Long polling Kill threads on server side

Good morning/evening,

I´m implementing a long pooling between client-server by ajax-java. And the long polling works properly on the client side, and every 30 seconds a new connection is throw and the previous one is aborted. But the problem is that in the server side all those request/threads keep alive until we have something to return to the client. But like I said the client maybe is not listening anymore. Here some code:

Client:

     // Long Polling (Recommened Technique - Creates An Open  Connection To Server ∴ Fast)
  (function poll(){
    var tenantName = $("#tenantName").val();
    $.ajax({
    method:"GET",
    url: "url",
    success: function(data){
        if (data === true) {
            bootbox.alert("Page has been modify <a href='javascript:void(0)' onclick='reload()'>reload</a>");
        }
     }, dataType: "json", complete: poll, timeout: 60000 });
})();

Server:

       /**
 * @return
 */
@RequestMapping(method = RequestMethod.GET)
@ResponseBody
public Boolean getSubStepStatus(@RequestParam("subStep") String subStep,
                                @RequestParam("tenantId") String tenantId) {
    if (!isInStep(subStep, tenantId)) {
        tenantsInStep.get(subStep).add(tenantId);
    }
    while (true) {
        String modifierTenantId = stepModifyByTenant.get(subStep);
        if (modifierTenantId != null && !modifierTenantId.equals(tenantId) && !isInStep(subStep, tenantId)) {
            tenantsInStep.get(subStep).remove(tenantId);
            return true;
        }
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

Problem like I said all threads are growing and growing in the server side every 30 seconds, what I´m doing wrong using this technique?