思路
def run(self):
'''Start scheduler loop'''
logger.info("scheduler starting...")
while not self._quit:
try:
time.sleep(self.LOOP_INTERVAL)
self.run_once()
self._exceptions = 0
except KeyboardInterrupt:
break
except Exception as e:
logger.exception(e)
self._exceptions += 1
if self._exceptions > self.EXCEPTION_LIMIT:
break
continue
logger.info("scheduler exiting...")
self._dump_cnt()
通过run发现，scheduler模块从队列拿到信息执行run_once这个方法。而run_once执行了下面的函数
self._update_projects()
self._check_task_done()
self._check_request()
while self._check_cronjob():
pass
self._check_select()
self._check_delete()
self._try_dump_cnt()
一个个看这些函数。
_update_projects
def _update_projects(self):
'''Check project update'''
now = time.time()
if (
not self._force_update_project
and self._last_update_project + self.UPDATE_PROJECT_INTERVAL > now
):
return
for project in self.projectdb.check_update(self._last_update_project):
self._update_project(project)
logger.debug("project: %s updated.", project['name'])
self._force_update_project = False
self._last_update_project = now
_update_projects 首先会进行一个检查现在和更新的时间差，如果满足条件调用_update_project 更新project状态。
_update_project
pyspider很喜欢具体的模块具体来实现，并且名字通过下划线来分别。_update_project就是具体的更新方法。
_check_task_done
def _check_task_done(self):
'''Check status queue'''
cnt = 0
try:
while True:
task = self.status_queue.get_nowait()
# check _on_get_info result here
if task.get('taskid') == '_on_get_info' and 'project' in task and 'track' in task:
if task['project'] not in self.projects:
continue
project = self.projects[task['project']]
project.on_get_info(task['track'].get('save') or {})
logger.info(
'%s on_get_info %r', task['project'], task['track'].get('save', {})
)
continue
elif not self.task_verify(task):
continue
self.on_task_status(task)
cnt += 1
except Queue.Empty:
pass
return cnt
从status_queue拿到task，这里的task长这个样子
{'taskid': '_on_get_info', 'project': 'baidu', 'url': 'data:,_on_get_info', 'track': {'process': {'time': 0.022366762161254883, 'ok': True, 'exception': None, 'result': None, 'follows': 0, 'logs': ''}, 'fetch': {'error': None, 'redirect_url': None, 'ok': True, 'time': 0, 'encoding': None, 'status_code': 200, 'headers': {}, 'content': None}, 'save': {'retry_delay': {}, 'min_tick': 86400, 'crawl_config': {}}}}
参数说明
- project,taskid,url 是字面意思。注意scheduler里面有一个self.projects进行 区别
- track里面的save，fetch， process。save是写爬虫存的参数，fetch应该用来给fetcher模块process用来个process模块。
之后从self.projects[task['project']]拿到project的信息 - on_get_info() 从info里面拿到信息
- on_task_status 判断task的process是否成功
_check_request
def _check_request(self):
'''Check new task queue'''
# check _postpone_request first
todo = []
for task in self._postpone_request:
if task['project'] not in self.projects:
continue
if self.projects[task['project']].task_queue.is_processing(task['taskid']):
todo.append(task)
else:
self.on_request(task)
self._postpone_request = todo
tasks = {}
while len(tasks) < self.LOOP_LIMIT:
try:
task = self.newtask_queue.get_nowait()
except Queue.Empty:
break
if isinstance(task, list):
_tasks = task
else:
_tasks = (task, )
for task in _tasks:
if not self.task_verify(task):
continue
if task['taskid'] in self.projects[task['project']].task_queue:
if not task.get('schedule', {}).get('force_update', False):
logger.debug('ignore newtask %(project)s:%(taskid)s %(url)s', task)
continue
if task['taskid'] in tasks:
if not task.get('schedule', {}).get('force_update', False):
continue
tasks[task['taskid']] = task
for task in itervalues(tasks):
self.on_request(task)
return len(tasks)
从头检查到尾，看这个task是否符合要求。
如果符合要求，加入tasks，并且最后运行
for task in itervalues(tasks):
self.on_request(task)
on_request
def on_request(self, task):
if self.INQUEUE_LIMIT and len(self.projects[task['project']].task_queue) >= self.INQUEUE_LIMIT:
logger.debug('overflow task %(project)s:%(taskid)s %(url)s', task)
return
oldtask = self.taskdb.get_task(task['project'], task['taskid'],
fields=self.merge_task_fields)
if oldtask:
return self.on_old_request(task, oldtask)
else:
return self.on_new_request(task)
把task分成old和new分别执行