Django / Heroku：致命：角色连接过多 [英] Django/Heroku: FATAL: too many connections for role
问题描述
因此，我刚刚通过Heroku（业余爱好）和Postgres（试用版）启动了一个包含Channels 2.0 Daphne 2.2.0和asgi的网站。当我启动我的网站时，我四处点击了几页，出现500错误。我收到的错误消息是 FATAL：角色的连接过多... c
So I just launched a website with Channels 2.0 Daphne 2.2.0 and asgi via Heroku (Hobby) and Postgres (trial). When I launch my website, I click around for a few pages and I get a 500 error. The error message I get emailed is FATAL: too many connections for role ..."
当我运行 heroku pg：killall 或等待足够长的时间，我可以单击几下直到错误消息再次出现。但是，当我运行 heroku pg 显示 Connections 0/20 。有人知道这是怎么回事，我该如何阻止错误发生？我可能打开了两个连接
When I run heroku pg:killall or wait long enough I can click around a few more times until the error message repeats itself. However, when I run heroku pg it shows Connections 0/20. Does anyone know what is going on and how I can stop the errors? It's possible that I have two many connections open for a second, but it doesn't seem that way.
File "/app/.heroku/python/lib/python3.6/site-
packages/django/contrib/sessions/backends/base.py" in _get_session
191. return self._session_cache
During handling of the above exception ('SessionStore' object has no attribute '_session_cache'), another exception occurred:
File "/app/.heroku/python/lib/python3.6/site-packages/django/db/backends/base/base.py" in ensure_connection
216. self.connect()
File "/app/.heroku/python/lib/python3.6/site-packages/django/db/backends/base/base.py" in connect
194. self.connection = self.get_new_connection(conn_params)
File "/app/.heroku/python/lib/python3.6/site-packages/django/db/backends/postgresql/base.py" in get_new_connection
168. connection = Database.connect(**conn_params)
File "/app/.heroku/python/lib/python3.6/site-packages/psycopg2/__init__.py" in connect
130. conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
The above exception (FATAL: too many connections for role "polewdwynmvyyt"
) was the direct cause of the following exception:
File "/app/.heroku/python/lib/python3.6/site-packages/django/core/handlers/exception.py" in inner
35. response = get_response(request)
File "/app/.heroku/python/lib/python3.6/site-packages/django/core/handlers/base.py" in _get_response
128. response = self.process_exception_by_middleware(e, request)
File "/app/.heroku/python/lib/python3.6/site-packages/django/core/handlers/base.py" in _get_response
126. response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "./myproject/views.py" in home_page
8. print(request.session.get("first_name","Unknown")) #getter
File "/app/.heroku/python/lib/python3.6/site-packages/django/contrib/sessions/backends/base.py" in get
66. return self._session.get(key, default)
File "/app/.heroku/python/lib/python3.6/site-packages/django/contrib/sessions/backends/base.py" in _get_session
196. self._session_cache = self.load()
File "/app/.heroku/python/lib/python3.6/site-packages/django/contrib/sessions/backends/db.py" in load
34. expire_date__gt=timezone.now()
File "/app/.heroku/python/lib/python3.6/site-packages/django/db/models/manager.py" in manager_method
82. return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/app/.heroku/python/lib/python3.6/site-packages/django/db/models/query.py" in get
397. num = len(clone)
File "/app/.heroku/python/lib/python3.6/site-packages/django/db/models/query.py" in __len__
254. self._fetch_all()
File "/app/.heroku/python/lib/python3.6/site-packages/django/db/models/query.py" in _fetch_all
1179. self._result_cache = list(self._iterable_class(self))
File "/app/.heroku/python/lib/python3.6/site-packages/django/db/models/query.py" in __iter__
53. results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
File "/app/.heroku/python/lib/python3.6/site-packages/django/db/models/sql/compiler.py" in execute_sql
1066. cursor = self.connection.cursor()
File "/app/.heroku/python/lib/python3.6/site-packages/django/db/backends/base/base.py" in cursor
255. return self._cursor()
File "/app/.heroku/python/lib/python3.6/site-packages/django/db/backends/base/base.py" in _cursor
232. self.ensure_connection()
File "/app/.heroku/python/lib/python3.6/site-packages/django/db/backends/base/base.py" in ensure_connection
216. self.connect()
File "/app/.heroku/python/lib/python3.6/site-packages/django/db/utils.py" in __exit__
89. raise dj_exc_value.with_traceback(traceback) from exc_value
File "/app/.heroku/python/lib/python3.6/site-packages/django/db/backends/base/base.py" in ensure_connection
216. self.connect()
File "/app/.heroku/python/lib/python3.6/site-packages/django/db/backends/base/base.py" in connect
194. self.connection = self.get_new_connection(conn_params)
File "/app/.heroku/python/lib/python3.6/site-packages/django/db/backends/postgresql/base.py" in get_new_connection
168. connection = Database.connect(**conn_params)
File "/app/.heroku/python/lib/python3.6/site-packages/psycopg2/__init__.py" in connect
130. conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
推荐答案
似乎连接没有被重用和/或为每个请求创建一个新线程。
Seems like the connections are not being reused and/or a new thread is being created for each request.
从 dj_database_url.config中删除在 CONN_MAX_AGE （默认= DATABASE_URL） settings.py 上（如果您使用的是dj_database_url）。
Remove the CONN_MAX_AGE from dj_database_url.config(default=DATABASE_URL) on settings.py (if you are using dj_database_url).
将环境变量 ASGI_THREADS 设置为小于您的 .asgi 文件或heroku网站->设置-> configVars。
如果使用daphne，则默认线程为CPU内核* 5，每个线程都有一个连接。
Set the environment variable ASGI_THREADS to a number of threads lower than your connections limit on your .asgi file or on heroku site -> settings -> configVars.
If you are using daphne, the default threads are CPU cores * 5, each thread with a connection.
example.asgi文件：
example.asgi file:
import os
import django
from channels.routing import get_default_application
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "yourAppName.settings")
os.environ['ASGI_THREADS']="4"
django.setup()
application = get_default_application()
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