Continue execution after sending response (Cloud Functions for Firebase)

Question

I'm using Firebase Functions with https triggers, and I was wondering how long after sending the response to the client, the functions keeps executing. I want to send a response to the client and then perform another operation (send a mail). Currently I'm doing this as following:

module.exports.doSomeJob = functions.https.onRequest((req, res) => {     doSomeAsyncJob()     .then(() => {         res.send("Ok");     })     .then(() => {         emailSender.sendEmail();     })     .catch(...); }); 

The above code is working for me, but I'm suspecting that the code only works because sending the mail has finished before the res.send has completed, so I was wondering how exactly the termination process is working to make sure the code will not break.

Answer 1

You should expect that the HTTP function terminates the moment after you send the response. Any other behavior is some combination of luck or a race condition. Don't write code that depends on luck.

If you need to send a response to the client before the work is fully complete, you will need to kick off a second function to continue where the HTTP function left off. It's common to use a pub/sub function to do with. Have the HTTP function send a pub/sub message to another function, then terminate the HTTP function (by sending a response) only after the message is sent.

Answer 2

If the expected response is not pegged to the outcome of the execution, then you can use

module.exports.doSomeJob = functions.https.onRequest((req, res) => { res.write('SUCCESS') return doSomeAsyncJob() .then(() => {     emailSender.sendEmail(); }) .then(() => {     res.end(); }) .catch(...); }); 

This sends back a response a soon as a request is received, but keeps the function running until res.end() is called Your client can end the connection as soon as a response is received back, but the cloud function will keep running in the background Not sure if this helps, but it might be a workaround where the client needs a response within a very limited time, considering that executing pub/sub requires some extra processing on its own and takes time to execute