PHP App Server (v12.11 LTS) - Runbook

Set Up Load Balancing

This ServerTemplate supports several load balancing options:

• HAProxy - Use RightScale's Load Balancer with HAProxy ServerTemplate to launch dedicated load balancing servers that use HAProxy for load balancing across servers in any cloud. 
• Elastic Load Balancing (ELB) - Load balancing service provided by Amazon. Use an ELB to load balance across servers in the same AWS cloud/region. For example, an ELB in 'us-east' can load balance across EC2 instances in the same region.
• Cloud Load Balancers (CLB) - Load balancing service provided by Rackspace. Use a CLB to load balance across servers in the Rackspace cloud. 

HAProxy

Define the following inputs at the deployment level.

ELB

Define the following inputs at the deployment level.

CLB

Warning: When using Rackspace CLB, you must wait until after launching your first application server before setting up your load balancer via the Rackspace API or control panel. This is because you cannot create a new CLB without at least one running cloud server or external node associated. Also, you must create the CLB in the same datacenter as your running servers; Rackspace randomly assigns you to one of their datacenters (e.g. ORD, DFW, etc.). For example, you cannot use a CLB created in ORD to load balance across servers in DSW. If you want to change the datacenter that you were assigned to, you must contact Rackspace.

To configure application servers to work with Rackspace CLB, set the below input values at the deployment level. Since you will configure these inputs before setting up your new Cloud Load Balancer on Rackspace, carefully note each entry so that your Rackspace configuration, upon setup, will match these values exactly.

Define the following inputs at the deployment level.

Start and Stop Apache

Use the following operational recipes to start or stop the Apache HTTP Server application:

• Run web_apache::do_stop to stop the Apache service.
• Run web_apache::do_start to start the Apache service.

Restart Apache

To restart the Apache HTTP service, run the web_apache::do_restart operational recipe.

Load Balancing: Add or Remove Application Server

Run one of the following scripts to add/remove an application server to/from the load balancing servers/service. 

• Run the lb::do_detach_request operational script if you no longer want an application server to receive new requests from the load balancer.
• Run the lb::do_attach_request operational script if you want an application server to start receiving requests from the load balancer.

Update Application Code

Application code is typically downloaded at boot time when an application server is launched. However, you can manually update the application code on a running server by executing an operational script. For example, you may want to retrieve the latest version of your application from a different branch in your software repository.

Run the following script to update the application code on a server.

• Run the app::do_update_code operational script.

Add or Remove a Firewall Rule

When iptables is enabled, which is the default behavior in all Linux-based v12 ServerTemplates, TCP ports 22, 80, and 443 are configured to be open to any IP address in order to enable minimum functionality and access. If you want to add or remove a firewall rule on a running (operational) server by opening or closing a port, you can set the following inputs accordingly and run the sys_firewall::setup_rule operational script.

If you want the firewall rules to be set at boot time, you can either add the Chef recipe to the end of the boot script list or update the sys_firewall::default recipe to change the list of default firewall permissions by explicitly opening up additional ports. However, you should only consider overriding the default recipe if you want to change the default behavior for all of your servers that use that cookbook.

Note: If the cloud provider supports security groups, you must also open or close the appropriate ports in the security group resource.

1. Go to the current server's Inputs tab and set the following inputs accordingly.
    

2. Run the sys_firewall::setup_rule operational script to add the firewall permission to the running server(s).

List Current Firewall Rules

For troubleshooting and security purposes, you may want to list a server's current firewall rules to make sure that a server has the expected IP/port permissions. This script is especially useful if you want to check the firewall rules across all servers in a deployment to validate that all of them have the same iptables rules. 

1. Go to the running server's Scripts tab and run the sys_firewall::do_list_rules operational script.
2. Go to the server's Audit Entries tab to view the output. The output will look similar to the following example.

22:25:03: ==================== do_list_rules : Firewall rules Begin ==================
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         
FWR        all  --  0.0.0.0/0            0.0.0.0/0           

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FWR (1 references)
target     prot opt source               destination         
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           state RELATED,ESTABLISHED 
ACCEPT     icmp --  0.0.0.0/0            0.0.0.0/0           
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:22 
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:443 
ACCEPT     tcp  --  10.123.456.22        0.0.0.0/0           tcp dpt:8000 
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:80 
REJECT     tcp  --  0.0.0.0/0            0.0.0.0/0           tcp flags:0x16/0x02 reject-with icmp-port-unreachable 
REJECT     udp  --  0.0.0.0/0            0.0.0.0/0           reject-with icmp-port-unreachable 
==================== do_list_rules : Firewall rules End ====================

If you want to perform the same action via SSH, follow the steps below.

1. SSH into the running server. (Requires 'server_login' user role privileges.)
2. Switch to the 'root' user.

# sudo -i

3. Type the following Unix command.

# /sbin/iptables -L

Update Reconverge List

Typically, an application server has a script (e.g app::do_loadbalancers_allow) listed in the 'Reconvergence List' input that tries to attach itself to the specified load balancer servers or service based on its tags. By default, all scripts listed in the Recovergence List input are run every 15 minutes. 

Go to the current server's Inputs tab and add any recipes that you want to periodically be executed on the running application server to the 'Reconverge List' input. Note: This functionality only applies to Chef recipes. RightScripts are not supported in the Recoverge List.

Go to the Scripts tab and run the sys::do_reconverge_list_enable operational script.

Enable or Disable Reconverge List

• Run the sys::do_reconverge_list_enable operational script to enable reconvergence. Scripts listed in the 'Reconvergence List' input will be periodically executed every 15 minutes.
• Run the sys::do_reconverge_list_disable operational script to disable reconvergence. Scripts listed in the 'Reconvergence List' input will not be periodically executed every 15 minutes.