implement resilience to warcprox outage, i.e. deal with brozzler.ProxyError in brozzler-worker

brozzler/worker.py

@@ -127,7 +127,7 @@ class BrozzlerWorker:
         elif self._warcprox_auto:
             svc = self._service_registry.available_service('warcprox')
             if svc is None:
-                raise Exception(
+                raise brozzler.ProxyError(
                         'no available instances of warcprox in the service '
                         'registry')
             site.proxy = '%s:%s' % (svc['host'], svc['port'])
@@ -417,6 +417,10 @@ class BrozzlerWorker:
     def brozzle_site(self, browser, site):
         try:
             page = None
+            self._frontier.honor_stop_request(site)
+            self.logger.info(
+                    "brozzling site (proxy=%s) %s",
+                    repr(self._proxy_for(site)), site)
             start = time.time()
             while time.time() - start < 7 * 60:
                 site.refresh()
@@ -449,6 +453,18 @@ class BrozzlerWorker:
             self._frontier.finished(site, "FINISHED_STOP_REQUESTED")
         # except brozzler.browser.BrowsingAborted:
         #     self.logger.info("{} shut down".format(browser))
+        except brozzler.ProxyError as e:
+            if self._warcprox_auto:
+                logging.error(
+                        'proxy error (site.proxy=%s), will try to choose a '
+                        'healthy instance next time site is brozzled: %s',
+                        site.proxy, e)
+                site.proxy = None
+            else:
+                # using brozzler-worker --proxy, nothing to do but try the
+                # same proxy again next time
+                logging.error(
+                        'proxy error (site.proxy=%s): %s', repr(site.proxy), e)
         except:
             self.logger.critical("unexpected exception", exc_info=True)
         finally:
@@ -508,9 +524,6 @@ class BrozzlerWorker:
                     try:
                         site = self._frontier.claim_site("%s:%s" % (
                             socket.gethostname(), browser.chrome.port))
-                        self.logger.info(
-                                "brozzling site (proxy=%s) %s",
-                                repr(self._proxy_for(site)), site)
                         th = threading.Thread(
                                 target=self._brozzle_site_thread_target,
                                 args=(browser, site),

setup.py

@@ -32,7 +32,7 @@ def find_package_data(package):
 
 setuptools.setup(
         name='brozzler',
-        version='1.1b11.dev235',
+        version='1.1b11.dev236',
         description='Distributed web crawling with browsers',
         url='https://github.com/internetarchive/brozzler',
         author='Noah Levitt',

tests/test_cluster.py

@@ -32,6 +32,7 @@ import requests
 import subprocess
 import http.server
 import logging
+import warcprox
 
 def start_service(service):
     subprocess.check_call(['sudo', 'service', service, 'start'])
@@ -579,3 +580,125 @@ def test_stop_crawl(httpd):
     sites[2].refresh()
     assert sites[2].status == 'FINISHED_STOP_REQUESTED'
 
