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Rosetta Load Balancer Example

by Moti Pearl September 28, 2016 (Updated: November 30, 2018)

Load Balancer Configuration:

Load balancing allows distribution of workloads across multiple Rosetta servers. Such configuration aims to optimize resource use, maximize throughput, minimize response time, and avoid overload of a single server.

In addition, configuring load balancing can provide SSL solutions for Rosetta. If you load balance on the HTTPS layer, then you’d install the SSL certificate on the load balancer alone, and use plain un-encrypted HTTP over the local network between the load balancer and the Rosetta servers.

Load Balancers can be configured on the hardware level (e.g F5) or on the software level (e.g Apache mod_ proxy). We will be using the Apache software solution for this example.

Rosetta Load Balancer Example:

For the purpose of this example I am using the following:

Two Rosetta servers – rosetta01.myinstitution.org and rosetta02.myinstitution.org. Both are “all in one”servers (DEP, REP, PER, DEL and IDX roles)

A Load Balancer machine: loadbalancer.myinstitution.org. Apache has been installed with mod_proxy and mod_ssl on this server under /httpd/

Before starting this procedure, shut down Apache (LB and PDS) and Rosetta.

The configuration consists of two parts: configuring the Rosetta servers and configuring the Load Balancer machine:

Rosetta Side Configuration:

You will need to edit the relevant properties in the global.properties file on all servers. In this example I am using SSL (port 443) for PDS requests only. I have updated the following global.properties on both rosetta01.myinstitution.org and rosetta02.myinstitution.org :

load.balancer.dep.port=80

load.balancer.del.port=80

load.balancer.rep.port=80

load.balancer.per.port=80

load.balancer.pds.port=443

load.balancer.dep.host=loadbalancer.myinstitution.org

load.balancer.del.host=loadbalancer.myinstitution.org

load.balancer.rep.host=loadbalancer.myinstitution.org

load.balancer.per.host=loadbalancer.myinstitution.org

load.balancer.pds.host=loadbalancer.myinstitution.org

load.balancer.dep=loadbalancer.myinstitution.org\:80

load.balancer.del=loadbalancer.myinstitution.org\:80

load.balancer.rep=loadbalancer.myinstitution.org\:80

load.balancer.per=loadbalancer.myinstitution.org\:80

load.balancer.pds=loadbalancer.myinstitution.org\:443

We have set all hosts to our LB machine with the standard https port for pds and the standard http port for other hosts.

If you are using SSL for PDS, I will explain the changes necessary at this point in the PDS module later in this blog.

Now all that’s left to do is Run dps_config and we are done with the Rosetta side configuration.

Load Balancer Machine Configuration:

In order to configure the LB you’ll need to edit the /httpd/conf/httpd.conf file for regular LB configuration Or the /httpd/conf/extra/httpd-ssl.conf file for SSL LB configuration

For SSL Load Balancing you will need to include the httpd-ssl.conf in the httpd.conf file by adding the following line:

Include /exlibris/dps/d4_3/lb/httpd/conf/extra/httpd-ssl.conf

You need to define the ports the LB will listen to in our case:

Listen 80 http

Listen 443 https

Define the proxy definitions and rules. For example, our PDS is located on rosetta01.myinstitution.org . Therefore, we will reroute all PDS http request received by the LB to there.

Proxy definition for PDS:

<Proxy balancer://pds>

      Order deny,allow
  
      Allow from all

      BalancerMember https://rosetta01.myinstitution.org.corp.exlibrisgroup.com:443/

  </Proxy>

ProxyPassReverse / https://rosetta01.myinstitution.org.corp.exlibrisgroup.com:443/

Proxy rule for PDS:

RewriteEngine On

RewriteRule   ^/pds(.*)  balancer://pds/pds$1 [P]

RewriteRule   ^/goto(.*)  balancer://pds/goto$1 [P]

RewriteRule   ^/calling_system-dps(.*)  balancer://pds/calling_system-dps$1 [P]

ProxyPassReverse / https://rosetta01.myinstitution.org.corp.exlibrisgroup.com:443/

You must define a sticky session for proxy rules that reroute to more than one server. This will insure that all requests will be redirected to the same Rosetta server during the same session. The following configuration redirects all requests to one of our Rosetta servers using a sticky session:

Proxy definition for Rosetta requests:

# staging end user

<Proxy balancer://staging-user>

    Order deny,allow

    Allow from all

    BalancerMember http://rosetta01.myinstitution.org:1801 route=rosetta01.myinstitution.org:1801

    BalancerMember http://rosetta02.myinstitution.org:1801 route=rosetta02.myinstitution.org.corp.exlibrisgroup.com:1801

    ProxySet stickysession=JSESSIONID lbmethod=byrequests nofailover=On

</Proxy>

Proxy rule for Rosetta Requests (everything not caught by the pds proxy rule):

RewriteEngine On

RewriteRule   ^(.*)$  balancer://staging-user$1 [P]

# ProxyPass / balancer://staging-user/ stickysession=JSESSIONID lbmethod=byrequests nofailover=On

ProxyPassReverse / https://rosetta01.myinstitution.org:1801

ProxyPassReverse / https://rosetta02.myinstitution.org:1801

Now all you need to do is start the Load Balancer and you are set to go!

