Add API to cancel async jobs (#14602)

* Implement API to cancel async jobs

Co-authored-by: sfan5 <sfan5@live.de>

* update AsyncJob:cancel documentation from review

* Use IPC to unblock async

* review

* review async unblocking

* review

* Apply suggestions from code review

Co-authored-by: sfan5 <sfan5@live.de>

* minor licensing

---------

Co-authored-by: y5nw <y5nw@protonmail.com>
Co-authored-by: sfan5 <sfan5@live.de>

src/script/cpp_api/s_async.cpp

@@ -96,38 +96,44 @@ void AsyncEngine::addWorkerThread()
 }
 
 /******************************************************************************/
-u32 AsyncEngine::queueAsyncJob(std::string &&func, std::string &&params,
-		const std::string &mod_origin)
+
+u32 AsyncEngine::queueAsyncJob(LuaJobInfo &&job)
 {
 	MutexAutoLock autolock(jobQueueMutex);
 	u32 jobId = jobIdCounter++;
 
-	jobQueue.emplace_back();
-	auto &to_add = jobQueue.back();
-	to_add.id = jobId;
-	to_add.function = std::move(func);
-	to_add.params = std::move(params);
-	to_add.mod_origin = mod_origin;
+	assert(!job.function.empty());
+	job.id = jobId;
+	jobQueue.push_back(std::move(job));
 
 	jobQueueCounter.post();
 	return jobId;
 }
 
+u32 AsyncEngine::queueAsyncJob(std::string &&func, std::string &&params,
+		const std::string &mod_origin)
+{
+	LuaJobInfo to_add(std::move(func), std::move(params), mod_origin);
+	return queueAsyncJob(std::move(to_add));
+}
+
 u32 AsyncEngine::queueAsyncJob(std::string &&func, PackedValue *params,
 		const std::string &mod_origin)
+{
+	LuaJobInfo to_add(std::move(func), params, mod_origin);
+	return queueAsyncJob(std::move(to_add));
+}
+
+bool AsyncEngine::cancelAsyncJob(u32 id)
 {
 	MutexAutoLock autolock(jobQueueMutex);
-	u32 jobId = jobIdCounter++;
-
-	jobQueue.emplace_back();
-	auto &to_add = jobQueue.back();
-	to_add.id = jobId;
-	to_add.function = std::move(func);
-	to_add.params_ext.reset(params);
-	to_add.mod_origin = mod_origin;
-
-	jobQueueCounter.post();
-	return jobId;
+	for (auto job = jobQueue.begin(); job != jobQueue.end(); job++) {
+		if (job->id == id) {
+			jobQueue.erase(job);
+			return true;
+		}
+	}
+	return false;
 }
 
 /******************************************************************************/
@@ -419,3 +425,19 @@ void* AsyncWorkerThread::run()
 	return 0;
 }
 
+u32 ScriptApiAsync::queueAsync(std::string &&serialized_func,
+		PackedValue *param, const std::string &mod_origin)
+{
+	return asyncEngine.queueAsyncJob(std::move(serialized_func),
+			param, mod_origin);
+}
+
+bool ScriptApiAsync::cancelAsync(u32 id)
+{
+	return asyncEngine.cancelAsyncJob(id);
+}
+
+void ScriptApiAsync::stepAsync()
+{
+	asyncEngine.step(getStack());
+}

src/script/cpp_api/s_async.h

@@ -26,6 +26,12 @@ class AsyncEngine;
 struct LuaJobInfo
 {
 	LuaJobInfo() = default;
+	LuaJobInfo(std::string &&func, std::string &&params, const std::string &mod_origin = "") :
+		function(func), params(params), mod_origin(mod_origin) {}
+	LuaJobInfo(std::string &&func, PackedValue *params, const std::string &mod_origin = "") :
+		function(func), mod_origin(mod_origin) {
+		params_ext.reset(params);
+	}
 
 	// Function to be called in async environment (from string.dump)
 	std::string function;
@@ -102,12 +108,26 @@ public:
 	u32 queueAsyncJob(std::string &&func, PackedValue *params,
 			const std::string &mod_origin = "");
 
+	/**
+	 * Try to cancel an async job
+	 * @param id The ID of the job
+	 * @return Whether the job was cancelled
+	 */
+	bool cancelAsyncJob(u32 id);
+
 	/**
 	 * Engine step to process finished jobs
 	 * @param L The Lua stack
 	 */
 	void step(lua_State *L);
 
+	/**
+	 * Get the maximum number of threads that can be used by the async environment
+	 */
+	unsigned int getThreadingCapacity() const {
+		return MYMAX(workerThreads.size(), autoscaleMaxWorkers);
+	}
+
 protected:
 	/**
 	 * Get a Job from queue to be processed
@@ -117,6 +137,13 @@ protected:
 	 */
 	bool getJob(LuaJobInfo *job);
 
+	/**
+	 * Queue an async job
+	 * @param job The job to queue (takes ownership!)
+	 * @return Id of the queued job
+	 */
+	u32 queueAsyncJob(LuaJobInfo &&job);
+
 	/**
 	 * Put a Job result back to result queue
 	 * @param result result of completed job
@@ -206,3 +233,23 @@ private:
 	// Counter semaphore for job dispatching
 	Semaphore jobQueueCounter;
 };
+
+class ScriptApiAsync:
+	virtual public ScriptApiBase
+{
+public:
+	ScriptApiAsync(Server *server): asyncEngine(server) {}
+
+	virtual void initAsync() = 0;
+	void stepAsync();
+
+	u32 queueAsync(std::string &&serialized_func,
+			PackedValue *param, const std::string &mod_origin);
+	bool cancelAsync(u32 id);
+	unsigned int getThreadingCapacity() const {
+		return asyncEngine.getThreadingCapacity();
+	}
+
+protected:
+	AsyncEngine asyncEngine;
+};