Firebase gen 2 task (cloud run) concurrency appears to have no effect

Question

I have a gen 1 firebase cloud function that iterates through a collection of users and enqueues messages to send to said users by means of a gen 2 firebase task. I upgraded the task to gen 2 in hopes of overcoming cold start delays when sending messages.

As a basic test, I have configured the firebase cloud task with concurrency and queued up a 20 message test, initiated by the function. The observed results are 1 message is dispatched per second. I would have expected all 20 to be delivered rapidly, but perhaps I am missing something. At this point, the gen 2 function is processing no faster than the gen 1 function was.

Currently I am targeting nodejs 14, planning to upgrade to 18 shortly. All 20 messages are dispatched at 1 per second and no errors were encountered in this message test.

Here is the code in question:

const {onTaskDispatched} = require("firebase-functions/v2/tasks");
const {logger} = require("firebase-functions/v2");
const client = require('twilio')(id, auth);

exports.sendMessage = onTaskDispatched({
    //minInstances: 0,
    memory: '1GiB',
    concurrency: 50,
    minBackoffSeconds: 10,
    maxBackoffSeconds: 600,
    rateLimits: {
        maxConcurrentDispatches: 100,
    }
    }, async (req) => {
        const message = req.data.message;
            if (message) {
                try {
                    const res = await client.messages.create(message);
                    return res.sid;
                } catch (error) {
                    logger.warn(`Error sending text to: ${message.to} - ${error}`);
                    throw(error);
                }
            }
    });

Answer 1

You need to set memory to at least 2 GiB:

See the documentation here: https://cloud.google.com/functions/docs/configuring/concurrency

Setting a concurrency value greater than 1 requires a function to have 1 or more vCPUs - see Memory limits for the default memory and vCPU values.