diff --git a/brozzler/cli.py b/brozzler/cli.py
old mode 100755
new mode 100644
diff --git a/brozzler/worker.py b/brozzler/worker.py
index 4955f2c..ba77ba7 100644
--- a/brozzler/worker.py
+++ b/brozzler/worker.py
@@ -129,13 +129,31 @@ class BrozzlerWorker:
         self._start_stop_lock = threading.Lock()
         self._shutdown = threading.Event()
 
+    def _choose_warcprox(self):
+        warcproxes = self._service_registry.available_services('warcprox')
+        if not warcproxes:
+            return None
+        reql = self._frontier.rr.table('sites').between(
+                ['ACTIVE', r.minval], ['ACTIVE', r.maxval],
+                index='sites_last_disclaimed')
+        active_sites = list(reql.run())
+        for warcprox in warcproxes:
+            address = '%s:%s' % (warcprox['host'], warcprox['port'])
+            warcprox['assigned_sites'] = len([
+                site for site in active_sites
+                if 'proxy' in site and site['proxy'] == address])
+        warcproxes.sort(key=lambda warcprox: (
+            warcprox['assigned_sites'], warcprox['load']))
+        # XXX make this heuristic more advanced?
+        return warcproxes[0]
+
     def _proxy_for(self, site):
         if self._proxy:
             return self._proxy
         elif site.proxy:
             return site.proxy
         elif self._warcprox_auto:
-            svc = self._service_registry.available_service('warcprox')
+            svc = self._choose_warcprox()
             if svc is None:
                 raise brozzler.ProxyError(
                         'no available instances of warcprox in the service '
diff --git a/tests/test_frontier.py b/tests/test_frontier.py
index b77c1e6..fdae726 100644
--- a/tests/test_frontier.py
+++ b/tests/test_frontier.py
@@ -855,3 +855,78 @@ def test_claim_site():
     # clean up
     rr.table('sites').get(claimed_site.id).delete().run()
 
+def test_choose_warcprox():
+    rr = doublethink.Rethinker('localhost', db='ignoreme')
+    svcreg = doublethink.ServiceRegistry(rr)
+    frontier = brozzler.RethinkDbFrontier(rr)
+
+    # avoid this of error: https://travis-ci.org/internetarchive/brozzler/jobs/330991786#L1021
+    rr.table('sites').wait().run()
+    rr.table('services').wait().run()
+    rr.table('sites').index_wait().run()
+    rr.table('services').index_wait().run()
+
+    # clean slate
+    rr.table('sites').delete().run()
+    rr.table('services').delete().run()
+    worker = brozzler.BrozzlerWorker(frontier, svcreg)
+    assert worker._choose_warcprox() is None
+
+    rr.table('services').insert({
+        'role': 'warcprox',
+        'first_heartbeat': doublethink.utcnow(),
+        'last_heartbeat': doublethink.utcnow(),
+        'host': 'host1', 'port': 8000,
+        'load': 0, 'ttl': 60}).run()
+    rr.table('services').insert({
+        'role': 'warcprox',
+        'first_heartbeat': doublethink.utcnow(),
+        'last_heartbeat': doublethink.utcnow(),
+        'host': 'host2', 'port': 8000,
+        'load': 0, 'ttl': 60}).run()
+    rr.table('services').insert({
+        'role': 'warcprox',
+        'first_heartbeat': doublethink.utcnow(),
+        'last_heartbeat': doublethink.utcnow(),
+        'host': 'host2', 'port': 8001,
+        'load': 0, 'ttl': 60}).run()
+    rr.table('services').insert({
+        'role': 'warcprox',
+        'first_heartbeat': doublethink.utcnow(),
+        'last_heartbeat': doublethink.utcnow(),
+        'host': 'host3', 'port': 8000,
+        'load': 0, 'ttl': 60}).run()
+    rr.table('services').insert({
+        'role': 'warcprox',
+        'first_heartbeat': doublethink.utcnow(),
+        'last_heartbeat': doublethink.utcnow(),
+        'host': 'host4', 'port': 8000,
+        'load': 1, 'ttl': 60}).run()
+
+    rr.table('sites').insert({
+        'proxy': 'host1:8000', 'status': 'ACTIVE',
+        'last_disclaimed': doublethink.utcnow()}).run()
+    rr.table('sites').insert({
+        'proxy': 'host1:8000', 'status': 'ACTIVE',
+        'last_disclaimed': doublethink.utcnow()}).run()
+    rr.table('sites').insert({
+        'proxy': 'host2:8000', 'status': 'ACTIVE',
+        'last_disclaimed': doublethink.utcnow()}).run()
+    rr.table('sites').insert({
+        'proxy': 'host2:8001', 'status': 'ACTIVE',
+        'last_disclaimed': doublethink.utcnow()}).run()
+
+    instance = worker._choose_warcprox()
+    assert instance['host'] == 'host3'
+    assert instance['port'] == 8000
+    rr.table('sites').insert({
+        'proxy': 'host3:8000', 'status': 'ACTIVE',
+        'last_disclaimed': doublethink.utcnow()}).run()
+
+    instance = worker._choose_warcprox()
+    assert instance['host'] == 'host4'
+    assert instance['port'] == 8000
+
+    # clean up
+    rr.table('sites').delete().run()
+    rr.table('services').delete().run()