dotnet publish -c Release -o out
 
-   # Service must listen to $PORT environment variable.
-   # This default value facilitates local development.
-   ENV PORT 8080
-
    # Run the web service on container startup.
    CMD ["dotnet", "out/helloworld-csharp.dll"]
    ```

docs/serving/samples/hello-world/helloworld-go/Dockerfile

@@ -19,9 +19,5 @@ FROM alpine
 # Copy the binary to the production image from the builder stage.
 COPY --from=builder /go/src/github.com/knative/docs/helloworld/helloworld /helloworld
 
-# Service must listen to $PORT environment variable.
-# This default value facilitates local development.
-ENV PORT 8080
-
 # Run the web service on container startup.
 CMD ["/helloworld"]

docs/serving/samples/hello-world/helloworld-go/README.md

@@ -79,10 +79,6 @@ recreate the source files from this folder.
    # Copy the binary to the production image from the builder stage.
    COPY --from=builder /go/src/github.com/knative/docs/helloworld/helloworld /helloworld
 
-   # Service must listen to $PORT environment variable.
-   # This default value facilitates local development.
-   ENV PORT 8080
-
    # Run the web service on container startup.
    CMD ["/helloworld"]
    ```

docs/serving/samples/hello-world/helloworld-java/Dockerfile

@@ -18,9 +18,5 @@ FROM openjdk:8-jre-alpine
 # Copy the jar to the production image from the builder stage.
 COPY --from=builder /app/target/helloworld-*.jar /helloworld.jar
 
-# Service must listen to $PORT environment variable.
-# This default value facilitates local development.
-ENV PORT 8080
-
 # Run the web service on container startup.
 CMD ["java","-Djava.security.egd=file:/dev/./urandom","-Dserver.port=${PORT}","-jar","/helloworld.jar"]

docs/serving/samples/hello-world/helloworld-java/README.md

@@ -106,10 +106,6 @@ recreate the source files from this folder.
    # Copy the jar to the production image from the builder stage.
    COPY --from=builder /app/target/helloworld-*.jar /helloworld.jar
 
-   # Service must listen to $PORT environment variable.
-   # This default value facilitates local development.
-   ENV PORT 8080
-
    # Run the web service on container startup.
    CMD ["java","-Djava.security.egd=file:/dev/./urandom","-Dserver.port=${PORT}","-jar","/helloworld.jar"]
    ```

docs/serving/samples/hello-world/helloworld-kotlin/Dockerfile

@@ -17,9 +17,5 @@ FROM openjdk:8-jre-alpine
 # Copy the jar to the production image from the builder stage.
 COPY --from=builder /home/gradle/build/libs/gradle.jar /helloworld.jar
 
-# Service must listen to $PORT environment variable.
-# This default value facilitates local development.
-ENV PORT 8080
-
 # Run the web service on container startup.
 CMD [ "java", "-jar", "-Djava.security.egd=file:/dev/./urandom", "/helloworld.jar" ]

docs/serving/samples/hello-world/helloworld-kotlin/README.md

@@ -127,10 +127,6 @@ recreate the source files from this folder.
    # Copy the jar to the production image from the builder stage.
    COPY --from=builder /home/gradle/build/libs/gradle.jar /helloworld.jar
 
-   # Service must listen to $PORT environment variable.
-   # This default value facilitates local development.
-   ENV PORT 8080
-
    # Run the web service on container startup.
    CMD [ "java", "-jar", "-Djava.security.egd=file:/dev/./urandom", "/helloworld.jar" ]
    ```

docs/serving/samples/hello-world/helloworld-nodejs/Dockerfile

@@ -16,9 +16,5 @@ RUN npm install --only=production
 # Copy local code to the container image.
 COPY . .
 
-# Service must listen to $PORT environment variable.
-# This default value facilitates local development.
-ENV PORT 8080
-
 # Run the web service on container startup.
 CMD [ "npm", "start" ]

docs/serving/samples/hello-world/helloworld-nodejs/README.md

@@ -103,10 +103,6 @@ recreate the source files from this folder.
    # Copy local code to the container image.
    COPY . .
 
