"Uncovering the Hidden Bug: Memory Leak in Google Maps caused by Map.panTo() Function in Javascript

Question

"Uncovering the Hidden Bug: Memory Leak in Google Maps caused by Map.panTo() Function in Javascript

I've been encountering Javascript Out of Memory errors with a Web App that involves loading a Google Map and continuously panning from one point to another. It typically takes around half a day before memory is depleted, but I'm aiming for much longer durability. I located the memory leak to be linked to the usage of the map.panTo method, although I suspect my handling of it might be the root cause (JavaScript isn't my strong suit). Could you take a look at this code and assist me in resolving this memory leak issue? In order to expedite debugging time, I have increased the interval for panning in this demo code (the leak can even be observed through Windows Task Manager). The app runs on ASP .Net 3.5 Web Forms without any PostBacks; the code entirely consists of HTML, CSS, and JavaScript. The memory leakage is most severe in IE (which is necessary for display purposes).

Edit:

Experimented with various versions of the Google Maps API (2, 3.0, and 3.6).
Realized that nesting the map in a Hashtable or Array within the example code is redundant and doesn't mitigate the memory leak.
Looking to evade temporary remedies such as periodic page refreshes or resorting to utilizing the static Google Maps API.
The bounty will be awarded to whoever manages to rectify the memory leak or offers substantial evidence demonstrating why it's impossible to eliminate (if applicable).

Code:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Map Shifter</title>
    <style type="text/css">
        #divMap { height: 400px; width:400px; position:absolute; top:10%; left:10%; border: 2px solid #ff1100; }    
    </style>
    <script type="text/javascript" src="http://maps.google.com/maps/api/js?v=2&sensor=false"></script>
    <script type="text/javascript" language="javascript">
        //Tried both HashTable and Array (Both Lead to Leakage)...
        var m_arrMaps = new HashTable(); //new Array();
        var m_Timer;
        function HashTable() {
            return this;
        }
        function LoadMapAndStartShifting() {
            var objMapCenterPoint = new google.maps.LatLng(20.5, -156);
            var objMapOptions = { zoom: 9, center: objMapCenterPoint, mapTypeId: google.maps.MapTypeId.ROADMAP,
                scaleControl: false, streetViewControl:false, zoomControl: false, mapTypeControl: false, panControl: false
            }
            var map = new google.maps.Map(document.getElementById("divMap"), objMapOptions);
            m_arrMaps["ShiftingMap"] = map;
            setTimeout("ShiftMap(20.5, -156);", 700);
        }
        function ShiftMap(decLat, decLng) {
            var objLatLong = new google.maps.LatLng(decLat, decLng);
            //Attempted setCenter instead of the preferred panTo, yet still encountering leaks!
            m_arrMaps["ShiftingMap"].panTo(objLatLong);
            if (decLat == 20.5) {
                //Leakage Persists...
                ResetTimer(39, -87);
            }
            else {
                //Leakage Endures...
                setTimeout("ShiftMap(20.5, -156);", 700);
            }
        }
        function ResetTimer(decLat, decLng) {
            m_Timer = setTimeout("ShiftMap(" + decLat + ", " + decLng + ");", 700);    
        }    
    </script>
</head>
<body onload="LoadMapAndStartShifting();">
    <form id="form1" runat="server">
    <div id="divMap"></div>
   </form>
</body>

javascript asp.net google-maps memory-leaks

Answer 1

Answer №1

Is there a specific reason for creating a hashtable for the map? Maybe consider making your map a global variable instead. Your mention of trying both HashTable and Array and encountering leaks raises questions about the necessity of using either option.

You could simplify your code by directly passing the options structure into the Map() function, eliminating the need for objMapOptions and objMapCenterPoint variables, as well as passing latLng directly into the panTo() functions.

<script type="text/javascript" language="javascript>
    var m_Timer, map;

    function LoadMapAndStartShifting() {
        map = new google.maps.Map(document.getElementById("divMap"), { zoom: 9, center: new google.maps.LatLng(20.5, -156), mapTypeId: google.maps.MapTypeId.ROADMAP,
            scaleControl: false, streetViewControl:false, zoomControl: false, mapTypeControl: false, panControl: false
        });
        setTimeout("ShiftMap(20.5, -156);", 700);
    }
    function ShiftMap(decLat, decLng) {
        map.panTo(new google.maps.LatLng(decLat, decLng));
        if (decLat == 20.5) {
            //Leaks...
            ResetTimer(39, -87);
        }
        else {
            //Still leaks...
            setTimeout("ShiftMap(20.5, -156);", 700);
        }
    }
    function ResetTimer(decLat, decLng) {
        m_Timer = setTimeout("ShiftMap(" + decLat + ", " + decLng + ");", 700);    
    }    
</script>

Have you considered caching the maps instead of constantly loading them? Using the static map API and caching images could potentially optimize the performance of your application, especially if it involves switching between two maps frequently.

