In the apache brooklyn web interface we would like to display some content for the sytsem managers. The content is too long to be served as a simple sensor value.
Our idea was to create a task and write the content into the output stream of the task, and then offer the REST based URL to the managers like this: /v1/activities/{task}/stream/stdout (Of course the link masked with some nice text)
The stream and task is created like this:
LOG.info("{} Creating Activity for ClusterReport Feed", this);
activity = Tasks.builder().
displayName("clusterReportFeed").
description("Output for the Cluster Report Feed").
body(new Runnable() {
@Override
public void run() {
//DO NOTHING
}
}).
parallel(true).
build();
LOG.info("{} Task Created with Id: " + activity.getId(), this);
Entities.submit(server, activity).getUnchecked();
The task seems to be created and the interraction works perfectly fine. However when I want to access the tasks output stream from my browser using a prepared URL I get the error that the task does not exist.
Our idea is that we are not in the right Management/Execution Context. The Web page is running in an other context compared to the entities and their sensors. How can we put a task so that it's visible for the web consoles context also.
Is it possible to write the content into a file and then offer it for download via Jetty(brooklyns web server)? That would be a much simpler way.
Many tasks in Brooklyn default to being transient - i.e. they are deleted shortly after they complete (things like effector invocations are by default non-transient).
You can mark your task as non-transient using the code below in your use of the task builder:
.tag(BrooklynTaskTags.NON_TRANSIENT_TASK_TAG)
However, note that (as of Brooklyn version 0.9.0) tasks are kept in-memory using soft references. This means the stdout of the task will likely be lost at some point in the future, when that memory is needed for other in-memory objects.
For your use-case, would it make sense to have this as an effector result perhaps?
Or could you write to an object store such as S3 instead? The S3-approach would seem best to me.
For writing it to a file, care must be taken when used with Brooklyn high-availability. Would you write to a shared volume?
If you do write to a file, then you'd need to provide a web-extension so that people can access the contents of that file. As of Brooklyn 0.9.0, you can add your own WARs in code when calling BrooklynLauncher (which calls BrooklynWebServer).