Here's the situation.
I have an application which for all intents and purposes I have to treat like a black box.
I need to be able to open multiple instances of this application each with a set of files. The syntax for opening this is executable.exe file1.ext file2.ext.
If I run executable.exe x amount of times with no arguments, new instances open fine.
If I run executable.exe file1.ext followed by executable.exe file2.ext then the second call opens file 2 in the existing window rather than creating a new instance. This interferes with the rest of my solution and is the problem.
My solution wraps this application and performs various management operations on it, here's one of my wrapper classes:
public class myWrapper
{
public event EventHandler<IntPtr> SplashFinished;
public event EventHandler ProcessExited;
private const string aaTrendLocation = #"redacted";
//private const string aaTrendLocation = "notepad";
private readonly Process _process;
private readonly Logger _logger;
public myWrapper(string[] args, Logger logger =null)
{
_logger = logger;
_logger?.WriteLine("Intiialising new wrapper object...");
if (args == null || args.Length < 1) args = new[] {""};
ProcessStartInfo info = new ProcessStartInfo(aaTrendLocation,args.Aggregate((s,c)=>$"{s} {c}"));
_process = new Process{StartInfo = info};
}
public void Start()
{
_logger?.WriteLine("Starting process...");
_logger?.WriteLine($"Process: {_process.StartInfo.FileName} || Args: {_process.StartInfo.Arguments}");
_process.Start();
Task.Run(()=>MonitorSplash());
Task.Run(() => MonitorLifeTime());
}
private void MonitorLifeTime()
{
_logger?.WriteLine("Monitoring lifetime...");
while (!_process.HasExited)
{
_process.Refresh();
Thread.Sleep(50);
}
_logger?.WriteLine("Process exited!");
_logger?.WriteLine("Invoking!");
ProcessExited?.BeginInvoke(this, null, null, null);
}
private void MonitorSplash()
{
_logger?.WriteLine("Monitoring Splash...");
while (!_process.MainWindowTitle.Contains("Trend"))
{
_process.Refresh();
Thread.Sleep(500);
}
_logger?.WriteLine("Splash finished!");
_logger?.WriteLine("Invoking...");
SplashFinished?.BeginInvoke(this,_process.MainWindowHandle,null,null);
}
public void Stop()
{
_logger?.WriteLine("Killing trend...");
_process.Kill();
}
public IntPtr GetHandle()
{
_logger?.WriteLine("Fetching handle...");
_process.Refresh();
return _process.MainWindowHandle;
}
public string GetMainTitle()
{
_logger?.WriteLine("Fetching Title...");
_process.Refresh();
return _process.MainWindowTitle;
}
}
My wrapper class all works fine until I start providing file arguments and this unexpected instancing behaviour kicks in.
I can't modify the target application and nor do I have access to its source to determine whether this instancing is managed with Mutexes or through some other feature. Consequently, I need to determine if there is a way to prevent the new instance seeing the existing one. Would anyone have any suggestions?
TLDR: How do I prevent an application that is limited to a single instance determining that there is already an instance running
To clarify (following suspicious comments), my company's R&D team wrote executable.exe but I don't have time to wait for their help in this matter (I have days not months) and have permission to do whatever required to deliver the required functionality (there's a lot more to my solution than this question mentions) swiftly.
With some decompiling work I can see that the following is being used to find the existing instance.
Process[] processesByName = Process.GetProcessesByName(Process.GetCurrentProcess().ProcessName);
Is there any way to mess with this short of creating multiple copies of the application with different names? I looked into renaming the Process on the fly but apparently this isn't possible short of writing kernel exploits...
I have solved this problem in the past by creating copies of the source executable. In your case, you could:
Save the 'original.exe' in a specific location.
Each time you need to call it, create a copy of original.exe and name it 'instance_xxxx.exe', where xxxx is a unique number.
