This is a more general question about which types of payloads to host in a Container. In our case we will use Service Fabric guest executables. For this post I will only use the word Container to refer to both. The reason I do this is they have similar properties and think more people may understand a container than a SF Guest Exe.
WebAPIs/Services that needs to scale are a good fit for containers, but this question is related to what we call a "Batch" job. This nomenclature comes out of the old .bat files, but in our case we are using a .NET Framework or Core .exe (console apps).
Currently Windows Task Scheduler kicks off the batch running under a service account on a VM. We want the processing to happen on a certain time of day or day of the week and not before or after. There is not any real scaling here. There is one instance which may or may not be multithreaded and on average they generally run between 2-15 minutes and then stop. Some run longer some run shorter. I understand there are limitations to this approach but this is the type of payload I'm discussing here.
As we modernize the Technology stack we are looking to use the Orchestrator as much as possible. As a technologist I've always tried to understand the different tools in our tool belts and not use a tool just because that's the one I used last, instead use the correct tool for the task.
We started out by not writing any more .net console apps. Instead we put the business logic of these "batches" into WebApi's. Then having the task scheduler call the API when it needed to perform its action. If I put this into Service Fabric and host it my concern is that the system resources are consumed for 23 hours and 45 minutes a day when they are not being used. That seems to be opposite of what you would expect when using a container.
Now if I could spin up a Service Fabric Guest Exe/Container on demand and then after it finishes destroy the instance of the app that could fit the need. Then I could have the benefits of the orchestrator without the determent of having it consume resources all the time. I would hope to retire the Batch Server (VM) as the hardware is usage is not optimized and instead add resources to the cluster.
UPDATE
Looking at Vaclav's Scalability Doco I think there might be a use case in here? https://learn.microsoft.com/en-us/azure/service-fabric/service-fabric-concepts-scalability He uses a "Workload Manager Service" combined with CreateServiceAsync, to spin up an instance of the service on demand. I guess I would deploy the app to the image store but not create an instance of the app until needed. Then I need to figure out how to end it, is it as simple as changing the infinite loop in Program.cs? The thing is it doesn't look like there is a Program.cs in a Guest Executable.
This looks like a way to run a package until completion, which was releases as part of 7.1. But how do we start a second execution of the service? I want to execute based on a request coming in.
https://learn.microsoft.com/en-us/azure/service-fabric/run-to-completion
Thoughts?
I have inherited a system that consists of a couple daemons that asynchronously process messages. I am trying to find a clean way to introduce integration testing into this system with minimal impact/risk on the existing programs. Here is a very simplified overview of their responsibilities:
Process 1 polls a queue for messages, and inserts a row into a DB for each one it dequeues.
Process 2 polls the DB for rows inserted by Process 1, does some calculations, and then deposits a file into a directory on the host and sends an email.
These processes are quite old and complex, and I am strongly inclined to avoid modifying them in any way. What I would like to do is put each of them in a container, and also stand up the dependencies (queue, DB, mail server) in other containers. This part is straightforward, but what I'm unsure about is the best way to orchestrate these tests. Since these processes consume and generate output asynchronously I will need to poll or wait for the expected outcome (mail sent, file created).
Normally I would just write a series of tests in a single test suite of my language of choice (Java, Go, etc), and make the setUp / tearDown hooks responsible for resetting the environment to the desired state. But because these processes have a lot of internal state I am afraid I cannot successfully "clean up" properly after each distinct test. This would be a problem if, for example, one test failed to generate the desired output in a specific period of time so I marked it as failed, but a subsequent test falsely got marked as passed because the original test case actually did output something (albeit much slower than anticipated) that was mistakenly attributed to the subsequent test. For these reasons I feel I need to recreate the world between each test.
In order to do this the only options I can see are:
Use a shell script to actually run my tests -- having it bring up the containers, execute a single test file, and then terminate my containers for each test.
Follow my usual pattern of setUp / tearDown in my existing test framework but call out to docker to terminate and start up the containers between each test.
Am I missing another option? Is there some kind of existing framework or pattern used for this sort of testing?
The situation right now:
Every Monday morning I manually check Jenkins jobs jUnit results that ran over the weekend, using Project Health plugin I can filter on the timeboxed runs. I then copy paste this table into Excel and go over each test case's output log to see what failed and note down the failure cause. Every weekend has another tab in Excel. All this makes tracability a nightmare and causes time consuming manual labor.
