asp.net - C# allowing one thread to run the method at a time after multiple requests triggerred to application server -

i building asp.net web.api service. there api needs more 2 minutes retrieve desired data, implemented cache mechanism, , every request sent api server, server return cached data , meanwhile start new thread load new data cache, issue if submitted lot of requests, lot of thread running , crashed server, want implement mechanism control thread @ time, know asp.net web.api inherently multi threads, how tell other request wait, because there 1 thread retrieving new set of data ?

[dependency]     public icachemanager<orderarray> orderarraycache { get; set; }     private readorderservice service = new readorderservice();     private const string _ckey = "all";     public dynamic get()     {         try         {             orderarray cache = orderarraycache.get(_ckey);             if(cache == null || cache.orders.length == 0)             {                 orderarray data = service.getallorders();                 orderarraycache.add(_ckey, data);                 return data;             }             else             {                 caching();                 return cache;             }         }         catch (exception error)         {             errorlog.writelog(config._systemname, this.gettype().name, system.reflection.methodbase.getcurrentmethod().name, error.tostring());             return 0;         }     }      public void caching()     {         thread worker = new thread(() => cacheworker());         worker.start();     }     public void cacheworker()     {         try         {             //activitylog.writelog(config._systemname, this.gettype().name, system.reflection.methodbase.getcurrentmethod().name, "cache worker starting work");             orderarray data = service.getallorders();             orderarraycache.put(_ckey, data);             //activitylog.writelog(config._systemname, this.gettype().name, system.reflection.methodbase.getcurrentmethod().name, "cache worker working hard");         }         catch(exception error)         {             //activitylog.writelog(config._systemname, this.gettype().name, system.reflection.methodbase.getcurrentmethod().name, error.tostring());         }     } 

without commenting on overall architecture, it's trivial setting flag you're working, , not starting thread if flag set.

of course in asp.net mvc/webapi context, controller instance created every request, simple field won't work. make static, that'll work per appdomain: 1 application can run in multiple appdomains, using multiple worker processes.

you solve using mutex, application in server farm, introducing whole shebang of new problems.

that being said, naive, static approach:

private static bool _currentlyretrievingcacheabledata = false;  public void caching() {     if (_currentlyretrievingcacheabledata)     {         return;     }      thread worker = new thread(() => cacheworker());     worker.start(); }  public void cacheworker() {     try     {         _currentlyretrievingcacheabledata = true;          // ...     }     catch(exception error)     {         // ...     }         {         _currentlyretrievingcacheabledata = false;     } } 

there's still race issue here, @ 2 threads can accessing cacheworker() method. can prevent using lock statement.

do note of workarounds doing obvious: let cache refreshing mechanism live outside web application code, example in windows service or scheduled task.