我目前正在我的 EC2 小型实例服务器上部署带有 Django-Rest-Framework 的 Django，以为几个 Android 应用程序提供一组 API。
问题是我面临着一个我必须分析的严重性能问题。我发现单个请求的大部分时间都花在了 DRF 的核心中。
很抱歉让这篇文章变得很长，但我认为我必须展示所有内容，以便我能得到正确的答案。让我继续：
我的设置是 nginx / uwsgi。这是我使用 upstart 运行 uwsgi 的方式：
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')
最后是类方法'get_most_viewed'（我知道使用类方法而不是管理器方法是错误的）
@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，被重定向到指定的视图，从 MySQL 获取数据，然后返回序列化结果。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上升到 ~ 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 个请求是非常令人失望的。~ 1700 由于超时错误而失败的请求也是因为我在这里面临的性能滞后。
说实话。我预计每秒约 60 - 70 个请求而无需缓存。我知道缓存加速了这个过程，但它也隐藏了我遇到的性能问题，这就是为什么我在缓存东西之前寻求解决这个问题的原因。
然后我决定使用 django-profiling 在 vmware CentOS 机器上对此进行分析，通过在请求中添加 ?prof 来显示调用堆栈：
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)
正如你所看到的，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什么吗？为什么请求这么慢？python / Django 可以扩展吗？我读到它确实可以，但是对于一个简单的数据库读取和渲染操作，例如我正在做的那个，我应该期望多少个请求/秒？