What I am looking for (and hoping that already exists to some degree):
A database that stores all failed tests for all jobs I specify. It parses the output log of a failed test case and based on some regex applies a 'tag' e.g. 'Audio' if a test regarding audio is failing. Since everything is in a database I could make or use a frontend that can apply filters at will.
For example, if I want to see all tests regarding audio failing over the weekend (over multiple jobs and multiple runs) I could run a query that returns all entries with the Audio tag.
I'm OK with manually tagging failed tests and the cause, as well as writing my own frontend, is there a way (Jenkins API perhaps?) to grab the failed tests (jUnit format and Jenkins plugin) and create such a system myself if it does not exist?
A good question. Unfortunately, it is very difficult in Jenkins to get such "meta statistics" that spans several jobs. There is no existing solution for that.
Basically, I see two options for getting what you want:
Post-processing Jenkins-internal data to get the statistics that you need.
Feeding a database on-the-fly with build execution data.
The first option basically means automating the tasks that you do manually right now.
you can use external scripting (Python, Perl,...) to process Jenkins-internal data (via REST or CLI APIs, or directly reading on-disk data)
or you run Groovy scripts internally (which will be faster and more powerful)
It's the most direct way to go. However, depending on the statistics that you need and depending on your requirements regarding data persistance , you may want to go for...
The second option: more flexible and completely decoupled from Jenkins' internal data storage. You could implement it by
introducing a Groovy post-build step for all your jobs
that script parses job results and puts data of interest in a custom, external database
Statistics you'd get from querying that database.
Typically, you'd start with the first option. Once requirements grow, you'd slowly migrate to the second one (e.g., by collecting internal data via explicit post-processing scripts, putting that into a database, and then running queries on it). You'll want to cut this migration phase as short as possible, as it eventually requires the effort of implementing both options.
You may want to have a look at couchdb-statistics. It is far from a perfect fit, but at least seems to do partially what you want to achieve.
I have a requirement in my MVC app.
I had an export to excel functionality that is taking 3 mins of time (user clicks on a export button and waits on).
This export downloads an excel that has multiple worksheets after applying certain rules on the data.
These rules are datamanipulations plus applying colors on the cells belonging to certain columns.
Inorder to avoid the wait time, I was asked to develop a code with in the MVC app that can run like a scheduled job.
This job has to export the excel to a dedicated folder with in the network on the scheduled time (daily once).
Also i was asked to develop a web page within the app which has links to download these excels.
Quesions here (Any help would be appreciated) :
I have chosen Quartz.NET to implement this requirement. This is an open source (to my little knowledge) that can
provide the facility to schedule a job (class developed in .NET). Is it the right choice or would there be any implications in future?
Is it really needed to develop a job like code or any other way of coding can address this?
I'm not very familiar with Quartz.net, but I do know that trying to run background/scheduled tasks from within the same process as the MVC application can be problematic.
Ref 1: http://haacked.com/archive/2011/10/16/the-dangers-of-implementing-recurring-background-tasks-in-asp-net.aspx/
Ref 2: http://www.hanselman.com/blog/HowToRunBackgroundTasksInASPNET.aspx
Essentially, you can't guarantee that the process will complete correctly when running it due to how IIS handles app pools (which is where you MVC process runs: assuming hosting on IIS anyway).
You mention running a scheduled task within your MVC app. Again, this is incorrect. Why can't you just slap a console app project into the solution and drive the code from there, then put it on the server and use the Windows Task Scheduler?
In terms of background tasks, the "correct" way to do this is to send a command from your MVC app to some sort of message queue, which can then ensure that the command doesn't get dropped. I've used RabbitMQ in the past (a middleware message broker). Perhaps this is the aim of Quartz.net.
This setup typically involves another app (for me, usually a console app run on the server) that receives the command message from the message queue and runs in it's own process, entirely separate from MVC and thus the issues inherent with IIS AppPools and background tasks.
A lot of work, really... one would think it'd be easier, but that's the surefire way to do it and maintain the integrity of the task to be run.
What are the cons and pros of windows services vs scheduled tasks for running a program repeatedly (e.g. every two minutes)?
Update:
Nearly four years after my original answer and this answer is very out of date. Since TopShelf came along Windows Services development got easy. Now you just need to figure out how to support failover...
Original Answer:
I'm really not a fan of Windows Scheduler. The user's password must be provided as #moodforall points out above, which is fun when someone changes that user's password.
