水平缩放Scrapyd

Question

如果需要，您会使用什么工具或工具集来水平扩展scrapyd，将新机器动态添加到scrapyd集群中，并让每台机器拥有N个实例。所有实例共享一个公共作业队列并不是必须的，但这将是非常棒的。

Scrapy-cluster似乎很适合这项工作，但我想要一个基于Scrapyd的解决方案，所以我听取了其他替代方案和建议。

Answer 1

我使用Scrapyd的API和一个wrapper为我自己的负载平衡器编写了脚本。

from random import shuffle
from scrapyd_api.wrapper import ScrapydAPI

class JobLoadBalancer(object):

    @classmethod
    def get_less_occupied(
            cls,
            servers_urls=settings.SERVERS_URLS,
            project=settings.DEFAULT_PROJECT,
            acceptable=settings.ACCEPTABLE_PENDING):

        free_runner = {'num_jobs': 9999, 'client': None}
        # shuffle servers optimization
        shuffle(servers_urls)
        for url in servers_urls:
            scrapyd = ScrapydAPI(target=url)
            jobs = scrapyd.list_jobs(project)
            num_jobs = len(jobs['pending'])

            if free_runner['num_jobs'] > num_jobs:
                free_runner['num_jobs'] = num_jobs
                free_runner['client'] = scrapyd
            # Optimization: if found acceptable pending operations in one server stop looking for another one
            if free_runner['client'] and free_runner['num_jobs'] <= acceptable:
                break

        return free_runner['client']

单元测试：

def setUp(self):
        super(TestFactory, self).setUp()
        # Make sure this servers are running
        settings.SERVERS_URLS = [
            'http://localhost:6800',
            'http://localhost:6900'
        ]
        self.project = 'dummy'
        self.spider = 'dummy_spider'
        self.acceptable = 0

    def test_get_less_occupied(self):
        # add new dummy jobs to first server so that choose the second one
        scrapyd = ScrapydAPI(target=settings.SERVERS_URLS[0])
        scrapyd.schedule(project=self.project, spider=self.spider)
        scrapyd.schedule(project=self.project, spider=self.spider)
        second_server_url = settings.SERVERS_URLS[1]
        scrapyd = JobLoadBalancer.get_less_occupied(
            servers_urls=settings.SERVERS_URLS,
            project=self.project,
            acceptable=self.acceptable)
        self.assertEqual(scrapyd.target, second_server_url)

这段代码针对的是一个旧版本的scrapyd，因为它是一年多前编写的。