Starting and stopping the Apache Load balancer is done by apachectl start or the apachectl stop commands located under the /httpd/bin directory.

SSL LB Configuration:

For SSL you will need a private key (server.key) and a signed certificate (server.crt).

For our example the following steps were necessary:

Copy the key and the certificate to apache conf: /httpd/conf
In order to redirect http requests to https, create a virtual Host that listens to port 80 and redirects to https. This is done in the /httpd/conf/extra/httpd.conf file:

<VirtualHost _default_:80>

ServerName loadbalancer.myinstitution.org

Redirect / https://loadbalancer.myinstitution.org/mng

</VirtualHost>

Now create a virtual host that listens to port 443 for all LB redirections to Rosetta. Here is where we define the proxy definitions and rules described in the Load Balancer configuration section of this document.

<VirtualHost _default_:443>

ServerName rosetta01.myinstitution.org

SSLEngine on

SSLProxyEngine On

SSLCertificateFile /httpd/conf/server.crt

SSLCertificateKeyFile /httpd/conf/server.key

<IfModule proxy_module>

       <Proxy balancer://pds>

            Order allow,deny

           Allow from all

          BalancerMember https://rosetta01.myinstitution.org

     </Proxy>

    RewriteEngine On

    RewriteRule   ^/pds(.*)  balancer://pds/pds$1 [P]

   RewriteRule   ^/goto(.*)  balancer://pds/goto$1 [P]

   RewriteRule   ^/calling_system-dps(.*)  balancer://pds/calling_system-dps$1 [P]

   ProxyPassReverse / https://rosetta01.myinstitution.org/

 

  # staging end user

   <Proxy balancer://staging-user>

     Order allow,deny

     Allow from all

     BalancerMember http://rosetta01.myinstitution.org:1801 route=rosetta01.myinstitution.org:1801

     BalancerMember http://rosetta02.myinstitution.org:1801 route=rosetta02.myinstitution.org:1801

     ProxySet stickysession=JSESSIONID lbmethod=byrequests nofailover=On

   </Proxy>

  RewriteRule   ^(.*)$  balancer://staging-user$1 [P]

  # ProxyPass / balancer://staging-user/ stickysession=JSESSIONID lbmethod=byrequests nofailover=On

  ProxyPassReverse / http://rosetta01.myinstitution.org:1801

  ProxyPassReverse / http://rosetta02.myinstitution.org:1801

 </IfModule>

</VirtualHost>

SSL PDS Configuration:

Go to pdsroot/program/PDSDefinitions and change the port to 443 and the protocol to https:

our ($server_httpd)      =  "loadbalancer.myinstitution.org:443";

our ($server_httpsd)     =  "loadbalancer.myinstitution.org:443";

our ($server_pds)        =  "loadbalancer.myinstitution.org:443/pds";

You will need to edit the relevant properties in the global.properties file on all servers. on both rosetta01.myinstitution.org and rosetta02.myinstitution.org :

load.balancer.dep.port=443

load.balancer.del.port=443

load.balancer.rep.port=443

load.balancer.per.port=443

load.balancer.pds.port=443

load.balancer.dep=loadbalancer.myinstitution.org\:443

load.balancer.del=loadbalancer.myinstitution.org\:443

load.balancer.rep=loadbalancer.myinstitution.org\:443

load.balancer.per=loadbalancer.myinstitution.org\:443

protocol.del=https

protocol.dep=https

protocol.pds=https

protocol.per=https

protocol.rep=https

Place your SSL key and certificate under pdsroot/apache/SSLconf/conf
Make sure -DSSL is set in the pdsroot/apache/bin/apachectl_auto:

$httpd_bin/httpd -d $httpd_root -DSSL

Make sure “User” is set to dps and”Group” is set to exlibris under pdsroot/apache/conf/httpd.conf
“su” to root, and run ./apachectl_stop and ./apachectl_auto under pdsroot/apache/bin/
Update tab_services (e.g pdsroot/conf_table/tab_service.INS00). Set port to 443 and SSL to “Y” for yes.

The code is also available on github.

One Reply to “Rosetta Load Balancer Example”

Alex Zelenko says:
February 19, 2019 at 9:58 am
When moving to an external Load Balancer topology, customers who use IP based access rights need to pay attention to configure
client_ip_header X-Forwarded-For
in the LB and in Rosetta Administration general parameters
See Rosetta_System_Administration_Guide in https://knowledge.exlibrisgroup.com/Rosetta/
and
https://knowledge.exlibrisgroup.com/Rosetta/Knowledge_Articles/How_to_Enable_IIIF_When_Using_a_Proxy
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Rosetta Load Balancer Example

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