ISTA 2023: ChatGPT: My Log

This whole transcript is accessible directly at ChatGPT. Below are all prompts and answers, on which I based the presentation contents.

Prompt 1

Dear ChatGPT, I want to create a web app, which will be separated in two Docker containers: one serving my frontend, and one serving my backend services. The backend services container will have a simple service that it built with Flutter and uses lightweight relational database from the same container. The frontend service container will serve a Flutter frontend application.

Let's start with you providing me with the instructions, needed to build the backend container.

Certainly! Let's break down the process for creating a Docker container for your backend services.

Answer 1

Backend Service Docker Container

Set Up the Environment

Make sure you have Docker installed on your machine. If not, follow the installation process from Docker's official documentation.
Choose a Base Image

Since you're building a Flutter service, which most likely implies you're using Dart for the backend, you'll need a base image that supports Dart.

Create a Dockerfile in your backend project directory.

Dockerfile for Backend

Here's a basic example of what your Dockerfile might look like:

# Use the official Dart image as a parent image
FROM google/dart:latest

# Set the working directory in the container
WORKDIR /app

# Copy the local package files to the container's workspace
ADD pubspec.yaml /app/pubspec.yaml
RUN pub get --offline

ADD . /app
RUN pub get --offline

# Make port 8080 available to the world outside this container
EXPOSE 8080

# Run the application
CMD ["dart", "bin/main.dart"]

This example assumes your entry point for the backend is bin/main.dart. Adjust as needed.

Setting Up the Database

If you're using a lightweight relational database that should run within the same container (though this might not be the best architecture choice for larger applications), add the necessary steps to your Dockerfile.

As an example, let's say you're using SQLite:
1. Ensure you have the necessary SQLite Dart package in your pubspec.yaml.
2. Install SQLite on your Docker image by adding the installation commands to your Dockerfile.
Build the Docker Image

Navigate to the directory containing your Dockerfile and run:
```
docker build -t your-backend-image-name .
```
Run the Docker Container
```
docker run -p 8080:8080 your-backend-image-name
```
This binds port 8080 of the container to port 8080 on your host.

Notes:

When it comes to production, you might want to use more optimized Docker images, ensure proper database management, and potentially decouple your database into a separate container or managed service.
If your backend service needs to talk to other services, consider using Docker Compose. This will allow you to define multi-container applications, making it easier to manage connections between services.
Make sure your application respects the Twelve-Factor App principles when deploying to Docker containers. This ensures smooth scaling and operation in cloud environments.
Remember, security is crucial. Always follow best practices for securing your containers, applications, and databases.

Once you have your backend container set up and working, you can then proceed with your frontend container in a similar manner.

Prompt 2

Please give me more detailed instructions about how to include SQLite in my Dockerfile.

Answer 2

Absolutely! Integrating SQLite into your Docker container requires a few additional steps. Let's build upon the earlier Dockerfile for your Dart backend.

Integrating SQLite with Docker

Add SQLite to your Dart Project

In your pubspec.yaml, add the necessary SQLite package for Dart:
```
dependencies:
  sqflite: latest_version
```
This sqflite package usually works with Flutter mobile apps by default, but if you're using Dart on the backend, you'll essentially just be interfacing with the SQLite database directly without sqflite. In that case, you may need a different package or method to interface with SQLite, such as dart-sqlite.

Modify the Dockerfile to Install SQLite

Update your Dockerfile to install SQLite:

# Use the official Dart image as a parent image
FROM google/dart:latest

# Set the working directory in the container
WORKDIR /app

# Install SQLite3
RUN apt-get update && apt-get install -y sqlite3 libsqlite3-dev

# Copy the local package files to the container's workspace
ADD pubspec.yaml /app/pubspec.yaml
RUN pub get --offline

ADD . /app
RUN pub get --offline

# Make port 8080 available to the world outside this container
EXPOSE 8080

# Run the application
CMD ["dart", "bin/main.dart"]

The key addition here is the RUN apt-get update && apt-get install -y sqlite3 libsqlite3-dev command, which installs SQLite and its development files. The development files (libsqlite3-dev) may be necessary if any Dart packages require them to interface with SQLite.

