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Script runs smoothly from start to finish, but the expected result doesn't happen

The project aims to study a new social media:
https://booyah.live/
My needs are:
1 - Collect data from profiles that follow a specific profile.
2 - My account use this data to follow the collected profiles.
3 - Among other possible options, also unfollow the profiles I follow.
The problem found in the current script:
The profile data in theory is being collected, the script runs perfectly until the end, but for some reason I can't specify, instead of following all the collected profiles, it only follows the base profile.
For example:
I want to follow all 250 profiles that follow the ID 123456
I activate the booyahGetAccounts(123456); script
In theory the end result would be my account following 250 profiles
But the end result I end up following only the 123456 profile, so the count of people I'm following is 1
Complete Project Script:
const csrf = 'MY_CSRF_TOKEN';
async function booyahGetAccounts(uid, type = 'followers', follow = 1) {
if (typeof uid !== 'undefined' && !isNaN(uid)) {
const loggedInUserID = window.localStorage?.loggedUID;
if (uid === 0) uid = loggedInUserID;
const unfollow = follow === -1;
if (unfollow) follow = 1;
if (loggedInUserID) {
if (csrf) {
async function getUserData(uid) {
const response = await fetch(`https://booyah.live/api/v3/users/${uid}`),
data = await response.json();
return data.user;
}
const loggedInUserData = await getUserData(loggedInUserID),
targetUserData = await getUserData(uid),
followUser = uid => fetch(`https://booyah.live/api/v3/users/${loggedInUserID}/followings`, { method: (unfollow ? 'DELETE' : 'POST'), headers: { 'X-CSRF-Token': csrf }, body: JSON.stringify({ followee_uid: uid, source: 43 }) }),
logSep = (data = '', usePad = 0) => typeof data === 'string' && usePad ? console.log((data ? data + ' ' : '').padEnd(50, '━')) : console.log('━'.repeat(50),data,'━'.repeat(50));
async function getList(uid, type, follow) {
const isLoggedInUser = uid === loggedInUserID;
if (isLoggedInUser && follow && !unfollow && type === 'followings') {
follow = 0;
console.warn('You alredy follow your followings. `follow` mode switched to `false`. Followings will be retrieved instead of followed.');
}
const userData = await getUserData(uid),
totalCount = userData[type.slice(0,-1)+'_count'] || 0,
totalCountStrLength = totalCount.toString().length;
if (totalCount) {
let userIDsLength = 0;
const userIDs = [],
nickname = userData.nickname,
nicknameStr = `${nickname ? ` of ${nickname}'s ${type}` : ''}`,
alreadyFollowedStr = uid => `User ID ${uid} already followed by ${loggedInUserData.nickname} (Account #${loggedInUserID})`;
async function followerFetch(cursor = 0) {
const fetched = [];
await fetch(`https://booyah.live/api/v3/users/${uid}/${type}?cursor=${cursor}&count=100`).then(res => res.json()).then(data => {
const list = data[type.slice(0,-1)+'_list'];
if (list?.length) fetched.push(...list.map(e => e.uid));
if (fetched.length) {
userIDs.push(...fetched);
userIDsLength += fetched.length;
if (follow) followUser(uid);
console.log(`${userIDsLength.toString().padStart(totalCountStrLength)} (${(userIDsLength / totalCount * 100).toFixed(4)}%)${nicknameStr} ${follow ? 'followed' : 'retrieved'}`);
if (fetched.length === 100) {
followerFetch(data.cursor);
} else {
console.log(`END REACHED. ${userIDsLength} accounts ${follow ? 'followed' : 'retrieved'}.`);
if (!follow) logSep(targetList);
}
}
});
}
await followerFetch();
return userIDs;
} else {
console.log(`This account has no ${type}.`);
}
}
logSep(`${follow ? 'Following' : 'Retrieving'} ${targetUserData.nickname}'s ${type}`, 1);
const targetList = await getList(uid, type, follow);
} else {
console.error('Missing CSRF token. Retrieve your CSRF token from the Network tab in your inspector by clicking into the Network tab item named "bug-report-claims" and then scrolling down in the associated details window to where you see "x-csrf-token". Copy its value and store it into a variable named "csrf" which this function will reference when you execute it.');
}
} else {
console.error('You do not appear to be logged in. Please log in and try again.');
}
} else {
console.error('UID not passed. Pass the UID of the profile you are targeting to this function.');
}
}
This current question is a continuation of that answer from the link:
Collect the full list of buttons to follow without having to scroll the page (DevTools Google Chrome)
Since I can't offer more bounty on that question, I created this one to offer the new bounty to anyone who can fix the bug and make the script work.
Access account on Booyah website to use for tests:
Access by google:
User: teststackoverflowbooyah#gmail.com
Password: quartodemilha

