Fix reloading tiles in case of an error with tile.load()

src/ol/ImageTile.js

@@ -112,7 +112,40 @@ class ImageTile extends Tile {
   }
 
   /**
-   * Load not yet loaded URI.
+   * Load the image or retry if loading previously failed.
+   * Loading is taken care of by the tile queue, and calling this method is
+   * only needed for preloading or for reloading in case of an error.
+   *
+   * To retry loading tiles on failed requests, use a custom `tileLoadFunction`
+   * that checks for error status codes and reloads only when the status code is
+   * 408, 429, 500, 502, 503 and 504, and only when not too many retries have been
+   * made already:
+   *
+   * ```js
+   * const retryCodes = [408, 429, 500, 502, 503, 504];
+   * const retries = {};
+   * source.setTileLoadFunction((tile, src) => {
+   *   const image = tile.getImage();
+   *   fetch(src)
+   *     .then((response) => {
+   *       if (retryCodes.includes(response.status)) {
+   *         retries[src] = (retries[src] || 0) + 1;
+   *         if (retries[src] <= 3) {
+   *           setTimeout(() => tile.load(), retries[src] * 1000);
+   *         }
+   *         return Promise.reject();
+   *       }
+   *       return response.blob();
+   *     })
+   *     .then((blob) => {
+   *       const imageUrl = URL.createObjectURL(blob);
+   *       image.src = imageUrl;
+   *       setTimeout(() => URL.revokeObjectURL(imageUrl), 5000);
+   *     })
+   *     .catch(() => tile.setState(3)); // error
+   * });
+   * ```
+   *
    * @api
    */
   load() {