Build and Run the Docker Image

As before, navigate to the directory containing your Dockerfile and run:
```
docker build -t your-backend-image-name .
```
Then run:
```
docker run -p 8080:8080 your-backend-image-name
```
Database File Management

Note that when you run SQLite in a Docker container, the database will be stored within the container's filesystem. This means that if the container is deleted, you'll lose the database unless you've mounted it to persistent storage.

If you want to persist data outside of the container, you should consider volume mounting:
```
docker run -p 8080:8080 -v /path/on/host:/app/db your-backend-image-name
```
This would store the SQLite database file in /path/on/host on your host machine and /app/db in your Docker container.

Adjust your backend's database path configuration to match the mounted directory.

Note: While SQLite is an excellent lightweight database, it's not typically used in production for web-based backends due to concurrency and scaling issues. If you plan to move to production with a larger user base, consider using a more robust database system.

Prompt 3

Trying to build the Dockerfile gave me errors because of missing pubscpec.yaml.

Give me the initial commands for building the backend app in Dart.

Answer 3

Of course! I apologize for the oversight. Let's start by setting up a simple Dart backend application. This guide will take you through initializing a Dart project and adding necessary dependencies for a web server.

Setting Up a Dart Backend Application

Install Dart SDK

If you haven't already installed the Dart SDK, do so by following the instructions at the official Dart website: https://dart.dev/get-dart.
Create a new Dart Project

Use the Dart tool to create a new project:
```
dart create my_backend_app
```
Navigate to the new project directory:
```
cd my_backend_app
```
Add Web Server Dependencies

To build a web server with Dart, you can use the shelf package. Open the pubspec.yaml in your project directory and add the following dependencies:
```
dependencies:
  shelf: ^1.2.0
```
Then, run:
```
dart pub get
```
This will fetch the required packages for your project.

Write a Simple Backend Web Server

Create a new Dart file for your web server. You can name it server.dart inside the bin directory:

import 'package:shelf/shelf.dart' as shelf;
import 'package:shelf/shelf_io.dart' as io;

void main() {
  var handler = const shelf.Pipeline().addMiddleware(shelf.logRequests())
      .addHandler(_echoRequest);

  io.serve(handler, 'localhost', 8080).then((server) {
    print('Serving at http://${server.address.host}:${server.port}');
  });
}

shelf.Response _echoRequest(shelf.Request request) {
  return shelf.Response.ok('Hello, Dart Backend!');
}

This sets up a basic server that responds with "Hello, Dart Backend!" for every request.

Run Your Backend

To run the server:
```
dart run bin/server.dart
```
You should be able to visit http://localhost:8080 in a browser and see the message "Hello, Dart Backend!".

Now that you have a basic Dart backend application set up, you can Dockerize it following the instructions provided in the previous answers. Ensure that the Dockerfile is in the root of your Dart project (same directory as pubspec.yaml) to avoid the missing pubspec.yaml error.

Prompt 4

I'm getting these errors when building my container:

#9 1.331 Resolving dependencies...
#9 1.695 The current Dart SDK version is 2.15.1.
#9 1.696 
#9 1.696 Because my_backend_app requires SDK version ^3.0.6, version solving failed.

What's wrong?

Answer 4

The error message indicates there's a mismatch between the Dart SDK versions:

Your Docker container is using Dart SDK version 2.15.1.
Your my_backend_app is requiring a Dart SDK version ^3.0.6 as specified in the pubspec.yaml.

To resolve this, you have a couple of options:

1. Update the Dart SDK in the Dockerfile

The simplest solution, if available, would be to use a newer Dart image that comes with the required SDK version. You can check the available tags on the Docker Hub for the Dart image to find a suitable version.

