Redis Salt State: MediaWiki Object Cache Configuration

The redis Salt state installs redis-server, renders a Jinja-templated redis.conf from pillar data, and keeps the service running and restarted whenever the configuration changes. Each redis* VM in the fleet carries a host-specific pillar file that overrides the maxmemory limit and eviction policy, while all other tunables inherit cluster-wide defaults from the base redis pillar.

State overview

Package installation

Installs the redis-server package via pkg.installed.

Configuration file

Renders /etc/redis/redis.conf from salt://redis/files/redis.conf.jinja, owned by root:redis, mode 0640. All values are sourced from the redis pillar key.

Service management

Ensures redis-server is running and enabled at boot, restarting automatically whenever the config file changes.

# salt/redis/init.sls
install_redis:
  pkg.installed:
    - name: redis-server

/etc/redis/redis.conf:
  file.managed:
    - source: salt://redis/files/redis.conf.jinja
    - template: jinja
    - user: root
    - group: redis
    - mode: '0640'
    - require:
      - pkg: install_redis

redis-server:
  service.running:
    - enable: True
    - watch:
      - file: /etc/redis/redis.conf

Configuration template

The template is intentionally minimal — every directive maps directly to a pillar key with a safe default, making it easy to override individual settings per host.

{%- set cfg = salt['pillar.get']('redis', {}) %}
{%- set saves = cfg.get('save', ['900 1', '300 10', '60 10000']) %}
# Managed by Salt — do not edit manually.

bind {{ cfg.get('bind', '127.0.0.1') }}
port {{ cfg.get('port', 6379) }}
protected-mode {{ cfg.get('protected_mode', 'yes') }}

timeout {{ cfg.get('timeout', 0) }}
tcp-keepalive {{ cfg.get('tcp_keepalive', 300) }}

loglevel {{ cfg.get('loglevel', 'notice') }}
logfile "{{ cfg.get('logfile', '') }}"

databases {{ cfg.get('databases', 16) }}

{%- for s in saves %}
save {{ s }}
{%- endfor %}

maxmemory {{ cfg.get('maxmemory', 0) }}
maxmemory-policy {{ cfg.get('maxmemory_policy', 'noeviction') }}

{%- if cfg.get('requirepass') %}
requirepass {{ cfg.get('requirepass') }}
{%- endif %}

appendonly {{ cfg.get('appendonly', 'no') }}
appendfsync {{ cfg.get('appendfsync', 'everysec') }}

dir /var/lib/redis

Pillar reference

All keys sit under the top-level redis mapping. The cluster-wide defaults are defined in pillar/redis/init.sls and selectively overridden in per-host pillar files.

Key	Default	Description
`bind`	`127.0.0.1`	Interface(s) Redis listens on; fleet uses `0.0.0.0` for internal reachability
`port`	`6379`	TCP port
`protected_mode`	`yes`	Reject connections from non-loopback clients if no password set; fleet sets `no`
`timeout`	`0`	Idle connection timeout in seconds; `0` disables
`tcp_keepalive`	`300`	TCP keepalive interval in seconds
`loglevel`	`notice`	Logging verbosity (`debug`, `verbose`, `notice`, `warning`)
`logfile`	`""`	Log file path; empty string sends logs to stdout / journald
`databases`	`16`	Number of logical databases
`maxmemory`	`0`	Memory cap; `0` = unlimited. Use `gb`/`mb` suffix (e.g. `12gb`)
`maxmemory_policy`	`noeviction`	Eviction policy when `maxmemory` is reached
`requirepass`	(unset)	Optional password; omit the key entirely to disable AUTH
`appendonly`	`no`	Enable AOF persistence (`yes`/`no`)
`appendfsync`	`everysec`	AOF fsync strategy (`always`, `everysec`, `no`)
`save`	`['900 1', '300 10', '60 10000']`	RDB save checkpoints as a list of `"seconds changes"` strings

The maxmemory_policy for all MediaWiki caching instances is set to allkeys-lru, which evicts the least-recently-used key from the entire keyspace when the memory limit is reached. This is the correct policy for object caches where every key is expendable.

Pillar examples

Cluster defaults (init.sls)
redis-us-east-011 (12 GB)
redis-us-east-012 (3 GB)
redis-us-east-021 (3 GB)

# pillar/redis/init.sls — applied to every redis* minion
redis:
  bind: 0.0.0.0
  port: 6379
  timeout: 0
  tcp_keepalive: 300
  loglevel: notice
  logfile: ""
  databases: 16
  maxmemory: 0
  maxmemory_policy: noeviction
  protected_mode: "no"
  appendonly: "no"
  appendfsync: everysec
  save:
    - "900 1"
    - "300 10"
    - "60 10000"

# pillar/redis/redis-us-east-011.sls
# Primary cache node — 12 GB limit, LRU eviction
redis:
  bind: 0.0.0.0
  maxmemory: 12gb
  maxmemory_policy: allkeys-lru

# pillar/redis/redis-us-east-012.sls
redis:
  bind: 0.0.0.0
  maxmemory: 3gb
  maxmemory_policy: allkeys-lru

# pillar/redis/redis-us-east-021.sls
redis:
  bind: 0.0.0.0
  maxmemory: 3gb
  maxmemory_policy: allkeys-lru

Fleet topology

redis-us-east-011

Primary US-East cache node. 12 GB memory cap, allkeys-lru eviction. VM ID 140 on metal-us-east-01.

redis-us-east-012

Secondary US-East cache node. 3 GB memory cap, allkeys-lru eviction. VM ID 141 on metal-us-east-01.

redis-us-east-021

US-East-02 cache node. 3 GB memory cap, allkeys-lru eviction. Hosted on metal-us-east-02 at 10.0.2.90.

Applying the state

# Apply to all redis* minions
salt 'redis*' state.apply redis

# Apply to a specific instance
salt 'redis-us-east-011*' state.apply redis

# Verify rendered configuration on a minion
salt 'redis-us-east-011*' pillar.get redis

# Test configuration without applying
salt 'redis*' state.apply redis test=True

After applying, confirm Redis is accepting connections and respecting the memory cap with:

salt 'redis-us-east-011*' cmd.run 'redis-cli INFO memory | grep used_memory_human'

Core

Web Tier

Data & Search

Infrastructure

Monitoring

Redis Salt State: MediaWiki Object Cache Configuration

State overview

Configuration template

Pillar reference

Pillar examples

Fleet topology

redis-us-east-011

redis-us-east-012

redis-us-east-021

Applying the state

Build docs developers (and LLMs) love

Core

Web Tier

Data & Search

Infrastructure

Monitoring

Documentation Index

​State overview

​Configuration template

​Pillar reference

​Pillar examples

​Fleet topology

redis-us-east-011

redis-us-east-012

redis-us-east-021

​Applying the state

Build docs developers (and LLMs) love

State overview

Configuration template

Pillar reference

Pillar examples

Fleet topology

Applying the state