Execute your new instance exe as required, and when it completes you can delete it
You could possibly even re-use the instances by creating a pool of them
Building on Dave Lucre's answer I solved it by creating new instances of the executable bound to my wrapper class. Initially, I inherited IDisposable and removed the temporary files in the Disposer but for some reason that was causing issues where the cleanup would block the application, so now my main program performs cleanup at the end.
My constructor now looks like:
public AaTrend(string[] args, ILogger logger = null)
{
_logger = logger;
_logger?.WriteLine("Initialising new aaTrend object...");
if (args == null || args.Length < 1) args = new[] { "" };
_tempFilePath = GenerateTempFileName();
CreateTempCopy(); //Needed to bypass lazy single instance checks
HideTempFile(); //Stops users worrying
ProcessStartInfo info = new ProcessStartInfo(_tempFilePath, args.Aggregate((s, c) => $"{s} {c}"));
_process = new Process { StartInfo = info };
}
With the two new methods:
private void CreateTempCopy()
{
_logger?.WriteLine("Creating temporary file...");
_logger?.WriteLine(_tempFilePath);
File.Copy(AaTrendLocation, _tempFilePath);
}
private string GenerateTempFileName(int increment = 0)
{
string directory = Path.GetDirectoryName(AaTrendLocation); //Obtain pass components.
string fileNameWithoutExtension = Path.GetFileNameWithoutExtension(AaTrendLocation);
string extension = Path.GetExtension(AaTrendLocation);
string tempName = $"{directory}\\{fileNameWithoutExtension}-{increment}{extension}"; //Re-assemble path with increment inserted.
return File.Exists(tempName) ? GenerateTempFileName(++increment) : tempName; //If this name is already used, increment an recurse otherwise return new path.
}
Then in my main program:
private static void DeleteTempFiles()
{
string dir = Path.GetDirectoryName(AaTrend.AaTrendLocation);
foreach (string file in Directory.GetFiles(dir, "aaTrend-*.exe", SearchOption.TopDirectoryOnly))
{
File.Delete(file);
}
}
As a side-note, this approach will only work for applications with (lazy) methods of determining instancing that rely on Process.GetProcessByName(); it won't work if a Mutex is used or if the executable name is explicitly set in the manifests.
Related
Basically, I have a "DON'T DO THIS" Sentinel scenario. Because Sentinel is not safe in such scenario, I've implemented the following
var main = "192.168.XXX.YY:6379,abortConnect=false";
var backup = "192.168.XXX.YY:6379,abortConnect=false";
IConnectionMultiplexer redis = ConnectionMultiplexer.Connect(main);
redis.ConnectionFailed += (src, args) =>
{
if ((src as ConnectionMultiplexer).Configuration != backup) {
using (var writer = new StringWriter()) {
writer.Write(backup);
(src as ConnectionMultiplexer).Configure(writer);
/**
* Just for checking. It does not save
**/
(src as ConnectionMultiplexer).GetDatabase().StringSet("aaa", "bbb");
}
}
};
So, when my main connection is down, I change the configuration, by calling (src as ConnectionMultiplexer).Configure(writer), so that ConnectionMultiplexer can use the new configuration. However, ConnectionMultiplexer continue to use the old one.
Question: How can I change ConnectionMultiplexer.configuration in the ConnectionFailed event ?
I looked at the source code of the library, it seems there is no desired functionality. There is internal method Reconfigure, but it tries to connect to other servers from the configuration.
I would suggest you to refactor, if your application is not very large. Make a wrapper over ConnectionMultiplexer, pass wrapper to objects where the connection is used. We do wrap method GetConnection, which returns all the links on a single object. All who need the connection will call this method, no needs to store connection. Inside the wrapper OnFailed subscribe to an event handler to create a new connection to a Backup.
