Lastly, I'm sure you've already done this, but to others: Please remember to do a file lock ( flock) so that the same script won't run multiple times at the same time in case of overlapping executions (often caused by (periodic) long execution times). However, the script will continue to be offset by a few micro- or milliseconds everytime it runs, which is not desirable. Normally MySQL supports stacked queries but because of database layer in most of the configurations its not possible to execute a second query in PHP-MySQL. This is easily achieved through a few microtime(true) calculations. Other requests waiting in their sessionstart () call to work with the session, which is currently used by the other PHP script. The real problem is that you are keeping the session open and locked in the thread using the sleep () statements. Crews offers an oral appliance that most patients find to be both surprisingly. Nick The problem is not the sleep () statement. There's a limit to Apache's ability to handle multiple LONG requests like this. That is, until you get five, or ten, or twenty of them doing this exact action and all of 'em waiting. That particular user-agent will be waiting and waiting until whatever happens. Then the execution time should be subtracted from the periodic sleep time, being 18 sec. An alternative to the traditional CPAP, which can be bulky and uncomfortable, Dr. Incidentally, it's that particular 'request' that's locked up. Say you want to execute something every 20 seconds, as in your case, but the script itself runs for 2 sec. Programmers may forget to take into account the execution time of the script itself. Additionally, the script will simply hang until the sleep timeout has been reached, just to occasionally realize it shouldn't run anymore. database or cache), but then it is internal logic inside the culprit script determining whether it should run or not. Some people use file locks and other persistence tools (e.g. Especially when called through a shell_exec, where you have absolutely no outside means of interrupting the script, short of restarting the server or identifying the PID and crashing it. I strong advice against using the poor-mans solution set_time_limit(0), which seems to pollute the web (Reddit, StackOverflow, Google Groups, etc.). It consumes unnecessarily many resources (CPU time and RAM), even when just hanging, and with little or no garbage collection. Notice that we need to use a then callback to make sure the second message is logged with a delay.PHP simply is not the right tool for this. This code will log “Hello”, wait for two seconds, then log “World!” Under the hood, we’re using the setTimeout method to resolve a promise after a given number of milliseconds. The standard way of creating a delay in JavaScript is to use its setTimeout method. Now that we have a better understanding of JavaScript’s execution model, let’s have a look at how JavaScript handles delays and asynchronous code. How to Use SetTimeout in JavaScript Properly If any of this is news to you, you should watch this excellent conference talk: What the heck is the event loop anyway? Rather, it will continue on its way, output “Hello!” to the console, and then when the request returns a couple of hundred milliseconds later, it will output the number of repos. It will not, however, wait for the request to complete. The JavaScript interpreter will encounter the fetch command and dispatch the request. Psychoeducation is a complementary alternative to the usual treatments for patients with sleep apnea, which allows them to learn to know their disease. This is because fetching data from an API is an asynchronous operation in JavaScript. If you run this code, it will output “Hello!” to the screen, then the number of public repos attributed to my GitHub account. Execution goes from top to bottom.Ĭontrast that with the equivalent JavaScript version: fetch ( '' ). The PHP sleep() and usleep() functions both pause execution of the script, but both behave a bit differently. It then parses the response, outputs the number of public repos attributed to my GitHub account and finally prints “Hello!” to the screen. This short tutorial will show you how to use the PHP sleep() and usleep() functions to pause script execution for a number of seconds/microseconds, and provide some code examples. get (uri ) )Īs one might expect, this code makes a request to the GitHub API to fetch my user data. Understanding this is crucial for effectively managing time and asynchronous operations in your code.Ĭonsider the following Ruby code: require 'net/http' require 'json' Now that we’ve got a quick solution under our belts, let’s delve into the mechanics of JavaScript’s execution model. Understanding JavaScript’s Execution Model
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