Issue with Cache, Maps and MarkerClusterer - google-maps

Question

I have a website built from Google Maps and using MarkerClusterer. This site works fine most of the time, but there will be times when multiple users will be online and a filtered marker sets request will be returned incorrectly.
Example: I filter to a set of markers based on a set of filter parameters. As this is processing someone else also filters to a different set of markers and those markers are returned to me instead of my request.
I can also see this issue occur if I sit on the page and just hit refresh. I have tested in our test environment with 2 users. By having one user filter to a set of markers and when the second user refreshes their browser window they see the same set of filtered markers. The markers of the first user.
I have seen example fixes were it is discussed to use a CacheBuster by adding the Date to the URL, but in using the MarkerCluserer code I do not see where to add that as an option. It has also been asked not to do this.
Data is coming from the server in an array object. markerclusterer.js is located locally in the Visual Studio Project. Here is the Script on the page that generates the map:
<script type="text/javascript" src="http://maps.google.com/maps/api/js?v=3.11&sensor=false"></script>
<script type="text/javascript" src="/Scripts/markerclusterer.js"></script>
<script type="text/javascript">
var infowindow;
var map;
var markerdataLength; //en - 5-8-2013
var prev;
$(document).ready(function () {
setTimeout("gmarkers()", 500);
});
function gmarkers() {
markerdataLength = 0;
$("#map_canvas").fadeTo(500, 0.3);
$("#pwait").show();
$.ajax({
type: "POST",
url: "MapSearch.aspx/GetMarkers",
data: "{}",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function (msg) {
$("#map_canvas").fadeTo(0, 0.3);
$("#pwait").show();
var markerdata;
markerdata = msg.d;
msg = null;
var latlng = new google.maps.LatLng(52.50, -98.35);
var myOptions = {
zoom: 3,
center: latlng,
//mapTypeId: google.maps.MapTypeId.HYBRID,
mapTypeId: google.maps.MapTypeId.TERRAIN,
mapTypeControl: true,
mapTypeControlOptions: {
position: google.maps.ControlPosition.TOP_RIGHT
},
panControl: true,
panControlOptions: {
position: google.maps.ControlPosition.TOP_LEFT
},
zoomControl: true,
zoomControlOptions: {
position: google.maps.ControlPosition.TOP_LEFT
},
scaleControl: true,
scaleControlOptions: {
position: google.maps.ControlPosition.BOTTOM_CENTER
},
streetViewControl: true,
streetViewControlOptions: {
position: google.maps.ControlPosition.TOP_LEFT
}
};
//initialize the info window (balloon popup)
infowindow = new google.maps.InfoWindow();
//draw the map with the above settings
map = new google.maps.Map(document.getElementById("map_canvas"), myOptions);
/***************************MARKER CLUSTERER **********************************************/
var imageUrl = 'http://chart.apis.google.com/chart?cht=mm&chs=24x24&chco=' +
'FFFFFF,008CFF,000000&ext=.png'; //Blue
var markers = [];
if (markerdata != "undefined" & markerdata.length > 0) { //run this code if the data is not null. data is the markers in json format
markerdataLength = markerdata.length; //en - 5-8-2013
var i = 0;
var ro = new RepeatingOperation(function () {
var dataWell = markerdata[i];
var mlatLng = new google.maps.LatLng(dataWell.la, dataWell.lo);
var marker = new google.maps.Marker({
id: dataWell.id,
position: mlatLng,
title: dataWell.t,
icon: imageUrl //iconstring
});
//set the marker click code to show the info window
var fn = markerClick(dataWell.id);
google.maps.event.addListener(marker, 'click', fn);
google.maps.event.addListener(marker, 'clusteringend', clusteringDone()); //en - 5-8-2013
markers.push(marker);
if (++i < markerdata.length) { ro.step(); }
else {
var mcOptions = {
gridSize: 90, //default grid size is 60 was using 35. higher #'s draw faster.
maxZoom: 20, //defines how close u are before no more clusters are drawn
minimumClusterSize: 15
};
var mc = new MarkerClusterer(map, markers, mcOptions);
}
}, 100);
ro.step();
}
else {
alert("No wells were found.");
$("#map_canvas").fadeTo(300, 1);
$("#pwait").hide();
}
}
});
}