Python SDK

Installation

pip install iii-sdk

Initialization

Create an III client and connect to the engine. Blocks until the WebSocket connection is established and ready.

from iii import register_worker, InitOptions
iii = register_worker('ws://localhost:49134', InitOptions(worker_name='my-worker'))

Methods

connect_async

Connect to the III Engine via WebSocket. Initializes OpenTelemetry (if configured), attaches the event loop, and establishes the WebSocket connection. This is called automatically during construction — use it only if you need to reconnect manually from an async context. Signature

async ()

create_channel

Create a streaming channel pair for worker-to-worker data transfer. The returned Channel contains a local writer / reader and their serializable refs (writer_ref, reader_ref) that can be passed as fields in invocation data to other functions. Signature

create_channel(buffer_size: int | None = None)

Parameters

Name	Type	Required	Description
`buffer_size`	`int \| None`	No	Buffer capacity for the channel. Defaults to `64`.

Example

ch = iii.create_channel()
fn = iii.register_function({"id": "producer"}, producer_handler)
iii.trigger({"function_id": "producer", "payload": {"output": ch.writer_ref}})

create_channel_async

async (buffer_size: int | None = None)

Parameters

Name	Type	Required	Description
`buffer_size`	`int \| None`	No	Buffer capacity for the channel. Defaults to `64`.

Example

ch = await iii.create_channel_async()
fn = iii.register_function({"id": "producer"}, producer_handler)
await iii.trigger_async({"function_id": "producer", "payload": {"output": ch.writer_ref}})

create_stream

Register a custom stream implementation, overriding the engine default. Registers 5 of the 6 IStream methods (get, set, delete, list, list_groups). The update method is not registered — atomic updates are handled by the engine’s built-in stream update logic. Signature

create_stream(stream_name: str, stream: IStream[Any])

Parameters

Name	Type	Required	Description
`stream_name`	`str`	Yes	Unique name for the stream.
`stream`	`IStream`[Any]	Yes	An object implementing the `IStream` interface.

Example

from iii.stream import IStream
class MyStream(IStream):
    async def get(self, input): ...
    async def set(self, input): ...
    async def delete(self, input): ...
    async def list(self, input): ...
    async def list_groups(self, input): ...
    async def update(self, input): ...
iii.create_stream("my-stream", MyStream())

get_connection_state

Return the current WebSocket connection state. Signature

get_connection_state()

list_functions

List all functions registered with the engine across all workers. Signature

list_functions()

Example

for fn in iii.list_functions():
    print(fn.function_id, fn.description)

list_functions_async

List all functions registered with the engine across all workers. Signature

async ()

Example

for fn in await iii.list_functions_async():
    print(fn.function_id, fn.description)

list_trigger_types

List all trigger types registered with the engine. Signature

list_trigger_types(include_internal: bool = False)

Parameters

Name	Type	Required	Description
`include_internal`	`bool`	No	If `True`, include engine-internal trigger types (e.g. `engine::functions-available`). Defaults to `False`.

Example

trigger_types = iii.list_trigger_types()
for tt in trigger_types:
    print(tt.id, tt.trigger_request_format)

list_trigger_types_async

List all trigger types registered with the engine. Signature

async (include_internal: bool = False)

Parameters

Name	Type	Required	Description
`include_internal`	`bool`	No	If `True`, include engine-internal trigger types (e.g. `engine::functions-available`). Defaults to `False`.

Example

trigger_types = await iii.list_trigger_types_async()

list_triggers

List all triggers registered with the engine. Signature

list_triggers(include_internal: bool = False)

Parameters

Name	Type	Required	Description
`include_internal`	`bool`	No	If `True`, include engine-internal triggers (e.g. `functions-available`). Defaults to `False`.

Example

triggers = iii.list_triggers()
internal = iii.list_triggers(include_internal=True)

list_triggers_async

List all triggers registered with the engine. Signature

async (include_internal: bool = False)

Parameters

Name	Type	Required	Description
`include_internal`	`bool`	No	If `True`, include engine-internal triggers (e.g. `functions-available`). Defaults to `False`.