+def test_warcprox_outage_resiliency(httpd):
+    '''
+    Tests resiliency to warcprox outage.
+
+    If no instances of warcprox are healthy when starting to crawl a site,
+    brozzler-worker should sit there and wait until a healthy instance appears.
+
+    If an instance goes down, sites assigned to that instance should bounce
+    over to a healthy instance.
+
+    If all instances of warcprox go down, brozzler-worker should sit and wait.
+    '''
+    rr = doublethink.Rethinker('localhost', db='brozzler')
+    frontier = brozzler.RethinkDbFrontier(rr)
+    svcreg = doublethink.ServiceRegistry(rr)
+
+    # run two instances of warcprox
+    opts = warcprox.Options()
+    opts.address = '0.0.0.0'
+    opts.port = 0
+
+    warcprox1 = warcprox.controller.WarcproxController(
+            service_registry=svcreg, options=opts)
+    warcprox2 = warcprox.controller.WarcproxController(
+            service_registry=svcreg, options=opts)
+    warcprox1_thread = threading.Thread(
+            target=warcprox1.run_until_shutdown, name='warcprox1')
+    warcprox2_thread = threading.Thread(
+            target=warcprox2.run_until_shutdown, name='warcprox2')
+
+    # put together a site to crawl
+    test_id = 'test_warcprox_death-%s' % datetime.datetime.utcnow().isoformat()
+    site = brozzler.Site(rr, {
+        'seed': 'http://localhost:%s/infinite/' % httpd.server_port,
+        'warcprox_meta': {'captures-table-extra-fields':{'test_id':test_id}}})
+
+    try:
+        # we manage warcprox instances ourselves, so stop the one running on
+        # the system, if any
+        try:
+            stop_service('warcprox')
+        except Exception as e:
+            logging.warn('problem stopping warcprox service: %s', e)
+
+        # queue the site for brozzling
+        brozzler.new_site(frontier, site)
+
+        # check that nothing happens
+        # XXX tail brozzler-worker.log or something?
+        time.sleep(30)
+        site.refresh()
+        assert site.status == 'ACTIVE'
+        assert not site.proxy
+        assert len(list(frontier.site_pages(site.id))) == 1
+
+        # start one instance of warcprox
+        warcprox1_thread.start()
+
+        # check that it started using that instance
+        start = time.time()
+        while not site.proxy and time.time() - start < 30:
+            time.sleep(0.5)
+            site.refresh()
+        assert site.proxy.endswith(':%s' % warcprox1.proxy.server_port)
+
+        # check that the site accumulates pages in the frontier, confirming
+        # that crawling is really happening
+        start = time.time()
+        while (len(list(frontier.site_pages(site.id))) <= 1
+               and time.time() - start < 60):
+            time.sleep(0.5)
+            site.refresh()
+        assert len(list(frontier.site_pages(site.id))) > 1
+
+        # stop warcprox #1, start warcprox #2
+        warcprox2_thread.start()
+        warcprox1.stop.set()
+        warcprox1_thread.join()
+
+        # check that it switched over to warcprox #2
+        start = time.time()
+        while ((not site.proxy
+                or not site.proxy.endswith(':%s' % warcprox2.proxy.server_port))
+               and time.time() - start < 30):
+            time.sleep(0.5)
+            site.refresh()
+        assert site.proxy.endswith(':%s' % warcprox2.proxy.server_port)
+
+        # stop warcprox #2
+        warcprox2.stop.set()
+        warcprox2_thread.join()
+
+        page_count = len(list(frontier.site_pages(site.id)))
+        assert page_count > 1
+
+        # check that it is waiting for a warcprox to appear
+        time.sleep(30)
+        site.refresh()
+        assert site.status == 'ACTIVE'
+        assert not site.proxy
+        assert len(list(frontier.site_pages(site.id))) == page_count
+
+        # stop crawling the site, else it can pollute subsequent test runs
+        brozzler.cli.brozzler_stop_crawl([
+            'brozzler-stop-crawl', '--site=%s' % site.id])
+        site.refresh()
+        assert site.stop_requested
+
+        # stop request should be honored quickly
+        start = time.time()
+        while not site.status.startswith(
+                'FINISHED') and time.time() - start < 120:
+            time.sleep(0.5)
+            site.refresh()
+        assert site.status == 'FINISHED_STOP_REQUESTED'
+    finally:
+        warcprox1.stop.set()
+        warcprox2.stop.set()
+        warcprox1_thread.join()
+        warcprox2_thread.join()
+        start_service('warcprox')
+

vagrant/run-tests.sh

@@ -17,5 +17,5 @@ vagrant ssh -- 'status warcprox ;
                 status vnc-websock'
 echo
 
-vagrant ssh -- 'source /opt/brozzler-ve34/bin/activate && pip install pytest'
+vagrant ssh -- 'set -x ; source /opt/brozzler-ve34/bin/activate && pip install pytest && pip install --upgrade --pre "warcprox>=2.1b1.dev71"'
 vagrant ssh -- "source /opt/brozzler-ve34/bin/activate && DISPLAY=:1 py.test -v /brozzler/tests $@"