I have to admit that it is really hard to read your code, I spent a lesser amount of time rewriting everything from scratch.
Stated that we need a code piece to be cut/pasted in the JavaScript console of web browsers able to store some data (i.e. expiration of followings and permanent followings) we need some considerations.
We can consider expiration of followings as volatile data: something that if lost can be reset to 1 day later from when we loose this data. window.localStorage is a perfect candidate to store these kind of data. If we change web browser the only drawback is that we loose the expiration of followings and we can tolerate to reset them to 1 day later from when we change browser.
While to store the list of permanent followings we need a permanent store even if we change web browser. The best idea that came to my mind is to create an alternative account with which to follow the users we never want to stop following. In my code I used uid 3186068 (a random user), once you have created your own alternative account, just replace the first line of the code block with its uid.
Another thing we need to take care is error handling: API could always have errors. The approach I chosen is to write myFetch which, in case of errors, retries twice the same call; if the error persists, probably we are facing a temporary booyah.live outage. Probably we just need to retry a bit later.
To try to provide a comfortable interface, the code blocks gathers the uid from window.location: to follow the followers of users, just cut/paste the code block on tabs opened on their profiles. For example I run the code from a tab open on https://booyah.live/studio/123456?source=44.
Last, to unfollow users the clean function is called 5 minutes later we paste the code (to not conflict with calls to follow followers) and than is executed one hour later it finishes its job. It is written to access the localStorage in an atomic way, so you can have many of them running simultaneously on different tabs of the same browser, you can not care about it. The only thing you need to take care it that when the window.location changes, all the JavaScript events in the tab are reset; so I suggest to keep a tab open on the home page, paste the code block on it, and forget about this tab; it will be the tab responsible of unfollowing users. Then open other tabs to do what you need, when you hit a user you want to follow the followers, paste the block on it, wait the job is finished and continue to use the tab normally.
// The account we use to store followings
const followingsUID = 3186068;
// Gather the loggedUID from window.localStorage
const { loggedUID } = window.localStorage;
// Gather the CSRF-Token from the cookies
const csrf = document.cookie.split("; ").reduce((ret, _) => (_.startsWith("session_key=") ? _.substr(12) : ret), null);
// APIs could have errors, let's do some retries
async function myFetch(url, options, attempt = 0) {
try {
const res = await fetch("https://booyah.live/api/v3/" + url, options);
const ret = await res.json();
return ret;
} catch(e) {
// After too many consecutive errors, let's abort: we need to retry later
if(attempt === 3) throw e;
return myFetch(url, option, attempt + 1);
}
}
function expire(uid, add = true) {
const { followingsExpire } = window.localStorage;
let expires = {};
try {
// Get and parse followingsExpire from localStorage
expires = JSON.parse(followingsExpire);
} catch(e) {
// In case of error (ex. new browsers) simply init to empty
window.localStorage.followingsExpire = "{}";
}
if(! uid) return expires;
// Set expire after 1 day
if(add) expires[uid] = new Date().getTime() + 3600 * 24 * 1000;
else delete expires[uid];
window.localStorage.followingsExpire = JSON.stringify(expires);
}
async function clean() {
try {
const expires = expire();
const now = new Date().getTime();
for(const uid in expires) {
if(expires[uid] < now) {
await followUser(parseInt(uid), false);
expire(uid, false);
}
}
} catch(e) {}
// Repeat clean in an hour
window.setTimeout(clean, 3600 * 1000);
}
async function fetchFollow(uid, type = "followers", from = 0) {
const { cursor, follower_list, following_list } = await myFetch(`users/${uid}/${type}?cursor=${from}&count=50`);
const got = (type === "followers" ? follower_list : following_list).map(_ => _.uid);
const others = cursor ? await fetchFollow(uid, type, cursor) : [];
return [...got, ...others];
}
async function followUser(uid, follow = true) {
console.log(`${follow ? "F" : "Unf"}ollowing ${uid}...`);
return myFetch(`users/${loggedUID}/followings`, {
method: follow ? "POST" : "DELETE",
headers: { "X-CSRF-Token": csrf },
body: JSON.stringify({ followee_uid: uid, source: 43 })
});
}
async function doAll() {
if(! loggedUID) throw new Error("Can't get 'loggedUID' from localStorage: try to login again");
if(! csrf) throw new Error("Can't get session token from cookies: try to login again");
console.log("Fetching current followings...");
const currentFollowings = await fetchFollow(loggedUID, "followings");
console.log("Fetching permanent followings...");
const permanentFollowings = await fetchFollow(followingsUID, "followings");
console.log("Syncing permanent followings...");
for(const uid of permanentFollowings) {
expire(uid, false);
if(currentFollowings.indexOf(uid) === -1) {
await followUser(uid);
currentFollowings.push(uid);
}
}
// Sync followingsExpire in localStorage
for(const uid of currentFollowings) if(permanentFollowings.indexOf(uid) === -1) expire(uid);
// Call first clean task in 5 minutes
window.setTimeout(clean, 300 * 1000);
// Gather uid from window.location
const match = /\/studio\/(\d+)/.exec(window.location.pathname);
if(match) {
console.log("Fetching this user followers...");
const followings = await fetchFollow(parseInt(match[1]));
for(const uid of followings) {
if(currentFollowings.indexOf(uid) === -1) {
await followUser(uid);
expire(uid);
}
}
}
return "Done";
}
await doAll();
The problem: I strongly suspect a booyah.live API bug
To test my code I run it from https://booyah.live/studio/123456?source=44.
If I run it multiple times I continue to get following output:
Fetching current followings...
Fetching permanent followings...
Syncing permanent followings...
Following 1801775...
Following 143823...
Following 137017...
Fetching this user followers...
Following 16884042...
Following 16166724...
There is bug somewhere! The expected output for subsequent executions in the same tab would be:
Fetching current followings...
Fetching permanent followings...
Syncing permanent followings...
Fetching this user followers...
After seeking the bug in my code without success, I checked booyah.live APIs: if I navigate following URLs (the uids are the ones the code continue to follow in subsequent executions)
https://booyah.live/studio/1801775
https://booyah.live/studio/143823
https://booyah.live/studio/137017
https://booyah.live/studio/16884042
https://booyah.live/studio/16166724
I can clearly see I follow them, but if I navigate https://booyah.live/following (the list of users I follow) I can't find them, neither if I scroll the page till the end.
Since I do exactly the same calls the website does, I strongly suspect the bug is in booyah.live APIs, exactly in the way they handle the cursor parameter.
I suggest you to open a support ticket to booyah.live support team. You could use the test account you provided us: I already provided you the details to do that. ;)

