Is there any times limitation or frequency limitation for an EWS Client connecting to EWS server

[sesa197614_brid]

Dear:

Is there any times limitation or frequency limitation for an EWS Client connecting to EWS server?

In some case, we need create a user-customized API, which will be used to poll data from SBO and then convert to other data format such as XML string.

If I have to create connection between Ews client and Server for every data polling procedure, then the create connection action will be very frequent.

I am just afraid there may be any limitation of SBO to allow client connecting with it. please help clarify.

-Austen Yin

[Adam_Summers]

Hi Austen Yin,

For me this is not a straight forward answer, there are lots of potential complications with creating services which poll an SBO EWS Server.

Before you begin coding, I'd recommend you take a look at the EcoStruxure Web Services Serve Performance Integration Guide produced by the Buildings StruxureLab, this will help understand the flow of EWS data and delays in which you should expect depending on the destination of the data you want to retrieve. Consider if your connector will talk to an Enterprise Server, is the value in the Enterprise Server or are you then going to talk to an Automation Server, which may have to talk to a field bus to retrieve a live value?

There is also a Big Data TVDA which discusses using Trend Logs and an Automation Server as an aggregator for big data applications.

https://community.se.com/servlet/JiveServlet/previewBody/14687-102-1-11526/EWS%20Serve%20Perform…

https://ecobuilding.schneider-electric.com/search#documentUUID/7615d952-2ae9-4148-bf2d-a7109f13c2a2/...

Those are important to understand more about how EWS will perform, from that, specifically to SmartConnector development, a couple of things I'd note is;

1) Make sure you find a way to cache and re-use your client object where possible if you plan on making many calls. EWS Servers use a cookie for client connections and I once wrote a Connector which created a new client each time, eventually after significant polling the EWS Server crashed as it could not issue more sessions!

2) Consider if your connector could be configured to distribute communication to Automation Servers rather than placing load on the ES if you don't follow the principle of mirroring values to the ES.

If you're looking to provide some kind of API over the top of EWS, you may want to consider waiting for the next release of SmartConnector. The team are working on deploying RESTful API services over the top of EWS servers and I understand you'll then also be able to leverage the framework over the top of any EWS server you create too. That would save you a lot of effort and if what it does out of the box doesn't work, maybe you could extend it to give you the functionality you need. Some time ago I already created a connector which did this (although not as well as what you'll get in the core of SmartConnector very soon). I have a processor which allows you to get JSON and XML results from EWS Servers in a restful manner. If you wanted to take a look at that I'd be happy to share the manual and processor with you. I can create a license for you valid for 30 days so you can see what it does. - Let me know if this will help you.

I'm sure the rest of the community might have some experience to share too

Adam

[sesa180908_brid · Accepted solution]

The short answer is “No”. If you are using SmartConnector’s EwsClient library there are no client side restrictions.  Those types of restrictions typically reside on the “server side” (SBO, PME, etc).  One tip though.  If you are using EwsClient to communicate with SBO, you should be careful how often you instantiate the client class.  Each time you instantiate the class it authenticates to SBO with the credentials you provided and since SBO has only a finite number of client connections available you could consume all connections in SBO pretty quickly if you’re not careful.  So if you need to make numerous calls, you should reuse your client instance.  You will additionally gain the benefit of SBO’s support for an auth cookie so each call won’t need to be authenticated (that would actually happen for you automatically anyway with the client but I figured I’d mention it anyway).  And as always, remember to call Dispose on EwsClient since it is IDisposable.

As Adam stated in his reply, SmartConnector 2.2 will include RESTful services for any EWS server – be it the internal SmartConnector EWS Server or an external one based on the SOAP EWS protocol (SBO for example). This API will also include authentication (OAuth) and throttling to ensure that the underlying server is not overwhelmed.  If you’re interested in demoing this, we can make a Beta version available to you. Release is currently expected towards the end of Q3 next month.

[sesa197614_brid]

Thanks Adam:

I am still not clear to used the session to keep the connection status for a EwsClient, it would be possible under below two situation

1. By using the SmartConnector framework, I may just never try the session, is it the version 2.0.11 supported since I am still use this one? Is there any sample to show how to use session?

2. To meet some simple requirement, I may only need use some of the library files of Mongoose to create my own API(just a dll file) for others to integrate with SBO, then I even not install the smartConnector at all, how could I create session in this way?

Cheers

Austen Yin

[JeffBowman]

Austen,

1. I would definitely update to the latest revision of SmartConnector first to get access to the latest functionality. This is 2.1.83. I don't know if there are any samples on how to use sessions. But I think the general idea would be to NOT to instantiate a new EwsClient for every request.. and as Mark said, make sure to dispose of the client when you are done. How often do you think you will be sending requests to SBO?
2. Although it is surely possible to create your own API using the EWS client library. We would not recommend doing this for a couple reasons.
   • Being released in version 2.2 (within the next month or so I believe). Is built in REST web services for EWS (as Adam mentioned above). This effectively converts easy to use REST web service calls to EWS behind the scenes, it can be used to extract data from SBO, or from a SmartConnector EWS server. And in the case of the SmartConnector EWS server, it allows for full CRUD.
   • Using just the EWS Client library, you don't have access to all the helper classes for reading/writing values/alarms/subscriptions/trends. These classes were written to simplify the execution and management of these types of reads/writes. Effectively the EWS Client logic is abstracted out, so you only need to focus on passing in the IDs you want to read/write and don't need to deal with error handling etc..
   • What exactly are these 'simple requirement' that you are referring to?

-Jeff