site_archiver@lists.apple.com Delivered-To: Darwin-dev@lists.apple.com On May 22, 2006, at 11:19 AM, Peter Seebach wrote: - Kevin _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.appl... What's the launchd way for my existing program which runs on 30 other UNIX platforms to request that it be launched only when a configuration file it needs is accessible? On other systems, I'd put it in startup after all the disk-mounting. What do I do in the launchd model? My program doesn't have any hooks for querying disk availability, *BECAUSE THAT IS THE JOB OF THE STARTUP SYSTEM*. Or at least, always has been. Historically it might have been safe to assume disk availability after "startup," but the whole point is that such assumptions are fragile at best, and therefore shouldn't be made. Disks (especially FireWire and USB) can come and go long after "startup," so it really isn't "the job of the startup system" to ensure that they're there. It's the job of the process. The complications of dependency checking have not been removed; they've been moved from specifications in the plist file (or rc file, or whatever) into extra code in my application. Correct. The StartupItem dependencies were not a panacea. In fact, a lot of third party applications had trouble with the dependency model as technologies moved from one startup item to the next (even before the shift to launchd). Maintaining dependency information in an abstract parallel universe is always prone to mistakes. The advantage of processes implicitly declaring dependencies (via blocking IPC etc.) or explicitly declaring them (via callbacks for system state changes) is inherently more robust. What's the launchd way for my existing program, which scans for running network interfaces and binds to them, to ensure that it's run only after the network is up? I don't care about laptop issues, I'm writing a server app. I don't want to have to add special code to my app to scan repeatedly because ONE SYSTEM won't let me just schedule my item "after the network is up". Actually you should have always tested for this in your code. configd is responsible for bringing up the network interfaces. Originally launched by a startup item, it was subsequently moved to a mach_init plist in Jaguar. The point is that there was never an explicit dependency here. If you want to replicate the historic behavior, then put a sleep(60) in your main() function and hope for the best, because this is essentially all that was ever happening anyway. Interfaces can come and go dynamically even on Mac OS X Server, so I don't really buy the argument that detecting this fact isn't necessary on server systems. Launchd has a lot to offer, especially for server processes, like process keep-alive. And the "new requirements" that lauchd "imposes" on your processes generally have been there all along, and it's just been a matter of luck that things worked without taking the time to address these issues. This email sent to site_archiver@lists.apple.com