How do I reject writing value to Firebase if have the same value in my DB? (Javascript)

I'm creating my custom order id with auto-increment generator function for my project. I will state my question here, if you want to know the whole story please read below.
As written in the title, I need a way to reject my set to Firebase and it has to be done in 1 query. Currently, it will write my orderID to Firebase without rejecting it. But I need to reject if there is the same ID in the table.
The short version of my code will be posted here, the whole function will be posted below.
firebase.database().ref('orderCounter/orderIDsChecker/'+orderID).set({
id: orderID,
}, function(error) {
if (error) {
console.log('Order ID fail to generate. Regenerating new ID')
createOrderID(orderCounterRef);
} else {
console.log('Order ID created!')
}
});
}
The story,
I'm creating my own custom order id with auto-increment generator function for my project. The problem is that if multiple users creating order at the same time, it will generate the same id. Yes, I can use transaction() to solve the problem but I have no idea how to use it. Therefore, I have created my own version of the "transaction". With my method, I am able to prevent duplicates id unless 2 or more users create order within 1 second of gap. Or if anyone is kind enough to show me an example of how to write a transaction for my function, I thank you in advance.
The flow of the code is,
Get "currentMonth" and "orderIdCounter" from Firebase -> orderIdCounter +1 and update to Firebase -> start the process of generating order id -> Send the generated id to firebase -> If return success "order ID created", If not "got duplicate id" Re-run the whole process.
Below is the code for my order id generator function.
function createOrderID(orderCounterRef){
var childData = [];
var orderID;
//Get the Current Month and Order ID Counter from Firebase
orderCounterRef.on('value', function(snap) { childData = snapshotToArrayWithoutID(snap); });
var currentMonth = childData[0];
var orderIDCounter = childData[1];
if (orderIDCounter !== undefined){
//Update orderIDCounter on Firebase.
//This is to prevent duplicate orderID when multiple users is creating order at the same time.
var IDCounter = parseInt(orderIDCounter) + 1;
//Set IDCounter to 3 digits
IDCounter = ('00' + IDCounter.toString()).slice(-3);
firebase.database().ref('orderCounter/orderIDCounter').set(IDCounter);
//Handle the process to generate Order ID. Return in YYMMxxx(auto increment) format.
orderID = handleCreateOrderID(currentMonth, (parseInt(orderIDCounter) - 1));
//Check if duplicate ID on firebase
firebase.database().ref('orderCounter/orderIDsChecker/'+orderID).set({
id: orderID,
}, function(error) {
if (error) {
console.log('Order ID fail to generate. Regenerating new ID')
createOrderID(orderCounterRef);
} else {
console.log('Order ID created!')
}
});
}
return orderID;
}
My DB:

You should indeed use a transaction as you have mentioned in your question.
The following should do the trick:
//Declare a function that increment a counter in a transaction
function createOrderID() {
var orderIdRef = firebase.database().ref('orderId');
return orderIdRef.transaction(function(currentId) {
return currentId + 1;
});
}
//Call the asynchronous createOrderID() function
createOrderID().then(function(transactionResult) {
console.log(transactionResult.snapshot.val());
});
If you want to start the counter at a specific value, just create an orderId node in your database and assign a specific value to it, e.g; 1912000.
If you just want to start at 1, you don't need to create a node, it will be automatically created with the first call to the createOrderID() function.

Thank you, #samthecodingman & #Renaud Tarnec for your advice.
I took #samthecodingman's code and change a bit to fit my project. But I use generateOrderID() only to call the result and it works well. But you won't get any value with just the code. I call out another function (connectToFirebase) whenever users enter the page. I am not sure why it works or if this is the right way, but it works for me and that's good enough.
export function generateOrderID(){
var orderId;
var childData = [];
const orderCounterRef = firebase.database().ref('orderCounter/');
//Get the Current Month from Firebase
orderCounterRef.on('value', function(snap) { childData = snapshotToArrayWithoutID(snap); });
//Check ID format YYMMXXX (XXX=auto_increment). Hanlde auto_increment for Year and Month
handleOrderIdFormat(childData[0], orderCounterRef)
//transaction
orderCounterRef.child('orderId').transaction(function(currentId) {
orderId = (currentId||0) +1;
return orderId;
}, function(err) {
if( err ) {
console.log(err)
}
});
return orderId;
}
export function connectToFirebase(){
//Connection Firebase Database
const orderCounterRef = firebase.database().ref('orderCounter/');
orderCounterRef.on('value', function(snap) { });
}

