What does it mean when a web service is asynchronous? Is this only used when you call it with Ajax and you have a part on your page that refreshes when the web service is done? Thank you.
I know this is an old topic, but whether a web service is synchronous or asynchronous depends on the design of the web service and has nothing to do with Ajax. An asynchronous web service transaction proceeds like this:
The client calls the web service. In the call the client sends a callback end point implemented as a service by the client.
The web service returns a "message received" reply.
...
(Some other processing occurs)
...
The web service completes its task, then calls the callback endpoint provided by the client.
The client callback replies with message received.
See Developing Asynchronous Web Services or How to: Create Asynchronous Web Service Methods
The question is whether it's the web service that's asynchronous, or your access to it. In the context of a web page, it's more likely that the service is synchronous, but that it is being accessed asynchronously.
Most likely, the service is being called via AJAX. The call is made to the service, and the page then continues. When the response comes in, either the success or the failure functions are executed, asynchronously.
Synchronous means that you call a web service (or function or whatever) and wait until it returns - all other code execution and user interaction is stopped until the call returns. Asynchronous means that you do not halt all other operations while waiting for the web service call to return. Other code executes and/or the user can continue to interact with the page (or program UI).
So, I would not say that the web service itself is asynchronous, I would say that your ajax call to the service is asynchronous.
When you call synchronous web service the service processes the request and return HTTP status code 200 OK (1) if everything went as expected, or error 4xx. The call is blocked while processing and the request and can take significant time.
When web service is asynchronous the main difference is that call should return instantly with HTTP 202 ACCEPTED (2) which means that request is taken in queue but not processed yet.
(1) 200 OK http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.2.1
(2) 202 ACCEPTED http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.2.3
An asynchronous web service allows a client to submit a request, process the request and respond to the client after a given time -- the client would not block all activity on receiving a response.
Comparatively, a web service that is synchronous would provide a client directly with a response, expecting the client to block all activity until a response is returned. In this case the web service would limit the client to process requests one at a time.
Related
I am trying to do a POC where i need to invoke a Stateful SOAP webservice . I need to do a login call first to SOAP webservice and get the session id(or cookie or something like that) and use the session id for making subsequent calls to the webservice . I want to know if there is any sample stateful SOAP webservice hosted on the internet for which i can generate the client and try invoking the webservice to verify Stateful operation. Any other pointers on how i can do this is also very welcome.
If this POC is successful we will be invoking a Stateful SOAP webservice hosted by one of our vendors and we will be using a TIBCO BW client to call the SOAP webservice.
You can invoke the WebServiceDefinitionLanguage from the WSDL attached in the link It brings encouraging quotes.
You may use SOAP activity in BW or import the WSDL as a resource first and then use any SOAP or web service activity.
Check this java project in github is a multi cloud java project that invokes WebServices and Rest services from many Cloud providers and Many sites. It gives you an idea on how to do it.
Of course in BW is really easy to do it. Basically: start activity, SOAP activity, log, call subprocess, catch errors, end process.
Stateful or Stateless SOAP webservice call is just like any another web-service call. In your case, since you have to get the response(i.e. receiving token) of the first webservice call and use it in the subsequent calls, I think you should focus on how would you cache the cookie/token that you receive from the first call. Also, if there is an expiry associated to the life of the token received in your response, work on the technique of refreshing the token for which the SOAP API provider will have to provide you an token expiry interval.
I have a chat web application and I want it to work offline. For this I use progressive web apps features (Service Workers) to use cache to get the shell app and the messages already loaded.
What I want to do is to be able to make a post message when I'm offline and let the service worker handle the connection issues (i.e.: keep the message somewhere till where are offline and as soon as we are online send the Post message).
I want to use Service Worker because I also want to send the message if the user as left the web app after posting a message with no connection.
What is the best API to use for this?
I saw the background sync API but it is not standard and it doesn't seem to be updated for almost 2 years.
If there is a way to do this in a manner that the client (the web app) is totally unaware of this mechanism it would be cool.
What I mean by that is I would like my app just do a
fetch("/message", {method : "post", body : {content : "hey there"})
And then the Service Worker just intercept the fetch, if we are online then it just send the fetch, but if we are offline it "wait" for the connection to be up again and then send the post.
I wonder if there is an event listener, available in the service worker, that will be activated when the connection change from offline to online. This way I should be able to store the request in indexDB when offline and then send the post when online.
I saw the navigator.onLine but it is not an event :(
Based from this post, you may use a Service Worker in running the app in the background either via its push event handler (triggered via an incoming push message), or via its sync event handler (triggered by an automatic replay of a task that previously failed).
You may check the Offline Storage for Progressive Web Apps documentation for storing data offline:
For URL addressable resources, use the Cache API (part of service workers).
For all other data, use IndexedDB (with a promises wrapper).
You can cache static resources, composing your application shell (JS/CSS/HTML files) using the Cache API and fill in the offline page data from IndexedDB.
I'm trying to create restful microservice.
So I have a client service and server service.
Client service wants to create and update some entitites via http with rest. And the server provides the service for that.
The client have a persitent state. Part of that state is entities that he created. So he need to store 'ids' of entities that server created for him.
One problem that I'm thinking about is what to do when client failed when server was executing create operation. So client executes /entities/ POST
Server gets the request and replies with {id = n, ...}, but client already dead.
So now client can't restore it's state after fail.
I know of course that I can do that without using http with persistent message queue and request-reply pattern (via rabbitmq or something else) but I really wan't to create a restful service.
PS And of course It can be achieved with storing storing client state on server one way or another. Like using some link to client in entity.
I wish to create a one way integration between a system that can only send SOAP requests and a system that can only respond to REST requests. I know very little about web services as it is not my specialty. But the source system can be configured to send a SOAP request to any WSDL and the 'destination' system has a REST API and provides me with a simple URL to which I can send requests to 'trigger' an event.
I would have thought it would be simple to find some web service that can receive the SOAP requests from the source system, which would be a simple request to send a REST request to the destination system.
Like some sort of intermediary, not actually converting the requests directly but forming a similar function. Is there anything that can do this?
In lightweight SOAs I've seen many designs that have a Web Server receives Client requests and send responses that are dependent upon responses from other services. I've also seen this done incorrectly resulting in unacceptable latency issues.
For Example:
Assume:
We have 1 Web API Server and 1 Service A API.
Web Server performs basic User Auth and other User functionality.
Service A performs database operations.
ZeroMQ (ZMQ, 0MQ, etc) REQ/RES user for service messaging
Work Flow:
Client makes request to Web API Server API.
Web Server performs database operations (auth etc).
Web Server makes request to Service A API.
Service A performs database operations.
Service A responds with data to Web Server.
Web Server receives response and sends response to client.
This pattern is different from the typical offline message queue processing work flow. As well it includes a request to a single service (A)
While trying to maintain separate system services is this a correct usage pattern with ZeroMQ?
I'm trying to figure out if ZeroMQ can be used to make service requests and send the results to client web service requests without significant performance issues.