Mod cluster Installation
External
- mod_cluster installation on EAP 6 in standalone mode: https://access.redhat.com/solutions/283263
- mod_cluster installation on EAP 6 in domain mode: https://access.redhat.com/solutions/173333
Internal
Download
Compiled bundles are available here: http://mod-cluster.jboss.org/downloads
Native Components Installation on Linux
This procedure assumes httpd was already installed, configured, and it works well without mod_cluster. Details on httpd installation and configuration are available here: httpd installation, httpd configuration.
At the time of the writing, the pre-compiled native components to be installed within an existing httpd are published on the download page as "mod_cluster modules for httpd". For example, the mod_cluster binaries for Linux x86 httpd are listed as "linux-x86_64 mod_cluster binaries". The file name is mod_cluster-1.3.1.Final-linux2-x64-so.tar.gz. It contains the pre-compiled httpd dynamic libraries (mod_advertise.so, mod_cluster_slotmem.so, mod_manager.so and mod_proxy_cluster.so).
Place the Dynamic Libraries in the modules Directory
Identify the httpd instance's module directory, by looking at the existing LoadModule directives specified in the configuration. It is usually /etc/httpd/modules.
It is good practice to include the mod_cluster version in the name of the dynamic library files, to make it obvious what version is used.
cp mod_advertise.so /etc/httpd/modules/mod_advertise-1.3.1.Final.so cp mod_cluster_slotmem.so /etc/httpd/modules/mod_cluster_slotmem-1.3.1.Final.so cp mod_manager.so /etc/httpd/modules/mod_manager-1.3.1.Final.so cp mod_proxy_cluster.so /etc/httpd/modules/mod_proxy_cluster-1.3.1.Final.so
Make sure the newly copied files have the same ownership and permissions as the existing modules.
Load Modules at Startup
A standard RHEL httpd installation has its modules configured in /etc/httpd/conf.modules.d. All files present in that directory are automatically included from httpd.conf:
... Include conf.modules.d/*.conf ...
Follow the same pattern to configure mod_cluster.
Add a new 99-mod_cluster.conf file in /etc/httpd/conf.modules.d with the following content:
# # This file configures mod_cluster # LoadModule proxy_cluster_module modules/mod_proxy_cluster-1.3.1.Final.so LoadModule cluster_slotmem_module modules/mod_cluster_slotmem-1.3.1.Final.so LoadModule manager_module modules/mod_manager-1.3.1.Final.so LoadModule advertise_module modules/mod_advertise-1.3.1.Final.so
Insure that Module Dependencies are Present and Loaded
mod_cluster needs mod_proxy to work. More details about mod_cluster dependency on mod_proxy are found here.
Make sure mod_proxy.so and mod_proxy_ajp.so are loaded. For a standard httpd installation, those modules are loaded in /etc/httpd/conf.modules.d/00-proxy.conf:
... LoadModule proxy_module modules/mod_proxy.so LoadModule proxy_ajp_module modules/mod_proxy_ajp.so ...
Remove Undesired Modules
mod_cluster's mod_proxy_cluster cannot work correctly if mod_proxy's mod_proxy_balancer, so mod_proxy_balancer must be removed from the httpd configuration.
For a standard httpd deployment, mod_proxy_balancer is loaded in /etc/httpd/conf.modules.d/00-proxy.conf.
SELinux Configuration
If the host has SELinux enabled, we will need to install additional policies to allow httpd to write mod_cluster-related files in /var/log/httpd, to perform multicast socket operations and bind on non-standard ports.
Start with a mod_cluster_1.te policy file:
module mod_cluster_1 1.0;
require {
type httpd_log_t;
type httpd_t;
type unreserved_port_t;
class tcp_socket name_bind;
class dir remove_name;
class file { write unlink };
class udp_socket name_bind;
}
#============= httpd_t ==============
allow httpd_t httpd_log_t:dir remove_name;
allow httpd_t httpd_log_t:file unlink;
allow httpd_t httpd_log_t:file write;
allow httpd_t unreserved_port_t:udp_socket name_bind;
allow httpd_t unreserved_port_t:tcp_socket name_bind;
Compile the policy:
checkmodule -M -m -o mod_cluster_1.mod mod_cluster_1.te
Create the module package:
semodule_package -o mod_cluster_1.pp -m mod_cluster_1.mod
Install the policy:
semodule -i mod_cluster_1.pp
Verify that the policy was installed:
semodule -l | grep mod_cluster_1
More details about managing SELinux policies are available here: SELinux Operations.
