How to connect to locahost OpenStreetMap tiling server ? (Failed to obtain image tile ERROR)

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Štěpán Křivanec

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Mar 12, 2015, 3:33:37 PM3/12/15
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Hello!

Following guide at switch2osm.org I was able to get my own OSM tile server running.
(Ubuntu linux 14.04, Apache 2.4.7, Cesium-1.6, node-v0.12.0, postgresql-9.3-postgis-2.1, osm2pgsql 0.87.2-dev, Mapnik 2.2.0)

I did have verify state of my OSM tile server by using webrowser. For example at http://localhost/osm_tiles/0/0/0.png I get small picture od world. Evertthing seems to be working at server side to me.

Cesium connected to online source of maps works fine as well.


Problem pops up, when i try connect Cesium to local OSM server. In Firefox console I get this error:

"An error occurred in "": Failed to obtain image tile X: 1 Y: 1 Level: 1." Cesium.js:381:25514
"An error occurred in "": Failed to obtain image tile X: 1 Y: 0 Level: 1." Cesium.js:381:25514
"An error occurred in "": Failed to obtain image tile X: 0 Y: 0 Level: 1." Cesium.js:381:25514
"An error occurred in "": Failed to obtain image tile X: 0 Y: 1 Level: 1." Cesium.js:381:25514


I'm already stuck with this problem for quite a few days. Here is what I have tried and found out so far:

  • Analyse Apache logfiles.

My DEFAULT_ERRORLOG is set to "logs/error_log", but there is no such file on my system. With documentation on apache.org i was able locate /var/log/apache2/error.log file.

Per request a identical line pops up in there :

debug: init_storage_backend: initialising file storage backend at: /var/lib/mod_tile
I was not able to find any difference in logs on Apache side between request from Cesium and webrowser.

  • Setting Apache and Cesium to run on same port

I was not able to achieve this. Cesium does not like that. Spits at me angrily this:

Error: Port 8080 is already in use, select a different port.
Example: node server.js --port 8081
{ [Error: listen EADDRINUSE] code: 'EADDRINUSE', errno: 'EADDRINUSE', syscall: 'listen' }

I achieved this by changing port numbers from 80 to 8080 in files /etc/apache2/ports.conf and /etc/apache2/sites-enabled/000-default.conf .


  • Set Cross Origin Resource Sharing (CORS) on Apache

Maybe I screwed up somewhere in the proces. Here is what I did:

Enabled mod_headers in Apache by

a2enmod headers

Changing Apache configuration file /etc/apache2/apache.conf  by adding line

Header set Access-Control-Allow-Origin "*"

to existing sections <Directory />, <Directory /var/www/> and creating own section <Directory /var/lib/mod_tile/> .

Did not forget obligatory reloading server by

sudo service apache2 reload

After that I have been left disappointed by result: Still getting the same error.


Pretty please: Do anyone have idea what am I doing wrong?


Here is sourcecode of webpage I'm running Cesium from:

<!DOCTYPE html>
<html lang="en">
<head>
<!-- Use correct character set. -->
<meta charset="utf-8">
<!-- Tell IE to use the latest, best version (or Chrome Frame if pre-IE11). -->
<meta http-equiv="X-UA-Compatible" content="IE=Edge,chrome=1">
<!-- Make the application on mobile take up the full browser screen and disable user scaling. -->
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, minimum-scale=1, user-scalable=no">
<title>Hello World!</title>
<script src="../Build/Cesium/Cesium.js"></script>
<style>
  @import url(../Build/Cesium/Widgets/widgets.css);
  html, body, #cesiumContainer {
      width: 100%; height: 100%; margin: 0; padding: 0; overflow: hidden;
  }
</style>
</head>
<body>
<div id="cesiumContainer"></div>
<script>

//Initialize the viewer widget with several custom options and mixins.
var viewer = new Cesium.Viewer('cesiumContainer', {
//Hide the base layer picker
baseLayerPicker : false,
//Use OpenStreetMaps
imageryProvider : new Cesium.OpenStreetMapImageryProvider({
    url : 'http://localhost/osm_tiles/'
  //url : '//a.tile.openstreetmap.org/'
}),

// Show Columbus View map with Web Mercator projection
//    mapProjection : new Cesium.WebMercatorProjection()
});

//Add basic drag and drop functionality
viewer.extend(Cesium.viewerDragDropMixin);

//Show a pop-up alert if we encounter an error when processing a dropped file
viewer.dropError.addEventListener(function(dropHandler, name, error) {
console.log(error);
window.alert(error);
});
</script>
</body>
</html>



Scott Hunter

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Mar 12, 2015, 4:18:12 PM3/12/15
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Check to make sure your CORS header is being properly set.


You should see:

Access-Control-Allow-Origin: *

in the response headers.

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Štěpán Křivanec

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Mar 13, 2015, 11:20:03 AM3/13/15
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Using
I don't get line saying
Access-Control-Allow-Origin: *

here is What I get:
* Hostname was NOT found in DNS cache
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0*   Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 80 (#0)
> GET /osm_tiles/0/0/0.png HTTP/1.1
> User-Agent: curl/7.35.0
> Host: localhost
> Accept: */*
>
< HTTP/1.1 200 OK
< Date: Fri, 13 Mar 2015 15:10:19 GMT
* Server Apache/2.4.7 (Ubuntu) is not blacklisted
< Server: Apache/2.4.7 (Ubuntu)
< ETag: "337ab9a3fb2a307a148786460b7b973b"
< Content-Length: 7898
< Cache-Control: max-age=1258
< Expires: Fri, 13 Mar 2015 15:31:17 GMT
< Content-Type: image/png
<
{ [data not shown]
100  7898  100  7898    0     0  1274k      0 --:--:-- --:--:-- --:--:-- 1542k
* Connection #0 to host localhost left intact


in configuration file /usr/local/etc/renderd.conf
tiles location is set to:
TILEDIR=/var/lib/mod_tile

Based on this I was thinking for this directory is needed to set CORS in Apache2.
So I added following lines to /etc/apache2/apache2.conf file :

<Directory /var/lib/mod_tile/>
#CORS settings: to allow Cesium get maptiles from mod_tile & renderd Apache plugins
    Header set Access-Control-Allow-Origin "*"
    Options Indexes FollowSymLinks
    AllowOverride None
    Require all granted
</Directory>


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