OpenEdx Codejail容器导入Matplotlib报错：无可用临时目录

问题背景 #

• 部署环境：Tutor搭建的OpenEdx平台（版本：openedx-mfe:14.0.1），安装eduNEXT的Codejail插件（版本：codejailservice:14.1.0）
• 异常现象：在Codejail容器内直接执行import matplotlib正常，但在OpenEdx高级模块（Advanced Block）的Problem代码块中执行相同导入时报错；import os可正常运行。

报错信息 #

cannot create LoncapaProblem block-v1:VUP+Math101+2022+type@problem+block@3319c4e42da64a74b0e40f048e3f2599: Error while executing script code: Couldn't execute jailed code: stdout: b'', stderr: b'Traceback (most recent call last):
  File "jailed_code", line 19, in <module>
    exec(code, g_dict)
  File "<string>", line 66, in <module>
  File "/sandbox/venv/lib/python3.8/site-packages/matplotlib/__init__.py", line 921, in <module>
    dict.update(rcParams, rc_params_in_file(matplotlib_fname()))
  File "/sandbox/venv/lib/python3.8/site-packages/matplotlib/__init__.py", line 602, in matplotlib_fname
    for fname in gen_candidates():
  File "/sandbox/venv/lib/python3.8/site-packages/matplotlib/__init__.py", line 599, in gen_candidates
    yield os.path.join(get_configdir(), 'matplotlibrc')
  File "/sandbox/venv/lib/python3.8/site-packages/matplotlib/__init__.py", line 239, in wrapper
    ret = func(**kwargs)
  File "/sandbox/venv/lib/python3.8/site-packages/matplotlib/__init__.py", line 502, in get_configdir
    return get_config_or_cache_dir(_get_xdg_config_dir())
  File "/sandbox/venv/lib/python3.8/site-packages/matplotlib/__init__.py", line 474, in get_config_or_cache_dir
    tempfile.mkdtemp(prefix="matplotlib-")
  File "/opt/pyenv/versions/3.8.6_sandbox/lib/python3.8/tempfile.py", line 347, in mkdtemp
    prefix, suffix, dir, output_type = sanitize_params(prefix, suffix, dir)
  File "/opt/pyenv/versions/3.8.6_sandbox/lib/python3.8/tempfile.py", line 117, in sanitize_params
    dir = gettempdir()
  File "/opt/pyenv/versions/3.8.6_sandbox/lib/python3.8/tempfile.py", line 286, in gettempdir
    tempdir = get_default_tempdir()
  File "/opt/pyenv/versions/3.8.6_sandbox/lib/python3.8/tempfile.py", line 218, in _get_default_tempdir
    raise FileNotFoundError(_errno.ENOENT,
FileNotFoundError: [Errno 2] No usable temporary directory found in ['/tmp', '/var/tmp', '/usr/tmp', '/tmp/codejail-lbfd69da']
' with status code: 1. For more information check Codejail Service logs.