Not sure if that would be acceptable, not exactly switching the config but more like rebuilding the multiplixer
private static Lazy<IConnectionMultiplexer> _redisMux = new Lazy<ConnectionMultiplexer>(CreateMultiplexer);
public static IConnectionMultiplexer Multiplexer { get { return _redisMux.Value; } }
private const string Main = "192.168.XXX.YY:6379,abortConnect=false";
private const string Backup = "192.168.XXX.YY:6379,abortConnect=false";
private static string ActiveConfig = Main;
private static ConnectionMultiplexer CreateMultiplexer()
{
var mux = ConnectionMultiplexer.Connect(ActiveConfig));
mux.ConnectionFailed += OnConnectionFailed;
return mux;
}
[MethodImpl(MethodImplOptions.Synchronized)]
private static void OnConnectionFailed(object sender, ConnectionFailedEventArgs e)
{
ActiveConfig = Backup;
try { Multiplexer.Dispose(); } catch { }
_redisMux = new Lazy<ConnectionMultiplexer>(CreateMultiplexer);
}
I have the following code that starts robocopy as a Process. I also need to do database queries to determine which directories I need to copy each time robocopy is called so I used ProcessStartInfo to control the arguments passed.
internal class Program
{
private static void Main(string[] args)
{
using (var context = new MyDbContext())
{
IEnumerable<ProcessStartInfo> processInfos = GetProcessInfos(context, args[0]);
foreach (ProcessStartInfo processInfo in processInfos)
{
// How can I reuse robocopy Process instances and
// how can I dispose of them properly?
Process.Start(processInfo);
}
}
}
private static IEnumerable<ProcessStartInfo> GetProcessInfos(MyDbContext context,
string directory)
{
const string defaultRobocopyFormatString = "{0} {1} /mir /tee /fft /r:3 /w:10 /xd *Temp*";
var directoryInfo = new DirectoryInfo(directory);
return from dir in directoryInfo.GetDirectories()
from myEntity in context.MyEntities
where dir.Name == myEntity.Name
select new ProcessStartInfo("robocopy",
string.Format(defaultRobocopyFormatString,
Path.Combine("C:\Test", dir.Name),
Path.Combine("C:\Test_bak", dir.Name)));
}
}
How can I reuse Process instances returned by the static Process.Start(ProcessStartInfo) inside the foreach loop and how can I Dispose of them properly?
You cannot re-use a Process object. The Process class behaves like all of the other .NET classes that wrap an operating system object. Like Socket, Bitmap, Mutex, FileStream, etcetera. They are tiny little cookies that are very cheap to bake and take very little space on the GC heap. They track the lifetime of the underlying OS object carefully, once the object is dead, the .NET wrapper object is no longer useful either.
The Process class signals that the cookie was eaten with its Exited event and HasExited property. It has some post-bite properties that are useful, ExitCode and ExitTime.
But that's where it ends, if you want to create another process then you have to bake another cookie. Simple to do with the new keyword or the Start() factory function. Don't try to optimize it, there's no point and it can't work. Re-using ProcessStartInfo is fine, it is not a wrapper class.
You don't really need to reuse the Process class - that's just a wrapper for the underlying process. And when processes end, they're gone, completely - that's the main point of having a process in the first place.
Instead, it seems like you really want to just make sure that only one of those robocopy processes runs at a time, which is pretty easy:
using (var context = new MyDbContext())
{
IEnumerable<ProcessStartInfo> processInfos = GetProcessInfos(context, args[0]);
foreach (ProcessStartInfo processInfo in processInfos)
{
using (var process = Process.Start(processInfo))
{
// Blocks until the process ends
process.WaitForExit();
}
// When the `using` block is left, `process.Dispose()` is called.
}
}
I have an application where I need to create files with a unique and sequential number as part of the file name. My first thought was to use (since this application does not have any other data storage) a text file that would contain a number and I would increment this number so then my application would always create a file with a unique id.
Then I thought that maybe at a time when there are more than one user submitting to this application at the same time, one process might be reading the txt file before it has been written by the previous process. So then I am looking for a way to read and write to a file (with try catch so then I can know when it's being used by another process and then wait and try to read from it a few other times) in the same 'process' without unlocking the file in between.
If what I am saying above sounds like a bad option, could you please give me an alternative to this? How would you then keep track of unique identification numbers for an application like my case?
