topic Re: How do I evaluate if a web service is running? in ArcGIS JavaScript Maps SDK Questions

How do I evaluate if a web service is running?

ChrisSergent — Mon, 11 May 2015 15:02:41 GMT

Before my code runs, I would like to evaluate if a web service is running. How would I do that in JavaScript?

Re: How do I evaluate if a web service is running?

ToddBlanchette — Sun, 12 Dec 2021 05:35:35 GMT

You can try and catch the error:

<script type="text/javascript">
      var gmap;
  
      function initialize() {
        gmap = new GMap2(document.getElementById("map_canvas"));
        gmap.enableScrollWheelZoom();
        gmap.setCenter(new GLatLng(0, 0), 2);
  
        new esri.arcgis.gmaps.DynamicMapServiceLayer("http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Demographics/Unknown_Map_Service/MapServer", null, 0.75, mapServiceLoaded);
      }
  
      function mapServiceLoaded(layer, error) {
        if (error) {
          // alert the error message to the user and return
          alert("Error " + error.code + ": " + (error.message || (error.details && error.details.join(" ")) || "Unknown error" ));
          return;
        }

        // add layer to the map
        gmap.addOverlay(layer);
      }
    </script>

Cheers,

Todd

Re: How do I evaluate if a web service is running?

SteveCole — Mon, 11 May 2015 15:22:29 GMT

I suppose one could use the map's layer-add-result event to populate a boolean variable to log each layer's status. A caveat being that this would only capture any initial efforts to add the layer. If something goes south after map load, this wouldn't help.

Re: How do I evaluate if a web service is running?

ChrisSmith7 — Sun, 12 Dec 2021 05:35:37 GMT

Chris,

A map service that doesn't exist, or is not running, should return a 500. Would something like this work for you?

$.ajax(serviceURL, {
   type: "POST",
   statusCode: {
      500: function (response) {
         alert('500 error');
      }
   }, success: function () {
      alert('success');
   },
});

Re: How do I evaluate if a web service is running?

ChrisSmith7 — Sun, 12 Dec 2021 05:35:40 GMT

Just to clarify, when I'm referring to the map service throwing a 500 when it doesn't exist, this is assuming the server does exist, e.g. myMapServer/arcgis/rest/services/base_services/1234_does_not_exist/MapServer

Throws a 500 because the server page will still exist (just indicating a status of 500 and that the map service does not exist). I verified in Fiddler the 500 code is still given. You could also add a case for a 404, if needed, so if the server was completely not found:

$.ajax(serviceURL, { 
   type: "POST", 
   statusCode: { 
      404: function (response) { 
         alert('404, not found'); 
      },
      500: function (response) { 
         alert('500 error'); 
      } 
   }, success: function () { 
      alert('success'); 
   }, 
});

Re: How do I evaluate if a web service is running?

AndyGup — Mon, 11 May 2015 15:57:24 GMT

Hey Chris, just some additional clarification for others that may come across your question. HTTP 404 error means not found - no page exists at a particular URL. Where an HTTP 500 error means something happened when the server tried to process the request and it failed. 500 errors can happen for a variety of reasons. Usually there is some additional indication in the 500 error message from ArcGIS Online giving a hint. One example might be you tried to add an attachment to a non-existent ObjectId in a feature service.

Re: How do I evaluate if a web service is running?

ChrisSmith7 — Mon, 11 May 2015 16:23:00 GMT

Chris mentioned about checking it before his code runs - I wasn't too sure if he meant before his mapping app loaded, or before some bit of code executed in the map app. If it's the latter, it looks like Todd has a better resolution in catching the error.

Re: How do I evaluate if a web service is running?

ChrisSergent — Mon, 11 May 2015 18:47:32 GMT

Okay, I have my service stopped right now at: test/StreetSignTest (FeatureServer)

The URL does not provide an error by opening the page; it just shows up as blank.

Re: How do I evaluate if a web service is running?

