Mav*_*ick 6 python django profiling mysql-python django-rest-framework
我目前正在我的EC2小型实例服务器上部署Django w/Django-Rest-Framework,为几个Android应用程序提供一组API.
问题是我遇到了一个严重的性能问题,我不得不介绍一下.我发现单个请求的大部分时间都花在了DRF的核心内部.
很抱歉让这篇文章很长,但我想我必须展示一切,这样我才能得到正确的答案.让我继续吧:
我的设置是nginx/uwsgi.以下是我使用upstart运行uwsgi的方法:
description "pycms"
start on [2345]
stop on [06]
respawn
# start from virtualenv path
chdir /www/python/apps/pycms/
exec uwsgi -b 25000 --chdir=/www/python/apps/pycms --module=wsgi:application --env DJANGO_SETTINGS_MODULE=settings --socket=127.0.0.1:8081 --processes=5 --harakiri=20 --max-requests=5000 --vacuum --master --pidfile=/tmp/pycms-master.pid
假设我请求以下API:
http://IP_ADDRESS/api/nodes/mostviewed/9/
符合以下规则:
url(r'^nodes/mostviewed/(?P<category>\d+)/$', MostViewedNodesList.as_view(), name='mostviewed-nodes-list'),
这是基于类的视图:
class MostViewedNodesList(generics.ListAPIView):
"""
API endpoint that lists featured nodes
"""
model = ObjectStats
serializer_class = NodeSerializer
permission_classes = (permissions.AllowAny,)
def get_queryset(self):
if(self.kwargs.has_key('category')):
category_id = self.kwargs.get('category')
return ObjectStats.get_most_viewed(category_id)
else:
return []
序列化程序类:
class NodeSerializer(serializers.ModelSerializer):
images = ImageSerializer()
favorite = ObjectField(source='is_favorite')
rating = ObjectField(source='get_rating')
meta = ObjectField(source='get_meta')
url = ObjectField(source='get_absolute_url')
channel_title = ObjectField(source='channel_title')
class Meta:
model = Node
fields = ('id', 'title', 'body', 'images', 'parent', 'type', 'rating', 'meta', 'favorite', 'url', 'channel_title')
最后是classmethod'get_most_viewed'(我知道使用classmethods而不是manager方法是错误的)
@classmethod
def get_most_viewed(cls, category_id):
return list(Node.objects.extra(
where=['objects.id=content_api_objectviewsstats.node_id', 'content_api_objectviewsstats.term_id=%s'],
params=[category_id],
tables=['content_api_objectviewsstats'],
order_by=['-content_api_objectviewsstats.num_views']
).prefetch_related('images', 'objectmeta_set').select_related('parent__parent'))
从这一切可以看出,这是一个正常的请求,它被重定向到指定的视图,从MySQL获取数据,然后返回序列化的结果.没有任何异常或任何复杂的处理.
执行:
ab -c 500 -n 5000 http://IP_HERE/api/nodes/mostviewed/9/
请注意,这是没有缓存的.经常记录以下内容:
HARAKIRI: --- uWSGI worker 5 (pid: 31015) WAS managing request /api/nodes/mostviewed/9/ since Sat Feb 16 13:07:21 2013 ---
DAMN ! worker 2 (pid: 31006) died, killed by signal 9 :( trying respawn ...
Respawned uWSGI worker 2 (new pid: 31040)
测试期间的平均负载达到~5.这是ab结果:
Concurrency Level: 500
Time taken for tests: 251.810 seconds
Complete requests: 1969
Failed requests: 1771
(Connect: 0, Receive: 0, Length: 1771, Exceptions: 0)
Write errors: 0
Non-2xx responses: 1967
Total transferred: 702612 bytes
HTML transferred: 396412 bytes
Requests per second: 7.82 [#/sec] (mean)
Time per request: 63943.511 [ms] (mean)
Time per request: 127.887 [ms] (mean, across all concurrent requests)
Transfer rate: 2.72 [Kbytes/sec] received
首先,每秒7个请求非常令人失望.由于超时错误导致的~1700次请求失败也是因为我在这里遇到的性能滞后.
要完全诚实.我期待每秒约60-70次请求而不进行缓存.我知道缓存加速了这个过程,但它也隐藏了我所遇到的性能问题,这就是为什么我要在缓存之前解决这个问题.
我决定使用django-profiling在vmware CentOS机器上对此进行分析,通过在请求中添加？prof显示调用堆栈:
Instance wide RAM usage
Partition of a set of 373497 objects. Total size = 65340232 bytes.