Example

triggers = await iii.list_triggers_async()
internal = await iii.list_triggers_async(include_internal=True)

list_workers

List all workers currently connected to the engine. Signature

list_workers()

Example

for w in iii.list_workers():
    print(w.name, w.worker_id)

list_workers_async

List all workers currently connected to the engine. Signature

async ()

Example

for w in await iii.list_workers_async():
    print(w.name, w.worker_id)

on_functions_available

Subscribe to function-availability events from the engine. The callback fires whenever the set of available functions changes (e.g. a new worker connects or a function is unregistered). Signature

on_functions_available(callback: Callable[None])

Parameters

Name	Type	Required	Description
`callback`	`Callable[None]`	Yes	-

Example

def on_change(functions):
    print("Available:", [f.function_id for f in functions])
unsub = iii.on_functions_available(on_change)
# later ...
unsub()

register_function

Register a function with the engine. Pass a handler for local execution, or an HttpInvocationConfig for HTTP-invoked functions (Lambda, Cloudflare Workers, etc.). Handlers can be synchronous or asynchronous. Sync handlers are automatically wrapped with run_in_executor so they do not block the event loop. Each handler receives a single data argument containing the trigger payload. When func_or_id is a str, the simplified API is used: request_format and response_format are auto-extracted from the handler’s type hints when not explicitly provided. Signature

register_function(func_or_id: RegisterFunctionInput | dict[str, Any] | str, handler_or_invocation: RemoteFunctionHandler | HttpInvocationConfig, description: str | None = None, metadata: dict[str, Any] | None = None, request_format: RegisterFunctionFormat | dict[str, Any] | None = None, response_format: RegisterFunctionFormat | dict[str, Any] | None = None)

Parameters

Name	Type	Required	Description
`func_or_id`	`RegisterFunctionInput` \| dict[str, Any] \| str	Yes	A `RegisterFunctionInput`, dict with `id`, or a plain string function ID. When a string is passed, use keyword arguments for `description`, `metadata`, `request_format`, and `response_format`.
`handler_or_invocation`	RemoteFunctionHandler \| `HttpInvocationConfig`	Yes	A callable handler or `HttpInvocationConfig`. Callable handlers receive one positional argument (`data` — the trigger payload) and may return a value.
`description`	`str \| None`	No	Human-readable description (only with string ID).
`metadata`	`dict[str, Any] \| None`	No	Arbitrary metadata (only with string ID).
`request_format`	`RegisterFunctionFormat` \| dict[str, Any] \| None	No	Schema describing expected input (only with string ID). Auto-extracted from handler type hints when omitted.
`response_format`	`RegisterFunctionFormat` \| dict[str, Any] \| None	No	Schema describing expected output (only with string ID). Auto-extracted from handler type hints when omitted.

Example

def greet(data):
    return {'message': f"Hello, {data['name']}!"}
fn = iii.register_function({"id": "greet", "description": "Greets a user"}, greet)
fn.unregister()
from pydantic import BaseModel
class GreetInput(BaseModel):
    name: str
class GreetOutput(BaseModel):
    message: str
async def greet(data: GreetInput) -> GreetOutput:
    return GreetOutput(message=f"Hello, {data.name}!")
fn = iii.register_function("greet", greet, description="Greets a user")

register_service

Register a logical service grouping with the engine. Services provide an organisational hierarchy for functions. A service can optionally reference a parent_service_id to form a tree visible in the engine dashboard. Signature

register_service(service: RegisterServiceInput | dict[str, Any])

Parameters

Name	Type	Required	Description
`service`	`RegisterServiceInput` \| dict[str, Any]	Yes	A `RegisterServiceInput` or dict with `id` and optional `name`, `description`, `parent_service_id`.

Example

iii.register_service({"id": "payments", "description": "Payment processing"})
iii.register_service({
    "id": "payments::refunds",
    "description": "Refund sub-service",
    "parent_service_id": "payments",
})

register_trigger

Bind a trigger configuration to a registered function. Signature

register_trigger(trigger: RegisterTriggerInput | dict[str, Any])

Parameters

Name	Type	Required	Description
`trigger`	`RegisterTriggerInput` \| dict[str, Any]	Yes	A `RegisterTriggerInput` or dict with `type`, `function_id`, and optional `config`.

