Monday, December 1, 2014

Docker: Adding HAProxy and Fig to my docker websites

In a previous post, I discussed moving my websites into Docker containers with their own separate httpd servers from their previous setup as virtual hosts on a single httpd server. This post will discuss integrating HAProxy and Fig into my installation. This will allow for load balancing, proper routing, and easy deployments.

To add HAProxy, I simply used the library haproxy image. You will just need to create your own Dockerfile and copy in your haproxy.cfg as the instructions state from the link. The first part of the config file is fairly standard:

1:  global  
2:   log local0  
3:   log local1 notice  
4:   chroot /var/lib/haproxy  
5:   user haproxy  
6:   group haproxy  
9:  defaults  
10:   log global  
11:   mode http  
12:   option httplog  
13:   option dontlognull  
14:   option forwardfor  
15:   option http-server-close  
16:   timeout connect 5000  
17:   timeout client 50000  
18:   timeout server 50000  
19:   errorfile 400 /etc/haproxy/errors/400.http  
20:   errorfile 403 /etc/haproxy/errors/403.http  
21:   errorfile 408 /etc/haproxy/errors/408.http  
22:   errorfile 500 /etc/haproxy/errors/500.http  
23:   errorfile 502 /etc/haproxy/errors/502.http  
24:   errorfile 503 /etc/haproxy/errors/503.http  
25:   errorfile 504 /etc/haproxy/errors/504.http  
26:   stats enable  
27:   stats uri /haproxy?stats  

It is the rest of the file that does the work for us. I have multiple websites served from the same server, and each website is also accessed by multiple domains (i.e. is also There may be a less verbose way of doing what I've done, but I haven't found that method. We need to declare our frontend and bind it to port 80 on any incoming IP address. We then define ACL's (Access Control Lists) for each domain and associate them with the appropriate generic host. We then associate each host with the backend cluster that will serve the calls to that website. We finally use cafezvous as the default cluster if no ACL is matched.

29:  frontend http-in  
30:      bind *:80  
32:      # Define hosts  
33:      acl host_cafezvous hdr(host) -i  
34:      acl host_cafezvous hdr(host) -i  
35:      acl host_cafezvous hdr(host) -i  
36:      acl host_cafezvous hdr(host) -i  
37:      acl host_cafezvous hdr(host) -i  
38:      acl host_cafezvous hdr(host) -i  
39:      acl host_cafezvous hdr(host) -i  
40:      acl host_cafezvous hdr(host) -i  
41:      acl host_cafezvous hdr(host) -i  
42:      acl host_cafezvous hdr(host) -i  
43:      acl host_dbdevs hdr(host) -i  
44:      acl host_dbdevs hdr(host) -i  
45:      acl host_dbdevs hdr(host) -i  
46:      acl host_dbdevs hdr(host) -i  
47:      acl host_dbdevs hdr(host) -i  
48:      acl host_dbdevs hdr(host) -i  
49:      acl host_dbdevs hdr(host) -i  
50:      acl host_dbdevs hdr(host) -i  
51:      acl host_dbdevs hdr(host) -i  
52:      acl host_dbdevs hdr(host) -i  
53:      acl host_danpluslaura hdr(host) -i  
54:      acl host_danpluslaura hdr(host) -i  
55:      acl host_danpluslaura hdr(host) -i  
56:      acl host_danpluslaura hdr(host) -i  
57:      acl host_danpluslaura hdr(host) -i  
58:      acl host_danpluslaura hdr(host) -i  
59:      acl host_danpluslaura hdr(host) -i  
60:      acl host_danpluslaura hdr(host) -i  
61:      acl host_danpluslaura hdr(host) -i  
62:      acl host_danpluslaura hdr(host) -i  
64:      ## figure out which one to use  
65:      use_backend cafezvous_cluster if host_cafezvous  
66:      use_backend dbdevs_cluster if host_dbdevs  
67:      use_backend danpluslaura_cluster if host_danpluslaura  
69:      default_backend cafezvous_cluster  