Index Count % Size % Cumulative % Kind (class / dict of class)
0 2270 1 7609040 12 7609040 12 dict of django.db.models.sql.query.Query
1 19503 5 6263400 10 13872440 21 dict (no owner)
2 63952 17 5739672 9 19612112 30 str
3 51413 14 5090344 8 24702456 38 list
4 58435 16 4991160 8 29693616 45 tuple
5 24518 7 4434112 7 34127728 52 unicode
6 8517 2 2384760 4 36512488 56 dict of django.db.models.base.ModelState
7 2270 1 2378960 4 38891448 60 dict of django.db.models.query.QuerySet
8 2268 1 2376864 4 41268312 63 dict of 0x14d6920
9 6998 2 2088304 3 43356616 66 django.utils.datastructures.SortedDict
<619 more rows. Type e.g. '_.more' to view.>
CPU Time for this request
663425 function calls (618735 primitive calls) in 2.037 CPU seconds
Ordered by: cumulative time
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 2.037 2.037 /usr/lib/python2.6/site-packages/django/views/generic/base.py:44(view)
1 0.000 0.000 2.037 2.037 /usr/lib/python2.6/site-packages/django/views/decorators/csrf.py:76(wrapped_view)
1 0.000 0.000 2.037 2.037 /usr/lib/python2.6/site-packages/rest_framework/views.py:359(dispatch)
1 0.000 0.000 2.036 2.036 /usr/lib/python2.6/site-packages/rest_framework/generics.py:144(get)
1 0.000 0.000 2.036 2.036 /usr/lib/python2.6/site-packages/rest_framework/mixins.py:46(list)
1 0.000 0.000 2.029 2.029 apps/content_api/views.py:504(get_queryset)
1 0.000 0.000 2.029 2.029 apps/objects_stats/models.py:11(get_most_viewed)
23/21 0.000 0.000 2.028 0.097 /usr/lib/python2.6/site-packages/django/db/models/query.py:92(__iter__)
4/2 0.003 0.001 2.028 1.014 /usr/lib/python2.6/site-packages/django/db/models/query.py:77(__len__)
1 0.000 0.000 1.645 1.645 /usr/lib/python2.6/site-packages/django/db/models/query.py:568(_prefetch_related_objects)
1 0.002 0.002 1.645 1.645 /usr/lib/python2.6/site-packages/django/db/models/query.py:1596(prefetch_related_objects)
2 0.024 0.012 1.643 0.822 /usr/lib/python2.6/site-packages/django/db/models/query.py:1748(prefetch_one_level)
2288 0.007 0.000 1.156 0.001 /usr/lib/python2.6/site-packages/django/db/models/manager.py:115(all)
6252 0.019 0.000 0.762 0.000 /usr/lib/python2.6/site-packages/django/db/models/query.py:231(iterator)
4544 0.025 0.000 0.727 0.000 /usr/lib/python2.6/site-packages/django/db/models/query.py:870(_clone)
4544 0.109 0.000 0.694 0.000 /usr/lib/python2.6/site-packages/django/db/models/sql/query.py:235(clone)
2270 0.004 0.000 0.619 0.000 /usr/lib/python2.6/site-packages/django/db/models/query.py:619(filter)
2270 0.013 0.000 0.615 0.000 /usr/lib/python2.6/site-packages/django/db/models/query.py:633(_filter_or_exclude)
1144 0.019 0.000 0.581 0.001 /usr/lib/python2.6/site-packages/django/db/models/fields/related.py:456(get_query_set)
1144 0.019 0.000 0.568 0.000 /usr/lib/python2.6/site-packages/django/db/models/fields/related.py:560(get_query_set)
55917/18180 0.192 0.000 0.500 0.000 /usr/lib64/python2.6/copy.py:144(deepcopy)
2270 0.003 0.000 0.401 0.000 /usr/lib/python2.6/site-packages/django/db/models/query.py:820(using)
正如您所看到的,大部分时间都花在了django视图和DRF视图上.
有人可以指出我在这里做错了吗？为什么请求这么慢？python/Django会扩展吗？我读到它确实如此,但我应该在简单的数据库读取和渲染操作(例如我正在进行的操作)上期望多少请求/秒？
python / django 是否可以扩展
Django 为一些相当庞大的服务提供支持，例如 Disqus 和 Instagram，所以它的扩展性很好。
然后我决定对此进行简介
正如您所看到的，几乎所有时间都花在 .get_most_viewed() 方法内，因此这看起来像是您遇到的问题。（那里可能是错误的，但你的个人资料表明 2.037 时间中有 2.028 时间花在那里，所以大约 99.6% 的时间）
我的 ORM 技能并不能真正弄清楚您应该如何处理相当复杂的查询，并且在任何情况下都需要查看模型定义，但您需要研究调试和简化该查询，而不是查看视图的其他部分。
您可能希望使用 manage.py shell 进入 Django shell，以便您可以分析该特定查询，并将其排除在视图的其余部分之外。
也可以尝试在此处或在 Django IRC 频道或 django 邮件列表上获取有关如何简化查询的一些帮助（如果您具体询问该查询，而不是更通用的 Django/REST 框架，您可能会更幸运这里的措辞问题，其中大部分实际上似乎与您所看到的问题无关。
希望这有助于为您指明解决此问题的正确方向。