Adapters

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

Each iii worker 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

workers:
  - name: iii-queue
    config:
      adapter:
        name: redis
        config:
          redis_url: ${REDIS_URL:redis://localhost:6379}

Every adapter entry has two fields:

• name — the adapter short name
• config — adapter-specific config (omit if not needed)

Adapter Reference

Queue

Adapter	Name	External dependency
Built-in	builtin	None
Redis	redis	Redis
RabbitMQ	rabbitmq	RabbitMQ

builtin

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

adapter:
  name: builtin

redis

adapter:
  name: redis
  config:
    redis_url: ${REDIS_URL:redis://localhost:6379}

rabbitmq

adapter:
  name: rabbitmq
  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 worker.

---

State

Adapter	Name	External dependency
KV Store	kv	None
Redis	redis	Redis
Bridge	bridge	Remote iii Engine

kv

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

adapter:
  name: kv
  config:
    store_method: file_based   # in_memory | file_based
    file_path: ./data/state
    save_interval_ms: 5000

redis

adapter:
  name: redis
  config:
    redis_url: ${REDIS_URL:redis://localhost:6379}

bridge

Forwards state operations to a remote iii Engine.

adapter:
  name: bridge

---

Stream

Adapter	Name	External dependency
KV Store	kv	None
Redis	redis	Redis

kv

Default. In-process only.

adapter:
  name: kv
  config:
    store_method: file_based   # in_memory | file_based
    file_path: ./data/stream_store
    save_interval_ms: 5000

redis

adapter:
  name: redis
  config:
    redis_url: ${REDIS_URL:redis://localhost:6379}

---

Cron

Adapter	Name	External dependency
KV Cron	kv	None
Redis Cron	redis	Redis

kv

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

adapter:
  name: kv

redis

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

adapter:
  name: redis
  config:
    redis_url: ${REDIS_URL:redis://localhost:6379}

---

PubSub

Adapter	Name	External dependency
Local	local	None
Redis	redis	Redis

local

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

adapter:
  name: local

redis

adapter:
  name: redis
  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}