NodeJS getting stuck in callback - node.js

Question

Im having troubles where my node app all a sudden starts to consume a lot of CPU. Im suspecting that the function below gets stuck somehow..
Client.prototype.countActiveChatsRedis = function (userID, agentID, obj, callback) {
var count = 0;
pub.keys("widgetActive:" + userID + ":*", function(err, key) {
if(err !== null) {
console.log("Redis error..... --> " + err);
callback(count, obj);
}
if(key && key.length > 0) {
pub.mget(key, function(err, data) {
if(data) {
for(var i = 0; i < data.length;i++) {
if(data[i]) {
var arr = data[i].split(",");
if(arr[2] == agentID) {
if (Number(arr[3]) > 0) {
count++;
}
}
}
}
callback(count, obj);
}
});
} else {
callback(count, obj);
}
});
}
Any ideas what the problem could be? Any case where it could avoid sending the callback?
This function runs around 50 times per second.

Answer 1

It is bad practice to use KEYS in a production environment. To quote the Redis master himself:
Warning: consider KEYS as a command that should only be used in
production environments with extreme care. It may ruin performance
when it is executed against large databases. This command is intended
for debugging and special operations, such as changing your keyspace
layout. Don't use KEYS in your regular application code. If you're
looking for a way to find keys in a subset of your keyspace, consider
using SCAN or sets.
Whenever you add a key with this prefix, just add it to a set called "widgetActive" the user's id or any other data you need.
you can also use HASH if you need to save some data for each entry.

Answer 2

you should always return your callbacks to make sure that your function terminates correctly and returns the control to the calling context:
Client.prototype.countActiveChatsRedis = function (userID, agentID, obj, callback) {
var count = 0;
pub.keys("widgetActive:" + userID + ":*", function(err, key) {
if(err !== null) {
console.log("Redis error..... --> " + err);
return callback(count, obj);
}
if(key && key.length > 0) {
pub.mget(key, function(err, data) {
if(data) {
for(var i = 0; i < data.length;i++) {
if(data[i]) {
var arr = data[i].split(",");
if(arr[2] == agentID) {
if (Number(arr[3]) > 0) {
count++;
}
}
}
}
return callback(count, obj);
}
});
} else {
return callback(count, obj);
}
});
}

Answer 3

It's stucked because in the case where there is no data, no callback is being called.
pub.mget(key, function(err, data) {
if(data) {
for(var i = 0; i < data.length;i++) {
if(data[i]) {
var arr = data[i].split(",");
if(arr[2] == agentID) {
if (Number(arr[3]) > 0) {
count++;
}
}
}
}
// callback(count, obj); // <==== move this callback outside of if (data)
}
callback(count, obj); // this ensures that callback always gets called
});