Example

trigger = iii.register_trigger({
  'type': 'http',
  'function_id': 'greet',
  'config': {'api_path': '/greet', 'http_method': 'GET'}
})
trigger = iii.register_trigger(RegisterTriggerInput(
    type="http", function_id="greet",
    config={'api_path': '/greet', 'http_method': 'GET'}
))
trigger.unregister()

register_trigger_type

Register a custom trigger type with the engine. Returns a :class:TriggerTypeRef handle with register_trigger and register_function methods. Signature

register_trigger_type(trigger_type: RegisterTriggerTypeInput | dict[str, Any], handler: TriggerHandler[Any])

Parameters

Name	Type	Required	Description
`trigger_type`	`RegisterTriggerTypeInput` \| dict[str, Any]	Yes	A `RegisterTriggerTypeInput` or dict with `id`, `description`, and optional `trigger_request_format` / `call_request_format` (Pydantic class or dict).
`handler`	`TriggerHandler`[Any]	Yes	A `TriggerHandler` instance.

Example

webhook = iii.register_trigger_type(
    RegisterTriggerTypeInput(
        id="webhook",
        description="Webhook trigger",
        trigger_request_format=WebhookConfig,
        call_request_format=WebhookCallRequest,
    ),
    WebhookHandler(),
)
webhook.register_function("handler", handle_webhook)
webhook.register_trigger("handler", WebhookConfig(url="/hook"))

shutdown

Gracefully shut down the client, releasing all resources. Cancels any pending reconnection attempts, rejects all in-flight invocations with an error, closes the WebSocket connection, and stops the background event-loop thread. After this call the instance must not be reused. Signature

shutdown()

Example

iii = register_worker('ws://localhost:49134')
# ... do work ...
iii.shutdown()

shutdown_async

async ()

Example

iii = register_worker('ws://localhost:49134')
# ... do work ...
await iii.shutdown_async()

trigger

Invoke a remote function. The routing behavior and return type depend on the action field:

No action: synchronous — waits for the function to return.
TriggerAction.Enqueue(...): async via named queue — returns EnqueueResult.
TriggerAction.Void(): fire-and-forget — returns None.

Signature

trigger(request: dict[str, Any] | TriggerRequest)

Parameters

Name	Type	Required	Description
`request`	dict[str, Any] \| `TriggerRequest`	Yes	A `TriggerRequest` or dict with `function_id`, `payload`, and optional `action` / `timeout_ms`.

Example

result = iii.trigger({'function_id': 'greet', 'payload': {'name': 'World'}})
iii.trigger({'function_id': 'notify', 'payload': {}, 'action': TriggerAction.Void()})

trigger_async

Invoke a remote function. The routing behavior and return type depend on the action field:

No action: synchronous — waits for the function to return.
TriggerAction.Enqueue(...): async via named queue — returns EnqueueResult.
TriggerAction.Void(): fire-and-forget — returns None.

Signature

async (request: dict[str, Any] | TriggerRequest)

Parameters

Name	Type	Required	Description
`request`	dict[str, Any] \| `TriggerRequest`	Yes	A `TriggerRequest` or dict with `function_id`, `payload`, and optional `action` / `timeout_ms`.

Example

result = await iii.trigger_async({'function_id': 'greet', 'payload': {'name': 'World'}})
await iii.trigger_async({'function_id': 'notify', 'payload': {}, 'action': TriggerAction.Void()})

unregister_trigger_type

Unregister a previously registered trigger type. Signature

unregister_trigger_type(trigger_type: RegisterTriggerTypeInput | dict[str, Any])

Parameters

Name	Type	Required	Description
`trigger_type`	`RegisterTriggerTypeInput` \| dict[str, Any]	Yes	A `RegisterTriggerTypeInput` or dict with `id` and optional `description`.