-   # Service must listen to $PORT environment variable.
-   # This default value facilitates local development.
-   ENV PORT 8080
-
    # Run the web service on container startup.
    CMD [ "npm", "start" ]
    ```

docs/serving/samples/hello-world/helloworld-php/Dockerfile

@@ -14,6 +14,3 @@ RUN sed -i 's/80/${PORT}/g' /etc/apache2/sites-available/000-default.conf /etc/a
 # https://hub.docker.com/_/php#configuration
 RUN mv "$PHP_INI_DIR/php.ini-development" "$PHP_INI_DIR/php.ini"
 
-# Service must listen to $PORT environment variable.
-# This default value facilitates local development.
-ENV PORT 8080

docs/serving/samples/hello-world/helloworld-php/README.md

@@ -51,10 +51,6 @@ recreate the source files from this folder.
    # RUN mv "$PHP_INI_DIR/php.ini-production" "$PHP_INI_DIR/php.ini"
    # https://hub.docker.com/_/php#configuration
    RUN mv "$PHP_INI_DIR/php.ini-development" "$PHP_INI_DIR/php.ini"
-
-   # Service must listen to $PORT environment variable.
-   # This default value facilitates local development.
-   ENV PORT 8080
    ```
 
 1. Create a new file, `service.yaml` and copy the following service definition

docs/serving/samples/hello-world/helloworld-python/Dockerfile

@@ -8,11 +8,10 @@ WORKDIR $APP_HOME
 COPY . .
 
 # Install production dependencies.
-RUN pip install Flask
+RUN pip install Flask gunicorn
 
-# Service must listen to $PORT environment variable.
-# This default value facilitates local development.
-ENV PORT 8080
-
-# Run the web service on container startup.
-CMD ["python", "app.py"]
+# Run the web service on container startup. Here we use the gunicorn
+# webserver, with one worker process and 8 threads.
+# For environments with multiple CPU cores, increase the number of workers
+# to be equal to the cores available.
+CMD exec gunicorn --bind :$PORT --workers 1 --threads 8 app:app

docs/serving/samples/hello-world/helloworld-python/README.md

@@ -57,14 +57,13 @@ recreate the source files from this folder.
    COPY . .
 
    # Install production dependencies.
-   RUN pip install Flask
+   RUN pip install Flask gunicorn
 
-   # Service must listen to $PORT environment variable.
-   # This default value facilitates local development.
-   ENV PORT 8080
-
-   # Run the web service on container startup.
-   CMD ["python", "app.py"]
+   # Run the web service on container startup. Here we use the gunicorn
+   # webserver, with one worker process and 8 threads.
+   # For environments with multiple CPU cores, increase the number of workers
+   # to be equal to the cores available.
+   CMD exec gunicorn --bind :$PORT --workers 1 --threads 8 app:app
    ```
 
 1. Create a new file, `service.yaml` and copy the following service definition

docs/serving/samples/hello-world/helloworld-ruby/Dockerfile

@@ -11,9 +11,5 @@ RUN bundle install
 # Copy local code to the container image.
 COPY . .
 
-# Service must listen to $PORT environment variable.
-# This default value facilitates local development.
-ENV PORT 8080
-
 # Run the web service on container startup.
 CMD ["ruby", "./app.rb"]

docs/serving/samples/hello-world/helloworld-ruby/README.md

@@ -55,10 +55,6 @@ recreate the source files from this folder.
    # Copy local code to the container image.
    COPY . .
 
-   # Service must listen to $PORT environment variable.
-   # This default value facilitates local development.
-   ENV PORT 8080
-
    # Run the web service on container startup.
    CMD ["ruby", "./app.rb"]
    ```

docs/serving/samples/helloworld-python/Dockerfile

@@ -0,0 +1,17 @@
+# Use the official Python image.
+# https://hub.docker.com/_/python
+FROM python
+
+# Copy local code to the container image.
+ENV APP_HOME /app
+WORKDIR $APP_HOME
+COPY . .
+
+# Install production dependencies.
+RUN pip install Flask gunicorn
+
+# Run the web service on container startup. Here we use the gunicorn
+# webserver, with one worker process and 8 threads.
+# For environments with multiple CPU cores, increase the number of workers
+# to be equal to the cores available.
+CMD exec gunicorn --bind :$PORT --workers 1 --threads 8 app:app