The other major annoyance with Windows Scheduler is that it runs interactively and not as a background process. When 15 MS-DOS windows pop up every 20 minutes during an RDP session, you'll kick yourself that didn't install them as Windows Services instead.
Whatever you choose I certainly recommend you separate out your processing code into a different component from the console app or Windows Service. Then you have the choice, either to call the worker process from a console application and hook it into Windows Scheduler, or use a Windows Service.
You'll find that scheduling a Windows Service isn't fun. A fairly common scenario is that you have a long running process that you want to run periodically. But, if you are processing a queue, then you really don't want two instances of the same worker processing the same queue. So you need to manage the timer, to make sure if your long running process has run longer than the assigned timer interval, it doesn't kick off again until the existing process has finished.
After you have written all of that, you think, why didn't I just use Thread.Sleep? That allows me to let the current thread keep running until it has finished and then the pause interval kicks in, thread goes to sleep and kicks off again after the required time. Neat!
Then you then read all the advice on the internet with lots of experts telling you how it is really bad programming practice:
http://msmvps.com/blogs/peterritchie/archive/2007/04/26/thread-sleep-is-a-sign-of-a-poorly-designed-program.aspx
So you'll scratch your head and think to yourself, WTF, Undo Pending Checkouts -> Yes, I'm sure -> Undo all today's work..... damn, damn, damn....
However, I do like this pattern, even if everyone thinks it is crap:
OnStart method for the single-thread approach.
protected override void OnStart (string args) {
// Create worker thread; this will invoke the WorkerFunction
// when we start it.
// Since we use a separate worker thread, the main service
// thread will return quickly, telling Windows that service has started
ThreadStart st = new ThreadStart(WorkerFunction);
workerThread = new Thread(st);
// set flag to indicate worker thread is active
serviceStarted = true;
// start the thread
workerThread.Start();
}
The code instantiates a separate thread and attaches our worker
function to it. Then it starts the thread and lets the OnStart event
complete, so that Windows doesn't think the service is hung.
Worker method for the single-thread approach.
/// <summary>
/// This function will do all the work
/// Once it is done with its tasks, it will be suspended for some time;
/// it will continue to repeat this until the service is stopped
/// </summary>
private void WorkerFunction() {
// start an endless loop; loop will abort only when "serviceStarted"
// flag = false
while (serviceStarted) {
// do something
// exception handling omitted here for simplicity
EventLog.WriteEntry("Service working",
System.Diagnostics.EventLogEntryType.Information);
// yield
if (serviceStarted) {
Thread.Sleep(new TimeSpan(0, interval, 0));
}
}
// time to end the thread
Thread.CurrentThread.Abort();
}
OnStop method for the single-thread approach.
protected override void OnStop() {
// flag to tell the worker process to stop
serviceStarted = false;
// give it a little time to finish any pending work
workerThread.Join(new TimeSpan(0,2,0));
}
Source: http://tutorials.csharp-online.net/Creating_a_.NET_Windows_Service%E2%80%94Alternative_1%3a_Use_a_Separate_Thread (Dead Link)
I've been running lots of Windows Services like this for years and it works for me. I still haven't seen a recommended pattern that people agree on. Just do what works for you.
Some misinformation here. Windows Scheduler is perfectly capable of running tasks in the background without windows popping up and with no password required. Run it under the NT AUTHORITY\SYSTEM account. Use this schtasks switch:
/ru SYSTEM
But yes, for accessing network resources, the best practice is a service account with a separate non-expiring password policy.
EDIT
Depending on your OS and the requirements of the task itself, you may be able to use accounts less privileged than Localsystem with the /ru option.
From the fine manual,
/RU username
A value that specifies the user context under which the task runs.
For the system account, valid values are "", "NT AUTHORITY\SYSTEM", or "SYSTEM".
For Task Scheduler 2.0 tasks, "NT AUTHORITY\LOCALSERVICE", and
"NT AUTHORITY\NETWORKSERVICE" are also valid values.
Task Scheduler 2.0 is available from Vista and Server 2008.
In XP and Server 2003, system is the only option.
In .NET development, I normally start off by developing a Console Application, which will run will all logging output to the console window. However, this is only a Console Application when it is run with the command argument /console. When it is run without this parameter, it acts as a Windows Service, which will stay running on my own custom coded scheduled timer.
Windows Services, I my mind, are normally used to manage other applications, rather than be a long running application. OR .. they are continuously-running heavyweight applications like SQL Server, BizTalk, RPC Connections, IIS (even though IIS technically offloads work to other processes).