Replace:

FROM google/dart:latest

With a version-specific tag that has the SDK version you need:

FROM google/dart:<desired_version>

However, as of my last training data (January 2022), Dart SDK v3.x was not released. Therefore, you might be referencing a future version or there might be an error in your pubspec.yaml file.

2. Update the SDK Version in `pubspec.yaml`

If the above method is not feasible because such a Dart version does not exist yet (or is not available as a Docker image), you might want to update your pubspec.yaml to match the Dart SDK version in the Docker container.

Open pubspec.yaml, and adjust the SDK version constraint:

environment:
  sdk: '>=2.15.1 <3.0.0'

This would allow your app to work with any SDK version from 2.15.1 up to (but not including) 3.0.0.

After making the changes, you can try building the Docker image again.

Note: If you adjust the SDK version in pubspec.yaml, ensure all your dependencies are compatible with that version. You might also want to verify why the project was requesting a Dart version that seems to be unavailable or yet-to-be-released. If the version was indeed a mistake, correcting it should resolve the problem.

Prompt 5

I get an error:

RUN pub get --offline

Answer 5

Sorry for the confusion earlier. Using --offline with pub get in a Docker container isn't suitable because the container doesn't have any packages cached yet. It requires internet access to fetch the packages for the first time.

Let's correct that.

Remove the --offline flag from the pub get commands in your Dockerfile:

...
ADD pubspec.yaml /app/pubspec.yaml
RUN pub get

ADD . /app
RUN pub get
...

This should resolve the error. When you run docker build, ensure that the Docker daemon has access to the internet so it can fetch the Dart packages.

Remember, using pub get without --offline will fetch packages from the internet. If you have any private or local packages, you'll need a more complex setup to make them available within the Docker build context.

Prompt 6

I still get the error:

 > [5/7] RUN pub get:
#9 0.201 /bin/sh: 1: pub: not found

Answer 6

I apologize for the oversight. This error means that the Docker container does not recognize the pub command directly because it's not in the system's PATH.

When using the Dart Docker image, the pub tool is not globally available as a command like dart. Instead, you should use it as dart pub.

Here's the correction for the Dockerfile:

Replace:

RUN pub get

With:

RUN dart pub get

So, your Dockerfile commands related to package retrieval should look like:

...
ADD pubspec.yaml /app/pubspec.yaml
RUN dart pub get

ADD . /app
RUN dart pub get
...

Try building the Docker container again after making these adjustments.

Prompt 7

it says:

docker run -p 8080:8080 your-backend-image-name

Serving at http://localhost:8080"

But I cannot open anything at http://localhost:8080

Answer 7

If your Docker container indicates that it's serving on http://localhost:8080 but you can't access the service from your host machine's browser, several factors could be responsible.

Let's troubleshoot:

Docker Network Mode:

By default, if you are on Docker for Windows or Docker for Mac, containers run in a virtual machine, and localhost in the container does not mean the host machine's localhost. The port forwarding with -p should handle this, but sometimes issues can arise.
App Listening Address:

If your Dart backend inside the Docker container is listening on localhost, it will only accept connections from within the container. To accept connections from outside the container, your application should listen on all network interfaces, often represented by the address 0.0.0.0.

Modify the Dart code where you call io.serve():

From:
```
io.serve(handler, 'localhost', 8080);
```
To:
```
io.serve(handler, '0.0.0.0', 8080);
```
Rebuild your Docker image and try running it again.
Docker Daemon Issues:

Occasionally, Docker can run into issues with networking. Restarting the Docker daemon can sometimes resolve these anomalies.
Firewall or Security Software:

Ensure that no firewall or security software on your machine is blocking the connection to port 8080.
Port Conflicts:

Ensure that no other service on your host machine is running on port 8080. You can check this with:
- On Linux/macOS: lsof -i :8080
- On Windows: netstat -an | find "8080"
If another service is using the port, you can either stop that service or choose another port for your Docker container.
Test Inside the Container:

You can exec into the container to test if the server is running inside the container:
```
docker exec -it <container_id_or_name> /bin/sh
```
Then, inside the container, you can use curl or wget to test:
```
curl http://localhost:8080
```
If this returns your expected response, it's a clear sign the issue is related to Docker's networking between the container and your host.
Container Logs:

Check the logs of your running container:
```
docker logs <container_id_or_name>
```
This can provide more insights if there's an issue inside the container or with the Dart server.