Thanks.
If it's a single application then you can store the current number in your application settings. Load that number at startup. Then with each request you can safely increment it and use the result. Save the sequential number when the program shuts down. For example:
private int _fileNumber;
// at application startup
_fileNumber = LoadFileNumberFromSettings();
// to increment
public int GetNextFile()
{
return Interlocked.Increment(ref _fileNumber);
}
// at application shutdown
SaveFileNumberToSettings(_fileNumber);
Or, you might want to make sure that the file number is saved whenever it's incremented. If so, change your GetNextFile method:
private readonly object _fileLock = new object();
public int GetNextFile()
{
lock (_fileLock)
{
int result = ++_fileNumber;
SaveFileNumbertoSettings(_fileNumber);
return result;
}
}
Note also that it might be reasonable to use the registry for this, rather than a file.
Edit: As Alireza pointed in the comments, it is not a valid way to lock between multiple applications.
You can always lock the access to the file (so you won't need to rely on exceptions).
e.g:
// Create a lock in your class
private static object LockObject = new object();
// and then lock on this object when you access the file like this:
lock(LockObject)
{
... access to the file
}
Edit2: It seems that you can use Mutex to perform inter-application signalling.
private static System.Threading.Mutex m = new System.Threading.Mutex(false, "LockMutex");
void AccessMethod()
{
try
{
m.WaitOne();
// Access the file
}
finally
{
m.ReleaseMutex();
}
}
But it's not the best pattern to generate unique ids. Maybe a sequence in a database would be better ? If you don't have a database, you can use Guids or a local database (even Access would be better I think)
I would prefer a complex and universal solution with the global mutex. It uses a mutex with name prefixed with "Global\" which makes it system-wide i.e. one mutex instance is shared across all processes. if your program runs in friendly environment or you can specify strict permissions limited to a user account you can trust then it works well.
Keep in mind that this solution is not transactional and is not protected against thread-abortion/process-termination.
Not transactional means that if your process/thread is caught in the middle of storage file modification and is terminated/aborted then the storage file will be left in unknown state. For instance it can be left empty. You can protect yourself against loss of data (loss of last used index) by writing the new value first, saving the file and only then removing the previous value. Reading procedure should expect a file with multiple numbers and should take the greatest.
Not protected against thread-abortion means that if a thread which obtained the mutex is aborted unexpectedly and/or you do not have proper exception handling then the mutex could stay locked for the life of the process that created that thread. In order to make solution abort-protected you will have to implement timeouts on obtaining the lock i.e. replace the following line which waits forever
blnResult = iLock.Mutex.WaitOne();
with something with timeout.
Summing this up I try to say that if you are looking for a really robust solution you will come to utilizing some kind of a transactional database or write a kind of such a database yourself :)
Here is the working code without timeout handling (I do not need it in my solution). It is robust enough to begin with.
using System;
using System.IO;
using System.Security.AccessControl;
using System.Security.Principal;
using System.Threading;
namespace ConsoleApplication31
{
class Program
{
//You only need one instance of that Mutex for each application domain (commonly each process).
private static SMutex mclsIOLock;
static void Main(string[] args)
{
//Initialize the mutex. Here you need to know the path to the file you use to store application data.
string strEnumStorageFilePath = Path.Combine(
Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
"MyAppEnumStorage.txt");
mclsIOLock = IOMutexGet(strEnumStorageFilePath);
}
//Template for the main processing routine.
public static void RequestProcess()
{
//This flag is used to protect against unwanted lock releases in case of recursive routines.
bool blnLockIsSet = false;
try
{
//Obtain the lock.
blnLockIsSet = IOLockSet(mclsIOLock);
//Read file data, update file data. Do not put much of long-running code here.
//Other processes may be waiting for the lock release.
}
finally
{
//Release the lock if it was obtained in this particular call stack frame.
IOLockRelease(mclsIOLock, blnLockIsSet);
}
//Put your long-running code here.
