I am working on a Windows service which needs to schedule tasks whenever one of it's web services is called. This could happen hundreds of times per second in a worst case scenario. The task needs to wait a period of time, typically a minute or two, then call a method passing a parameter.
We tried to build our own scheduler class to do this:
public void ScheduleTask<T>(TimeSpan delay, Action<T> task, T arg)
{
Thread.Sleep(delay);
threadPool.ExecuteAsync(task, arg);
}
But we figured this wouldn't be appropriate because we could theoretically end up with hundreds of Thread Pool threads all waiting. I am under the impression that there is a finite number of Thread Pool threads available and that this could potentially lock up the system.
I then turned to Quartz.NET and read on their features page that:
Job class instances can be instantiated by Quartz.NET, or by your application's framework.
and on page 3 of their tutorial that the Scheduler creates instances of your Job class (not you) and as such:
it does not make sense to have data-members defined on the job class as their values would be 'cleared' every time the job executes.
Feel free to yell at me, but how do I get a reference to my Job class instance before it executes so I can set a property on it?
The property is doing the job of a
parameter so i have no interest in it
after the Job has executed.
I also want to minimise the number of
objects it takes to acheive this to
keep my code neat and simple.
Finally, I seriously dislike using
Dictionaries so would prefer to avoid the JobDataMap object.
I don't understand exactly what your use case is and why you would need to set a property on the job, but to answer your question: to get access to your job before it executes you need to create a job listener (implement IJobListener). The job listener gets called just before the job gets executed, so you could set a property at that point.
Some links:
The documentation on job listeners
I wrote a blog post detailing the creation of listeners, here.
Related
In my locustfile I defined test_on_start and test_on_stop events to read a file needed for the test and to write detailed statistics in a CSV at the end of the test. when running in distributed mode, these events occur on the master, not the worker. I am assembling a list of detailed stats for each task in a task sequence and at the end of the test writing a CSV file when the test stops. I found this stackoverflow question which references a setup and teardown. I added these to my class User(HttpUser): but they appear to not be executed.
How can I mimic these events when the test is running on a worker in distributed mode?
Is there a better way?
I am using User on_start and on_stop already - my on_start calls a function to select a random user from a list which was created when the #events.test_start.add_listener is fired, which only happens on the master and not on the workers, so the worker doesn't have any user login data.
It seems counter productive to open the file, read it, select a user at random and close it every time the User on_start method is called. User on_start also sets up the iteration list [] which is where i store the times per task.
When the task sequence is done, meaning the last task is executed, i do a self.interrupt() which runs on_stop, which is where I take the iteration times, and put them into a second list, which is later written using the CSV module. maybe it would be better to just write the data to the CSV during on_stop
The setup/teardown for individual Users has been removed (because they were confusing, as it was run on the first instance of that User class, and when people set properties on that instance got very confused by the fact that later instances didnt get that). Tbh, I wish they had just been replaced by class methods...
The User still has on_start/stop methods though, and if you combine that with a flag it may be able to do what you want. Something like this:
class MyUser(HttpUser):
stopped = False
...
def on_stop(self):
if not MyUser.stopped:
MyUser.stopped = True
# write your csv
# this doesnt guarantee that all your Users are finished though.
https://docs.locust.io/en/stable/writing-a-locustfile.html#on-start-and-on-stop-methods
I am trying to create a Quartz scheduler using Java which will be able to call an API and pass in data.
I am totally new to Quartz but now I understand the Job concept and how to create one. I understand the trigger concept and how to trigger one
and I understand how the scheduler works.
What I am having difficult with is how can I pass in the information which is required to be passed to the API. I have an example of an API being called and the data is entered into the DB but the information has been hard coded into the class be passed into the JobDetails.
Ie. the user passes a message to the system which needs to be sent to the user in 12 hours and not before, so what i was planning was create a Job and a trigger in to set the execute time to 12 hours. How to do i pass the message into the scheduler? Where should this message be stored? Is what I am trying to do possible? Have i misunderstood what Quartz is capable of doing?
Thank you for your time. Any assistance would be greatly appreciated.
Take a look at JobDataMap. If you are creating a new job for each user action you can store the message in there which will be available during the execution.
JobDataMap Holds state information for Job instances.
JobDataMap instances are stored once when the Job is added to a scheduler. They are also re-persisted after every execution of jobs annotated with #PersistJobDataAfterExecution.