Answer 2

Is there a specific reason for creating a hashtable for the map? Maybe consider making your map a global variable instead. Your mention of trying both HashTable and Array and encountering leaks raises questions about the necessity of using either option.

You could simplify your code by directly passing the options structure into the Map() function, eliminating the need for objMapOptions and objMapCenterPoint variables, as well as passing latLng directly into the panTo() functions.

<script type="text/javascript" language="javascript>
    var m_Timer, map;

    function LoadMapAndStartShifting() {
        map = new google.maps.Map(document.getElementById("divMap"), { zoom: 9, center: new google.maps.LatLng(20.5, -156), mapTypeId: google.maps.MapTypeId.ROADMAP,
            scaleControl: false, streetViewControl:false, zoomControl: false, mapTypeControl: false, panControl: false
        });
        setTimeout("ShiftMap(20.5, -156);", 700);
    }
    function ShiftMap(decLat, decLng) {
        map.panTo(new google.maps.LatLng(decLat, decLng));
        if (decLat == 20.5) {
            //Leaks...
            ResetTimer(39, -87);
        }
        else {
            //Still leaks...
            setTimeout("ShiftMap(20.5, -156);", 700);
        }
    }
    function ResetTimer(decLat, decLng) {
        m_Timer = setTimeout("ShiftMap(" + decLat + ", " + decLng + ");", 700);    
    }    
</script>

Have you considered caching the maps instead of constantly loading them? Using the static map API and caching images could potentially optimize the performance of your application, especially if it involves switching between two maps frequently.

Answer 3

Answer №2

After some more consideration, it occurred to me that you are requesting version 2 of this API while the latest version available is actually 3.6. I recommend trying to update the version number or simply removing the v parameter to access the most recent stable release and see if that helps. It's possible that any issues related to garbage collection have been addressed in the newer versions.

Answer 4

After some more consideration, it occurred to me that you are requesting version 2 of this API while the latest version available is actually 3.6. I recommend trying to update the version number or simply removing the v parameter to access the most recent stable release and see if that helps. It's possible that any issues related to garbage collection have been addressed in the newer versions.

Answer 5

Answer №3

It appears that the "Hashtable" Object is only storing one element - ["ShiftingMap"] - instead of multiple maps. Consider using a global variable to hold the map object.

The only instance of repeated allocation is the

new google.maps.LatLng(decLat, decLng)

, which is created every time the map is panned.

Here are some suggestions:

1) The documentation for LatLng does not mention needing to explicitly free objects, so the garbage collector should handle it automatically.

2) When continuously panning a Google map for 6 hours or more, consider if the issue lies in your code or within Google Maps itself. It's possible that downloaded map image tiles are kept locally for quicker access when panning back.

To test this, try panning back and forth between two points rather than across the globe to see if memory leakage occurs consistently over time.

3) Test if different browsers behave differently with the issue, especially Google Chrome.

Additional Note

I revised your demo code by moving the LatLng call out of the loop, but the memory leak still persists. I also adjusted the use of non-string values in the setTimeout calls and followed the recommended doctype from the Maps API tutorial.

The result shows consistent memory leaks on Firefox and Chrome. I have posted about this on the official Google Maps API v3 forum.

It appears that the .panTo method is causing the memory leak. You may need to wait for a response from a member of the Google team regarding this issue.

View the test case demo here

Revised test case:

<!DOCTYPE html>
<html>
<!-- http://sandbox.kluger.com/map_demo.html -->
<!-- See tutorial http://code.google.com/apis/maps/documentation/javascript/tutorial.html -->
<head>
    <title>Map Shifter</title>
    <style type="text/css">
        #divMap { height: 400px; width:400px; position:absolute; top:10%; 
                  left:10%; border: 2px solid #ff1100; } 
    </style>
    <script type="text/javascript" 
            src="http://maps.google.com/maps/api/js?sensor=false"></script>
    <script type="text/javascript" language="javascript">
        // Globals
        var map,
            mapCenterPoints,
            currentPoint;