Example

iii.unregister_trigger_type({"id": "webhook", "description": "Webhook trigger"})
iii.unregister_trigger_type(RegisterTriggerTypeInput(id="webhook", description="Webhook trigger"))

Logger

Structured logger that emits logs as OpenTelemetry LogRecords. Every log call automatically captures the active trace and span context, correlating your logs with distributed traces without any manual wiring. When OTel is not initialized, Logger gracefully falls back to Python logging. Pass structured data as the second argument to any log method. Using a dict of key-value pairs (instead of string interpolation) lets you filter, aggregate, and build dashboards in your observability backend.

debug

Log a debug-level message. Signature

debug(message: str, data: Any = None)

Parameters

Name	Type	Required	Description
`message`	`str`	Yes	Human-readable log message.
`data`	`Any`	No	Structured context attached as OTel log attributes. Use dicts of key-value pairs to enable filtering and aggregation in your observability backend (e.g. Grafana, Datadog, New Relic).

Example

logger.debug('Cache lookup', {'key': 'user:42', 'hit': False})

error

Log an error-level message. Signature

error(message: str, data: Any = None)

Parameters

Name	Type	Required	Description
`message`	`str`	Yes	Human-readable log message.
`data`	`Any`	No	Structured context attached as OTel log attributes. Use dicts of key-value pairs to enable filtering and aggregation in your observability backend (e.g. Grafana, Datadog, New Relic).

Example

logger.error('Payment failed', {
    'order_id': 'ord_123',
    'gateway': 'stripe',
    'error_code': 'card_declined',
})

info

Log an info-level message. Signature

info(message: str, data: Any = None)

Parameters

Name	Type	Required	Description
`message`	`str`	Yes	Human-readable log message.
`data`	`Any`	No	Structured context attached as OTel log attributes. Use dicts of key-value pairs to enable filtering and aggregation in your observability backend (e.g. Grafana, Datadog, New Relic).

Example

logger.info('Order processed', {'order_id': 'ord_123', 'status': 'completed'})

warn

Log a warning-level message. Signature

warn(message: str, data: Any = None)

Parameters

Name	Type	Required	Description
`message`	`str`	Yes	Human-readable log message.
`data`	`Any`	No	Structured context attached as OTel log attributes. Use dicts of key-value pairs to enable filtering and aggregation in your observability backend (e.g. Grafana, Datadog, New Relic).

Example

logger.warn('Retry attempt', {'attempt': 3, 'max_retries': 5, 'endpoint': '/api/charge'})

Types

InitOptions · ReconnectionConfig · TelemetryOptions · HttpInvocationConfig · RegisterFunctionFormat · RegisterFunctionInput · RegisterServiceInput · RegisterTriggerInput · RegisterTriggerTypeInput · TriggerActionEnqueue · TriggerActionVoid · TriggerRequest · IStream · OtelConfig · TriggerHandler

InitOptions

Options for configuring the III SDK.

Name	Type	Required	Description
`enable_metrics_reporting`	`bool`	No	Enable worker metrics via OpenTelemetry. Default `True`.
`headers`	`dict[str, str] \| None`	No	-
`invocation_timeout_ms`	`int`	No	Default timeout for `trigger()` in milliseconds. Default `30000`.
`otel`	`OtelConfig` \| dict[str, Any] \| None	No	OpenTelemetry configuration. Enabled by default. Set `\{'enabled': False\}` or env `OTEL_ENABLED=false` to disable.
`reconnection_config`	`ReconnectionConfig` \| None	No	WebSocket reconnection behavior.
`telemetry`	`TelemetryOptions` \| None	No	Internal telemetry metadata.
`worker_name`	`str \| None`	No	Display name for this worker. Defaults to `hostname:pid`.

ReconnectionConfig

Configuration for WebSocket reconnection behavior.

Name	Type	Required	Description
`backoff_multiplier`	`float`	No	Exponential backoff multiplier. Default `2.0`.
`initial_delay_ms`	`int`	No	Starting delay in milliseconds. Default `1000`.
`jitter_factor`	`float`	No	Random jitter factor (0—1). Default `0.3`.
`max_delay_ms`	`int`	No	Maximum delay cap in milliseconds. Default `30000`.
`max_retries`	`int`	No	Maximum retry attempts. `-1` for infinite. Default `-1`.

