Concurrency Issues between Google Cloud Functions and Sheets v4 API

Question

I have 2 problems related to managing concurrency between Google Cloud Functions.

The setup is I have a slackbot enabling use of a "checkoff" slash command. This slash command sends another Slack user yes/no buttons whether to authorize the checkoff. When the user clicks an option, it sends that response to a Google Cloud Function which 1) Sends a response back to Slack to close the buttons and 2) Records the checkoff if authorized in a Google Sheet using the Sheets v4 API (spreadsheets.values.append)

Issue #1: Users who spam the yes/no buttons trigger multiple Slack requests to the Cloud Function before the Function can acknowledge and close the buttons. This leads to multiple Cloud Functions spawning and multiple checkoffs being recorded in the sheet. If I could maintain state, I could save unique information from the request and check to make sure that request had not been already serviced. Is there a pattern to do this with Cloud Functions?

Issue #2: Sometimes multiple checkoffs are authorized at similar times by independent users. These requests spawn independent Cloud Function instances which attempt to append to the Sheet. There is a rare case where another Function writes in between the first Function's read then write causing an overwrite. I would use a read-write lock to deal with this but there's no way to share concurrency resources between Cloud Functions I'm aware of.

(Less important) Issue #3: I'd really love to batch the spreadsheet writes but it seems against the grain of serverless computing in the 1st place. Is there a way to do this?

Any help is appreciated.

question from:https://stackoverflow.com/questions/65928608/concurrency-issues-between-google-cloud-functions-and-sheets-v4-api

Answer 1

I had a similar issues with Cloud Functions and Firestore. In my case I was receiving notifications about new and updated data in the form of 'order/123', I was then creating a copy of the order in Firestore, the problem was that sometimes multiple notifications arrived at the same time resulting in duplicated orders because of race conditions. My solution to the problem was to use Google Cloud Tasks, https://console.cloud.google.com/cloudtasks, I have a cloud function that receives the notification, that adds a message to the queue to be processed with concurrency of 1, then other cloud function takes care of the processing.

Receive notification -> Post message to queue (concurrency 1) -> Process message 

In this case I have 1 queue per customer, I am sure there a better ways but for now this is good enough. You can later on route customers to the same queues but always having the same customer on the same queue.