Adapters

Pluggable backends for iii modules — swap between in-memory, file-based, Redis, and RabbitMQ without changing your application code.

Each iii module that needs persistence or distribution uses an adapter — a pluggable backend that implements a fixed interface. Swap adapters in iii-config.yaml without touching application code.

Pattern

modules:
  - class: modules::queue::QueueModule
    config:
      adapter:
        class: modules::queue::RedisAdapter
        config:
          redis_url: ${REDIS_URL:redis://localhost:6379}

Every adapter entry has two fields:

• class — the full adapter path
• config — adapter-specific config (omit if not needed)

Adapter Reference

Queue

Adapter	Class	External dependency
Built-in	modules::queue::BuiltinQueueAdapter	None
Redis	modules::queue::RedisAdapter	Redis
RabbitMQ	modules::queue::RabbitMQAdapter	RabbitMQ

modules::queue::BuiltinQueueAdapter

Default. In-process only with retries and DLQ — does not share messages across engine instances.

adapter:
  class: modules::queue::BuiltinQueueAdapter

modules::queue::RedisAdapter

adapter:
  class: modules::queue::RedisAdapter
  config:
    redis_url: ${REDIS_URL:redis://localhost:6379}

modules::queue::RabbitMQAdapter

adapter:
  class: modules::queue::RabbitMQAdapter
  config:
    amqp_url: ${RABBITMQ_URL:amqp://localhost:5672}
    max_attempts: 3
    prefetch_count: 10
    queue_mode: standard   # standard | fifo

For retry behavior, dead-letter queues, and full config reference, see the Queue module.

---

State

Adapter	Class	External dependency
KV Store	modules::state::adapters::KvStore	None
Redis	modules::state::adapters::RedisAdapter	Redis
Bridge	modules::state::adapters::Bridge	Remote iii Engine

modules::state::adapters::KvStore

Default. Supports in-memory or file-based persistence.

adapter:
  class: modules::state::adapters::KvStore
  config:
    store_method: file_based   # in_memory | file_based
    file_path: ./data/state
    save_interval_ms: 5000

modules::state::adapters::RedisAdapter

adapter:
  class: modules::state::adapters::RedisAdapter
  config:
    redis_url: ${REDIS_URL:redis://localhost:6379}

modules::state::adapters::Bridge

Forwards state operations to a remote iii Engine.

adapter:
  class: modules::state::adapters::Bridge

---

Stream

Adapter	Class	External dependency
KV Store	modules::stream::adapters::KvStore	None
Redis	modules::stream::adapters::RedisAdapter	Redis

modules::stream::adapters::KvStore

Default. In-process only.

adapter:
  class: modules::stream::adapters::KvStore
  config:
    store_method: file_based   # in_memory | file_based
    file_path: ./data/stream_store
    save_interval_ms: 5000

modules::stream::adapters::RedisAdapter

adapter:
  class: modules::stream::adapters::RedisAdapter
  config:
    redis_url: ${REDIS_URL:redis://localhost:6379}

---

Cron

Adapter	Class	External dependency
KV Cron	modules::cron::KvCronAdapter	None
Redis Cron	modules::cron::RedisCronAdapter	Redis

modules::cron::KvCronAdapter

Default. Process-local locks — jobs may run on every instance in multi-instance deployments.

adapter:
  class: modules::cron::KvCronAdapter

modules::cron::RedisCronAdapter

Distributed locking via Redis — ensures each job runs only once across all instances.

adapter:
  class: modules::cron::RedisCronAdapter
  config:
    redis_url: ${REDIS_URL:redis://localhost:6379}

---

PubSub

Adapter	Class	External dependency
Local	modules::pubsub::LocalAdapter	None
Redis	modules::pubsub::RedisAdapter	Redis

modules::pubsub::LocalAdapter

Default. In-process broadcast — subscribers must be in the same engine process.

adapter:
  class: modules::pubsub::LocalAdapter

modules::pubsub::RedisAdapter

adapter:
  class: modules::pubsub::RedisAdapter
  config:
    redis_url: ${REDIS_URL:redis://localhost:6379}

---

Choosing an Adapter

	Single instance	Multi-instance
Queue	BuiltinQueueAdapter	RedisAdapter or RabbitMQAdapter
State	KvStore (file_based)	RedisAdapter
Stream	KvStore	RedisAdapter
Cron	KvCronAdapter	RedisCronAdapter
PubSub	LocalAdapter	RedisAdapter

Use ${VAR:default} syntax in iii-config.yaml to switch adapters per environment without changing the file:

redis_url: ${REDIS_URL:redis://localhost:6379}