![All file paths must be absolute from the hard disk root – [include] does not work](https://image.slidesharecdn.com/corryasyncthreads-091124005754-phpapp02/85/Asynchronous-Threads-in-Lasso-8-5-17-320.jpg)
![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.](https://image.slidesharecdn.com/corryasyncthreads-091124005754-phpapp02/85/Asynchronous-Threads-in-Lasso-8-5-20-320.jpg)
![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](https://image.slidesharecdn.com/corryasyncthreads-091124005754-phpapp02/85/Asynchronous-Threads-in-Lasso-8-5-21-320.jpg)
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.
- 3. Why Use Async Threads? Off-load tasks Improve response time to enduser by off-loading tasks that do not need to provide immediate feedback to the enduser Recurring events Lasso Scheduled Events, Email Queue, etc all are async threads. Network-hooked services lp_site_restart sets up a TCP listener that receives commands to restart Lasso
- 4. Typical Lasso Request Model Browser sends HTTP request to the web server
- 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
- 10. Lasso Async Thread Model Lasso page initiates new thread
- 11. Just like a normal page, the thread will run until: It terminates normally
- 12. It crashes
- 13. It is terminated for taking too long
- 14. Lasso site or server is shut down When configured as such, some threads never terminate
- 15. Lasso Async Thread Model (cont) Because the request comes from Lasso itself, async threads do NOT have access to the web request info, such as client_headers, action_params, etc.
- 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
- 18. Lasso Async Thread Model (cont) Output from the async thread is not available, so alternative methods must be used, such as logging to a file, a database, global variable or the Lasso console
- 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.
- 24. Two Important Settings [Lasso_ExecutionTimeLimit] Specifies the maximum number of seconds to let this thread run. Setting it to zero will allow the thread to run continuously [Thread_SetPriority] Can set to high or low, setting it to low (Thread_Priority_Low) gives more priority to enduser requests
- 25. Off-Loading Tasks Improve the response time to the enduser by off-loading tasks on the page that meet the following criteria: Code for task is relatively self-contained
- 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!'; ?>
- 30. Creating a Recurring Event Use [while(true)] to create a continuous thread
- 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
- 33. Use [sleep] to pause the event between runs Very important! If the thread doesn't sleep, it will consume Lasso and the processor
- 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.
- 35. Debugging Async threads are tricky to debug because they do not directly output the browser. Test async code outside of ->asasync
- 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]
- 40. Send Debug Messages to External Source File
- 41. Database
- 42. Lasso Errors
- 43. Lasso Console
- 44. Email
- 45. Global Var