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function Poller(config)
{
// CONFIGURABLE
var endpoints = {
up: "/status/poll", // url to poll when the server is up
down: "/status" // url to poll at regular intervals when the server is down
};
var timeout = 60000 * 2; // how many ms between polling attempts
var intervalMs = 1000; // ms between polls when the server is down
// INTERNAL STATE
var up = true; // whether or not we can connect to the server
var req; // the pending ajax request
var downPoller; // the setInterval for polling when the server is down
var self = this;
if (typeof config === 'object')
{
if (typeof config.endpoints === 'object')
{
endpoints.up = config.endpoints.up;
endpoints.down = config.endpoints.down;
}
if (config.timeout)
timeout = config.timeout;
if (config.interval)
intervalMs = config.interval;
}
$(self).on('pollstart', function(event, data) {
log("Started poller");
}).on('pollstop', function(event, data) {
log("Stopped poller");
});
this.start = function()
{
if (req)
return false;
doPoll();
$(self).trigger('pollstart', {url: endpoints.up, timeout: timeout});
return true;
};
this.stop = function()
{
if (!req)
return false;
req.abort();
req = undefined;
stopped = true;
stopDownPoller();
$(self).trigger('pollstop', {});
return true;
};
this.setTimeout = function(tmout)
{
timeout = tmout; // takes effect at next poll
};
this.isUp = function()
{
return up;
};
function doPoll()
{
req = $.ajax({
url: endpoints.up + "?timeout=" + timeout,
timeout: timeout
}).done(pollSuccess).fail(pollFailed);
}
function pollSuccess(data, message, jqxhr)
{
stopDownPoller();
doPoll();
var wasUp = up;
up = true;
status = data;
var arg = {
status: status,
data: data,
jqxhr: jqxhr
};
if (!wasUp)
$(convey.poller).trigger('serverstarting', arg);
else
$(self).trigger('pollsuccess', arg);
}
function pollFailed(jqxhr, message, exception)
{
if (message === "timeout")
{
log("Poller timeout; re-polling...", req);
doPoll(); // in our case, timeout actually means no activity; poll again
return;
}
up = false;
downPoller = setInterval(function()
{
// If the server is still down, do a ping to see
// if it's up; pollSuccess() will do the rest.
if (!up)
$.get(endpoints.down).done(pollSuccess);
}, intervalMs);
$(self).trigger('pollfail', {
exception: exception,
message: message,
jqxhr: jqxhr
});
}
function stopDownPoller()
{
if (!downPoller)
return;
clearInterval(downPoller);
downPoller = undefined;
}
}
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