27-04-2022

Bloomreach Experience Manager Load Balancing Requirements

Server affinity required for running Bloomreach Experience Manager behind a load balancer

Running Bloomreach Experience Manager behind a load balancer requires server affinity to be configured in the load balancer.

Bloomreach Experience Manager supports two different load balancer server affinity strategies:

Source IP affinity

With this strategy the load balancer directs all client traffic from a specific source IP to the same backend server.
This is a robust solution, but has the disadvantage that the traffic can be unevenly distributed when a large group of users are accessing the CMS from behind a shared NAT.
For example from within a corporate network all users then might end up being served by a single backend server.

Injecting a dedicated server affinity cookie

With this strategy the load balancer injects a dedicated cookie which keeps track of the server affinity.
It is important to use a separate cookie and not (re)use the session cookies set by the application.

This is the recommended strategy.

As an illustration how to configure this, the following HAProxy backend configuration fragment will inject a SERVERID cookie to track the server affinity:

backend hippo 
  balance roundrobin
  cookie SERVERID insert nocache httponly maxidle 1h
  server node1 10.10.10.1:8080 check cookie node1
  server node2 10.10.10.2:8080 check cookie node2
The above configuration fragment is just an example!
Different loadbalancers require a different setup and a complete loadbalancer configuration is beyond the scope of BloomReach support.
  

Cookie Path

The Path of the SERVERID cookie must be on / . After logging in into the CMS there must be a Cookie something like

Name Value Domain Path
SERVERID 16cad8c0e739011127f5b12db02ce241763079f2 cms.my.domain /

If the Path is for example /cms, the Experience Manager perspective won't work, most likely showing a 409 status code for some requests, see Channel Manager Troubleshooting.

Headless Integration and Single Page Applications (SPA)

As of Bloomreach Experience Manager 14.2, the preview data in the Delivery API can be accessed using JSON Web Token-based authentication. When Bloomreach Experience Manager is running behind a load balancer, server affinity is required to access the preview data. That requirement is applicable only to the preview integration and must not be used in live mode.

Apart from the SERVERID cookie, there is a possibility to pass a Server-Id header in the outgoing Delivery API request. When Bloomreach Experience Manager is running behind a load balancer, the value for the Server-Id header will be passed in the server-id query string parameter. The parameter will be appended next to the token parameter to the URL configured for a channel in the org.hippoecm.hst.configuration.channel.PreviewURLChannelInfo_url parameter.

The SPA SDK supports the server-id query parameter handling and the integration should work out of the box without extra configuration.

Technical background

The CMS Experience manager provides preview access to and management for the Delivery Tier (the site applications).

To be able to do so it now is required that both the CMS and Site web application(s) are hosted on the same appllication server (Tomcat) and that the client access is coordinated to be server from the same backend application server.

In previous versions the CMS and Site application used a secret-based SSO handshake to validate and ensure this communication, and even allowed for so called skewed coordination across multiple application servers through the use of a shared hippo.cluster.sso.key environment parameter.

For both functional and technical reasons skewed application coordination across multiple application servers no longer is possible as of Bloomreach Experience Manager 7.9.15, 10.2.3 and 11.0 (GA), and the secret-based SSO handshake no longer used nor needed.

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