背景

Docker + Nginx + uWSGI + Flask 部署的环境，以前一直都能好好跑，这次把基础镜像的 Python 版本由原来的 3.6 升级到了 3.8，就报了标题的错。

Docker + Nginx + uWSGI + Flask 部署可以参考 这篇文章

问题分析

先看一下 Docker 的启动日志：

Starting nginx: nginx.,
*** Starting uWSGI 2.0.18-debian (64bit) on [Tue Aug 17 02:21:46 2021] ***,
[uWSGI] getting INI configuration from uwsgi.ini,
compiled with version: 8.2.0 on 10 February 2019 02:42:46,
os: Linux-3.10.0-957.el7.x86_64 #1 SMP Thu Nov 8 23:39:32 UTC 2018,
nodename: 9c8cc3ffd4ed,
machine: x86_64,
pcre jit disabled,
detected number of CPU cores: 2,
clock source: unix,
current working directory: /code,
detected binary path: /usr/bin/uwsgi-core,
uWSGI running as root, you can use --uid/--gid/--chroot options,
chdir() to /code,
*** WARNING: you are running uWSGI as root !!! (use the --uid flag) *** ,
*** WARNING: you are running uWSGI without its master process manager ***,
your memory page size is 4096 bytes,
detected max file descriptor number: 1048576,
lock engine: pthread robust mutexes,
thunder lock: disabled (you can enable it with --thunder-lock),
uwsgi socket 0 bound to TCP address :5000 fd 3,
uWSGI running as root, you can use --uid/--gid/--chroot options,
*** WARNING: you are running uWSGI as root !!! (use the --uid flag) *** ,
Python version: 3.7.3 (default, Jan 22 2021, 20:04:44)  [GCC 8.3.0],
Python main interpreter initialized at 0x55fa4f5a8990,
uWSGI running as root, you can use --uid/--gid/--chroot options,
*** WARNING: you are running uWSGI as root !!! (use the --uid flag) *** ,
python threads support enabled,
your server socket listen backlog is limited to 100 connections,
your mercy for graceful operations on workers is 60 seconds,
mapped 825016 bytes (805 KB) for 8 cores,
*** Operational MODE: preforking+threaded ***,
Traceback (most recent call last):,
  File "run.py", line 20, in <module>,
    from server import create_app,
  File "./server/__init__.py", line 14, in <module>,
    from flask import Flask,
unable to load app 0 (mountpoint='') (callable not found or import error),
*** no app loaded. going in full dynamic mode ***,
uWSGI running as root, you can use --uid/--gid/--chroot options,
*** WARNING: you are running uWSGI as root !!! (use the --uid flag) *** ,
*** uWSGI is running in multiple interpreter mode ***,
spawned uWSGI worker 1 (pid: 21, cores: 2),
spawned uWSGI worker 2 (pid: 22, cores: 2),
spawned uWSGI worker 3 (pid: 23, cores: 2),
spawned uWSGI worker 4 (pid: 24, cores: 2)

从中可以看出来，就是在引用 flask 的时候报错了。

那什么原因会导致这个问题呢？

就是程序在跑起来的时候没有找到 python 库（flask），就报错了。

这里咱们先不管他为什么没找到，既然没找到的话，那我们就主动告诉他去哪找就行了。

解决方案

修改 uwsgi.ini，设定 pythonpath 的值为 /usr/local/lib/python3.8/site-packages/。

修改后的 uwsgi.ini 文件内容为：

[uwsgi]
chdir = /code
socket = :5000
pythonpath = /usr/local/lib/python3.8/site-packages/
wsgi-file = run.py
callable = app
chmod-socket = 666
plugins = python3
buffer-size = 65535
processes = 4
threads = 2

好了，问题解决。

其他问题

好了，解决了能跑的问题，还有一个比较重要的问题，为什么不能跑呢？

之前在 Python3.6 的容器里面都能直接跑，为什么在 Python3.8 的容器里面就需要指定 PYTHONPATH 呢？

还望大佬不吝赐教。

以上。

祝大家变的更强。