Latest Contributions by DavidMartin

Thanks Robert. That clears it up nicely! ... View more

That's probably my confusion, rather than yours! I'm just after a normal WAB widget that will enable me to show/hide layers on startup in a 2D Web App, as specified by custom URL querystring parameters. I may be looking at the wrong reference area? ... View more

Great! Thanks Robert. Would the widget's startup method still be the place to put such code? (I see from this site that the method may be deprecated: Widget | API Reference | ArcGIS API for JavaScript 4.7  And if my url parameters (that specify the layers to show) first require mapping to layer IDs (because the calling system has different names for them), would you have any thoughts as to whether it would be better to maintain such a mapping (3rd party layer name : Web Map Layer ID) in a config file or a feature service? In either case, does the ArcGIS API offer a quick way of handling such custom config data? ... View more

Now I get it. I hadn't fully appreciated the extent of the event distribution role that Kafka was performing in allocating events with a common TRACK_ID to an individual server, with failover for resilience. It's presumably a reason to be careful about how (/if?) you populate TRACK_ID on your events, as unless you actually need to maintain track state, it could otherwise reduce the effectiveness of event distribution in a multiple-machine site? Thank you, rsunderman-esristaff‌. I couldn't have asked for better support. ... View more

Again RJ, thanks for a very comprehensive reply. (And sorry for calling you Josh before!) Just one point has confused me a little. In suggesting use of a Load Balancer (LB) to act as a single endpoint for inputs that are actively sent to GeoEvent Server (such as http requests - with input data packaged in a POST / GET), I was imagining that the LB would distribute those requests across machines in a multiple-machine site. As all machines in such a site share the same configuration, any one of them can presumably handle the input? Your suggestion that a "sticky session" might be required leads me to believe there might be a problem with my original understanding, and makes me wonder what the point would be of having the LB in the first place? I do appreciate, however, that where stateful processing is required (Track Gap Detection, Incident Detection, and spatial operations such as ENTER and EXIT), use of an LB in this fashion would not be suitable, as multiple-machine sites don't share a track's last-known state across machines.   My summary understanding: A multiple-machine GeoEvent Server site offers: - shared configuration (input/output connectors, processors etc) - provided by Zookeeper - event distribution - provided by Kafka ... but does NOT offer: - shared track state (a site-level understanding of a track's last-known state) - a single endpoint to which inputs can actively be sent ... View more

Actually, I have another...:-) If you’re using an input like a JSON REST receiver, or the TCP/Text input, to push data to GeoEvent, then the burden is on the data provider to specify which machine, endpoint, port, (etc.) to push the data to. I take it from this that a multiple-machine site exposes no single endpoint for receipt of an http request (whether POST or GET)? If that's the case, then I guess a suitable load balancer needs to be added up-front which can health-check each machine in order to distribute such requests only to healthy ones? Which could just as easily be done with a suite of single-machine sites, for inputs of this nature, provided no gap detection, geo-fencing or similar is required? For "guaranteed" receipt, the onus would then just remain on the sender (or middleware) to re-send if no 200 OK response is received from GeoEvent Server? ... View more

Thank you Josh - I couldn't have asked for a more comprehensive reply! Just 2 further questions arise from your response: 1/ Is there a scheduled release date (or approximate ETA) for the 10.6 patch? 2/ In a multiple-machine site (minimum 3 nodes), should we expect to have to license each and every node with a GeoEvent Server license? (i.e. pay for 3 licenses) ... View more

Thanks for the useful pointers. The conversation (at 10.6) focuses on SCALABILITY to cope with: high message volumes resulting from accumulation from multiple sources where the recommendation appears to be to use multiple single-machine sites so that different sites can consume messages from different sources high message volumes from large single sources where the recommendation appears to be to use a multiple-machine site (perhaps waiting first for a patch!) so that the messages can be load-balanced across machines However, what about solution AVAILABILITY, which could manifest as a requirement even when consuming very low message volumes, but where the business criticality of the solution is high? I assume that this is best met using a multiple-machine site (once patched)? There appears to be a recommendation, however, that multiple-machine sites should have a minimum of 3 GeoEvent Servers. This could feel a bit excessive where message volumes are low. QUESTION 1: Is there a good reason why a multiple-machine site can't just have 2 GeoEvent Servers? Another caveat with a multiple-machine site appears to be that outputs cannot include Stream Services. As such, there will be a need to store geoevents prior to displaying them in a client, and the client will need to poll a feature service to retrieve them. QUESTION 2: Is that assumption correct? That then gives rise to the question of whether the spatiotemporal data store (with a potentially higher-cost, multi-node deployment) is overkill for low volume messages. QUESTION 3: Do you have any recommendations as to when to consider deployment of the spatiotemporal data store? (e.g. a threshold level of throughput). That's probably enough questions for one post... 🙂 ... View more

I see that the same question has in fact already been asked, but no answers as yet: HTTP POST form content type Input possible? ... View more

Hi Freddie, Thanks for your response. The issue was that I wanted some initialisation code to run at the point the tool was activated (prior to map interaction). A button enables code to run when it is clicked. A tool does not. Hence I was trying to activate the tool from the button (after the onclick code had run). I've since moved to alternative methods, but I'd be interested in any solution, for the future! ... View more

Ah - I hadn't been aware of that new functionality. A good introduction! So is it ILayerDescriptor (as opposed to ILayerDescription) that you need then? ArcObjects Help for .NET developers You can get an array of LayerDescriptors from a dataframe using IMapDescriptor interface. ArcObjects Help for .NET developers You can get an array of MapDescriptors (one for each dataframe) from the map using the IMxdServer interface. ArcObjects Help for .NET developers (Or you can get LayerDescriptors for the whole map from the IMxdServer interface directly) And to get a reference to an IMxdServer interface (which shouldn't require ArcGIS for Server), it looks like you can use IMxdServer.Start: ArcObjects Help for .NET developers Does that work? ... View more

You can't set Layer ID. It is pre-determined by the order of the layers in the document, and represents the layer's position in the TOC. Maintaining a unique reference to a layer always used to be a challenge for this reason, as if you insert a layer, then the layer ID of other layers could change. The layer name is not guaranteed unique either, as you can have several layers in an mxd all with the same name. Your best option used to be to hold onto a Layer object itself, "heavyweight" though that might be, although that of course depends on what you're actually trying to achieve. ... View more