我在尝试使cron作业在docker容器中运行时遇到的几个问题是:
列表中存在特定于cron的问题和特定于docker的问题,但是无论如何都必须解决它们以使cron正常工作。
为此,我目前对问题提出的解决方案如下:
创建一个docker卷,在cron下运行的所有脚本都将写入其中:
# Dockerfile for test-logs
# BUILD-USING: docker build -t test-logs .
# RUN-USING: docker run -d -v /t-logs --name t-logs test-logs
# INSPECT-USING: docker run -t -i --volumes-from t-logs ubuntu:latest /bin/bash
FROM stackbrew/busy@R_148_2419@:latest
# Create logs volume
VOLUME /var/log
CMD ["true"]
将在cron下运行的脚本是test.py
:
#!/usr/bin/env python
# python script which needs an environment variable and runs as a cron job
import datetime
import os
test_environ = os.environ["TEST_ENV"]
print "Cron job has run at %s with environment variable '%s'" %(datetime.datetime.Now(), test_environ)
为了将环境变量传递给,我想在cron下运行,遵循托马斯的建议,并把一个crontab片段为每个脚本(或脚本组)的脚本,在需要的泊坞窗环境变量的/etc/cron.d
一个占位符XXXXXXX
,必须被设置。
# placed in /etc/cron.d
# TEST_ENV is an docker environment variable that the script test.py need
TEST_ENV=XXXXXXX
#
* * * * * root python /test.py >> /var/log/test.log
除了直接调用cron之外,还可以将cron包装在执行以下操作的python脚本中:1.从docker环境变量读取环境变量,并将环境变量设置为crontab片段。
#!/usr/bin/env python
# run-cron.py
# sets environment variable crontab fragments and runs cron
import os
from subprocess import call
import fileinput
# read docker environment variables and set them in the appropriate crontab fragment
environment_variable = os.environ["TEST_ENV"]
for line in fileinput.input("/etc/cron.d/cron-python",inplace=1):
print line.replace("XXXXXXX", environment_variable)
args = ["cron","-f", "-L 15"]
call(args)
该Dockerfile
说的容器,其中cron作业运行如下:
# BUILD-USING: docker build -t test-cron .
# RUN-USING docker run --detach=true --volumes-from t-logs --name t-cron test-cron
FROM debian:wheezy
#
# Set correct environment variables.
ENV HOME /root
ENV TEST_ENV test-value
RUN apt-get update && apt-get install -y software-properties-common python-software-properties && apt-get update
# Install Python Setuptools
RUN apt-get install -y python cron
RUN apt-get purge -y python-software-properties software-properties-common && apt-get clean -y && apt-get autoclean -y && apt-get autoremove -y && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
ADD cron-python /etc/cron.d/
ADD test.py /
ADD run-cron.py /
RUN chmod a+x test.py run-cron.py
# Set the time zone to the local time zone
RUN echo "America/New_York" > /etc/timezone && dpkg-reconfigure --frontend noninteractive tzdata
CMD ["/run-cron.py"]
最后,创建容器并运行它们: