lovette / fmpfeedbackgcpservice

FMPFeedbackForm Sender for Google Cloud Platform hosted endpoints

FMPFeedbackGCPService

FMPFeedbackGCPService compliments the FMPFeedbackForm project by providing Google Cloud Platform hosted endpoints to store feedback submitted through an in-app feedback form within your macOS application. Endpoints are served using Google Cloud Functions and data is stored in Google Cloud Firestore.

Everything you need for a turnkey (and potentially free, if not low-cost) solution is included:

• Objective-C FMPFeedbackGCPServiceSender implementation
• Cloud Functions endpoints written in Python 3
• A handler to forward feedback via email through email service provider Mailgun using their REST API.

To get up and running, you need to setup and configure a few Google Cloud Platform services and integrate FMPFeedbackForm and FMPFeedbackGCPServiceSender into your macOS app.

Services Architecture

The architecture involes a few services but is overall not too complicated.

The basic workflow is:

1. macOS app (client) submits feedback to public Cloud Functions.
2. Cloud Functions store feedback in a Firestore collection.
3. A message is published to a Pub/Sub topic that notifies subscribers feedback was submitted.
4. Pub/Sub subscribers take action on the feedback, such as forwarding via email.
5. A periodic task performs housekeeping on the Firestore collection.

Google Cloud Platform Deployment

Google Cloud Platform provides a wide range of services with a boundless number of ways to get started. While the instructions below should give you a general idea what you need to accomplish, for the most part you're on your own in setting up an account and configuring your project.

Basic steps that you need to take include:

• Create a Service Account Identity
• Create a Pub/Sub Topic
• Create a few Cloud Functions
• Create a Cloud Scheduler Job

Service Account Identity

Create a Service Account that the Cloud Functions and other services will assume as their identity. We use the name fmpfeedback below.

The service account will need these roles:

• Cloud Datastore User
• Pub/Sub Editor

Download the JSON keyfile for the service account and set the Runtime Environment Variable GOOGLE_APPLICATION_CREDENTIALS in file .env to its path. This will enable local development access to authentication credentials.

Pub/Sub Topic

Create a Pub/Sub Topic that will receive a message when feedback is submitted. The default Topic ID is fmpfeedback. The topic name can be customized with the Runtime Environment Variable FEEDBACK_FIRESTORE_COLLECTION set in the Cloud Function properties or in a .env file saved alongside each Clound Function source.

Cloud Functions

Create a Cloud Function for each of the functions in the cloudfunctions directory. The configuration properties for each function are detailed below.

Directory	Function name	Trigger	Executed function
fmpfeedback_caretaker	fmpfeedback_caretaker	HTTP	fmpfeedback_caretaker
fmpfeedback_comment	fmpfeedback_comment	HTTP	fmpfeedback_comment
fmpfeedback_mailgun	fmpfeedback_mailgun_pubsub	Pub/Sub	fmpfeedback_mailgun_pubsub
fmpfeedback_upload	fmpfeedback_upload	HTTP	fmpfeedback_upload

The cloudfunctions directory contains the source code for each function. A quick way to get started is to copy and paste the code from main.py and requirements.txt into the Inline Editor.

You can also deploy directly from this repository with Cloud Source Repository. Connect the repository to your project then choose the repository and set the Directory with source code to the corresponding cloudfunctions subdirectory. (Additional configuration will be required to redeploy Functions automatically when the underlying source code changes. See this CI/CD tutorial for information on how to set this up.)

HTTP Cloud Functions Properties

Property	Setting
Name	Entry point function name
Trigger type	HTTP
Authentication	Allow unauthenticated invocations
Advanced > Service account	fmpfeedback
Advanced > Runtime Environment Variables	See .env file alongside function source for details
Code > Runtime	Python 3.9
Code > Entry point	Entry point function name

All HTTP Cloud Functions should be created with the same Region selected and therefore be invoked using the same Trigger URL domain name.

Pub/Sub Cloud Function Properties

Property	Setting
Name	Entry point function name
Trigger type	Cloud Pub/Sub
Topic	projects/YOUR-PROJECT-ID/topics/fmpfeedback
Service account	fmpfeedback
Advanced > Runtime Environment Variables	See .env file alongside function source for details
Runtime	Python 3.9
Entry point	Entry point function name

Cloud Scheduler Job

Create a Cloud Scheduler job that will invoke the fmpfeedback_caretaker task on a regular schedule. This task performs routine housekeeping tasks on the feedback collection.

Property	Setting
Name	fmpfeedback_caretaker
Description	Trigger fmpfeedback caretaker daily
Frequency	15 14 * * * (2 PM daily)
Timezone	GMT
Target	HTTP
URL	The https:// URL assigned to fmpfeedback_caretaker Cloud Function
HTTP method	POST
Body	{}

App integration and deployment

macOS app

You should have FMPFeedbackForm integrated and operational prior to setting up FMPFeedbackGCPService. Then all you need to do is switch your "sender" to FMPFeedbackGCPServiceSender.

Sender domain

All HTTP Cloud Functions should be created with the same region selected and therefore be invoked using the same Trigger URL domain name. Pass this domain name as the domain parameter to the initWithDomain function of FMPFeedbackGCPServiceSender.

For example, with the HTTP trigger URL https://REGION-PROJECT.cloudfunctions.net/ENTRY_POINT you would pass REGION-PROJECT.cloudfunctions.net as the domain parameter.

Sender authentication token

The macOS app and the Cloud Functions share a secret token that authenticates the app with the endpoints. This token can be any random sequence of characters and must be referenced in Functions fmpfeedback_comment and fmpfeedback_upload.

1. Generate a token by some means, such as head -n 4096 /dev/urandom | openssl sha256

2. Set the token as the value of Runtime Environment Variable FEEDBACK_SENDER_AUTHTOKEN either as a Cloud Function property or in a .env file uploaded alongside each Function source.

3. Pass the token as the authToken parameter to the initWithDomain function of FMPFeedbackGCPServiceSender.

Mailgun ESP authentication and settings

The fmpfeedback_mailgun module provides a handler that forwards each feedback submission as an email message using the ESP Mailgun REST API. You need to have an account with them if you want to use the module.

The fmpfeedback_mailgun module requires a few Runtime Environment Variables be set either as properties of the fmpfeedback_mailgun_pubsub Cloud Function or in a .env file uploaded alongside the Function source.

Variable	Value
MAILGUN_API_KEY	Mailgun API authentication token.
MAILGUN_API_DOMAIN	Mailgun API sending domain.
MAILGUN_SENDER	Email address to send email feedback from.
MAILGUN_RECIPIENT	Email address to send feedback to.

See the module .env file for more specific details.

Local development

You need to have Python 3 and a web server such as Caddy 2 installed and setup to develop locally.

Create a virtualenv and install packages:

make virtualenv
source .venv/bin/activate
make pip-sync

Start Python app in a terminal using gunicorn:

dotenv run gunicorn main:app

Start caddy server in a second terminal to facilitate HTTPS endpoints:

caddy run

You can then hit the endpoints:

https://localhost/fmpfeedback_comment
https://localhost/fmpfeedback_upload

The Visual Studio Code workspace provided makes it easy to run and debug functions locally. Run the workspace Task caddyserver to facilitate HTTPS endpoints.