A Web server is one of the most basic examples used to illustrate how containers work. The procedure in this document does the following:
- Builds an Apache (httpd) Web server inside a container
- Exposes the service on port 80 of the host
- Serves a simple index.html file
- Displays data from a backend server (needs additional MariaDB container that you can find here)
Creating and running the Apache Web Server Container
Install system: Install a RHEL 7 or RHEL Atomic system that includes the docker package and start the docker service.
Pull image: Pull the rhel7 image by typing the following:
# docker pull rhel7:latest
Get tarball with supporting files: Download the tarball file attached to this article (get it here: web_cont.tgz), download it to a new mywebcontainer directory, and untar it as follows:
# mkdir ~/mywebcontainer # cp web_cont*.tgz ~/mywebcontainer # cd ~/mywebcontainer # tar xvf web_cont*.tgz action Dockerfile
Modify action CGI script: Edit the action file as needed, which will be used to get data from the backend database server container. This script assumes that the docker0 interface on the host system is at IP address 172.17.42.1, you can login to the database with the dbuser1 user account and redhat as the password, and use the database named gss. If that is the IP address and you use the database container described here, you don't need to modify this script. (You can also just ignore this script and just use the Web server to get HTML content.)
#!/usr/bin/python # -*- coding: utf-8 -*- import MySQLdb as mdb import os con = mdb.connect(os.getenv('DB_SERVICE_SERVICE_HOST','172.17.42.1'), 'dbuser1', 'redhat', 'gss') with con: cur = con.cursor() cur.execute("SELECT MESSAGE FROM atomic_training") rows = cur.fetchall() print 'Content-type:text/html\r\n\r\n' print '<html>' print '<head>' print '<title>My Application</title>' print '</head>' print '<body>' for row in rows: print '<h2>' + row + '</h2>' print '</body>' print '</html>' con.close()
Check the Dockerfile: Modify the Dockerfile file in the ~/mywebcontainer directory as needed (perhaps only modify Maintainer_Name to add your name). Here are the contents of that file:
# Webserver container with CGI python script # Using RHEL 7 base image and Apache Web server # Version 1 # Pull the rhel image from the local repository FROM rhel7:latest USER root MAINTAINER Maintainer_Name # Fix per https://bugzilla.redhat.com/show_bug.cgi?id=1192200 RUN yum -y install deltarpm yum-utils --disablerepo=*-eus-* --disablerepo=*-htb-* \ --disablerepo=*-ha-* --disablerepo=*-rt-* --disablerepo=*-lb-* --disablerepo=*-rs-* --disablerepo=*-sap-* RUN yum-config-manager --disable *-eus-* *-htb-* *-ha-* *-rt-* *-lb-* *-rs-* *-sap-* > /dev/null # Update image RUN yum update -y RUN yum install httpd procps-ng MySQL-python -y # Add configuration file ADD action /var/www/cgi-bin/action RUN echo "PassEnv DB_SERVICE_SERVICE_HOST" >> /etc/httpd/conf/httpd.conf RUN chown root:apache /var/www/cgi-bin/action RUN chmod 755 /var/www/cgi-bin/action RUN echo "The Web Server is Running" > /var/www/html/index.html EXPOSE 80 # Start the service CMD ["-D", "FOREGROUND"] ENTRYPOINT ["/usr/sbin/httpd"]
Build Web server container: From the directory containing the Dockerfile file and other content, type the following:
# docker build -t webwithdb . Sending build context to Docker daemon 4.096 kB Sending build context to Docker daemon Step 0 : FROM rhel7:latest ---> bef54b8f8a2f Step 1 : USER root ---> Running in 00c28d347131 ---> cd7ef0fcaf55 ...
Start the Web server container: To start the container image, run the following command:
# docker run -d -p 80:80 --name=mywebwithdb webwithdb
Test the Web server container: To check that the Web server is operational, run the first curl command below. If you have the backend database container running, try the second command:
# curl http://localhost/index.html The Web Server is Running # curl http://localhost/cgi-bin/action <html> <head> <title>My Application</title> </head> <body> <h2>RedHat rocks</h2> <h2>Success</h2> </body> </html> </tt></pre>
If you have a Web browser installed on the localhost, you can open a Web browser to see as better representation of the few lines of output. Just open the browser to this URL: http://localhost/cgi-bin/action
Tips for this container
Here are some tips to help you use the Web Server container:
Modify for MariaDB: To use this container with the MariaDB container (described in Building a Simple Database Server in a Docker Container), you may need to edit the action script and change the IP address from 172.17.42.1 to the host IP on the docker0 interface. To find what that address is on your host, type the following:
# ip a | grep docker0 | grep inet inet 172.17.42.1/16 scope global docker0
Adding content: You can include your own content, mounted from the local host, by using the -v option on the docker run command line. For example:
# docker run -d -p 80:80 -v /var/www/html:/var/www/html \ --name=mywebwithdb webwithdb
Orchestrate containers: A better way to manage this container with other containers is to use Kubernetes to orchestrate them into pods. See the following documents for details on how to orchestrate this with other containers using Kubernetes:
Get Started Orchestrating Docker Containers with Kubernetes: Describes how to create a simple Kubernetes environment to try out on a single system.
Creating a Kubernetes Cluster to Run Docker Format Containers: Tells how to create a multi-on Kubernetes setup with Flannel networking, Kubernetes services, replication controllers, and pod deployment.