问题
I'm after some advice on polling an external web service every 30 secs from a Domino server side action.
A quick bit of background...
We track the location of cars thru the TomTom api. We now have a requirement to show this in our web app, overlayed onto a map (google, bing, etc.) and mashed up with other lat long data from our application. Think of it as dispatching calls to taxis and we want to assign those calls to the taxis (...it's not taxis\ calls, but it is similar process). We refresh the dispatch controllers screens quite aggressively, so they can see the status of all the objects and assign to the nearest car. If we trigger the pull of data from the refresh of the users screen, we get into some tricky controlling server side, else we will hit the max allowable requests per minute to the TomTom api.
Originally I was going to schedule an agent to poll the web service, write to a cached object in our app, and the refreshing dispatch controllers screen pulls the data from our cache....great, except, user requirement is our cache must be updated every 30secs. I can create a program doc that runs every 1 min, but still not aggressive enough.
So we are currently left with: our .net guy will create a service that polls TomTom every 30secs, and we retrieve from his service, or I figure out a way to do in Domino. It would be nice to do in Domino database, and not some stand alone java app or .net, to keep as much of the logic as possible in one system (Domino).
We use backing beans heavily in our system. I will be testing this later today I hope, but would this seem like a sensible route to go down..?: Spawning threads in a JSF managed bean for scheduled tasks using a timer ...or are their limitations I am not aware of, has anyone tackled this before in Domino or have any comments?
Thanks in advance,
Nick
回答1:
Check out DOTS (Domino OSGi Tasklet Service): http://www.openntf.org/internal/home.nsf/project.xsp?action=openDocument&name=OSGI%20Tasklet%20Service%20for%20IBM%20Lotus%20Domino
It allows you to define background Java tasks on a Domino server that have all the advantages of agents (can be scheduled or triggered) with none of the performance or maintenance issues.
回答2:
If you cache the data in a bean (application or session scoped). Have a date object that contains the last refreshed date. When the data is requested, check last cached date against current time. If it's more than/equal to 30 seconds, refresh data.
回答3:
A way of doing it would be to write a managed bean which is created in the application scope ( aka there can only be one..). In this managed bean you take care of the 30sec polling of the webservice by good old java webservice implementation and a java thread which you start at the creation of your managed-bean something like
public class ServicePoller{
private static myThread = null;
public ServicePoller(){
if(myThread == null){
myThread = new ServicePollThread();
(new Thread(myThread)).start());
}
}
}
class ServicePollThread implements Runnable(){
private hashMap yourcache = null;
public ServicePollThread(){
}
public void run(){
while(running){
doPoll();
Thread.sleep(4000);
}
}
....
}
This managed bean will then poll every 30 seconds the webservice and save it's findings in a hashmap or some other managed-bean classes. This way you dont need to run an agent or something like that and you achieve when you use the dispatch screen to retrieve data from the cache.
Another option would be to write an servlet ( that would be possible with the extlib but I cant find the information right now ) which does the threading and reading the service for you. Then in your database you should be able to read the cache of the servlet and use it wherever you need.
回答4:
As Tim said DOTS or as jjtbsomhorst said a thread or an Eclipse job.
I've created a video describing DOTS: http://www.youtube.com/watch?v=CRuGeKkddVI&list=UUtMIOCuOQtR4w5xoTT4-uDw&index=4&feature=plcp
Next Monday I'll publish a sample how to do threads and Eclipse jobs. Here is a preview video: http://www.youtube.com/watch?v=uYgCfp1Bw8Q&list=UUtMIOCuOQtR4w5xoTT4-uDw&index=1&feature=plcp
来源：https://stackoverflow.com/questions/9702743/30-sec-periodic-task-to-poll-external-web-service-and-cache-data