Firebase Cloud Functions Cron Async Func Multiple Calls - node.js

Question

I have a cloud function. It is triggered by an App Engine Cron job. It triggers my Firebase Cloud Function every hour with a Google Cloud Pub/Sub. I fetch my Firebase Realtime Database once, and loop for every value. The problem is my main.async function called multiple times. I use an i variable for loop and my console logs more i count than my database length. I mean that if my database length is 4, but for loop runs 8 or 15 or 23 times. This values change randomly. I want to loop for my each database value,fetch some data on internet,and when it is done, go for next value. Here is the code:
use strict';
const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);
var request = require('request-promise').defaults({ encoding: null });
var fs = require('fs');
// Get a reference to the Cloud Vision API component
const Vision = require('#google-cloud/vision');
const vision = new Vision.ImageAnnotatorClient();
var os = require("os");
var databaseArray = [];
var uniqueFilename = require('unique-filename')
exports.hourly_job = functions.pubsub
.topic('hourly-job')
.onPublish((event) => {
console.log("Hourly Job");
var db = admin.database();
var ref = db.ref("myData")
ref.once("value").then(function(allData) {
allData.forEach(function(deviceToken) {
deviceToken.forEach(function(firebaseIDs) {
var deviceTokenVar = deviceToken.key;
var firebaseIDVar = firebaseIDs.key;
var firstvalue = firebaseIDs.child("firstvalue").val();
var secondvalue = firebaseIDs.child("secondvalue").val();
var items = [deviceTokenVar, firebaseIDVar, firstvalue, secondvalue];
databaseArray.push(items);
});
});
return databaseArray;
}).then(function (databasem) {
main().catch(console.error);
});
return true;
});
const main = async () => {
var i;
for (i = 0; i < databaseArray.length; i++) {
console.log("Database Arrays " + i + ". elements: ");
if (databaseArrayfirst != "") {
var apiUrl = "http://api.blabla;
try {
const apiBody = await request.get(apiUrl);
///////////////////////////vison start//////////////////////
const visionResponseBody = await vision.documentTextDetection(apiBody)
var visionResponse = visionResponseBody[0].textAnnotations[0].description;
...some logic here about response...
/////////////////////////////////////////////////
var getdatabasevar = await admin.database().ref("myData/" + databaseArrayDeviceToken + "/" + databaseArrayFirebaseID);
await getdatabasevar.update({
"firstvalue": visionResponse
});
/////////////////////////////////////////////////
} catch (error) {
console.error(error);
}
///////////////////////////vison end//////////////////////
}
};
return true;
};
Thank you.