Can an executable jar file can restart itself? For instance, after a user made some choice, the program says "Restart the app?" and the user clicks "Yes" then the jar shuts down and restarts itself.
Needing to restart an application is a sign of bad design.
I would definitely try hard to be able to "reinitialize" the application (reread config files, reestablish connections or what ever) instead of forcing the user to terminate / start the application (even if it's done automatically).
A half-way "hack" would be to encapsulate your application in some runner-class that's implements something like:
public class Runner {
public static void main(String... args) {
while (true) {
try {
new YourApplication().run();
return;
} catch (RestartException re) {
}
}
}
}
Well, if you know the location of the Jar file on the file system, you could programatically run the Jar. And then exit the currently running version.
Runtime runtime = Runtime.getRuntime();
Process proc = runtime.exec("java -jar locatio/of/the/jar");
System.exit(0);
Related
I have a simple application with a Quartz scheduler started from a servlet listener. The code is available at https://github.com/ike3/quartz-and-ejb
The only interesting part is that the job calls a remote EJB:
InitialContext initialContext = new InitialContext();
PpaJobRemote remote = (PpaJobRemote) initialContext.lookup(beanName);
remote.process();
The code is packaged as EAR containing EJB-JAR and WAR and then deployed on the WildFly 18 application server. To be sure: there are no duplicated interfaces in EAR/lib and WEB-INF/lib.
Everything works fine until the module is restarted. Then suddenly the lookup fails with an exception:
Caused by: javax.ejb.NoSuchEJBException: EJBCLIENT000079: Unable to discover destination
for request for EJB StatelessEJBLocator for "fz44-test-jobs-ear/fz44-test-jobs-ejb/SendMailMessageJob",
view is interface ru.lanit.fz44.ejb.job.PpaJobRemote, affinity is None
The problem occurs only from a Quartz Job. I have servlet calling the same job in the same WAR - it works fine after such restart. So I think there is some weird bug between Quartz thread pool and Widlfly classloaders.
If I restart the whole server (not the single module) the error is gone. The problem is worse that deploy scripts in the CI server use jboss CLI effectively restarting the module now and then.
Can anyone suggest any workarounds of this issue?
Seems I figured it out. The problem is that I didn't shutdown the scheduler. Aparently Quartz reuses the same scheduler even after the app is restarted.
Adding this to the servlet listener fixed the issue.
public void contextDestroyed(ServletContextEvent event) {
try {
if (sched.isStarted()) {
sched.shutdown();
}
} catch (Exception e) {
LOGGER.error(e.getMessage(), e);
}
}
One more example that all the resources must be closed after use and forgetting to do so can lead to strange issues.
Trying to figure out why my console app won't stop running.
Using the following approach in a dotnet core application main method:
await new HostBuilder().
...
.ConfigureServices((hostContext, services) =>
{
services.AddHostedService<MyHostedService>();
})
.UseConsoleLifetime()
.Build()
.RunAsync();
Publishing and scheduling that task from the Windows Task Scheduler using the following settings works:
All good so far. All code is properly executed. However, the task stays running, the process never ends. (not even after pressing refresh on the UI of the task scheduler)
Is this expected? If not, how do I get the process to terminate?
If expected, does it still make sense then, to use Generic Host / Hosted Service in a scheduled console app that just starts, runs, and stops?
Answer based on Microsoft.Extensions.Hosting 2.2.0
This behavior is expected, due to your usage of the Generic Host:
It keeps running until shut down or disposed, and you have no shutdown mechanism in place. I assume you expect the Generic Host to shut down after IHostedService.StartAsync(CancellationToken) of your MyHostedService ran to completion. This is not the case, because there might be other IHostedService implementations registered and executed in sequence, and/or a long running BackgroundService which returns control when its ExecuteAsync(CancellationToken) is not completing synchronously to allow other services to run in parallel.