Meteor setInterval and query

I want to have a function that checks every 5 seconds for all entries in database for some value is false and if finds then checks some logic condition and changes the value to true if the logic condition is met.
My function works well until I have something with isItReady: false in my collection. When I don't have, it obviously doesn't find anything and I start getting errors.
How should I do this correctly? I don't want to stop my interval because maybe something will be entered into the collection soon and then my inverval is stopped?
How can I do something like this:
If nothing matches my search criterea - productDate = Products.findOne({isItReady: false}); the interval is stopped and as soon as something new gets inserted I will start the inverval again?
var logicCheck = Meteor.setInterval( function () {
productDate = Products.findOne({isItReady: false}); //query to find all entries with isItReady: false
var timeNow = Date();
var timeCreated = productDate.startOfCountdown;
timeCreated = timeCreated.toString(); //converts timeCreated from object to String(in Mongo its a object)
var productId = productDate._id;
console.log(typeof timeNow) //string
console.log(typeof timeCreated) //string
console.log(timeNow + "timeNow")
console.log(timeCreated + "timeCreated")
if (timeCreated <= timeNow) {
console.log("check") //this works well
Products.update({_id: productId}, {$set: {isItReady: true}}, function(error, result) {
console.log(productId) //all good
if (error){
console.log(error.reason) //check the error
} else{
console.log("File with the id: " + result + " just get update")
}
});
}
}, 5000);

Your approach of polling MongoDB every 5 seconds is very non-Meteoric. You'd be much better off creating a Tracker.autorun function to instantly react to any product that has isItReady == false
For example:
Tracker.autorun(function(){
var notReadyProducts = Products.find({ isItReady: false });
notReadyProducts.forEach(function(p){
if ( your logic ... ) Products.update({ _id: p._id },{ $set: { isItReady: true }});
});
});
This assumes by the way that you're publishing (on the server) and subscribing to (on the client) a set of Products that is going to include these not ready products.
With this pattern no code will be running 99.99% of the time and then at the precise moment that a product is made not ready this code will kick in.
You might want to take a look at this video to learn more about reactive programming and how it completely changes the way you approach common problems. There are many other resources available as well.

Do I ever need to synchronize node.js code like in Java?