}
private static SMutex IOMutexGet(string iMutexNameBase)
{
SMutex clsResult = null;
clsResult = new SMutex();
string strSystemObjectName = #"Global\" + iMutexNameBase.Replace('\\', '_');
//Give permissions to all authenticated users.
SecurityIdentifier clsAuthenticatedUsers = new SecurityIdentifier(WellKnownSidType.AuthenticatedUserSid, null);
MutexSecurity clsMutexSecurity = new MutexSecurity();
MutexAccessRule clsMutexAccessRule = new MutexAccessRule(
clsAuthenticatedUsers,
MutexRights.FullControl,
AccessControlType.Allow);
clsMutexSecurity.AddAccessRule(clsMutexAccessRule);
//Create the mutex or open an existing one.
bool blnCreatedNew;
clsResult.Mutex = new Mutex(
false,
strSystemObjectName,
out blnCreatedNew,
clsMutexSecurity);
clsResult.IsMutexHeldByCurrentAppDomain = false;
return clsResult;
}
//Release IO lock.
private static void IOLockRelease(
SMutex iLock,
bool? iLockIsSetInCurrentStackFrame = null)
{
if (iLock != null)
{
lock (iLock)
{
if (iLock.IsMutexHeldByCurrentAppDomain &&
(!iLockIsSetInCurrentStackFrame.HasValue ||
iLockIsSetInCurrentStackFrame.Value))
{
iLock.MutexOwnerThread = null;
iLock.IsMutexHeldByCurrentAppDomain = false;
iLock.Mutex.ReleaseMutex();
}
}
}
}
//Set the IO lock.
private static bool IOLockSet(SMutex iLock)
{
bool blnResult = false;
try
{
if (iLock != null)
{
if (iLock.MutexOwnerThread != Thread.CurrentThread)
{
blnResult = iLock.Mutex.WaitOne();
iLock.IsMutexHeldByCurrentAppDomain = blnResult;
if (blnResult)
{
iLock.MutexOwnerThread = Thread.CurrentThread;
}
else
{
throw new ApplicationException("Failed to obtain the IO lock.");
}
}
}
}
catch (AbandonedMutexException iMutexAbandonedException)
{
blnResult = true;
iLock.IsMutexHeldByCurrentAppDomain = true;
iLock.MutexOwnerThread = Thread.CurrentThread;
}
return blnResult;
}
}
internal class SMutex
{
public Mutex Mutex;
public bool IsMutexHeldByCurrentAppDomain;
public Thread MutexOwnerThread;
}
}
In C# (.NET), can two threads running in the same application have DIFFERENT "WorkingFolders"??
As best I can tell, the answer would be "NO". I think the WORKING DIR is set by the PROCESS in Win32.. Am I wrong here?
According to the following test code, (as well the Win32 SetCurrentDirectory API call), this is NOT possible, but has anyone figured out a way to MAKE it possible?
using System;
using System.Threading;
public class TestClass {
public ManualResetEvent _ThreadDone = new ManualResetEvent(false);
public static void Main() {
Console.WriteLine(Environment.CurrentDirectory);
Thread _Thread = new Thread(new ParameterizedThreadStart(Go));
TestClass test = new TestClass();
_Thread.Start(test);
if(test._ThreadDone.WaitOne()) {
Console.WriteLine("Thread done. Checking Working Dir...");
Console.WriteLine(Environment.CurrentDirectory);
}
}
public static void Go(object instance) {
TestClass m_Test = instance as TestClass;
Console.WriteLine(Environment.CurrentDirectory);
System.IO.Directory.SetCurrentDirectory("L:\\Projects\\");
Console.WriteLine(Environment.CurrentDirectory);
m_Test._ThreadDone.Set();
}
}
I know SOMEONE out there has to have ran across this before!
I'm going to guess what you're trying to do is to make code such as File.Open("Foo.txt") behave differently on different threads. Can you do this? The short answer is No - nor should you be trying to do this. On Windows, the current working directory is set at the process level. The .NET framework does not violate that rule.