To stop your application gracefully after your MyHostedService completes when running the host via RunAsync, you should constructor-inject the IApplicationLifetime into your MyHostedService and call StopApplication after your Task has completed.
internal class MyHostedService : IHostedService
{
private readonly IApplicationLifetime _appLifetime;
public MyHostedService(IApplicationLifetime appLifetime)
{
_appLifetime = appLifetime;
}
public async Task StartAsync(CancellationToken cancellationToken)
{
await Task.Delay(1000); //your scheduled work
_appLifetime.StopApplication();
}
public Task StopAsync(CancellationToken cancellationToken)
{
return Task.CompletedTask;
}
}
Also, the application may be stopped via either AppDomain.CurrentDomain.ProcessExit or Console.CancelKeyPress, both events are subscribed to by the ConsoleLifetime, which is pre-registered as the default lifetime implementation.
You can read more about lifetime management in the docs.
Microsoft.Extensions.Hosting 3.0.0 - currently in preview - marked IApplicationLifetime obsolete and recommends using IHostApplicationLifetime instead
I try to call an .exe file from a webapplication.
But I want the file called by the user that is impersonalisated by windoes authentication from the website.
Process process = new Process();
try
{
process.StartInfo.UseShellExecute = false;
process.StartInfo.FileName = ConfigData.PVDToBudgetDBexePath;
process.StartInfo.CreateNoWindow = false;
process.Start();
log.Info("Process started by " + WindowsIdentity.GetCurrent().Name + " with ID: " + process.Id);
process.WaitForExit();
log.Info("After WaitForExit Process ID: " + process.Id);
}
catch (Exception ex)
{
log.Error("Error executing file with message " + ex.Message);
}
Both info log texts are logged correctly. There is no error occuring.
But the called Program does not do anything. No logging, no writing in Database.
The user has executable rights on the file.
When I call the same Code from Development Server it works fine.
I use .Net 4.5 and IIS 7
I found posts concerning this topic only for very old versions of .Net and IIS and that could not help me.
What am i doing wrong?
Or how can I find out whats going wrong?
many thanks,
EDIT:
To better make clear what I intend:
I have this (self made) exe file that imports Data from Excel Sheets into a Database. That needs some time. While doing this it logs its Progress whith log4net also into the database.
I want an UI (web application) were the user can trigger the import.
on this UI there is also an ajax progressbar that shows the progress of the import takten from the log table in the database.
I want maximum one instance of this import process to run in the same time. So I have a function that checks wheter the process is still running.
If so it does not allow to start another process. If not you can start it again.
private bool IsRunning(string name)
{
Process[] processlist = Process.GetProcesses();
if (Process.GetProcessesByName(name).Length > 0 )
{
return true;
}
else
{
return false;
}
}
I solved the problem now by starting the exe file via TimeScheduler.
path = filepath to the exe file
arguments = arguments to start the exe file with
using Microsoft.Win32.TaskScheduler;
using (TaskService taskService = new TaskService())
{
var taskDefinition = taskService.NewTask();
taskDefinition.RegistrationInfo.Author = WindowsIdentity.GetCurrent().Name;
taskDefinition.RegistrationInfo.Description = "Runs exe file";
var action = new ExecAction(path, arguments);
taskDefinition.Actions.Add(action);
taskService.RootFolder.RegisterTaskDefinition("NameOfTask", taskDefinition);
//get task:
var task = taskService.RootFolder.GetTasks().Where(a => a.Name == "NameOfTask").FirstOrDefault();
try
{
task.Run();
}
catch (Exception ex)
{
log.Error("Error starting task in TaskScheduler with message: " + ex.Message);
}
}
If you mean by development server the web server that is launched by Visual Studio, than this gives you a false test case since that server is launched by Visual Studio and uses your Windows account to run, while a standard configured IIS does not run under a "user" account but a very limited system account (luckily !!). Even if the user is logged in with a domain account in your website, the IIS process will not run under this account (that wouldn't make sense anyway). That is the reason why this code will not run in IIS and will run in your development server. Even if you get the exe to launch, it will run using the system account of IIS since you didn't supply any account, which is a limited account which will again run the exe different than you expected.
