github.com/jogo/docker@v1.7.0-rc1/docs/sources/articles/cfengine_process_management.md (about) 1 page_title: Process management with CFEngine 2 page_description: Managing containerized processes with CFEngine 3 page_keywords: cfengine, process, management, usage, docker, documentation 4 5 # Process management with CFEngine 6 7 Create Docker containers with managed processes. 8 9 Docker monitors one process in each running container and the container 10 lives or dies with that process. By introducing CFEngine inside Docker 11 containers, we can alleviate a few of the issues that may arise: 12 13 - It is possible to easily start multiple processes within a 14 container, all of which will be managed automatically, with the 15 normal `docker run` command. 16 - If a managed process dies or crashes, CFEngine will start it again 17 within 1 minute. 18 - The container itself will live as long as the CFEngine scheduling 19 daemon (cf-execd) lives. With CFEngine, we are able to decouple the 20 life of the container from the uptime of the service it provides. 21 22 ## How it works 23 24 CFEngine, together with the cfe-docker integration policies, are 25 installed as part of the Dockerfile. This builds CFEngine into our 26 Docker image. 27 28 The Dockerfile's `ENTRYPOINT` takes an arbitrary 29 amount of commands (with any desired arguments) as parameters. When we 30 run the Docker container these parameters get written to CFEngine 31 policies and CFEngine takes over to ensure that the desired processes 32 are running in the container. 33 34 CFEngine scans the process table for the `basename` of the commands given 35 to the `ENTRYPOINT` and runs the command to start the process if the `basename` 36 is not found. For example, if we start the container with 37 `docker run "/path/to/my/application parameters"`, CFEngine will look for a 38 process named `application` and run the command. If an entry for `application` 39 is not found in the process table at any point in time, CFEngine will execute 40 `/path/to/my/application parameters` to start the application once again. The 41 check on the process table happens every minute. 42 43 Note that it is therefore important that the command to start your 44 application leaves a process with the basename of the command. This can 45 be made more flexible by making some minor adjustments to the CFEngine 46 policies, if desired. 47 48 ## Usage 49 50 This example assumes you have Docker installed and working. We will 51 install and manage `apache2` and `sshd` 52 in a single container. 53 54 There are three steps: 55 56 1. Install CFEngine into the container. 57 2. Copy the CFEngine Docker process management policy into the 58 containerized CFEngine installation. 59 3. Start your application processes as part of the `docker run` command. 60 61 ### Building the image 62 63 The first two steps can be done as part of a Dockerfile, as follows. 64 65 FROM ubuntu 66 MAINTAINER Eystein Måløy Stenberg <eytein.stenberg@gmail.com> 67 68 RUN apt-get update && apt-get install -y wget lsb-release unzip ca-certificates 69 70 # install latest CFEngine 71 RUN wget -qO- http://cfengine.com/pub/gpg.key | apt-key add - 72 RUN echo "deb http://cfengine.com/pub/apt $(lsb_release -cs) main" > /etc/apt/sources.list.d/cfengine-community.list 73 RUN apt-get update && apt-get install -y cfengine-community 74 75 # install cfe-docker process management policy 76 RUN wget https://github.com/estenberg/cfe-docker/archive/master.zip -P /tmp/ && unzip /tmp/master.zip -d /tmp/ 77 RUN cp /tmp/cfe-docker-master/cfengine/bin/* /var/cfengine/bin/ 78 RUN cp /tmp/cfe-docker-master/cfengine/inputs/* /var/cfengine/inputs/ 79 RUN rm -rf /tmp/cfe-docker-master /tmp/master.zip 80 81 # apache2 and openssh are just for testing purposes, install your own apps here 82 RUN apt-get update && apt-get install -y openssh-server apache2 83 RUN mkdir -p /var/run/sshd 84 RUN echo "root:password" | chpasswd # need a password for ssh 85 86 ENTRYPOINT ["/var/cfengine/bin/docker_processes_run.sh"] 87 88 By saving this file as Dockerfile to a working directory, you can then build 89 your image with the docker build command, e.g., 90 `docker build -t managed_image`. 91 92 ### Testing the container 93 94 Start the container with `apache2` and `sshd` running and managed, forwarding 95 a port to our SSH instance: 96 97 $ docker run -p 127.0.0.1:222:22 -d managed_image "/usr/sbin/sshd" "/etc/init.d/apache2 start" 98 99 We now clearly see one of the benefits of the cfe-docker integration: it 100 allows to start several processes as part of a normal `docker run` command. 101 102 We can now log in to our new container and see that both `apache2` and `sshd` 103 are running. We have set the root password to "password" in the Dockerfile 104 above and can use that to log in with ssh: 105 106 ssh -p222 root@127.0.0.1 107 108 ps -ef 109 UID PID PPID C STIME TTY TIME CMD 110 root 1 0 0 07:48 ? 00:00:00 /bin/bash /var/cfengine/bin/docker_processes_run.sh /usr/sbin/sshd /etc/init.d/apache2 start 111 root 18 1 0 07:48 ? 00:00:00 /var/cfengine/bin/cf-execd -F 112 root 20 1 0 07:48 ? 00:00:00 /usr/sbin/sshd 113 root 32 1 0 07:48 ? 00:00:00 /usr/sbin/apache2 -k start 114 www-data 34 32 0 07:48 ? 00:00:00 /usr/sbin/apache2 -k start 115 www-data 35 32 0 07:48 ? 00:00:00 /usr/sbin/apache2 -k start 116 www-data 36 32 0 07:48 ? 00:00:00 /usr/sbin/apache2 -k start 117 root 93 20 0 07:48 ? 00:00:00 sshd: root@pts/0 118 root 105 93 0 07:48 pts/0 00:00:00 -bash 119 root 112 105 0 07:49 pts/0 00:00:00 ps -ef 120 121 If we stop apache2, it will be started again within a minute by 122 CFEngine. 123 124 service apache2 status 125 Apache2 is running (pid 32). 126 service apache2 stop 127 * Stopping web server apache2 ... waiting [ OK ] 128 service apache2 status 129 Apache2 is NOT running. 130 # ... wait up to 1 minute... 131 service apache2 status 132 Apache2 is running (pid 173). 133 134 ## Adapting to your applications 135 136 To make sure your applications get managed in the same manner, there are 137 just two things you need to adjust from the above example: 138 139 - In the Dockerfile used above, install your applications instead of 140 `apache2` and `sshd`. 141 - When you start the container with `docker run`, 142 specify the command line arguments to your applications rather than 143 `apache2` and `sshd`.