c# - async and await code behaving differently if we run it from different processes -

please bear me long question.

scenario: have filesystemwatcher on root-directory watching lastwrite change on control-file each inside control-directory. looks this:-

root-directory (filesystemwatcher instance watching root directory)

|

|-----control-directory_0 \ control-file

                      \ data-file 

|-----control-directory_1 \ control-file

                      \ data-file 

|-----control-directory_2 \ control-file

                      \ data-file 

|-----control-directory_3 \ control-file

                      \ data-file 

.........more similar structure (but 1 root-directory)

sorry creative drawing.

the problem facing, there can many control-directories inside root-directory (approx 200-500) , along control-directory's control-file, have data-file in (in each of them) continuous writes happening.

i watching notifyfilter.lastwrite , filter = control-file. internalbuffersize set 4kb (please don't ask increase this, not allowed modify , event make 8kb (default one) due requirements , can't use filesystemwatcher each control-file take lot of precious non-paged memory).

my eventhandler looks this

  private void onchange(object sender, filesystemeventargs eventargs)   {      //result = cpu bound work here      //evaluating result   } 

currently, handling 300 control-files. due lots of writes happening on data-file , lots of requests coming control-file buffer overflowing quite regularly.

then thought of idea. (async , await rescue task battle tank)

  async private void onchange(object sender, filesystemeventargs eventargs)   {      var result = await task.run(() => work.cpuboundwork());      //evaluating result   } 

it working fine , able handle lots of requests (even tested 1000 events 4kb buffer).

now comes interesting part. how testing it?

there 2 entities involved, one, writing control or data-file , second, handling events generated writes control-file. went , created console app, both of things.

static void main(string[] args) {   int controlfilecount = convert.toint32(args[0]);   string basepath = args[1];   //createfolderstructure(basepath, controlfilecount); first run.   filesystemwatcher basedirectorywatcher = new filesystemwatcher();   setupfilesystemwatcher(basedirectorywatcher, basepath);   writetocontrolfilesparallely(basepath, controlfilecount);   console.read(); }  public void setupfilesystemwatcher(filesystemwatcher basedirectorywatcher, string path) {   //setting properties of watcher.   basedirectorywatcher.notifyfilter = notifyfilter.lastwrite;   basedirectorywatcher.filter = "control-file";   basedirectorywatcher.internalbuffersize = 4096;   basedirectorywatcher.path = path;   basedirectorywatcher.includesubdirectories = true;   basedirectorywatcher.enableraisingevents = true; }  public void writetocontrolfilesparallely(string basepath, int controlfilecount) {   parallel.for(0, controlfilecount, (i) =>   {     string filepath = helper.getfilepath(basepath, i);     helper.writedata(filepath, "data");   }); } 

next, tested 2 console applications:-

first, responsible of writing data various control files parallelly - (writer_app).

second, responsible handling events - (event_handling_app).

note: there's no code change in core instead of writing , handling events in same console app writing 1 , handling form other.

so separated 2 entities old console app (starting simulation actual environment). started testing running first event_handling_app , write control-file running writer_app , things have become strange , application facing internalbufferoverflow exception same number of control-files , same number of writes when didn't have async , await in first implementation.

i again tested 1 console app (which having both responsibilities) , working fine.

so, why 2 console applications make magic of async , await (along task) disappear while 1 console application working great?

is related inter process communication?

i wondering if work in production because using handler code in web application , other process can write these files on network.

finally, able figure out this, when using single console app running exe (through cmd) when trying 2 console app running app inside visual studio (in release mode) due (with load of visual studio) getting exception , blaming async , await.

so, run application exe if dealing code tight.