ChrisSergent — Mon, 11 May 2015 18:48:43 GMT

I just wanted to evaluate the URL. All the information should exist independent of my application running, so I wanted to check if I could see any information before consuming the service.

Re: How do I evaluate if a web service is running?

ChrisSergent — Mon, 11 May 2015 18:49:39 GMT

I'm currently not receiving any error messages when I paste in the URL for a stopped service. Any ideas?

Re: How do I evaluate if a web service is running?

ChrisSergent — Mon, 11 May 2015 18:55:22 GMT

I am currently not receiving any errors when I pasted in the URL for the stopped web service. Any ideas why?

Here is the stopped service location: test/StreetSignTest (FeatureServer)

Re: How do I evaluate if a web service is running?

ChrisSmith7 — Mon, 11 May 2015 18:55:57 GMT

I'm unsure, but could you check by pulling the first layer?

http://maps.decaturil.gov/arcgis/rest/services/test/StreetSignTest/FeatureServer/0

Re: How do I evaluate if a web service is running?

RobertScheitlin__GISP — Mon, 11 May 2015 18:58:51 GMT

Chris,

Just checking the html return from that url does not show the error but if you use http://maps.decaturil.gov/arcgis/rest/services/test/StreetSignTest/FeatureServer?f=json Then you will see error code 500

Re: How do I evaluate if a web service is running?

AndyGup — Mon, 11 May 2015 18:59:17 GMT

Yes, my recommendation is to use the layer and return json: http://maps.decaturil.gov/arcgis/rest/services/test/StreetSignTest/FeatureServer/0?f=json.

If you just hit the feature service it returns a 200. Not sure why, but that's why you aren't getting an error.

Re: How do I evaluate if a web service is running?

ChrisSergent — Mon, 11 May 2015 19:19:11 GMT

I think that is the right way to go. I got the following message when I tried that layer:

Error: Error handling service request : Could not find a service with the name 'test/MapServer/StreetSignTest' in the configured clusters. Service may be stopped or ArcGIS Server may not be running.

Code: 500

So, do you or Andy Gup know what I should write to evaluate an error of 500 in my code for that URL? I have looked up how to read JSON responses, but I can find code to evaluate this.

Re: How do I evaluate if a web service is running?

ChrisSergent — Mon, 11 May 2015 19:22:00 GMT

Exactly. I just want to know how to read the value of 500 from my code. Even an alert would help, as I want to exit my code if this code exists.

Re: How do I evaluate if a web service is running?

RobertScheitlin__GISP — Sun, 12 Dec 2021 05:35:43 GMT

Chris,

Use esriRequest.

        var requestHandle = esriRequest({
          url: "http://maps.decaturil.gov/arcgis/rest/services/test/StreetSignTest/FeatureServer/0",
          content: {
            f: 'json'
          },
          handleAs: "json"
        });

        requestHandle.then(function(lyrJSON, io){
          console.info(lyrJSON);
        }

Re: How do I evaluate if a web service is running?

ChrisSergent — Mon, 11 May 2015 20:12:27 GMT

This one I could not get to work. It just errored out if a web service was not running but did not write to the console log.

Re: How do I evaluate if a web service is running?

RobertScheitlin__GISP — Sun, 12 Dec 2021 05:35:46 GMT

Chris,

OK, I forgot you were looking for the error.

Try this:

      requestHandle.then(
        function(lyrJSON, io){  
          console.info(lyrJSON);  
        }, function(err){
          console.info(err);
        }
      );

Re: How do I evaluate if a web service is running?

ChrisSergent — Sun, 12 Dec 2021 05:35:48 GMT

I might have modified it incorrectly; here is what I updated and still get an error with a stopped web service:

var requestHandle = esriRequest({ 
        url: "http://maps.decaturil.gov/arcgis/rest/services/test/StreetSignTest/FeatureServer/0", 
        content: { 
            f: 'json' 
        }, 
        handleAs: "json" 
    }); 

    requestHandle.then(
        function (lyrJSON, io) {
            console.info(lyrJSON);
        }, function (err) {
            console.info(err);
        }
      );