Add ClusterSessions for redis sessions migration

What does this MR do and why?

This MR adds a new Redis class ClusterSessions which is going to be the new Redis Cluster store for the existing Sessions Redis store. Migration is done by wrapping the Sessions class with Multistore, which handles dual writes to both stores via FF toggles.

This is the 3rd MR in the series of MR in gitlab-com/gl-infra/data-access/durability/team#35 (closed).

FF warning

❗ ❗ BIG WARNING: Ensure use_primary_store_as_default_for_sessions FF is disabled (currently enabled from seemingly previous migration), otherwise traffic would start going into Redis SharedState (like what happened in gitlab-com/gl-infra/production#19028 (closed)).

✅ FF state as per 2024-01-21 06:36

References

Please include cross links to any resources that are relevant to this MR. This will give reviewers and future readers helpful context to give an efficient review of the changes introduced.

• gitlab-com/gl-infra/data-access/durability/team#28 (closed)

MR acceptance checklist

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Before	After

How to set up and validate locally

1. Setup Redis Cluster https://gitlab.com/gitlab-org/gitlab-development-kit/-/blob/main/doc/howto/redis_cluster.md

2. Configure cluster_sessions to use the Redis Cluster in config/redis.yml:

   development:
     cluster_sessions:
       cluster:
         - redis://localhost:6001

3. Enable dual write FF use_primary_and_secondary_stores_for_sessions

4. Monitor Redis Cluster commands by opening 3 terminal sessions and run redis-cli -p 6000 monitor , redis-cli -p 6001 monitor , redis-cli -p 6002 monitor

5. Visit GitLab, login

6. You should see some set , setex and setadd in the monitored Redis Cluster, eg:

   1737368969.459424 [0 127.0.0.1:55015] "setex" "session:user:gitlab::v2:1:2::f3a107b4f25e381a57ba463357f92b7338d1d126efb5d33a56445434d258a4c0" "604800" "v2:{\"ip_address\":\"127.0.0.1\",\"browser\":\"Chrome\",\"os\":\"Mac\",\"device_name\":null,\"device_type\":\"desktop\",\"created_at\":\"2025-01-17T12:07:14.057Z\",\"updated_at\":\"2025-01-20T10:29:29.456Z\",\"session_private_id\":\"2::f3a107b4f25e381a57ba463357f92b7338d1d126efb5d33a56445434d258a4c0\",\"is_impersonated\":false,\"admin_mode\":false}"
   1737368969.459475 [0 127.0.0.1:55015] "sadd" "session:lookup:user:gitlab:1" "2::f3a107b4f25e381a57ba463357f92b7338d1d126efb5d33a56445434d258a4c0"
   1737368969.978883 [0 127.0.0.1:59891] "setex" "session:user:gitlab::v2:1:2::f3a107b4f25e381a57ba463357f92b7338d1d126efb5d33a56445434d258a4c0" "604800" "v2:{\"ip_address\":\"127.0.0.1\",\"browser\":\"Chrome\",\"os\":\"Mac\",\"device_name\":null,\"device_type\":\"desktop\",\"created_at\":\"2025-01-17T12:07:14.057Z\",\"updated_at\":\"2025-01-20T10:29:29.959Z\",\"session_private_id\":\"2::f3a107b4f25e381a57ba463357f92b7338d1d126efb5d33a56445434d258a4c0\",\"is_impersonated\":false,\"admin_mode\":false}"
   1737368969.978923 [0 127.0.0.1:59891] "sadd" "session:lookup:user:gitlab:1" "2::f3a107b4f25e381a57ba463357f92b7338d1d126efb5d33a56445434d258a4c0"
   1737368972.862414 [0 127.0.0.1:55015] "setex" "session:user:gitlab::v2:1:2::f3a107b4f25e381a57ba463357f92b7338d1d126efb5d33a56445434d258a4c0" "604800" "v2:{\"ip_address\":\"127.0.0.1\",\"browser\":\"Chrome\",\"os\":\"Mac\",\"device_name\":null,\"device_type\":\"desktop\",\"created_at\":\"2025-01-17T12:07:14.057Z\",\"updated_at\":\"2025-01-20T10:29:32.860Z\",\"session_private_id\":\"2::f3a107b4f25e381a57ba463357f92b7338d1d126efb5d33a56445434d258a4c0\",\"is_impersonated\":false,\"admin_mode\":false}"
   1737368972.862454 [0 127.0.0.1:55015] "sadd" "session:lookup:user:gitlab:1" "2::f3a107b4f25e381a57ba463357f92b7338d1d126efb5d33a56445434d258a4c0"
   
   1737368972.882436 [0 127.0.0.1:55020] "set" "session:gitlab:2::f3a107b4f25e381a57ba463357f92b7338d1d126efb5d33a56445434d258a4c0" "\x04\bo: ActiveSupport::Cache::Entry\t:\x0b@value{\x0cI\"\x1alast_authn_request_id\x06:\x06ETI\"*_8450f672-bfe8-46c2-955e-e240fd521f50\x06;\aTI\"\rsaml_uid\x06;\aTI\"\x062\x06;\aTI\"\x17saml_session_index\x06;\aTI\"0_d1f49a4d232ec1da0c98a0fe4f881feeefebaa22af\x06;\aTI\"\x19warden.user.user.key\x06;\aT[\a[\x06i\x06I\"\"$2a$10$y7/L42WUBppyY8sKToazCu\x06;\aTI\" ask_for_usage_stats_consent\x06;\aFFI\"\x10_csrf_token\x06;\aFI\"06-CSnU1p6xMg4KPBR9_Pcn60cL25vmwj45XPR5fzXMU\x06;\aFI\"\x17redirect_return_to\x06;\aTI\"\r/twitter\x06;\aT:\r@version0:\x10@created_atf\x060:\x10@expires_inf\x171737973772.8784032" "PX" "604800000"

7. Redis Cluster should have some data now

   ❯ redis-cli -p 6000 keys '*'
   (empty array)
   ❯ redis-cli -p 6001 keys '*'
   1) "session:user:gitlab::v2:1:2::f3a107b4f25e381a57ba463357f92b7338d1d126efb5d33a56445434d258a4c0"
   2) "session:lookup:user:gitlab:1"
   ❯ redis-cli -p 6002 keys '*'
   1) "session:gitlab:2::f3a107b4f25e381a57ba463357f92b7338d1d126efb5d33a56445434d258a4c0"

8. Switch over read by enabling FF use_primary_store_as_default_for_sessions

9. You should still be logged in.

10. One of the Redis port should receive a get command now

    1737368325.929292 [0 127.0.0.1:55020] "get" "session:gitlab:2::f3a107b4f25e381a57ba463357f92b7338d1d126efb5d33a56445434d258a4c0"