Codejail服务日志 #

{"log":"[pid: 6|app: 0|req: 20/39] 172.18.0.10 () {36 vars in 483 bytes} [Tue Nov 22 11:24:59 2022] POST /api/v0/code-exec => generated 1978 bytes in 742 msecs (HTTP/1.1 200) 2 headers in 73 bytes (1 switches on core 0)\n","stream":"stderr","time":"2022-11-22T11:25:00.151315626Z"} 
{"log":"2022-11-22 11:26:23,304 INFO 9 [codejailservice.app] code_exec_service.py:52 - Running problem_id:53fbaa04859f41989ab967c15a12c013 jailed code for course_id:course-v1:VUP+Math101+2022 ...\n","stream":"stderr","time":"2022-11-22T11:26:23.30489438Z"} 
{"log":"2022-11-22 11:26:23,343 INFO 9 [codejailservice.app] code_exec_service.py:73 - Jailed code was executed in 0.03849988000001758 seconds.\n","stream":"stderr","time":"2022-11-22T11:26:23.343618965Z"} 
{"log":"[pid: 9|app: 0|req: 20/40] 172.18.0.10 () {36 vars in 483 bytes} [Tue Nov 22 11:26:23 2022] POST /api/v0/code-exec => generated 73 bytes in 40 msecs (HTTP/1.1 200) 2 headers in 71 bytes (1 switches on core 0)\n","stream":"stderr","time":"2022-11-22T11:26:23.344178308Z"} 
{"log":"2022-11-23 04:15:24,786 INFO 6 [codejailservice.app] code_exec_service.py:52 - Running problem_id:3319c4e42da64a74b0e40f048e3f2599 jailed code for course_id:course-v1:VUP+Math101+2022 ...\n","stream":"stderr","time":"2022-11-23T04:15:24.786287416Z"} 
{"log":"2022-11-23 04:15:25,582 ERROR 6 [codejailservice.app] code_exec_service.py:70 - Error found while executing jailed code.\n","stream":"stderr","time":"2022-11-23T04:15:25.582527974Z"} 
{"log":"[pid: 6|app: 0|req: 21/41] 172.18.0.10 () {36 vars in 483 bytes} [Wed Nov 23 04:15:24 2022] POST /api/v0/code-exec => generated 1978 bytes in 798 msecs (HTTP/1.1 200) 2 headers in 73 bytes (1 switches on core 0)\n","stream":"stderr","time":"2022-11-23T04:15:25.583132326Z"} 
{"log":"2022-11-23 06:00:15,150 INFO 9 [codejailservice.app] code_exec_service.py:52 - Running problem_id:3319c4e42da64a74b0e40f048e3f2599 jailed code for course_id:course-v1:VUP+Math101+2022 ...\n","stream":"stderr","time":"2022-11-23T06:00:15.15073834Z"} 
{"log":"2022-11-23 06:00:15,891 ERROR 9 [codejailservice.app] code_exec_service.py:70 - Error found while executing jailed code.\n","stream":"stderr","time":"2022-11-23T06:00:15.8916806Z"} 
{"log":"[pid: 9|app: 0|req: 21/42] 172.18.0.10 () {36 vars in 483 bytes} [Wed Nov 23 06:00:15 2022] POST /api/v0/code-exec => generated 1978 bytes in 742 msecs (HTTP/1.1 200) 2 headers in 73 bytes (1 switches on core 0)\n","stream":"stderr","time":"2022-11-23T06:00:15.892225441Z"}

原因分析 #

Matplotlib初始化时会尝试创建临时配置目录，但Codejail的沙箱环境对临时目录的读写权限做了限制，导致无法创建或访问指定的临时目录，从而抛出FileNotFoundError。

解决方案 #

1. 代码层面预配置Matplotlib #

在Problem代码块中，先配置环境变量和Matplotlib参数，避免初始化时尝试创建临时目录：

<problem>
<script type="loncapa/python">
import os
# 指定Matplotlib配置目录为沙箱内可访问路径
os.environ['MPLCONFIGDIR'] = '/tmp/codejail-matplotlib'
# 确保目录存在
os.makedirs(os.environ['MPLCONFIGDIR'], exist_ok=True)
# 设置非交互式后端（避免图形界面依赖）
import matplotlib
matplotlib.use('Agg')
# 后续可正常使用Matplotlib
import matplotlib.pyplot as plt
</script>
</problem>

2. 调整Codejail沙箱权限配置 #

• 进入Codejail容器：

tutor exec codejail bash

• 编辑Codejail配置文件（通常路径为/etc/codejail/config.py），添加允许访问的临时目录：

SAFE_TMP_DIRS = ['/tmp', '/tmp/codejail-*', '/tmp/codejail-matplotlib']

• 重启Codejail服务：

tutor restart codejail

3. 预生成Matplotlib配置文件 #

在Codejail沙箱环境中提前生成Matplotlib配置文件，避免运行时创建：

• 进入沙箱Python环境：

tutor exec codejail /opt/pyenv/versions/3.8.6_sandbox/bin/python

• 执行以下代码生成配置：

import matplotlib
matplotlib.use('Agg')
matplotlib.matplotlib_fname()

验证 #

在OpenEdx的Problem代码块中运行修改后的代码，检查是否能正常导入Matplotlib并执行绘图逻辑，无权限类报错即为修复成功。

内容的提问来源于stack exchange，提问作者Ishfaq Babar