[OpenLayers-Users] CORB problem with TileArcGISRest layer in OpenLayers 5 client

Wed Sep 25 09:33:01 PDT 2019

Hi Alex,

Thanks for chiming in on my question.

First, I should note that I’m NOT seeing a response with content type
text/html in the Chrome Dev tools. (I’m seeing no response whatsoever
there.) I only see what looks like text/html response in the Firefox dev
tools. I’m confused by this, and wonder if the response quoted in my
original message is really being returned or if it’s cooked up by the
Firefox dev tools. (This is not to point fingers – it’s just that I’m not
seeing any “response data” at all in Chrome.)

I understand your point about the “tiles.arcgis.com” URL, but what’s not
clear to me is why the* OL 2 client is working just fine using
“tiles.arcgis.com <http://tiles.arcgis.com>” URLs*. (!)

If you run the OL 2 client in the debugger, and look at the network
traffic, you’ll see that tiles with URLs of the form
http://tiles.arcgis.com/... are returned successfully.

My best hypothesis is that *in the OL 5 world*  I’m not using the right
type of layer and/or the right “source” for that layer, or that there are
some options I need to pass when creating the “layer” or “source”.

In the world of the OL 5 client:

·         The layers in question are vanilla *Layer*s

·         Their “source”s are *TileArcGISRest*

In short, what’s the correct “translation” of *OpenLayers.Layer.ArcGISCache*
in OL2-speak into OL5-speak?

Best,

Ben

*From:* Alex Rice [mailto:rice.guido at gmail.com]
*Sent:* Wednesday, September 25, 2019 12:08 PM
*To:* Benjamin Krepp <bkrepp at ctps.org>
*Cc:* openlayers-users at lists.osgeo.org; Saul Farber <saul at peoplegis.com>
*Subject:* Re: [OpenLayers-Users] CORB problem with TileArcGISRest layer in
OpenLayers 5 client

The tiles.arcgis.com URL seems to be invalid because it's returning
content-type: text/html instead of a tile, as you observed. I would try to
solve that before even thinking about CORB/CORS problem. Maybe that problem
will go away when you are getting a tiles response (the http headers will
likely be different as well).

On Wed, Sep 25, 2019 at 8:37 AM Benjamin Krepp <bkrepp at ctps.org> wrote:

Dear colleagues,

I’m running into difficulty using a tiled basemap layer with an
TileArcGISRest data source in an OpenLayers 5 client.

I’ve able to successfully use this layer in OpenLayers 2 clients, and
don’t’ understand the problem I’m running into and what needs to be done to
address it.

The layer in question is one of MassGIS’s (the Massachusetts State GIS
Agency’s) tiled basemaps. It is described here:
https://www.mass.gov/service-details/massgis-base-map

My sample OL 2 client, which works just fine, may be found here:
https://www.ctps.org/geoserver/www/apps/MassGIS_basemap_OL_v2/index.html

My sample OL 5 client, which runs into errors, may be found here:
https://www.ctps.org/geoserver/www/apps/MassGIS_basemap_OL_v5/index.html

The code for my OL 5 client is based on a sample on the OpenLayers website:
 https://openlayers.org/en/latest/examples/arcgis-tiled.html

When run in the Chrome browser, the OL 5 client gets cross-origin read
blocking (CORB) errors, reported in the developer’s console:

Cross-Origin Read Blocking (CORB) blocked cross-origin response
https://tiles.arcgis.com/tiles/hGdibHYSPO59RG1h/arcgis/rest/services/MassGIS_Basemap_Detailed_Features/MapServer/export?F=image&FORMAT=PNG32&TRANSPARENT=true&SIZE=256%2C256&BBOX=-71.103515625%2C42.275390625%2C-71.015625%2C42.36328125&BBOXSR=4326&IMAGESR=4326&DPI=90
with MIME type text/html. See
https://www.chromestatus.com/feature/5629709824032768 for more details.

The layer also fails to render when the sample client is run in Firefox,
IE, Edge, and Opera.

I checked the developer’s console in Firefox, and there no CORB errors are
reported. Looking at the responses to the requests for tiles in the
‘Network’ tab, I see the following:

<html>

<body>

<h2>Error</h2>

<div class=”restbody”>

<h3>Operation not supported.</h3><br/>

<b> Code: <b>404<br/><br/>

</div>

</body>

</html>

So, in spite of the lack of an error message in the console, it’s clear
that the server isn’t sending tiles back in response to requests.

Due to the big changes in the OpenLayers API between versions 2 and 3, my
first hypothesis is that I’ve not correctly “translated” my OL 2 code into
OL 3/4/5.

This having been said, it’s not clear to me what a “correct” translation
might look like – the sample on the OL site noted above is the only thing
I’ve been able to find to use as a model.

If anyone can shed light on what I might be doing wrong here, it would be
much appreciated.

Thanks and best regards,

Ben

*Benjamin Krepp*  |  Chief GIS Programmer/Analyst

CENTRAL TRANSPORTATION PLANNING STAFF

857.702.3670  | *bkrepp at ctps.org <bkrepp at ctps.org>*

www.ctps.org

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*Please be advised that the Massachusetts Secretary of State considers
e-mail to be a public record, and therefore subject to the Massachusetts
Public Records Law, M.G.L. c. 66 § 10. *
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-- 

Alex G Rice
rice.guido at gmail.com
+1 505-603-5639

-- 
*Please be advised that the Massachusetts Secretary of State considers 
e-mail to be a public record, and therefore subject to the Massachusetts 
Public Records Law, M.G.L. c. 66 § 10. *
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