TelemetryOptions

Telemetry metadata to be reported to the engine.

Name	Type	Required	Description
`amplitude_api_key`	`str \| None`	No	Amplitude API key for product analytics.
`framework`	`str \| None`	No	Framework name (e.g. `motia`) if applicable.
`language`	`str \| None`	No	Programming language of the worker (e.g. `python`).
`project_name`	`str \| None`	No	Name of the project this worker belongs to.

HttpInvocationConfig

Config for HTTP external function invocation.

Name	Type	Required	Description
`auth`	`HttpAuthConfig \| None`	No	Authentication configuration (bearer, HMAC, or API key).
`headers`	`dict[str, str] \| None`	No	Additional HTTP headers to include in the request.
`method`	`Literal['GET', 'POST', 'PUT', 'PATCH', 'DELETE']`	No	HTTP method. Defaults to `'POST'`.
`timeout_ms`	`int \| None`	No	Request timeout in milliseconds.
`url`	`str`	No	Target URL for the HTTP invocation.

RegisterFunctionFormat

Format definition for function parameters.

Name	Type	Required	Description
`body`	list[`RegisterFunctionFormat`] \| None	No	Nested fields for object types.
`description`	`str \| None`	No	Human-readable description of the parameter.
`items`	`RegisterFunctionFormat` \| None	No	Item schema for array types.
`name`	`str`	Yes	Parameter name.
`required`	`bool`	No	Whether the parameter is required.
`type`	`str`	Yes	Type string (`string`, `number`, `boolean`, `object`, `array`, `null`, `map`).

RegisterFunctionInput

Input for registering a function — matches Node.js RegisterFunctionInput.

Name	Type	Required	Description
`description`	`str \| None`	No	Human-readable description.
`id`	`str`	No	Unique function identifier.
`invocation`	`HttpInvocationConfig` \| None	No	HTTP invocation config for externally hosted functions.
`metadata`	`dict[str, Any] \| None`	No	Arbitrary metadata attached to the function.
`request_format`	`RegisterFunctionFormat` \| dict[str, Any] \| None	No	Schema describing expected input.
`response_format`	`RegisterFunctionFormat` \| dict[str, Any] \| None	No	Schema describing expected output.

RegisterServiceInput

Input for registering a service (matches Node SDK’s RegisterServiceInput).

Name	Type	Required	Description
`description`	`str \| None`	No	Description of the service.
`id`	`str`	No	Unique service identifier.
`name`	`str \| None`	No	Human-readable service name.
`parent_service_id`	`str \| None`	No	ID of the parent service for hierarchical grouping.

RegisterTriggerInput

Input for registering a trigger (matches Node SDK’s RegisterTriggerInput).

Name	Type	Required	Description
`config`	`Any`	No	Trigger-type-specific configuration.
`function_id`	`str`	No	ID of the function this trigger invokes.
`metadata`	`dict[str, Any] \| None`	No	Arbitrary metadata attached to the trigger.
`type`	`str`	No	Trigger type identifier (e.g. `http`, `queue`, `cron`).

RegisterTriggerTypeInput

Input for registering a trigger type.

Name	Type	Required	Description
`call_request_format`	`Any \| None`	No	JSON Schema describing the payload sent to functions.
`description`	`str`	No	Human-readable description of the trigger type.
`id`	`str`	No	Unique identifier for the trigger type.
`trigger_request_format`	`Any \| None`	No	JSON Schema describing the expected trigger config.

TriggerActionEnqueue

Routes the invocation through a named queue for async processing.

Name	Type	Required	Description
`queue`	`str`	Yes	Name of the target queue.
`type`	`Literal['enqueue']`	No	Always `'enqueue'`.

TriggerActionVoid

Fire-and-forget routing. No response is returned.

Name	Type	Required	Description
`type`	`Literal['void']`	No	Always `'void'`.

TriggerRequest

Request object for trigger().