After verifying and applying necessary changes from the above steps, try accessing http://localhost:8080 again. If you're still facing issues, please provide any additional error messages or logs, and I'll help you further troubleshoot the situation.

Prompt 8

Let's add /users backend API, which will be a testig stub for list of users, providing five example users with a fixed data.

Answer 8

Sure, let's add a /users endpoint to our Dart backend that returns a list of five example users.

Modify your Dart Backend

In your server.dart file inside the bin directory, let's make some modifications:

import 'dart:convert';
import 'package:shelf/shelf.dart' as shelf;
import 'package:shelf/shelf_io.dart' as io;

void main() {
  var handler = const shelf.Pipeline().addMiddleware(shelf.logRequests())
      .addHandler(_router);

  io.serve(handler, '0.0.0.0', 8080).then((server) {
    print('Serving at http://${server.address.host}:${server.port}');
  });
}

shelf.Response _router(shelf.Request request) {
  switch (request.url.path) {
    case 'users':
      return _usersHandler(request);
    default:
      return shelf.Response.notFound('Not Found');
  }
}

shelf.Response _usersHandler(shelf.Request request) {
  final users = [
    {'id': 1, 'name': 'Alice', 'email': 'alice@example.com'},
    {'id': 2, 'name': 'Bob', 'email': 'bob@example.com'},
    {'id': 3, 'name': 'Charlie', 'email': 'charlie@example.com'},
    {'id': 4, 'name': 'David', 'email': 'david@example.com'},
    {'id': 5, 'name': 'Eva', 'email': 'eva@example.com'},
  ];

  return shelf.Response.ok(
    json.encode(users),
    headers: {'content-type': 'application/json'}
  );
}

Here, I introduced a router function, _router, that directs incoming requests based on their paths. The /users path returns a static list of five users in JSON format. Other paths will return a "Not Found" message.

Rebuild and Run the Docker Image

Rebuild the Docker image:

docker build -t your-backend-image-name .

Run the Docker container:

docker run -p 8080:8080 your-backend-image-name

Access the /users Endpoint

After running the Docker container, visit http://localhost:8080/users in a web browser or use a tool like curl:
```
curl http://localhost:8080/users
```
You should receive a JSON response containing the list of five example users.

With this setup, you've created a simple stub API that provides fixed user data. As you expand the functionality of your backend, you can extend the _router function to handle more routes and incorporate more complex logic and data sources.

Prompt 9

Good! Now we should create the Frontend. I want the frontend to run on a different container, and connect with the backend container throughout the already exposed API. Please, write the frontend by using Flutter and taking into account it'll produce a web application only.

Answer 9

Certainly! To achieve this, we'll follow these steps:

Set Up the Flutter Web Project
Write the Flutter Web Application to Fetch Users from the Backend
Dockerize the Flutter Web Application

1. Set Up the Flutter Web Project

If you haven't already, make sure to enable web support for Flutter:

flutter channel stable
flutter upgrade
flutter config --enable-web

Now, create a new Flutter project:

flutter create flutter_web_frontend
cd flutter_web_frontend

Then, add http package to your pubspec.yaml file to allow for API calls:

dependencies:
  flutter:
    sdk: flutter
  http: ^0.13.3

Run flutter pub get to fetch the dependencies.