You will have to use impersonation, if you really want to go this way, but you will have to launch that process "impersonating" the user that is logged in in the website, asuuming that user account used to login even makes sense at that point. E.g. if it is a domain account, this might work, but if you use some other kind of authentication, like forms authentication, this has no meaning on OS level and thus you cannot use those credentials for impersonation in IIS.
In my experience, and I have done this a few times, impersonation in IIS is always a bad thing and is always creating issues, the same goes for launching command line process by the way.Luckily there is always a better/alternative solution when you think about it. Also the wait for a process to end in your code is not really a good practice. What if the process blocks? It will block website.
Luckily there is always a better/alternative solution when you think about it. A better/possible solution here is to use message queuing for example, where you just push a message to execute the task, and on the other end an application which processes the messages, which might use this command line tool then. That application can run under any user account you want, without you having to let IIS run under a different account. Later on you must of course come back to find the result of the operation, but that can be done using a callback in the background of your website. though this solution is a little bigger than what you are trying to do, it will have a better result on almost every field (responsiveness of your site, maintainability, scalability,..) the only thing where it is worse is the lines of code that you will need, but that is seldomly a valid factor to take into account
If you write the appplication for excel processing yourself, you can use a table in the DB as some kind of queue instead of using a message bus. Your web application then just needs to add rows with all necesarry info for the process in that table, the status and progress being one of them. Extend your processing application to monitor this table continuously and as soon as it detects a new record, it can then start to do the necessary task and update the db accordingly progress and status and end result). This avoids the messaging sub-system, will work equally good and will avoid you to have to launch a process with impersonation, which was the evil thing to start with.
You can modify the excel process to a windows service so that it runs continuously and starts with the system, but, if you don't want to, there are also tools to run any command line application as a windows service).
This technique would be much easier than the impersonation and allows your website to run in it's protected environment
I am using Azure web job to run some logic continuously. The function is a singleton function. However, I am getting "Waiting for lock" message after I tried to run this function after a restart of the web app. Does it mean that another instance of the same function is keeping the lock? How can I resolve this?
The function:
namespace Ns
{
public class Functions
{
[Singleton]
[NoAutomaticTriggerAttribute]
public static async Task ProcessMethod()
{
while(true){
//process logic here
await Task.Delay(TimeSpan.FromSeconds(20));}
}
}
}
The main program:
namespace ns
{
class Program
{
static void Main()
{
var host = new JobHost();
host.RunAndBlock();
}
}
}
The message that I got:
According to the Singleton attribute description the lock is adquired during function execution by a Blob lease.
If another function instance is triggered while this function is
running it will wait for the lock, periodically polling for it.
If you have more than one instance of your App Service Plan, this means that there are more than one Webjob and thus the Dashboard might be showing the locked status of the other Webjobs while one is running.
You can view the blob lease locks that are created on your storage account.
Another option is to try Listener Singletons but I never tried it with Manual triggers.
I disabled the production function in Azure and set the listenerlockPeriod to 15 seconds as described above.
This lessened the locking behavior significantly.
I have this function that executes an async task run and return results
public bool CheckNetworkDrive(string drive)
{
var task = new Task<bool>(() => { return CheckNetworkDriveMethod(drive); });
task.Start();
//make async call to check network path to avoid lock in case of not exist
if (task.Wait(5000) && task.Result)
return true;
return false;
}
in local host everything works fine but in webgarden its not seems to work and I can’t figure the exact reason, so can you help or suggest an alternative !
ps, the check method will check network path, if it’s not responding it will block the whole code, so that why I need fire and async wait method.
sorry for inconvenience, it turned out that the problem is not with the parallel task in particular,I'm using window identity impersonation to access network drives and somehow the task is seems to lose impersonation so after I passed the impersonated user to the task everything worked fine.
I found this that helped
How do I set the user identity for tasks when calling Task.WaitAll()