Name	Type	Required	Description
`action`	`TriggerActionEnqueue` \| `TriggerActionVoid` \| None	No	Routing action — `None` for sync, `TriggerAction.Enqueue(...)` for queue, `TriggerAction.Void()` for fire-and-forget.
`function_id`	`str`	No	ID of the function to invoke.
`payload`	`Any`	No	Data to pass to the function.
`timeout_ms`	`int \| None`	No	Override the default invocation timeout.

IStream

Abstract interface for stream operations.

OtelConfig

Configuration for OpenTelemetry initialization.

Name	Type	Required	Description
`enabled`	`bool \| None`	No	Enable OTel. Defaults to True. Set OTEL_ENABLED=false/0/no/off to disable.
`engine_ws_url`	`str \| None`	No	III Engine WebSocket URL. Defaults to env III_URL or ‘ws://localhost:49134’.
`fetch_instrumentation_enabled`	`bool`	No	Auto-instrument urllib HTTP calls via URLLibInstrumentor. Defaults to True.
`logs_batch_size`	`int \| None`	No	Maximum number of log records exported per batch. Defaults to 1 when not set.
`logs_enabled`	`bool \| None`	No	Enable OTel log export via EngineLogExporter. Defaults to True when OTel is enabled.
`logs_flush_interval_ms`	`int \| None`	No	Log processor flush delay in milliseconds. Defaults to 100ms when not set.
`metrics_enabled`	`bool`	No	Enable OTel metrics export via EngineMetricsExporter. Defaults to True.
`metrics_export_interval_ms`	`int`	No	Metrics export interval in milliseconds. Defaults to 60000 (60 seconds).
`service_instance_id`	`str \| None`	No	Service instance ID. Defaults to a random UUID.
`service_name`	`str \| None`	No	Service name. Defaults to env OTEL_SERVICE_NAME or ‘iii-python-sdk’.
`service_namespace`	`str \| None`	No	Service namespace attribute.
`service_version`	`str \| None`	No	Service version. Defaults to env SERVICE_VERSION or ‘unknown’.

TriggerHandler

Abstract base class for trigger handlers.

SDKs

​Installation

​Initialization

​Methods

​connect_async

​create_channel

​Parameters

​Example

​create_channel_async

​Parameters

​Example

​create_stream

​Parameters

​Example

​get_connection_state

​list_functions

​Example

​list_functions_async

​Example

​list_trigger_types

​Parameters

​Example

​list_trigger_types_async

​Parameters

​Example

​list_triggers

​Parameters

​Example

​list_triggers_async

​Parameters

​Example

​list_workers

​Example

​list_workers_async

​Example

​on_functions_available

​Parameters

​Example

​register_function

​Parameters

​Example

​register_service

​Parameters

​Example

​register_trigger

​Parameters

​Example

​register_trigger_type

​Parameters

​Example

​shutdown

​Example

​shutdown_async

​Example

​trigger

​Parameters

​Example

​trigger_async

​Parameters

​Example

​unregister_trigger_type

​Parameters

​Example

​Logger

​debug

​Parameters

​Example

​error

​Parameters

​Example

​info

​Parameters

​Example

​warn

​Parameters

​Example

​Types

​InitOptions

​ReconnectionConfig

​TelemetryOptions

Installation

Initialization

Methods

connect_async

create_channel

Parameters

Example

create_channel_async

Parameters

Example

create_stream

Parameters

Example

get_connection_state

list_functions

Example

list_functions_async

Example

list_trigger_types

Parameters

Example

list_trigger_types_async

Parameters

Example

list_triggers

Parameters

Example

list_triggers_async

Parameters

Example

list_workers

Example

list_workers_async

Example

on_functions_available

Parameters

Example

register_function

Parameters

Example

register_service

Parameters

Example

register_trigger

Parameters

Example

register_trigger_type

Parameters

Example

shutdown

Example

shutdown_async

Example

trigger

Parameters

Example

trigger_async

Parameters

Example

unregister_trigger_type

Parameters

Example

Logger

debug

Parameters

Example

error

Parameters

Example

info

Parameters

Example

warn

Parameters

Example

Types

InitOptions

ReconnectionConfig

TelemetryOptions

HttpInvocationConfig