I have only recently started developing for node.js, so forgive me if this is a stupid question - I come from Javaland, where objects still live happily sequentially and synchronous. ;)
I have a key generator object that issues keys for database inserts using a variant of the high-low algorithm. Here's my code:
function KeyGenerator() {
var nextKey;
var upperBound;
this.generateKey = function(table, done) {
if (nextKey > upperBound) {
require("../sync/key-series-request").requestKeys(function(err,nextKey,upperBound) {
if (err) { return done(err); }
this.nextKey = nextKey;
this.upperBound = upperBound;
done(nextKey++);
});
} else {
done(nextKey++);
}
}
}
Obviously, when I ask it for a key, I must ensure that it never, ever issues the same key twice. In Java, if I wanted to enable concurrent access, I would make make this synchronized.
In node.js, is there any similar concept, or is it unnecessary? I intend to ask the generator for a bunch of keys for a bulk insert using async.parallel. My expectation is that since node is single-threaded, I need not worry about the same key ever being issued more than once, can someone please confirm this is correct?
Obtaining a new series involves an asynchronous database operation, so if I do 20 simultaneous key requests, but the series has only two keys left, won't I end up with 18 requests for a new series? What can I do to avoid that?
UPDATE
This is the code for requestKeys:
exports.requestKeys = function (done) {
var db = require("../storage/db");
db.query("select next_key, upper_bound from key_generation where type='issue'", function(err,results) {
if (err) { done(err); } else {
if (results.length === 0) {
// Somehow we lost the "issue" row - this should never have happened
done (new Error("Could not find 'issue' row in key generation table"));
} else {
var nextKey = results[0].next_key;
var upperBound = results[0].upper_bound;
db.query("update key_generation set next_key=?, upper_bound=? where type='issue'",
[ nextKey + KEY_SERIES_WIDTH, upperBound + KEY_SERIES_WIDTH],
function (err,results) {
if (err) { done(err); } else {
done(null, nextKey, upperBound);
}
});
}
}
});
}
UPDATE 2
I should probably mention that consuming a key requires db access even if a new series doesn't have to be requested, because the consumed key will have to be marked as used in the database. The code doesn't reflect this because I ran into trouble before I got around to implementing that part.
UPDATE 3
I think I got it using event emitting:
function KeyGenerator() {
var nextKey;
var upperBound;
var emitter = new events.EventEmitter();
var requesting = true;
// Initialize the generator with the stored values
db.query("select * from key_generation where type='use'", function(err, results)
if (err) { throw err; }
if (results.length === 0) {
throw new Error("Could not get key generation parameters: Row is missing");
}
nextKey = results[0].next_key;
upperBound = results[0].upper_bound;
console.log("Setting requesting = false, emitting event");
requesting = false;
emitter.emit("KeysAvailable");
});
this.generateKey = function(table, done) {
console.log("generateKey, state is:\n nextKey: " + nextKey + "\n upperBound:" + upperBound + "\n requesting:" + requesting + " ");
if (nextKey > upperBound) {
if (!requesting) {
requesting = true;
console.log("Requesting new series");
require("../sync/key-series-request").requestSeries(function(err,newNextKey,newUpperBound) {
if (err) { return done(err); }
console.log("New series available:\n nextKey: " + newNextKey + "\n upperBound: " + newUpperBound);
nextKey = newNextKey;
upperBound = newUpperBound;
requesting = false;
emitter.emit("KeysAvailable");
done(null,nextKey++);
});
} else {
console.log("Key request is already underway, deferring");
