OpenLayers + MapServer - Finding reason for random missing tile

Question

I am testing an application this is developed in OpenLayers 2.13 with Chrome, and I am using MapServer as the map provider.

I have noticed some tiles occasionally does not render, when I pan/zoom the map. There is no specific way to recreate this problem on my application, the missing tiles are random. But I can say that the problem is common enough for most users to notice.

MapServer is running on an dedicated core i7 desktop with 16GB of RAM. I do not understand if it is a hardware issue, software issue, or load handling issue.

I have found some links that specifies the solution to hide the pink image XYZ Layer in OpenLayers has missing tiles

But I am interested to know what is the cause of missing tiles? What are the possible factors causing missing tiles.

UPDATE

Sometimes it will also appear that the tiles are loaded or what appear to be loaded correctly, turned from map tiles into blank tiles.

Answer 1

In Firefox you could do a rightclick on the blank tile and choose "open image in New tab" to see if it is displayed outside your app. Apart from that you could try this to see if there is an image load error: OpenLayers.Util.onImageLoadError = function() {console.log("error");}; 

or use the CSS-Class:

.olImageLoadError { /* when OL get's a Error 404 mark the tile with a red border */ border:3px solid red; }

for testing purposes you could just load your layer into QGIS and test if there are also tiles missing