Normally our backends would be associated to some IP address, but we don't know what the IP address of a container will be until it's created. We could wait until all of the servers are started to then add each IP address and port individually, but that doesn't seem reasonable or easy. Also, we'd be creating a new container for each restart. We could also map each website to a particular port on the host and then update this with the host IP address/localhost and port. The problem isn't as bad with this solution, but this won't scale well. Plus, the smart guys at Docker have thought of a clever way to associate an IP with a container. They create an entry in /etc/hosts when the --link command is used to link containers together. So, the cafezvous container can be referenced by cafezvous with a trailing port number. And dbdevs is referenced the same way. All of them can continue to use the common port of 80 and this can be deployed anywhere without checking to make sure a port isn't already mapped to the host.

71:  backend cafezvous_cluster  
72:      balance leastconn  
73:      option httpclose  
74:      option forwardfor  
75:      cookie JSESSIONID prefix  
76:      server node1 cafezvous:80 cookie A check  
78:  backend dbdevs_cluster  
79:      balance leastconn  
80:      option httpclose  
81:      option forwardfor  
82:      cookie JSESSIONID prefix  
83:      server node1 dbdevs:80 cookie A check  
85:  backend danpluslaura_cluster  
86:      balance leastconn  
87:      option httpclose  
88:      option forwardfor  
89:      cookie JSESSIONID prefix  
90:      server node1 danpluslaura:80 cookie A check  

Now we can start our containers:

 $ docker run -dtP --name dbdevs barkerd427/dbdevs  
 $ docker run -dtP --name cafezvous barkerd427/cafezvous  
 $ docker run -dtP --name danpluslaura barkerd427/danpluslaura  
 $ docker run -dtP --name haproxy --link cafezvous:cafezvous --link dbdevs:dbdevs --link danpluslaura:danpluslaura barkerd427/haproxy  
 $ docker ps -a -s  
 CONTAINER ID    IMAGE                         COMMAND               CREATED          STATUS          PORTS                                                NAMES         SIZE  
 7971754d55d1    barkerd427/haproxy:0.1        "bash /haproxy-start  18 seconds ago   Up 6 seconds>443/tcp,>80/tcp  haproxy       0 B  
 8ea8b1261d2e    barkerd427/danpluslaura:0.20  "httpd -DFOREGROUND"  2 minutes ago    Up 2 minutes>80/tcp                             danpluslaura  2 B  
 ec7bfaf06985    barkerd427/cafezvous:0.4      "httpd -DFOREGROUND"  2 minutes ago    Up 2 minutes>80/tcp                             cafezvous     2 B  
 ed2ac1134324    barkerd427/dbdevs:0.4         "httpd -DFOREGROUND"  3 minutes ago    Up 2 minutes>80/tcp                             dbdevs        2 B  

This is a bit cumbersome to have to add all of these links individually, especially as the infrastructure becomes more complex. So, we'll go ahead and add a simple Fig configuration file to the mix and get all of these commands condensed into one. Here's the configuration fig.yml file:

  image: barkerd427/haproxy
   - "80:80"
   - cafezvous  
   - dbdevs  
   - danpluslaura  
  image: barkerd427/cafezvous
   - "80"  
  image: barkerd427/dbdevs
   - "80"  
  image: barkerd427/danpluslaura
   - "80"  

We explicitly call out the port mapping for HAProxy to the host, but we leave the others to be assigned by Docker. We don't really care what the ports are on the host for this purpose, but we do need to know that the container port 80 is mapped generically. We also explicitly call out the links that HAProxy needs to the other container names. Now when I run fig up -d, everything will start in the correct order and run in the background. If you don't add the -d, then everything will shutdown when that session ends.

To run fig up, you need to be in the directory with the fig.yml file or reference that file with the -f or --file option. The project name defaults to the directory name, but this can be overridden with -p or --project-name. You can also attach to fig to see the output of the containers by using fig logs.

