Added code to avoid building the same document multiple times concurrently

Also avoids compiling too many PDF at the same time (configurable)
Also skips useless build tasks (if another build task is already pending to start)

src/app.py

@@ -2,6 +2,7 @@ import os
 import random
 import string
 from web_utils.business_exception import BusinessException
+from web_utils.task import Resource
 from flask import Flask, render_template
 
 import data.document
@@ -39,6 +40,11 @@ def create_app():
 		from werkzeug.middleware.proxy_fix import ProxyFix
 		app.wsgi_app = ProxyFix(app.wsgi_app, x_for=1, x_proto=1, x_host=1, x_prefix=1)
 		
+	Resource.register('__thread', app.config['MAX_CONCURRENT_TASK_THREADS'])
+	Resource.register('__process', app.config['MAX_CONCURRENT_TASK_PROCESSES'])
+	Resource.register('document_files', 1, False)
+	Resource.register('intensive_task', app.config['MAX_CONCURRENT_INTENSIVE_TASKS'])
+
 	from api import api_document
 	app.register_blueprint(api_document.bp)
 	

src/app_config.py

@@ -8,3 +8,7 @@ DOCUMENT_ROOT_DIR = os.path.realpath(DATA_ROOT_DIR+'/doc')
 ADMIN_PASSWORD = '' # You must override this in config.py or the application won't start
 
 BEHIND_REVERSE_PROXY = False
+
+MAX_CONCURRENT_TASK_THREADS = 10
+MAX_CONCURRENT_TASK_PROCESSES = 5
+MAX_CONCURRENT_INTENSIVE_TASKS = 1

src/data/document.py

@@ -75,6 +75,8 @@ class Document:
 		
 		cmd = []
 		
+		is_intensive_task = False
+
 		# update source files from git
 		cmd.append(['git', 'pull'])
 		
@@ -88,6 +90,8 @@ class Document:
 			
 			if type(self.settings['build_pdf']) is list:
 				for pdf_branch_name in self.settings['build_pdf']:
+					is_intensive_task = True
+					
 					# Extract the source files to a temporary directory
 					cmd.append(['rm', '-rf', self.doc_path + '/tmp_source'])
 					cmd.append(['mkdir', self.doc_path + '/tmp_source'])
@@ -107,6 +111,8 @@ class Document:
 			cmd.append(['make', 'html', 'BUILDDIR=../build'])
 			
 			if self.settings['build_pdf']:
+				is_intensive_task = True
+				
 				# build the PDF version
 				cmd.append(['make', 'pdf', 'BUILDDIR=../build'])
 
@@ -120,8 +126,12 @@ class Document:
 		else:
 			cmd.append(['mv', self.doc_path + '/build/html/', self.doc_path + '/dist/'])
 		
-		task = ProcessTask(cmd, cwd = self.doc_path + "/repo")
-		task.start()
+		resource_usage = [('document_files', self.doc_path)]
+		if is_intensive_task:
+			resource_usage.append(('intensive_task', ''))
+		
+		task = ProcessTask(cmd, cwd = self.doc_path + "/repo", resource_usage = resource_usage)
+		task.start(skip_if_another_pending = self.doc_path)
 		
 		return task
 	

src/web_utils/task.py

@@ -1,18 +1,85 @@
-from threading import Thread, Lock
+from threading import Thread, Lock, RLock
 from io import StringIO
 from subprocess import Popen, PIPE, STDOUT, DEVNULL
 import uuid
+from datetime import datetime
 from web_utils.business_exception import BusinessException
+import time
+
+resources = {}
 
 tasks = {}
+pending_tasks = {}
+
+task_management_mutex = RLock()
+resource_mutex = RLock()
+
+class Resource:
+	def __init__(self, type_id, amount, is_single_resource):
+		self.type_id = type_id
+		self.amount = amount
+		self.is_single_resource = is_single_resource
+		self.available_amount = {}
+		
+	def get_available_amount(self, resource_id):
+		assert(resource_id == '' or not self.is_single_resource)
+		resource_mutex.acquire()
+		if resource_id in self.available_amount:
+			result = self.available_amount[resource_id]
+		else:
+			result = self.amount
+		resource_mutex.release()
+		return result
+	
+	def acquire(self, resource_id, amount):
+		assert(resource_id == '' or not self.is_single_resource)
+		resource_mutex.acquire()
+		if resource_id not in self.available_amount:
+			self.available_amount[resource_id] = self.amount
+		available_amount = self.available_amount[resource_id]
+		assert(available_amount >= amount)
+		self.available_amount[resource_id] = available_amount - amount
+		resource_mutex.release()
+		
+	def release(self, resource_id, amount):
+		assert(resource_id == '' or not self.is_single_resource)
+		resource_mutex.acquire()
+		assert(resource_id in self.available_amount)
+		available_amount = self.available_amount[resource_id]
+		assert(available_amount + amount <= self.amount)
+		self.available_amount[resource_id] = available_amount + amount
+		resource_mutex.release()
+		
+	@staticmethod
+	def register(type_id, amount, is_single_resource = True):
+		assert(type_id not in resources)
+		resources[type_id] = Resource(type_id, amount, is_single_resource)
 	
