Firestore cloud functions (Python 3.7 Runtime)

Introduction

Cloud Firestore (In Beta at time of writing) is a flexible, scalable database for mobile, web, and server development from Firebase and Google Cloud Platform. Like Firebase Realtime Database, it keeps your data in sync across client apps through realtime listeners and offers offline support for mobile and web so you can build responsive apps that work regardless of network latency or Internet connectivity.

More info: https://firebase.google.com/docs/firestore/

use cases for cloud functions:

Notify users when something happens
realtime maintainance and cleanup
execute extensive tasks which cannot be done on the client
integrate with third party services
increment/decrement counters upon some event

More info: https://firebase.google.com/docs/functions/use-cases

Announcement

Google finally announced support for python 3.7 runtime although the docs aren't updated yet.

Scenerio

Consider the following structure

finalDb/
      account_1/
            projects/
                    closedTaskCount (integer)
                    createedTime (timestamp)
                    creator (string)
                    deleted (boolean)
                    description (string)
                    projectDueDate (timestamp)
                    projectTags (map)
                    startDate (timestamp)
                    taskCount (integer)
                    
            tasks/
                    attachments (map)
                    createdTime (timestamp)
                    creator (string)
                    deleted (boolean)
                    dueDate (timestamp)
                    lastUpdatedTime (timestamp)
                    project (string)
                    owner (string)
                    status (string)
                    subTasks (map)
                    tags (map)
                    taskName (string)
                    taskUsers (map)
                    
            messages/
            tags/
            users/
            activities/
            .....
            
           
      account_2/
      account_3/
      .....
      account_n/

Description

users can create tasks with 5 statuses : open, closed, pause, yet to start, suspended
A task can exist independently without being included in the project
closed task count is incremented when task changes its state from open to closed and decremented when its state changes from closed to open
taskcount is incremented/decremented whenever a new task is added or removed respectively

Goal

To increment/decrement the counters i.e; taskCount and closedTaskCount in projects collection whenever a task is created and references a project

Reason to use cloud function

To achieve consistency across all clients using transactions. Whenever a user makes changes, it must be consistent across all users and since transactions fail to execute whenever a device is offline, cloud functions are used to keep sanity with the value of counters when the device is online.

More info on transactions: https://firebase.google.com/docs/firestore/manage-data/transactions

Trigger a firestore cloud function

The Cloud Functions for Firebase SDK exports a functions.firestore object that allows you to create handlers tied to specific events. Cloud Firestore supports create, update, delete, and write events.

More info: https://firebase.google.com/docs/firestore/extend-with-functions

Steps to create a cloud function in python 3.7

Goto google cloud console > cloud functions
Click on create function
Fill in function details such as function name, RAM.
Select appropriate Trigger (in this case: cloud firestore)
Select event type (create, update or delete or write)
Provide a Document path to listen to changes. In this case: finalDb/{orgId}/tasks/{taskId}
select source code type (inline editor/zip)
Select runtime as python 3.7
Provide the entry point i.e the function to start execution.

Note:

Add firebase-admin==2.11.0 in requirements.txt file

Refer my stack overflow answer for screenshots:
https://stackoverflow.com/questions/48772583/python-in-google-cloud-functions/51466795#51466795

minseok-kr/firestore-cloud-functions