Personally, I favour scheduled tasks over Window Services for repititive maintenance tasks and applications such as file copying/synchronisations, bulk email sending, deletion or archiving of files, data correction (when other workarounds are not available).
For one project I have been involved in the development of 8 or 9 Windows Services, but these sit around in memory, idle, eating 20MB or more memory per instance. Scheduled tasks will do their business, and release the memory immediately.
What's the overhead of starting and quitting the app? Every two minutes is pretty often. A service would probably let the system run more smoothly than executing your application so frequently.
Both solutions can run the program when user isn't logged in, so no difference there. Writing a service is somewhat more involved than a regular desktop app, though - you may need a separate GUI client that will communicate with the service app via TCP/IP, named pipes, etc.
From a user's POV, I wonder which is easier to control. Both services and scheduled tasks are pretty much out of reach for most non-technical users, i.e. they won't even realize they exist and can be configured / stopped / rescheduled and so on.
The word 'serv'ice shares something in common with 'serv'er. It is expected to always be running, and 'serv'e. A task is a task.
Role play. If I'm another operating system, application, or device and I call a service, I expect it to be running and I expect a response. If I (os, app, dev) just need to execute an isolated task, then I will execute a task, but if I expect to communicate, possibly two way communication, I want a service. This has to do with the most effective way for two things to communicate, or a single thing that wants to execute a single task.
Then there's the scheduling aspect. If you want something to run at a specific time, schedule. If you don't know when you're going to need it, or need it "on the fly", service.
My response is more philosophical in nature because this is very similar to how humans interact and work with another. The more we understand the art of communication, and "entities" understand their role, the easier this decision becomes.
All philosophy aside, when you are "rapidly prototyping", as my IT Dept often does, you do whatever you have to in order to make ends meet. Once the prototyping and proof of concept stuff is out of the way, usually in the early planning and discovering, you have to decide what's more reliable for long term sustainability.
OK, so in conclusion, it's highly dependent on a lot of factors, but hopefully this has provided insight instead of confusion.
A Windows service doesn't need to have anyone logged in, and Windows has facilities for stopping, starting, and logging the service results.
A scheduled task doesn't require you to learn how to write a Windows service.
It's easier to set up and lock down windows services with the correct permissions.
Services are more "visible" meaning that everyone (ie: techs) knows where to look.
This is an old question but I will like to share what I have faced.
Recently I was given a requirement to capture the screenshot of a radar (from a Meteorological website) and save it in the server every 10 minutes.
This required me to use WebBrowser.
I usually make windows services so I decided to make this one service too but it would keep crashing.
This is what I saw in Event Viewer
Faulting module path: C:\Windows\system32\MSHTML.dll
Since the task was urgent and I had very less time to research and experiment, I decided to use a simple console application and triggered it as a task and it executed smoothly.
I really liked the article by Jon Galloway recommended in accepted answer by Mark Ransom.
Recently passwords on the servers were changed without acknowledging me and all the services failed to execute since they could not logon.
So ppl claiming in the article comments that this is a problem. I think windows services can face same problem (Pls. correct me if I am wrong, I am jus a newbie)
Also the thing mentioned, if using task scheduler windows pop up or the console window pops up.
I have never faced that. It may pop up but it is at least very instantaneous.
Why not provide both?
In the past I've put the 'core' bits in a library and wrapped a call to Whatever.GoGoGo() in both a service as well as a console app.
With something you're firing off every two minutes the odds are decent it's not doing much (e.g. just a "ping" type function). The wrappers shouldn't have to contain much more than a single method call and some logging.
Generally, the core message is and should be that the code itself must be executable from each and every "trigger/client". So it should not be rocket science to switch from one to the other approach.
In the past we used more or less always Windows Services but since also more and more of our customers switch to Azure step by step and the swap from a Console App (deployed as a Scheduled Task) to a WebJob in Azure is much easier than from a Windows Service, we focus on Scheduled Tasks for now. If we run into limitations, we just ramp up the Windows Service project and call the same logic from there (as long as customers are working OnPrem..) :)
BR,
y
Windows services want more patience until it's done.
It has a bit hard debug and install. It's faceless.
If you need a task which must be done in every second, minute or hour,
you should choice Windows Service.
Scheduled Task is quickly developed and has a face.
If you need a daily or weekly task, you can use Scheduled Task.