Basic httpd.conf Configuration
This is a simple configuration that can be used to conduct smoke tests. It consists in just one mod_cluster-enabled virtual host. Note that access is allowed to all, you may want to configure stricter security in production. Also note that /mod_cluster-manager access is enabled. More complex configurations are of course possible. For more details on how to configure mod_cluster, go to mod_cluster Configuration.
...
<VirtualHost 1.2.3.4:8088>
# LogLevel debug
<Directory />
Allow from all
</Directory>
# this is critical - if not enabled, JBoss nodes won't be able to talk to the httpd node
EnableMCPMReceive
KeepAliveTimeout 60
MaxKeepAliveRequests 0
ManagerBalancerName mycluster
# multicast advertising
#ServerAdvertise On
#AdvertiseGroup 224.0.1.105:23364
#AdvertiseFrequency 5
# JBoss nodes will connect to a fixed list of httpd hosts
ServerAdvertise Off
<Location /mod_cluster-manager>
SetHandler mod_cluster-manager
Allow from all
</Location>
</VirtualHost>
...
Important
- the default httpd configuration restricts access to the root directory, so you may want to comment out the following. Can do better than that.
#<Directory /> # AllowOverride none # Require all denied #</Directory>
AdvertiseGroup
- The multicast address and port used by AdvertiseGroup must be synchronized with the values used by JBoss nodes. See AdvertiseGroup.
Native Component Installation on Windows
TODO, manual page 6, section 2.2.4 Install on Windows.
iptables Configuration
If iptables is enabled, make sure the multicast, MCPM, HTTP and AJP traffic are allowed:
MCPM
On the httpd node, make sure MCPM inbound traffic is allowed:
-A INPUT -i eth0 -p tcp -m tcp --dport 8088 -m state --state NEW -j ACCEPT
HTTP and AJP Traffic
On the JBoss nodes, add this to /etc/sysconfig/iptables:
-A INPUT -i eth0 -p tcp -m tcp --dport 8080 -m state --state NEW -j ACCEPT -A INPUT -i eth0 -p tcp -m tcp --dport 8009 -m state --state NEW -j ACCEPT
Multicast Traffic
Multicast traffic should propagate from the httpd nodes to the JBoss node and maybe back? Are JBoss nodes multicasting to httpd? Research that.. Normally iptables is configured to leave all traffic out by default, so the httpd nodes should be fine. However, JBoss nodes must be enabled to allow the multicast traffic in, so add this to /etc/sysconfig/iptables:
-A INPUT -m pkttype --pkt-type multicast -j ACCEPT
More details on configuring iptables are available here: iptables configuration examples.
JBoss Components Installation
standard-ha and standard-full-ha WildFly 9 profiles come with mod_cluster enabled.
Make sure the advertise multicast address and port as the same on the httpd nodes and JBoss nodes.
Also make sure multicast propagates between httpd and the JBoss nodes (see #Multicast_Traffic).
JBoss mod_cluster Configuration
WildFly 8
TODO
This example uses uses a static proxy server list, instead of multicast httpd server advertising.
...
<subsystem xmlns="urn:jboss:domain:modcluster:1.2">
<mod-cluster-config proxy-list="10.10.10.10:6666" advertise="false" connector="ajp">
<dynamic-load-provider>
<load-metric type="busyness"/>
</dynamic-load-provider>
</mod-cluster-config>
</subsystem>
...
Dynamic:
...
<subsystem xmlns="urn:jboss:domain:modcluster:2.0">
<mod-cluster-config advertise-socket="modcluster" connector="ajp">
<dynamic-load-provider>
<load-metric type="cpu"/>
</dynamic-load-provider>
</mod-cluster-config>
</subsystem>
...
TODO: dynamic server advertising
WildFly 9
TODO
This example uses uses a static proxy server list, instead of multicast httpd server advertising.
...
<subsystem xmlns="urn:jboss:domain:modcluster:2.0">
<mod-cluster-config proxies="mod-cluster-server-1" advertise="false" connector="ajp">
<dynamic-load-provider>
<load-metric type="cpu"/>
</dynamic-load-provider>
</mod-cluster-config>
</subsystem>
...
<socket-binding-group name="standard-sockets"...>
...
<outbound-socket-binding name="mod-cluster-server-1">
<remote-destination host="172.20.2.41" port="8088"/>
</outbound-socket-binding>
</socket-binding-group>
...
TODO: dynamic server advertising
Test Initial Installation
Start httpd, it should start without warnings or errors.
mod_cluster will create a set of new files in (by default) /var/log/httpd: manager.*.slotmem and manager.*.lock.
Start all JBoss nodes.
Try http://httpd-virtual-host:httpd-virtual-post/mod_cluster-manager