Make Daemon Memory Killer be the default for Sidekiq

changelogs/unreleased/232765-make-daemon-memory-killer-default-for-sidekiq.yml

+---
+title: Make Daemon Memory Killer be the default for Sidekiq
+merge_request: 41847
+author:
+type: other

config/initializers/sidekiq.rb

@@ -18,7 +18,7 @@ queues_config_hash[:namespace] = Gitlab::Redis::Queues::SIDEKIQ_NAMESPACE
 
 enable_json_logs = Gitlab.config.sidekiq.log_format == 'json'
 enable_sidekiq_memory_killer = ENV['SIDEKIQ_MEMORY_KILLER_MAX_RSS'].to_i.nonzero?
-use_sidekiq_daemon_memory_killer = ENV["SIDEKIQ_DAEMON_MEMORY_KILLER"].to_i.nonzero?
+use_sidekiq_daemon_memory_killer = ENV.fetch("SIDEKIQ_DAEMON_MEMORY_KILLER", 1).to_i.nonzero?
 use_sidekiq_legacy_memory_killer = !use_sidekiq_daemon_memory_killer
 
 Sidekiq.configure_server do |config|

doc/administration/operations/sidekiq_memory_killer.md

@@ -26,8 +26,8 @@ run as a process group leader (e.g., using `chpst -P`). If using Omnibus or the
 
 The MemoryKiller is controlled using environment variables.
 
-- `SIDEKIQ_DAEMON_MEMORY_KILLER`: defaults to 0. When set to 1, the MemoryKiller
-  works in _daemon_ mode. Otherwise, the MemoryKiller works in _legacy_ mode.
+- `SIDEKIQ_DAEMON_MEMORY_KILLER`: defaults to 1. When set to 0, the MemoryKiller
+  works in _legacy_ mode. Otherwise, the MemoryKiller works in _daemon_ mode.
 
   In _legacy_ mode, the MemoryKiller checks the Sidekiq process RSS after each job.
 

doc/user/gitlab_com/index.md

@@ -413,7 +413,7 @@ and the following environment variables:
 
 | Setting                                    | GitLab.com | Default   |
 |--------                                    |----------- |--------   |
-| `SIDEKIQ_DAEMON_MEMORY_KILLER`             | -          | -         |
+| `SIDEKIQ_DAEMON_MEMORY_KILLER`             | -          | `1`       |
 | `SIDEKIQ_MEMORY_KILLER_MAX_RSS`            | `2000000`  | `2000000` |
 | `SIDEKIQ_MEMORY_KILLER_HARD_LIMIT_RSS`     | -          | -         |
 | `SIDEKIQ_MEMORY_KILLER_CHECK_INTERVAL`     | -          | `3`       |