2. Write the Flutter Web Application

Here's a basic Flutter web application to fetch and display the list of users:

// lib/main.dart
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Web Frontend',
      theme: ThemeData(primarySwatch: Colors.blue),
      home: UserListPage(),
    );
  }
}

class UserListPage extends StatefulWidget {
  @override
  _UserListPageState createState() => _UserListPageState();
}

class _UserListPageState extends State<UserListPage> {
  List<dynamic> users = [];

  @override
  void initState() {
    super.initState();
    fetchUsers();
  }

  fetchUsers() async {
    var response = await http.get(Uri.parse('http://backend:8080/users'));
    if (response.statusCode == 200) {
      setState(() {
        users = json.decode(response.body);
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("Users")),
      body: ListView.builder(
        itemCount: users.length,
        itemBuilder: (context, index) {
          return ListTile(
            title: Text(users[index]['name']),
            subtitle: Text(users[index]['email']),
          );
        },
      ),
    );
  }
}

Take note of the URL http://backend:8080/users in the fetchUsers method. When running in containers, you can use the name of the backend container (as long as they are in the same network) to communicate between containers. In this case, we've assumed the name "backend" for the backend container, but you can adjust it according to your Docker setup.

3. Dockerize the Flutter Web Application

Create a Dockerfile in the root of your flutter_web_frontend directory:

# Use the official Flutter SDK as the builder image
FROM google/flutter:latest as builder

# Set working directory
WORKDIR /app

# Copy everything over
COPY . .

# Build the web version of the app
RUN flutter pub get
RUN flutter build web

# Use nginx for serving the built web app
FROM nginx:alpine

# Copy the build files from the build environment
COPY --from=builder /app/build/web/ /usr/share/nginx/html

# Expose port 80 for nginx
EXPOSE 80

Build and run the frontend container:

docker build -t flutter-web-frontend-image .
docker run -p 80:80 flutter-web-frontend-image

Now, your frontend will be available at http://localhost. Remember, you'll need to ensure the backend container is running and the frontend container can communicate with it using the assumed container name "backend" or whatever you've set it to.

In a real-world scenario, using Docker Compose can make managing multi-container applications significantly more straightforward. If you need a Docker Compose setup for these two containers, do let me know!

Prompt 10

I'm getting this error in my console when trying to access the backend:

Access to XMLHttpRequest at 'http://localhost:8080/users' from origin 'http://localhost:64817' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

How to fix it?

Answer 10

The error you're seeing is due to the Cross-Origin Resource Sharing (CORS) policy, which is a security feature implemented by web browsers to control requests made to different origins.

To resolve this, you'll need to enable CORS support on your backend so that it sends the appropriate headers allowing the request from the Flutter web app.

Here's how to enable CORS for your Dart backend using the shelf_cors package:

Add shelf_cors to your Backend's pubspec.yaml

Add the shelf_cors package to your backend project's pubspec.yaml:
```
dependencies:
  shelf: ^1.2.0
  shelf_cors: ^1.0.1
  # ... other dependencies ...
```
And then run dart pub get.

Update the Backend to Use CORS Middleware

Modify your Dart backend code to include CORS headers:

import 'package:shelf/shelf.dart' as shelf;
import 'package:shelf/shelf_io.dart' as io;
import 'package:shelf_cors/shelf_cors.dart' as shelf_cors;

// ... rest of your code ...

void main() {
  var handler = const shelf.Pipeline()
      .addMiddleware(shelf.logRequests())
      .addMiddleware(shelf_cors.createCorsHeadersMiddleware(
        headers: {
          'Access-Control-Allow-Origin': '*',
          // You can add more headers if needed
        },
      ))
      .addHandler(_router);

  io.serve(handler, '0.0.0.0', 8080).then((server) {
    print('Serving at http://${server.address.host}:${server.port}');
  });
}

// ... rest of your code ...

Rebuild and Restart Your Backend Container

After making the above changes, rebuild your backend Docker image and run it. The backend should now accept requests from the frontend even if they're on different ports or domains due to the CORS headers.

Do note that the configuration I provided ('Access-Control-Allow-Origin': '*') allows any origin to access the resources. In a production environment, you'd want to be more restrictive and specify only the trusted domains.