var that = this;
emitter.once("KeysAvailable", function() { console.log("Executing deferred call"); that.generateKey(table,done); });
}
} else {
done(null,nextKey++);
}
}
}
I've peppered it with logging outputs, and it does do what I want it to.

As another answer mentions, you will potentially end up with results different from what you want. Taking things in order:
function KeyGenerator() {
// at first I was thinking you wanted these as 'class' properties
// and thus would want to proceed them with this. rather than as vars
// but I think you want them as 'private' members variables of the
// class instance. That's dandy, you'll just want to do things differently
// down below
var nextKey;
var upperBound;
this.generateKey = function (table, done) {
if (nextKey > upperBound) {
// truncated the require path below for readability.
// more importantly, renamed parameters to function
require("key-series-request").requestKeys(function(err,nKey,uBound) {
if (err) { return done(err); }
// note that thanks to the miracle of closures, you have access to
// the nextKey and upperBound variables from the enclosing scope
// but I needed to rename the parameters or else they would shadow/
// obscure the variables with the same name.
nextKey = nKey;
upperBound = uBound;
done(nextKey++);
});
} else {
done(nextKey++);
}
}
}
Regarding the .requestKeys function, you will need to somehow introduce some kind of synchronization. This isn't actually terrible in one way because with only one thread of execution, you don't need to sweat the challenge of setting your semaphore in a single operation, but it is challenging to deal with the multiple callers because you will want other callers to effectively (but not really) block waiting for the first call to requestKeys() which is going to the DB to return.
I need to think about this part a bit more. I had a basic solution in mind which involved setting a simple semaphore and queuing the callbacks, but when I was typing it up I realized I was actually introducing a more subtle potential synchronization bug when processing the queued callbacks.
UPDATE:
I was just finishing up one approach as you were writing about your EventEmitter approach, which seems reasonable. See this gist which illustrates the approach. I took. Just run it and you'll see the behavior. It has some console logging to see which calls are getting deferred for a new key block or which can be handled immediately. The primary moving part of the solution is (note that the keyManager provides the stubbed out implementation of your require('key-series-request'):
function KeyGenerator(km) {
this.nextKey = undefined;
this.upperBound = undefined;
this.imWorkingOnIt = false;
this.queuedCallbacks = [];
this.keyManager = km;
this.generateKey = function(table, done) {
if (this.imWorkingOnIt){
this.queuedCallbacks.push(done);
console.log('KG deferred call. Pending CBs: '+this.queuedCallbacks.length);
return;
};
var self=this;
if ((typeof(this.nextKey) ==='undefined') || (this.nextKey > this.upperBound) ){
// set a semaphore & add the callback to the queued callback list
this.imWorkingOnIt = true;
this.queuedCallbacks.push(done);
this.keyManager.requestKeys(function(err,nKey,uBound) {
if (err) { return done(err); }
self.nextKey = nKey;
self.upperBound = uBound;
var theCallbackList = self.queuedCallbacks;
self.queuedCallbacks = [];
self.imWorkingOnIt = false;
theCallbackList.forEach(function(f){
// rather than making the final callback directly,
// call KeyGenerator.generateKey() with the original
// callback
setImmediate(function(){self.generateKey(table,f);});
});
});
} else {
console.log('KG immediate call',self.nextKey);
var z= self.nextKey++;
setImmediate(function(){done(z);});
}
}
};

