Getting Started with Linux-HA (Heartbeat 2)

Pacemaker is the Project Successor

• Note Pacemaker is the Project Successor of "Heartbeat Version 2".

If you are looking for documentation and information for the "Version 2" heartbeat, you should really be reading the Pacemaker home page at http://clusterlabs.org[1].

If you are stuck with Heartbeat 2.1.3 or Heartbeat 2.1.4, the best fitting Documentation is probably that for Pacemaker 0.6, which can also be found on the Pacemaker Documentation[2] page

Quoting the first paragraph from v2[3] (in this wiki):

Special Note for Version 2 Users

The CRM is now maintained as an independent project called Pacemaker[1] and now has many new features including support for the OpenAIS[4] cluster stack.

Heartbeat 2.1.4 was the last release to contain the CRM or "Version 2 Resource Manager" and since then all development and maintenance is performed as part of the Pacemaker project and all CRM code has been removed from Heartbeat.

For more details on Pacemaker, including latest versions, installation details and documentation, please visit http://clusterlabs.org[1].

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Intro

Let me preface this document by saying most of this is _not_ original work. My purpose for writing this document is just trying to contribute in some way to possibly help those who REALLY get things done. The "work" I am contributing is a revised version of the Getting Started[5] page by Rudy Pawul and bits and pieces from other HA v1/v2 documents into a document that can help novices get started on Heartbeat 2[3] without pestering the developers and to cut down on repeat and simple questions on the mailing list.

This document is a sort of quickstart into Heartbeat 2[3]. As I said, it contains lots of bits and pieces from other documents. The problem is that this could lead to out of sync documentation. Therefore, if something doesn't work or you just want to know more, go to GettingStartedV2[6].

The goal is to have one page that describes a simple Heartbeat 2 configuration, for people who are beginning with Heartbeat 2. English is not my first language, so feel free to correct any mistakes.

What is Heartbeat

Your "cluster[7]" is established via a "heartbeat" between two or more computers (nodes[8]) generated by the software package of the same name[9].

The basic goal of the High Availability Linux project is to:

• Provide a high-availability (clustering) solution for Linux which promotes reliability, availability, and serviceability (RAS) through a community development effort.

Why Heartbeat v2?

The most important features why to use Heartbeat 2:

• You can use more than 2 nodes

• Heartbeat v2 can monitor resources without using "mon[10]", "ldirectord[11]" or others

• More features to express dependancies

Definitions

• Node[8]: An Instance that runs an OS

• Resource[12]: A service or facility you want to be highly-available

• RA: Resource Agent[13]

• CRM[14]:

• More to come....

Getting Started

What you need:

• At least two computers. You don't need to have identical hardware in both machines (or amount of memory, kernel, etc.).
• One or more media to send the heartbeat packages (serial, USB or Ethernet cable(s)).
• A Linux OS and the media between the 2 nodes configured and working.

High Availibility as good as it gets:

Avoiding a single point of failure is the whole idea of the setup. This also means it is advised to use more than one communications method between the nodes. It is also advised not to use only Ethernet cables or one single type of media, because in that case the mediastack would be a single point of failure.

The Setup

This quickstart will describe a full installation and configuration of Heartbeat 2 and some resources on Debian Unstable. It is a quickstart so we will configure a simple and common configuration. We will make an Apache 2 service highly available on a shared IP (Active/Passive[15]). The configuration will contain monitors and starting the resources will be done using a group. Completing this document should give you a basic understanding of Heartbeat 2.

For simplicity, we use only one media, an Ethernet cable between the hosts:

• The primary node: hostname = mars, ipaddr = 10.0.0.10
• The slave node: hostname = venus, ipaddr = 10.0.0.20
• The IP Apache listens to: 10.0.0.30

Installing Heartbeat

Heartbeat is available at:

• Download Software[16]

You can build it from source:

tar -xvzf /path_to_downloaded_tarball/heartbeat-x.x.x
./ConfigureMe configure
make && make install 

or use the RPM or .deb binaries available. If you use Gentoo, you can simply emerge it.

I used the .deb binaries for Debian so I added the following line to /etc/apt/sources.list

deb http://ftp.belnet.be/debian/ unstable main contrib non-free 

and then

apt-get update
apt-get install heartbeat-2

Configuring Heartbeat

General Configuration Info

Configuring Heartbeat v2 is a little more tricky than Heartbeat v1, but Heartbeat v2 can also be used with a Heartbeat v1 configuration. If you would like to try out the v1 configuration first, read this[5].

There are 3 files you need to configure - you have to create these files:

Configuring Authkeys

The authkeys[17] file is used to authenticate the members of the clusters. There are three types of authentication methods available:

• crc: Has as good as none security, and doesn't use much resources. Don't use this on real networks.
• md5: Has security and doesn't use a lot of CPU resources
• sha1: Best security currently available

In this example we are going to use md5. If you want to know more about authkeys, look at this document[17].

A sample of the /etc/ha.d/authkeys file could be:

auth 1 
1 md5 key-for-md5-any-text-you-want

Whatever index you put after the keyword auth must be found below in the keys listed in the file. If you put "auth 4", then there must be a "4 signaturetype" line in the list below.

The file permissions MUST be safe so do:

chmod 600 /etc/ha.d/authkeys 

Configuring ha.cf

#logfacility local7 
#logfile /var/log/ha-log
#debugfile /var/log/ha-debug
use_logd on
udpport 694
keepalive 1 # 1 second
deadtime 10
initdead 80
bcast eth0
#serial /dev/ttyS0 #if you use serial
#baud 19200 #if you use serial
node linuxha1 linuxha2
crm yes 
auto_failback yes

Log and debug explained:

If the logging daemon is used, logfile[18]/debugfile[19]/logfacility[20] in this file are not meaningful any longer. You should check the config file for logging daemon (the default is /etc/logd.cf). Example in /usr/share/doc/heartbeat-2/ha_logd.cf.

If use_logd[21] is not used, all log messages will be written to log files directly. The logging daemon is started/stopped in heartbeat script.

Time & Network:

Note that mcast[22] and ucast[23] can be used in place of bcast if desired.

Other:

Note: When you want to use a Heartbeat 1 setup set crm to off.

I want to know more about the ha.cf file[24]

Configuring Resources

/var/lib/heartbeat/crm/cib.xml: Basically this file specifies the services for the cluster and who the default owner is.

A simple example setup that explains a basic resource configuration can be found here: v2/Examples/Simple[25].

An example that explains some more advanced configuration is here: v2/Examples/Advanced[26].

And more advanced things are here: ClusterInformationBase/UserGuide[27].

Other configuration

Apache

You need to configure 2 things for our setup, these you can simply configure in the Apache config.

In Debian: /etc/apache2/apache2.conf

Define the IP that Apache has to listen to:

Listen 10.7.200.30:80

For the monitoring:

# Allow server status reports, with the URL of http://servername/server-status
# Change the ".your_domain.com" to match your domain to enable.
#
<Location /server-status>
    SetHandler server-status
    Order allow,deny
    Allow from all 
</Location>

DRBD

If you want to use DRBD[28] instead of shared storage, then you need to configure it

OCF Scripts

We recommend that any resources agents you write be OCF resource agents[29].

Using Heartbeat

Testing Heartbeat

See Also

Getting Started With Heartbeat Version 2[6]

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This information provided courtesy of the Linux-HA project at http://linux-ha.org/