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Foglight 7.3.0 - High Availability Field Guide

Tuning the Management Server

If you encounter these HA issues, consider performing the following tuning exercise.

To tune the Management Server:
1
Ensure the servers have synchronized system clocks. Out of sync server system clocks greatly increase the risk of communication errors.
 
* 
IMPORTANT: If the system clock is out of sync by 5 seconds or more during HA server startup, a warning message similar to the following appears in the log:

Warning: system time not in sync with primary server, Mon Aug 30 11:47:57 ECT 2010 vs Mon Sug 30 11:48:52 EDT 2010.)

2
Reconfigure JGroup to use TCP instead of UDP as the communication protocol. This is suitable for clusters with a small number (less than five) of predetermined servers.
 
* 
IMPORTANT: You must make the following changes to each server in the cluster.
a
Shut down the servers.
b
Edit the config/jgroups-config.xml file.
a
Uncomment the TCP block:
<TCP
   ....
/>
b
Uncomment the TCPPING block:
<TCPPING
   ....
/>
c
Comment out the UDP block:
<UDP
   ....
/>
d
Comment out the PING block:
<PING
   ....
/>
c
Make these changes on both your primary and secondary HA servers:
a
Find the line beginning with:
<TCPPING initial_hosts="${jgroups.bind_addr}[7800],otherhost[7800]"
port_range="3"
b
Change otherhost to the host name of the secondary server in the cluster. For example:
<TCPPING initial_hosts="${jgroups.bind_addr}[7800],host2[7800]"
port_range="3"
c
If there are more than two servers in the cluster, add those servers to the list as well. For example:
<TCPPING initial_hosts="${jgroups.bind_addr}[7800],host2[7800],
host3[7800]" port_range="3"
d
Repeat the edit on your secondary HA host, to the initial HA host name. For example:
<TCPPING initial_hosts="$[7800],host1[7800]" port_range="3"
If there are more than two servers in the cluster, add those servers to the list as well. For example:
<TCPPING initial_hosts="$ {jgroups.bind_addr}[7800],host1[7800],
host3[7800]"
 
* 
NOTE: In these examples, 7800 is the port number used for TCP communication. For more information about the HA ports used by the Management Server, see Configuring High Availability mode ports .
e
Save your changes.
f
Start the primary server. Wait for the primary server to start up completely, then restart the secondary server(s).

Managing hosts with multiple network interfaces

When configuring Foglight® Management Servers that are installed on hosts with multiple network interfaces (that is, with multiple IP addresses and host names), you can specify the IP address that is to be used for communication with the server. To specify the IP address and host name, configure the following parameters in the server.config file:

server.bind.address = "X.X.X.X";
server.remote.address = "host_name";

Where:

•
X.X.X.X is the desired IP address.
•
host_name is the DNS (Domain Name System) host name or the IP address.
Example A
server.bind.address = "192.0.2.2";
server.remote.address = "host1.example.com";

If a DNS host name is not available for the bind address, the IP address can be used:

server.bind.address = "192.0.2.2";
server.remote.address = "192.0.2.2";

When the Management Server is configured to run in HA mode, you also need to reconfigure the restarter to perform server health check with the same host name or IP address. To do that, open the restart_monitor.config file, locate the health.check.url and server.host properties, and set their values to the one specified by the server.remote.address parameter (in server.config).

Example B
server.bind.address = "host1.example.com";

If a DNS name is available for the desired bind address, the name can be used instead of the raw address.

For more information about server.bind.address and server.remote.address, see the comments in server.config.

JDK with IPv6 on Linux

Management Servers running on a VMware® Linux® x86_64 image fail to start up and a “jave.net.BindException: Cannot assign requested address exception” is raised. (85262)

This is a JDK issue with IPv6 on Linux, not a true High Availability issue. It also impacts standalone servers. However, the issue is documented here because it occurs when the JGroup cluster service is starting up.

Workaround: Start the Management Server with the following command:

-Djava.net.preferIPv4Stack=true

For more information, see: the JGroups FAQ (http://community.jboss.org/wiki/JGroupsFAQ) and Oracle® Bugs for it (http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6521974).

Foglight Management Server automatically restarted

Sometimes, after what appears to be a normal and successful startup, an HA server is automatically shut down and restarted. The most likely reason for this is a misconfiguration of health check URL in the restart_monitor.config file.

For example, you may have reconfigured the HTTP port of the Management Server or reconfigured the IP address that the server is bound to, but forgotten to reconfigure the health check URL of the restarter. If the restarter cannot contact the Management Server for health check, it considers the Management Server not responsive and restarts it.

You can check the server_restarter_xxxx-xx-xx_xxxxx_xxx.log file to determine if this scenario is what caused the restart. If so, edit the restart_monitor.config file by locating the line beginning with health.check.url and configuring the URL properly.

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