 $ fig up -d  
 Creating websitefig_danpluslaura_1...  
 Creating websitefig_dbdevs_1...  
 Creating websitefig_cafezvous_1...  
 Creating websitefig_haproxy_1...  
 $ fig ps  
      Name                  Command              State   Ports  
 websitefig_cafezvous_1     httpd -DFOREGROUND   Up>80/tcp  
 websitefig_danpluslaura_1  httpd -DFOREGROUND   Up>80/tcp  
 websitefig_dbdevs_1        httpd -DFOREGROUND   Up>80/tcp  
 websitefig_haproxy_1       bash /haproxy-start  Up      443/tcp,>80/tcp  
 $ docker ps -a -s  
 CONTAINER ID    IMAGE                         COMMAND               CREATED             STATUS             PORTS                           NAMES                      SIZE  
 81ee5adf1aa3    barkerd427/haproxy:0.1        "bash /haproxy-start  About a minute ago  Up 59 seconds      443/tcp,>80/tcp  websitefig_haproxy_1       0 B  
 7df01566911e    barkerd427/cafezvous:0.4      "httpd -DFOREGROUND"  About a minute ago  Up 59 seconds>80/tcp        websitefig_cafezvous_1     2 B  
 0f7c971a41aa    barkerd427/dbdevs:0.4         "httpd -DFOREGROUND"  About a minute ago  Up About a minute>80/tcp        websitefig_dbdevs_1        2 B  
 e02f0cdc37b1    barkerd427/danpluslaura:0.20  "httpd -DFOREGROUND"  About a minute ago  Up About a minute>80/tcp        websitefig_danpluslaura_1  2 B  
 $ fig logs  
 Attaching to websitefig_cafezvous_1, websitefig_dbdevs_1, websitefig_danpluslaura_1  
 danpluslaura_1 | [Mon Dec 01 14:30:59.367252 2014] [mpm_event:notice] [pid 1:tid 140438754260864] AH00489: Apache/2.4.10 (Unix) configured -- resuming normal operations  
 danpluslaura_1 | [Mon Dec 01 14:30:59.367462 2014] [core:notice] [pid 1:tid 140438754260864] AH00094: Command line: 'httpd -D FOREGROUND'  
 dbdevs_1    | [Mon Dec 01 14:30:59.708416 2014] [mpm_event:notice] [pid 1:tid 140529524463488] AH00489: Apache/2.4.10 (Unix) configured -- resuming normal operations  
 dbdevs_1    | [Mon Dec 01 14:30:59.708595 2014] [core:notice] [pid 1:tid 140529524463488] AH00094: Command line: 'httpd -D FOREGROUND'  
 cafezvous_1  | [Mon Dec 01 14:31:00.034189 2014] [mpm_event:notice] [pid 1:tid 140501628454784] AH00489: Apache/2.4.10 (Unix) configured -- resuming normal operations  
 cafezvous_1  | [Mon Dec 01 14:31:00.034919 2014] [core:notice] [pid 1:tid 140501628454784] AH00094: Command line: 'httpd -D FOREGROUND'  
 cafezvous_1  | - - [01/Dec/2014:14:31:15 +0000] "GET / HTTP/1.1" 200 18045  
 danpluslaura_1 | - - [01/Dec/2014:14:31:19 +0000] "GET / HTTP/1.1" 200 24280  
 dbdevs_1    | - - [01/Dec/2014:14:31:26 +0000] "GET / HTTP/1.1" 200 11154  

We can then bring everything down by using the command fig stop. We can restart them all by using fig up again, which will actually reuse the containers from the previous run unless there has been an update. In fact, you don't even have to call fig stop to make an update. Simply run fig up and containers with an update will be updated.

Currently this is a good solution for my often unvisited websites, but if I made a serious push to make a business out of these sites, then this solution would not suffice. Currently, I cannot add another website container for cafezvous to scale its ability to handle additional workloads. This is something that is definitely needed, and I will post my experiences in the future with Serf and hopefully Kubernetes. These systems will allow for dynamically growing my services if needed.

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