CODEWITHSUNDEEP
javascriptmemory-leaksweb-worker
r90t
r90t

Reputation: 386

Memory leaks in js web-workers

I`ve got memory leak when i try to use web workers. I have 4Gb RAM and i5 processor. Usually i have free ram near 80% and 90% CPU, but when i running this script my computer freezes in two minutes, when memory ends. I do not know how to investigate the problem. I made some heap snapshots but did not find the problem(i have not any experience in mem leaks). Can anybody help me? A can provide any additional info. The main task is to find primes and save it to database. I think that the problem can be in working with db or sending data from client to worker and vice versa. Sorry for my english. thx

    $(document).ready( function() {
  $('#start_button').click( function() {
    toggleButton();
  });
});
var db = openDatabase("primeNumbers", "0.1", "Prime numbers db", 200000);

//check if db can be used
if(!db){alert("Failed to connect to database.");}

var currNumber = 2;
var work;

//create db if not exists
db.transaction(function (tx) {
  tx.executeSql("CREATE TABLE  IF NOT EXISTS primeNumbers (id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, value INTEGER NOT NULL UNIQUE)", [], null, null);
});

//create worker for async calculations
var blob = new Blob([
  "                                                     \
  onmessage = function(event) {                         \
    self.postMessage(isPrime(parseInt(event.data)));    \
  };                                                    \
  function isPrime(n) {                                 \
    if(n < 2) return '{\"status\":\"false\"}';          \
    var q = parseInt(Math.sqrt(n));                     \
    for(var i = 2; i <= q; i++) {                       \
      if (n % i == 0) {                                 \
        return '{\"status\":\"false\"}';                \
      };                                                \
    };                                                  \
    return '{\"status\":\"true\",\"value\":\"'+n+'\"}'; \
  };"
]);
var blobURL = window.URL.createObjectURL(blob);
var worker = new Worker(blobURL);

//worker event listener
worker.onmessage = function(event) {
  json = $.parseJSON(event.data);
  switch(Boolean(json['status'])) {
    case true:
      writeDataToDatabase(json['value']);
      work && finder();
      break;
    case false:
      currNumber++;
      work && finder();
      break;
    default:
      alert('Something went wrong');
  };
};

function finder() {
  if(work) {
    worker.postMessage(currNumber);
    currNumber++;
  };
};

function writeDataToDatabase(value) {
  db.transaction(function(tx) {
    tx.executeSql('INSERT INTO primeNumbers (value) VALUES ('+ parseInt(value) +')');
  });
};

function getMaxPrimeFromDb() {
 var res;
 db.transaction(function(tx) {
   tx.executeSql('select max(value) as highestvalue from primenumbers', [], function(tx, result) {
     res = result.rows.item(0)['highestvalue'];
   });
   if(res != undefined) {
     currNumber = parseInt(res) + 1;
   };
 });
};

function toggleButton() {
  btn = $('#start_button');
  if(btn.text() != 'pause_calculations') {
    btn.text('pause_calculations');
    work = true;
    getMaxPrimeFromDb();
    finder();
  } else {
    btn.text('resume_calculations');
    work = false;
  };
};

Upvotes: 0

Views: 738

Answers (1)

Ryan Wheale
Ryan Wheale

Reputation: 28420

I haven't worked much web workers or browser database storage, but it appears the footprint for the database commands are asynchronous - meaning you must wait for them to finish before doing anything. At a quick glance, I would expect all calls to executeSql to have a "done" handler in which you call things like finder() and work && finder(). You would need to be able to pass a callback function around:

function writeDataToDatabase( value, callback ) {
    db.transaction(function(tx) {
        tx.executeSql('INSERT INTO primeNumbers (value) VALUES ('+ parseInt(value) +')', [], function() {
            if( typeof callback === "function" ) callback();
        });
    });
};

function getMaxPrimeFromDb( callback ) {
    var res;
    db.transaction(function(tx) {
        tx.executeSql('select max(value) as highestvalue from primenumbers', [], function(tx, result) {
            res = result.rows.item(0)['highestvalue'];

            if(res != undefined) {
                currNumber = parseInt(res) + 1;
            };

            if( typeof callback === "function" ) callback();
        });
    });
};

And then use it in your code like this:

...
writeDataToDatabase(json['value'], function() {
    work && finder();
});
...


...
getMaxPrimeFromDb(function() {
    finder();
});
...

Upvotes: 1

Related Questions