A better approach would be to create an abstraction on top of Environment.CurrentDirectory that is thread specific. Something like:
public static class ThreadEnvironment
{
[ThreadStatic]
static string _currentDir;
public static string CurrentDirectory
{
get
{
if (_currentDir == null) // If Current Directory has not been set on this thread yet, set it to the process default
{
_currentDir = Environment.CurrentDirectory;
}
return _currentDir;
}
set
{
if (value == null)
throw new ArgumentException("Cannot set Current Directory to null.");
_currentDir = value;
}
}
}
You can then refer to ThreadEnvironment.CurrentDirectory to get that thread's current directory, which will default to the process directory if it has not been set on that thread. For example:
static void Main(string[] args)
{
(new Thread(Thread1)).Start();
(new Thread(Thread2)).Start();
}
static void Thread1()
{
Console.WriteLine("Thread1 Working Dir is: {0}", ThreadEnvironment.CurrentDirectory);
ThreadEnvironment.CurrentDirectory = #"C:\";
Console.WriteLine("Thread1 Working Dir is: {0}", ThreadEnvironment.CurrentDirectory);
}
static void Thread2()
{
Console.WriteLine("Thread2 Working Dir is: {0}", ThreadEnvironment.CurrentDirectory);
ThreadEnvironment.CurrentDirectory = #"C:\Windows";
Console.WriteLine("Thread2 Working Dir is: {0}", ThreadEnvironment.CurrentDirectory);
}
You would, of course, then need to qualify that path whenever dealing with file IO, however this is arguably a safer design anyway.
has anyone figured out a way to MAKE it possible?
It's simply not possible. You can't even have different working directories per App Domain.
The windows rule is: one Environment set per Process. Running in .NET won't change the basic rules.
Instead of that, if you experienced problem in loading assemblies, consider adding the corresponding folder to the PATH environment variable.
Does anyone know how to dispose of AddIns created using System.AddIn. All the examples online seem to show how to easily load and use an addin, but none show how to dispose of them once they're alive. My Problem is I create addins in new processes, and these processes never get garbage collected, obviously a problem.
Below is some sample code illustrating my problem. Assume that the user never exits this application, but instead creates many instances of ICalculator. How do these addIn processes ever get disposed of?
static void Main(string[] args)
{
string addInRoot = GetExecutingDirectory();
// Update the cache files of the pipeline segments and add-ins
string[] warnings = AddInStore.Update(addInRoot);
// search for add-ins of type ICalculator
Collection<AddInToken> tokens = AddInStore.FindAddIns(typeof(ICalculatorHost), addInRoot);
string line = Console.ReadLine();
while (true)
{
AddInToken calcToken = ChooseCalculator(tokens);
AddInProcess addInProcess = new AddInProcess();
ICalculatorHost calc = calcToken.Activate<ICalculatorHost>(addInProcess, AddInSecurityLevel.Internet);
// run the add-in
RunCalculator(calc);
}
}
I managed to find a solution to the above problem, it's making use of the AddInController class and it's shutdown method. Now to see if I can get this to work in my application, not just this example:
static void Main(string[] args)
{
string addInRoot = GetExecutingDirectory();
string[] warnings = AddInStore.Update(addInRoot);
Collection<AddInToken> tokens = AddInStore.FindAddIns(typeof(ICalculatorHost), addInRoot);
while (true)
{
AddInToken calcToken = ChooseCalculator(tokens);
AddInProcess addInProcess = new AddInProcess();
ICalculatorHost calc = calcToken.Activate<ICalculatorHost>(addInProcess, AddInSecurityLevel.Internet);
// run the add-in
RunCalculator(calc);
// shutdown the add-in when the RunCalculator method finishes executing
AddInController controller = AddInController.GetAddInController(calc);
controller.Shutdown();
}
}
your solution didn't work for me.
Since you are creating a new process for your addin you can simply
addInProcess.Shutdown();
the external process will shutdown