If your Node.js code to calculate the next key didn't need to execute an async operation then you wouldn't run into synchronization issues because there is only one JavaScript thread executing code. Access to the nextKey/upperBound variables will be done in sequence by only one thread (i.e. request 1 will access first, then request 2, then request 3 et cetera.) In the Java-world you will always need synchronization because multiple threads will be executing even if you didn't make a DB call.
However, in your Node.js code since you are making an async call to get the nextKey you could get strange results. There is still only one JavaScript thread executing your code, but it would be possible for request 1 to make the call to the DB, then Node.js might accept request 2 (while request 1 is getting data from the DB) and this second request will also make a request to the DB to get keys. Let's say that request 2 gets data from the DB quicker than request 1 and update nextKey/upperBound variables with values 100/150. Once request 1 gets its data (say values 50/100) then it will update nextKey/upperBound. This scenario wouldn't result in duplicate keys, but you might see gaps in your keys (for example, not all keys 100 to 150 will be used because request 1 eventually reset the values to 50/100)
This makes me think that you will need a way to sync access, but I am not exactly sure what will be the best way to achieve this.

Batch requests in Node.js

My program is communicating with a web service that only accepts ~10 requests per second. From time to time, my program sends 100+ concurrent requests to the web service, causing my program to crash.
How do I limit concurrent requests in Node.js to 5 per second? Im using the request library.
// IF EVENT AND SENDER
if(data.sender[0].events && data.sender[0].events.length > 0) {
// FIND ALL EVENTS
for(var i = 0; i < data.sender[0].events.length; i++) {
// IF TYPE IS "ADDED"
if(data.sender[0].events[i].type == "added") {
switch (data.sender[0].events[i].link.rel) {
case "contact" :
batch("added", data.sender[0].events[i].link.href);
//_initContacts(data.sender[0].events[i].link.href);
break;
}
// IF TYPE IS "UPDATED"
} else if(data.sender[0].events[i].type == "updated") {
switch (data.sender[0].events[i].link.rel){
case "contactPresence" :
batch("updated", data.sender[0].events[i].link.href);
//_getContactPresence(data.sender[0].events[i].link.href);
break;
case "contactNote" :
batch("updated", data.sender[0].events[i].link.href);
// _getContactNote(data.sender[0].events[i].link.href);
break;
case "contactLocation" :
batch("updated", data.sender[0].events[i].link.href);
// _getContactLocation(data.sender[0].events[i].link.href);
break;
case "presenceSubscription" :
batch("updated", data.sender[0].events[i].link.href);
// _extendPresenceSubscription(data.sender[0].events[i].link.href);
break;
}
}
};
And then the homegrown batch method:
var updated = [];
var added = [];
var batch = function(type, url){
console.log("batch called");
if (type === "added"){
console.log("Added batched");
added.push(url);
if (added.length > 5) {
setTimeout(added.forEach(function(req){
_initContacts(req);
}), 2000);
added = [];
}
}
else if (type === "updated"){
console.log("Updated batched");
updated.push(url);
console.log("Updated length is : ", updated.length);
if (updated.length > 5){
console.log("Over 5 updated events");
updated.forEach(function(req){
setTimeout(_getContactLocation(req), 2000);
});
updated = [];
}
}
};
And an example of the actual request:
var _getContactLocation = function(url){
r.get(baseUrl + url,
{ "strictSSL" : false, "headers" : { "Authorization" : "Bearer " + accessToken }},
function(err, res, body){
if(err)
console.log(err);
else {
var data = JSON.parse(body);
self.emit("data.contact", data);
}
}
);
};