Prompt 11

I'm getting this error when updating dependencies:

Because my_backend_app depends on shelf_cors ^1.0.1 which doesn't match any
  versions, version solving failed.

Answer 11

It seems like the version of shelf_cors I specified doesn't exist or there's an issue fetching it. My apologies for the oversight.

Let's take a different approach:

Check the Available Versions

First, check for the latest available versions of the shelf_cors package on the pub.dev website.
Update pubspec.yaml

Once you've identified the correct version, update your pubspec.yaml file with that version. For example:
```
dependencies:
  shelf: ^1.2.0
  shelf_cors: ^X.X.X  # replace X.X.X with the correct version you found
```
Run dart pub get Again

After updating the pubspec.yaml, run dart pub get again to fetch the new dependencies.
Proceed with the Previous Instructions

Continue with the instructions I provided in the previous message to implement the CORS headers in your backend server using shelf_cors.

If you still face any difficulties or encounter further issues, please let me know, and I'll assist you further!

Prompt 12

It seems that the shelf_cors package is unusable anymore. Is there any other way to do it?

Answer 12

Absolutely! If shelf_cors is not usable anymore, we can manually add the CORS headers to the backend response.

Here's a simple modification to your _router function (or wherever you're processing requests) to include the necessary CORS headers:

shelf.Response _router(shelf.Request request) {
  switch (request.url.path) {
    case 'users':
      return _addCorsHeaders(_usersHandler(request));
    default:
      return shelf.Response.notFound('Not Found');
  }
}

// Add this function to manually insert the CORS headers
shelf.Response _addCorsHeaders(shelf.Response response) {
  return response.change(headers: {
    'Access-Control-Allow-Origin': '*',
    'Access-Control-Allow-Methods': 'GET, POST, PUT, DELETE, OPTIONS',
    'Access-Control-Allow-Headers': 'Origin, Content-Type',
  });
}

The _addCorsHeaders function can be applied to any response that should support CORS. In the example above, it's added to the /users endpoint.

With this modification, you've manually added the CORS headers to the backend response, which should resolve the CORS issue you were facing with the frontend.

Remember: The configuration provided ('Access-Control-Allow-Origin': '*') allows any origin to access the resources. In a production environment, you'd want to be more restrictive and specify only the trusted domains.

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ChatGPT Log.md

ChatGPT Log.md

ISTA 2023: ChatGPT: My Log

Prompt 1

Answer 1

Backend Service Docker Container

Prompt 2

Answer 2

Integrating SQLite with Docker

Prompt 3

Answer 3

Setting Up a Dart Backend Application

Prompt 4

Answer 4

1. Update the Dart SDK in the Dockerfile

2. Update the SDK Version in `pubspec.yaml`

Prompt 5

Answer 5

Prompt 6

Answer 6

Prompt 7

Answer 7

Prompt 8

Answer 8

Prompt 9

Answer 9

1. Set Up the Flutter Web Project

2. Write the Flutter Web Application

3. Dockerize the Flutter Web Application

Prompt 10

Answer 10

Prompt 11

Answer 11

Prompt 12

Answer 12

Files

ChatGPT Log.md

Latest commit

History

ChatGPT Log.md

File metadata and controls

ISTA 2023: ChatGPT: My Log

Prompt 1

Answer 1

Backend Service Docker Container

Prompt 2

Answer 2

Integrating SQLite with Docker

Prompt 3

Answer 3

Setting Up a Dart Backend Application

Prompt 4

Answer 4

1. Update the Dart SDK in the Dockerfile

2. Update the SDK Version in pubspec.yaml

Prompt 5

Answer 5

Prompt 6

Answer 6

Prompt 7

Answer 7

Prompt 8

Answer 8

Prompt 9

Answer 9

1. Set Up the Flutter Web Project

2. Write the Flutter Web Application

3. Dockerize the Flutter Web Application

Prompt 10

Answer 10

Prompt 11

Answer 11

Prompt 12

Answer 12

2. Update the SDK Version in `pubspec.yaml`