Presentation at LDC09: Introduction to Asynchronous Threads in Lasso 8.5

1. Advanced Track: Asynchronous Threads Bil Corry lasso.pro

2. What Are Async Threads? Code that executes in parallel to the currently processing page.

5. Web server determines the request is for Lasso and passes it to the Lasso connector

6. Lasso connector communicates with Lasso Server and sends the request

7. Lasso Server parses request, replies to Lasso connector

8. Lasso connector replies to web server

9. Web server replies to browser

12. It crashes

13. It is terminated for taking too long

16. It will also not have access to the variables of the page that created it.

17. All file paths must be absolute from the hard disk root – [include] does not work

19. An async thread will execute according to its priority and the load on Lasso

20. Basic Example Async threads are surrounded by curly-braces and initiated using ->asasyn c: [{'Hello World'}->asasync] The above code doesn't show anything in the browser, but it does run asynchronously.

21. Sending Data to Async Thread ->asasync allows you to add params to pass into the async thread [{ var('p1') = params->find('p1')->get(1)->value } ->asasync(-params=array('p1'=1, 'p2'=2))] Can also use globals (or other shared resources), but take care to correctly send the right message to the right thread and use [thread_atomic] to keep access to the global thread-safe

22. Template For Copying Vars To Async Thread <?LassoScript // from: http://www.lassotech.com/async // stuff on your page not async here... // -------------- BEGIN OF ASYNC CODE -------------- { // -------------- BEGIN OF ASYNC CODE -------------- // -------------------- // process async! // -------------------- // // NOTE: Code below this point is processed in it's own thread! // Lasso_ExecutionTimeLimit(60 * 60); // in seconds, set this to something reasonable Thread_SetPriority(Thread_GetCurrentID, Thread_Priority_Low); // set priority // recreate vars - this makes all the vars on the page available to the async thread iterate: params->(find:'-vars')->(get:1)->value, local:'var'; (var: #var->name) = #var->value; /iterate; // do stuff here that you want in it's own thread... // -------------- END OF ASYNC CODE -------------- }->(asasync: -params=(array: '-vars' = vars)); // -------------- END OF ASYNC CODE -------------- // do more stuff on the current page... ?>

23. Creating Context To create context within async threads, use variables to store the context of the current page (such as client_headers, file path, action_params) and use the template to pass the context into the async thread.

26. Task does not need to return data for the enduser to view

27. Task does not have to be finished by the time the concurrent page is served

28. Example of Off-Loading a Task Page originally created related records and made the enduser wait: [ loop(500); // create related record inline(-sql=”INSERT INTO mytable (id,this,that) VALUES (”+integer($userid)+”,”+integer($this)+”,”+integer($that)+”)”); /loop; 'Thanks for waiting!'; ]

29. Example of Off-Loading a Task (cont) Page now off-loads the related records creation and response much quicker to the enduser: <?LassoScript // from: http://www.lassotech.com/async // -------------- BEGIN OF ASYNC CODE -------------- { // -------------- BEGIN OF ASYNC CODE -------------- Lasso_ExecutionTimeLimit(60 * 60); // in seconds, set this to something reasonable Thread_SetPriority(Thread_GetCurrentID, Thread_Priority_Low); // set priority // recreate vars - this makes all the vars on the page available to the async thread iterate: params->(find:'-vars')->(get:1)->value, local:'var'; (var: #var->name) = #var->value; /iterate; loop(500); // create related record inline(-sql=”INSERT INTO mytable (id,this,that) VALUES (”+integer($userid)+”,”+integer($this)+”,”+integer($that)+”)”); /loop; // -------------- END OF ASYNC CODE -------------- }->(asasync: -params=(array: '-vars' = vars)); // -------------- END OF ASYNC CODE -------------- 'Thanks for waiting!'; ?>

31. Use [Lasso_ExecutionTimeLimit(0)] to permit the thread to run continuously

32. Can use a global to use as a switch to shut down the thread – [while(global('on'))] – just be sure to use [thread_atomic] to make it thread-safe

34. Example of a Recurring Event Creating a thread to watch a folder for new files to process: [{ Lasso_ExecutionTimeLimit(0); // run forever Thread_SetPriority(Thread_GetCurrentID, Thread_Priority_Low); // low priority while(true); iterate(file_listdirectory('///path/from/disk/root/'),local('file')); // do something with #file /iterate; Sleep(1000*60*10); // sleep 10 minutes (in milliseconds) /while; }->asasync] This would be placed in your LassoStartup folder.

36. Trap for errors

37. Send debug messages to an external source (file, database, etc.)

38. Test Outside of Async Easiest testing method, comment out the ->asasync container and try running your code, does it work? For recurring event threads, you'll have to limit the number of loop_counts and shorten the sleep: [//{ Lasso_ExecutionTimeLimit(0); // run forever Thread_SetPriority(Thread_GetCurrentID, Thread_Priority_Low); // low priority while(true); loop_count > 10 ? loop_abort; iterate(file_listdirectory('///path/from/disk/root/'),local('file')); // do something with #file /iterate; Sleep(1000*60*2); // sleep 2 minutes (in milliseconds) /while; //}->asasync ]

39. Trapping for Errors Place async code within [protect] to log errors: [{ Lasso_ExecutionTimeLimit(0); // run forever Thread_SetPriority(Thread_GetCurrentID, Thread_Priority_Low); // low priority protect; handle_error; log_critical('Folder watcher encounter an error: '+error_msg); /handle_error; while(true); iterate(file_listdirectory('///path/from/disk/root/'),local('file')); // do something with #file /iterate; Sleep(1000*60*10); // sleep 10 minutes (in milliseconds) /while; /protect; }->asasync]

41. Database

42. Lasso Errors

43. Lasso Console

44. Email

45. Global Var

46. Thank You! Questions?