-class Task(Thread):
-	def __init__(self):
-		Thread.__init__(self)
-		self.task_id = uuid.uuid4()
+	@staticmethod
+	def get(type_id):
+		return resources[type_id]
+
+class Task:
+	def __init__(self, resource_usage):
+		self.__thread = None
+		self.task_id = str(uuid.uuid4())
 		self.__mutex = Lock()
 		self.__output = StringIO()
-		tasks[str(self.task_id)] = self
+		self.__resource_usage = list(resource_usage)
+		self.__resource_usage.append(('__thread', ''))
+		self.__has_logged_waiting = ''
+		self.__skip_id = ''
+		self.__finished_at = None
+		
+		# Check all required resources are registered
+		for required_resource in self.__resource_usage:
+			resource = Resource.get(required_resource[0])
+			single = (required_resource[1] == '')
+			assert(single == resource.is_single_resource)
+		
+		task_management_mutex.acquire()
+		tasks[self.task_id] = self
+		task_management_mutex.release()
 		
 	def print(self, str):
 		self.__mutex.acquire()
@@ -25,13 +92,133 @@ class Task(Thread):
 		self.__mutex.release()
 		return result
 	
+	def start(self, skip_if_another_pending = None):
+		task_management_mutex.acquire()
+		
+		skip_me = False
+		self.__skip_id = skip_if_another_pending
+		if skip_if_another_pending is not None:
+			for id, other_task in pending_tasks.items():
+				if other_task.__skip_id == skip_if_another_pending:
+					skip_me = True
+					break
+		
+		if skip_me:
+			print('Task ' + self.task_id + ' skipped')
+			self.print('Task skipped (another identical task is already pending for execution)\n')
+		else:
+			pending_tasks[self.task_id] = self
+		
+		task_management_mutex.release()
+		Task.__update_pending_tasks()
+		
+	def is_alive(self):
+		task_management_mutex.acquire()
+		alive = self.task_id in pending_tasks
+		if self.__thread is not None:
+			alive = self.__thread.is_alive()
+		task_management_mutex.release()
+		return alive
+	
+	def join(self):
+		task_management_mutex.acquire()
+		
+		while self.__thread is None and self.is_alive():
+			task_management_mutex.release()
+			time.sleep(1)
+			task_management_mutex.acquire()
+		
+		if self.__thread is not None:
+			task_management_mutex.release()
+			self.__thread.join()
+		else:
+			task_management_mutex.release()
+		
+	def __start_thread(self):
+		print('Starting task ' + self.task_id)
+		task_management_mutex.acquire()
+		assert(self.__thread is None)
+		self.__thread = Thread(target=self.__run)
+		task_management_mutex.release()
+		self.__thread.start()
+		
+	def __run(self):
+		self.run()
+		print('Task ' + self.task_id + ' has finished')
+		self.__finished_at = datetime.now()
+		Task.__free_resources(self)
+		Task.__update_pending_tasks()
+	
 	@staticmethod
 	def get(task_id):
-		return tasks[task_id]
+		task_management_mutex.acquire()
+		result = tasks[task_id]
+		task_management_mutex.release()
+		return result
+	
+	@staticmethod
+	def __update_pending_tasks():
+		task_management_mutex.acquire()
+		
+		# Clear finished tasks
+		now = datetime.now()
+		to_remove = []
+		for key, task in tasks.items():
+			if task.__finished_at is not None and (now - task.__finished_at).total_seconds() > 60:
+				to_remove.append(key)
+		for key in to_remove:
+			print('Dropping task ' + key)
+			tasks.pop(key)
+		
+		for key, task in pending_tasks.items():
+			can_start = True
+			
+			all_wait_causes = ''
+			has_same_wait_cause = False
+			
+			resource_mutex.acquire()
+			for required_resource in task.__resource_usage:
+				resource = Resource.get(required_resource[0])
+				if resource.get_available_amount(required_resource[1]) < 1:
+					can_start = False
+					wait_cause = required_resource[0] + (' ('+required_resource[1]+')' if required_resource[1] != '' else '')
+					if wait_cause == task.__has_logged_waiting:
+						has_same_wait_cause = True
+					all_wait_causes = all_wait_causes + (', ' if all_wait_causes != '' else '') + wait_cause
+					
+			if not can_start:
+				if not has_same_wait_cause:
+					task.__has_logged_waiting = wait_cause
+					task.print('Waiting for resource(s): '+all_wait_causes+'\n')
+				resource_mutex.release()
+				continue
+				
+			for required_resource in task.__resource_usage:
+				resource = Resource.get(required_resource[0])
+				resource.acquire(required_resource[1], 1)
+			resource_mutex.release()
+			
+			pending_tasks.pop(key)
+			task.__start_thread()
+			break
+		
+		task_management_mutex.release()
+		
+	@staticmethod
+	def __free_resources(task):
+		task_management_mutex.acquire()
+		resource_mutex.acquire()
+		for required_resource in task.__resource_usage:
+			resource = Resource.get(required_resource[0])
+			resource.release(required_resource[1], 1)
+		resource_mutex.release()
+		task_management_mutex.release()
 
 class ProcessTask(Task):
-	def __init__(self, commands, cwd = None, hide_passwords = []):
-		Task.__init__(self)
+	def __init__(self, commands, cwd = None, hide_passwords = [], resource_usage = []):
+		resource_usage = list(resource_usage)
+		resource_usage.append(('__process', ''))
+		Task.__init__(self, resource_usage)
 		self.__commands = commands
 		self.__cwd = cwd
 		self.__hide_passwords = hide_passwords