Using the async library, the mapLimit function does exactly what you want. I can't provide an example for your specific use case as you did not provide any code.
From the readme:
mapLimit(arr, limit, iterator, callback)
The same as map only no more than "limit" iterators will be simultaneously
running at any time.
Note that the items are not processed in batches, so there is no guarantee that
the first "limit" iterator functions will complete before any others are
started.
Arguments
arr - An array to iterate over.
limit - The maximum number of iterators to run at any time.
iterator(item, callback) - A function to apply to each item in the array.
The iterator is passed a callback(err, transformed) which must be called once
it has completed with an error (which can be null) and a transformed item.
callback(err, results) - A callback which is called after all the iterator
functions have finished, or an error has occurred. Results is an array of the
transformed items from the original array.
Example
async.mapLimit(['file1','file2','file3'], 1, fs.stat, function(err, results){
// results is now an array of stats for each file
});
EDIT: Now that you provided code, I see that your use is a bit different from what I assumed. The async library is more useful when you know all the tasks to run up front. I don't know of a library off hand that will easily solve this for you. The above note is likely still relevant to people searching this topic so I'll leave it in.
Sorry, I don't have time to restructure your code, but this is an (un-tested) example of a function that makes an asynchronous request while self-throttling itself to 5 requests per second. I would highly recommend working off of this to come up with a more general solution that fits your code base.
var throttledRequest = (function () {
var queue = [], running = 0;
function sendPossibleRequests() {
var url;
while (queue.length > 0 && running < 5) {
url = queue.shift();
running++;
r.get(url, { /* YOUR OPTIONS HERE*/ }, function (err, res, body) {
running--;
sendPossibleRequests();
if(err)
console.log(err);
else {
var data = JSON.parse(body);
self.emit("data.contact", data);
}
});
}
}
return function (url) {
queue.push(url);
sendPossibleRequests();
};
})();
Basically, you keep a queue of all the data to be asynchronously processed (such as urls to be requested) and then after each callback (from a request) you try to launch off as many remaining requests as possible.

This is precisely what node's Agent class is designed to address. Have you done something silly like require('http').globalAgent.maxSockets = Number.MAX_VALUE or passed agent: false as a request option?
With Node's default behavior, your program will not send more than 5 concurrent requests at a time. Additionally, the Agent provides optimizations that a simple queue cannot (namely HTTP keepalives).
If you try to make many requests (for example, issue 100 requests from a loop), the first 5 will begin and the Agent will queue the remaining 95. As requests complete, it starts the next.
What you probably want to do is create an Agent for your web service requests, and pass it in to every call to request (rather than mixing requests in with the global agent).
var http=require('http'), svcAgent = http.Agent();
request({ ... , agent: svcAgent });