OpenLayers GetFeatureInfo requests not being triggered

Question

I'm creating a little web page containing a map using the Google Maps API and the OpenLayers JS library (v2.13). The base layer of the map is Google Street Maps, and that works fine, I can pan around the map, zoom in etc.

I'm adding a number of layers to the map, which come from a Web Mapping Service hosted on a remote server that I don't own or have access to (the code, I mean). And that works fine too, the layers overlay onto the Google Map just fine.

The problem is when I click on the layer features on the map, the WMSGetFeatureInfo controls are not working. No request is sent to the specified URL, no callback function is triggered, nothing happens at all. Here's some code:

var remoteGeoServer = "https://www.remotegeoserver.com/geoserver/wms";
var options = {
    controls: [],
    maxExtent: new OpenLayers.Bounds(420000, 485000, 770000, 985000),
    projection: "EPSG:2157",
    units: 'm',
    scales: [5000000, 2500000, 1250000, 600000, 400000, 200000, 100000, 50000, 25000]
};
var map = new OpenLayers.Map('map-container', options);
// ... define styles, rules etc.

var overlayLayer = new OpenLayers.Layer.WMS("Overlayed Layer", remoteGeoServer, {<some_options>}); // other layers are created too...

var infoControls = {
    click: new OpenLayers.Control.WMSGetFeatureInfo({
        url: "/geoserver/wms",
        title: 'Identify features by clicking',
        layers: [overlayedLayer],
        infoFormat: 'text/plain',
        queryVisible: true
    })
};
var baseLayer = new OpenLayers.Layer.Google("Google Streets", {numZoomLevels: 20});
map.addLayers( [baseLayer, overlayLayer] );
map.setBaseLayer( baseLayer );

for (var i in infoControls) {
    infoControls[i].events.register("getfeatureinfo", this, showInfo);
    map.addControl(infoControls[i]);
}

// ... and later
function showInfo(evt) {
    console.log("Hurray!");
}

infoControls.click.activate();

I should explain that, even though the url in the infoControls is called "/geoserver/wms", there is no web mapping server running on my server. I just forward on the GetFeatureInfo request to the remote server that runs the actual geoserver. Otherwise the same-origin policy kicks in and the GetFeatureInfo requests are rejected.

But nothing happens, my "/geoserver/wms" endpoint never gets called. Am I doing something wrong? Also, and this isn't my main question, but why am I able to successfully give OpenLayers the remote server URL when creating the layers (should same-origin policy not apply - the map still works fine though, and the GET image requests to the remote server are successful).

Something else worth noting is that when I replace the local url path in infoControls with the remote server url, clicking the map triggers the same-origin policy error in the debug console.

Updated your question to include infoControls.click.activate(); and deleted my answer. If you could put a jsfiddle together using a publicly available server, like the one in OL example, openlayers.org/dev/examples/getfeatureinfo-control.html, it will be easier to debug. — John Powell
Do you know if the remote server layers support WMS GetFeatureInfo requests? this is required and can verified using the WMS GetCapabilities request. You can view the XML is a browser window if you have the address, add REQUEST="GetCapabilities". This will list the layers and whether they support GetFeatureInfo. — Aerokneeus

RTF RTF · Accepted Answer · 2014-06-29T10:48:30

I found a few different potential solutions for this problem that other people were having but none of them worked for me. In the end, the only thing that did work was this:

The URL used in the layer creation constructor(s) (in OpenLayers.Layer.WMS) MUST be the same as the URL used for the GetFeatureInfo constructor (in OpenLayers.Control.WMSGetFeatureInfo)

Otherwise, the map layers will work but the GetFeatureInfo requests will fail. I don't know if just the domain needs to be the same, or the full URL.

I'm not particularly happy about this. It means that I have to create an endpoint on my server that acts as a proxy and routes GetMap requests to the actual remote geoserver. I didn't need to do this before (why not - same-origin policy ??) and now it drives up latency for the layers showing up in the map (not to mention my server gets hammered with GetMap requests).

This seems to be an issue with OpenLayers (but I'm not sure of that). I'd be very interested in hearing about a solution if anyone knows of one.

OpenLayers GetFeatureInfo requests not being triggered

1 Answers