        var ShiftMap = function() {
            currentPoint = currentPoint == 0 ? 1 : 0; // update
            map.panTo(mapCenterPoints[currentPoint]);
            setTimeout(ShiftMap, 700);           
        }

        function LoadMapAndStartShifting() {
            mapCenterPoints = [new google.maps.LatLng(20.5, -156),
                               new google.maps.LatLng(39, -87)];
            currentPoint = 0;

            var objMapOptions = { zoom: 9, 
                                  center: mapCenterPoints[currentPoint], 
                                  mapTypeId: google.maps.MapTypeId.ROADMAP,
                                  scaleControl: false, streetViewControl:false, 
                                  zoomControl: false, mapTypeControl: false, 
                                  panControl: false
            }

            map = new google.maps.Map(document.getElementById("divMap"), 
                        objMapOptions);
            setTimeout(ShiftMap, 700);
        }
    </script>
</head>
<body onload="LoadMapAndStartShifting();">
      <div id="divMap"></div>
</body>
</html>

Answer 6

It appears that the "Hashtable" Object is only storing one element - ["ShiftingMap"] - instead of multiple maps. Consider using a global variable to hold the map object.

The only instance of repeated allocation is the

new google.maps.LatLng(decLat, decLng)

, which is created every time the map is panned.

Here are some suggestions:

1) The documentation for LatLng does not mention needing to explicitly free objects, so the garbage collector should handle it automatically.

2) When continuously panning a Google map for 6 hours or more, consider if the issue lies in your code or within Google Maps itself. It's possible that downloaded map image tiles are kept locally for quicker access when panning back.

To test this, try panning back and forth between two points rather than across the globe to see if memory leakage occurs consistently over time.

3) Test if different browsers behave differently with the issue, especially Google Chrome.

Additional Note

I revised your demo code by moving the LatLng call out of the loop, but the memory leak still persists. I also adjusted the use of non-string values in the setTimeout calls and followed the recommended doctype from the Maps API tutorial.

The result shows consistent memory leaks on Firefox and Chrome. I have posted about this on the official Google Maps API v3 forum.

It appears that the .panTo method is causing the memory leak. You may need to wait for a response from a member of the Google team regarding this issue.

View the test case demo here

Revised test case:

<!DOCTYPE html>
<html>
<!-- http://sandbox.kluger.com/map_demo.html -->
<!-- See tutorial http://code.google.com/apis/maps/documentation/javascript/tutorial.html -->
<head>
    <title>Map Shifter</title>
    <style type="text/css">
        #divMap { height: 400px; width:400px; position:absolute; top:10%; 
                  left:10%; border: 2px solid #ff1100; } 
    </style>
    <script type="text/javascript" 
            src="http://maps.google.com/maps/api/js?sensor=false"></script>
    <script type="text/javascript" language="javascript">
        // Globals
        var map,
            mapCenterPoints,
            currentPoint;

        var ShiftMap = function() {
            currentPoint = currentPoint == 0 ? 1 : 0; // update
            map.panTo(mapCenterPoints[currentPoint]);
            setTimeout(ShiftMap, 700);           
        }

        function LoadMapAndStartShifting() {
            mapCenterPoints = [new google.maps.LatLng(20.5, -156),
                               new google.maps.LatLng(39, -87)];
            currentPoint = 0;

            var objMapOptions = { zoom: 9, 
                                  center: mapCenterPoints[currentPoint], 
                                  mapTypeId: google.maps.MapTypeId.ROADMAP,
                                  scaleControl: false, streetViewControl:false, 
                                  zoomControl: false, mapTypeControl: false, 
                                  panControl: false
            }

            map = new google.maps.Map(document.getElementById("divMap"), 
                        objMapOptions);
            setTimeout(ShiftMap, 700);
        }
    </script>
</head>
<body onload="LoadMapAndStartShifting();">
      <div id="divMap"></div>
</body>
</html>

Answer 7

Answer №4

If you find yourself struggling with high memory usage in your JavaScript code, consider refreshing the page after looping through your data. This could help free up some memory being consumed by the script running on the page:

Check out this link for information on how to redirect to another webpage using JavaScript/jQuery

Answer 8

If you find yourself struggling with high memory usage in your JavaScript code, consider refreshing the page after looping through your data. This could help free up some memory being consumed by the script running on the page:

Check out this link for information on how to redirect to another webpage using JavaScript/jQuery

"Uncovering the Hidden Bug: Memory Leak in Google Maps caused by Map.panTo() Function in Javascript

Answer №1

Answer №2

Answer №3

Answer №4

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