JobDataMap instances can also be stored with a Trigger. This can be useful in the case where you have a Job that is stored in the scheduler for regular/repeated use by multiple Triggers, yet with each independent triggering, you want to supply the Job with different data inputs.
The JobExecutionContext passed to a Job at execution time also contains a convenience JobDataMap that is the result of merging the contents of the trigger's JobDataMap (if any) over the Job's JobDataMap (if any).
In case you have a single job but for each user action you are creating a new trigger, you can follow the solution given here.
Third option will be, for each user action, persist the message and time to send email to the database. Have a job that runs periodically and scans through database for eligible records for which email has to be sent
I have a program, it loads a few tasks from a file prepared by user and start executing them according the scheduling shown in the file.
Example: taskFile.txt
Task1: run every hour
Task2: run every 2 seconds
...
TaskN: run every monday at 10:00
This first part is Ok, i solved by using ScheduledExecutorService and i am very satisfied. The tasks are load and run as they should.
Now, let's image that the user, by GUI (at runtime), decides that Task2 should run every minute, and he wants to remove Task3.
I cannot find any way to access one specific task in the pool, in order to remove/modify it.
So I cannot update tasks at runtime. When user changes a task, I can only modify the taskFile.txt and restart the application, in order to reload all tasks according the newly updated taskFile.txt.
Do you know any way to access a single task in order to modify/delete it?
Or even, a way to remove one given task, so i can insert a new one in the pool, with the modifications wanted by the user.
Thanks
This is not elegant, but works.
Let's suppose you need 10 threads, and sometimes you need to manage a specific thread.
Instead to have a pool with 10 thread, use 10 pools with one thread for each, keep them in your favourite data structure, and act on the pool_1 when you want to modify thread_1.
It's possible to remove the older Runnable from the pool and put a new one with the needed changes.
Otherways, anything put in the pool became anonymous and will be not directly manageable.
If somebody has a better solution...
I'm working on a project with Quartz and has been a problem with the dependencies with jobs.
we have a setup where A and B aren't dependent on eachother, though C is:
A and B can run at the same time, but C can only run when both A and B are complete.
Is there a way to set this kind of scenario up in Quartz, so that C will only trigger when A and B finish?
Not directly AFAIK, but it should be not too hard to use a TriggerListener to implement such a functionality (a TriggerListener is run both a start and end of jobs, and you can set them up for individual triggers or trigger groups).
EDIT: there is even a specific FAQ Topic about this problem:
There currently is no "direct" or "free" way to chain triggers with
Quartz. However there are several ways you can accomplish it without
much effort. Below is an outline of a couple approaches:
One way is to use a listener (i.e. a TriggerListener, JobListener or
SchedulerListener) that can notice the completion of a job/trigger and
then immediately schedule a new trigger to fire. This approach can get
a bit involved, since you'll have to inform the listener which job
follows which - and you may need to worry about persistence of this
information. See the listener
org.quartz.listeners.JobChainingJobListener which ships with Quartz -
as it already has some of this functionality.
Another way is to build a Job that contains within its JobDataMap the
name of the next job to fire, and as the job completes (the last step
in its execute() method) have the job schedule the next job. Several
people are doing this and have had good luck. Most have made a base
(abstract) class that is a Job that knows how to get the job name and
group out of the JobDataMap using pre-defined keys (constants) and
contains code to schedule the identified job. This abstract Job's
implementation of execute() delegates to an abstract template method
such as "doWork()" (where the extending Job class's real work goes)
and then it contains the code for scheduling the follow-up job. Then
they simply make extensions of this class that included the work the
job should do. The usage of 'durable' jobs, or the overloaded
addJob(JobDetail, boolean, boolean) method (added in Quartz 2.2) helps
the application define all the jobs at once with their proper data,
without yet creating triggers to fire them (other than one trigger to
fire the first job in the chain).
In the future, Quartz will provide a much cleaner way to do this, but
until then, you'll have to use one of the above approaches, or think
of yet another that works better for you.
I have a requirement to execute a small set of related tasks on a custom thread created for them. The tasks will be scheduled from different classes.
I'm planning to use GCD's dispatch_queue_create to create the custom thread and schedule the task on it. Note that all the related tasks must execute only on that one thread in order.So my question is if I call dispatch_queue_create("my_custom_thread_label", NULL) with the same label from many classes in my codebase, would it all eventually map to just one thread? Or do I need to create it in one place and get a reference to it whenever needed? Thanks.
You need to create it in one place and pass the pointer around.