This changes how the AsyncPool works so that it does not immediately always start all of the workers in the pool.
Instead, workers will be started only when an idle worker was not found.
This allows for significant memory footprint reductions while idle.
In effect the async-workers setting in pocketmine.yml now dictates a _maximum_ pool size, not a fixed pool size.
This change breaks pretty much all API pertaining to synchronous task scheduling.
Significant changes:
- Server->getScheduler() has been removed
- Plugin->getScheduler() has been added - every plugin now has its own scheduler
- Because schedulers are now per-plugin, it is now unnecessary for PluginTask to exist because stopping plugin tasks on plugin disable is as simple as destroying the plugin's scheduler. Therefore PluginTask has now been removed and it is expected for things to now use the base Task class instead.
For the most part, plugins will simply need to change Plugin->getServer()->getScheduler()->... to Plugin->getScheduler()->...
Another highlight is that plugin tasks now no longer have global IDs - they are unique to each scheduler.
This commit contains quite a few breaking changes with respect to how AsyncTasks are handled. This is necessary to allow separation of the ServerScheduler and the AsyncPool, because in the future the ServerScheduler may be removed and instead there will be isolated per-plugin sync-task schedulers - but we cannot have every plugin with its own worker pool for memory usage reasons if nothing else.
The following things have changed:
- ServerScheduler: scheduleAsyncTask(), scheduleAsyncTaskToWorker(), getAsyncTaskPoolSize(), increaseAsyncTaskPoolSize() and similar methods have all been removed. Additionally the static \$WORKERS field has been removed.
- Server: added API method getAsyncPool(). This grants you direct access to the server's AsyncPool. Calls to getScheduler()->scheduleAsyncTask() and scheduleAsyncTaskToWorker() should be replaced with getAsyncPool()->submitTask() and submitTaskToWorker() respectively.
this implementation was god-awful bad and it was entirely avoidable to make it this complicated.
This utilizes the fact that pthreads treats static properties as thread-local. AsyncTask local storage now utilizes a \SplObjectStorage stored in an AsyncTask private static field.
Far too often I see people using IDEs which generate the constructors for them and then accidentally unintentionally store things in the object store. This parent constructor behaviour is unexpected. If a developer wants to store something, they should now do so explicitly by calling storeLocal().
