In T107498#1497340, @bd808 wrote:

/etc/nutcracker/nutcracker.yml on deployment-bastion is missing config sections. It has

memcached:
   auto_eject_hosts: true
   distribution: ketama
   hash: md5
   listen: 127.0.0.1:11212
   preconnect: true
   redis: false
   server_connections: 2
   server_failure_limit: 3
   server_retry_timeout: 30000
   timeout: 250
   servers:
   - 10.68.16.14:11211:1
   - 10.68.16.15:11211:1

but deployment-mediawiki01 has

mc-unix:
  auto_eject_hosts: true
  distribution: ketama
  hash: md5
  listen: /var/run/nutcracker/nutcracker.sock 0666
  preconnect: true
  server_connections: 1
  server_failure_limit: 3
  server_retry_timeout: 30000
  servers:
    - 10.68.16.14:11211:1
    - 10.68.16.15:11211:1
  timeout: 250
memcached:
  auto_eject_hosts: true
  distribution: ketama
  hash: md5
  listen: 127.0.0.1:11212
  preconnect: true
  server_connections: 1
  server_failure_limit: 3
  server_retry_timeout: 30000
  servers:
    - 10.68.16.14:11211:1
    - 10.68.16.15:11211:1
  timeout: 250
session-redis:
  auto_eject_hosts: true
  distribution: ketama
  hash: md5
  listen: 127.0.0.1:6380
  preconnect: true
  redis: true
  redis_auth: Q6dzak4k9vjYjh341fHS
  server_connections: 1
  server_failure_limit: 3
  server_retry_timeout: 30000
  servers:
    - 10.68.16.177:6379:1
    - 10.68.16.231:6379:1
  timeout: 1000

In T107498#1497348, @ori wrote:

This should work now, because I made CommonSettings.php once again consult $sessionRedis as defined in the realm-specific session.php file. But a proper fix would be to get Nutcracker fully working in Beta, which requires fixing the configuration / Puppetization, as @bd808 notes above.