backend.ai-common 26.3.2

Backend.AI commons library

Backend.AI Common Package

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Overview

The Backend.AI Common package provides utilities, infrastructure, and shared components used across all Backend.AI components (Manager, Agent, Storage Proxy, Webserver, App Proxy, etc.).

Package Structure

Entry Point System

Core event-based communication and asynchronous task processing framework for Backend.AI.

• events/ - Event Dispatcher System

  • Asynchronous event-based communication between components
  • Broadcast and Anycast event type support
  • Message queue-based event delivery
  • Event handler registration and routing

• bgtask/ - Background Task Handler System

  • Process long-running tasks asynchronously
  • Issue Task IDs and track tasks
  • Progress monitoring and Heartbeat
  • Notify via event publishing upon completion

Infrastructure Components

Client and abstraction layer for integration with external services and systems.

• clients/ - External service client wrappers

  • Agent client (ZeroMQ RPC)
  • Storage Proxy client (HTTP)
  • Valkey/Redis client
  • etcd client

• message_queue/ - Message queue interface and implementation

  • Provide message publish/subscribe interface
  • Currently implemented based on Redis Streams
  • Consumer Group management
  • Future support for other message queue systems planned

• service_discovery/ - Service registration and integration

  • etcd-based service registration and discovery
  • Provide service information for Prometheus metrics collection
  • Automatic health check and update
  • Future expansion of additional service discovery features planned

• resilience/ - Inter-layer communication resilience patterns

  • Generalize request processing between layers
  • Retry, Timeout, Circuit Breaker
  • Automatic metric collection
  • Fallback support

Data and Types

Common structures for data exchange and type definitions between components.

• dto/ - Data Transfer Objects (for inter-component communication)

  • Data structures used for inter-component communication
  • Request/Response models
  • Event payloads
  • Recommended to use Pydantic-based

• types.py - Common type definitions (for internal logic)

  • Domain types used within components (SessionId, AgentId, AccessKey, etc.)
  • Shared Enum types
  • Common constants
  • Mainly used in internal business logic

Utilities

Utility modules for development convenience and common functionality.

• metrics/ - Metrics collection and Prometheus integration

  • Metric observer pattern
  • Prometheus metric types (Counter, Gauge, Histogram)
  • HTTP metrics middleware

• auth/ - Authentication utilities

  • Authentication between Webserver (Gateway) and Manager
  • JWT token generation/verification
  • Signature generation/verification
  • API Key management

• web/ - Web utilities

  • HTTP helper functions
  • CORS configuration
  • Request/response processing

• middlewares/ - Common middlewares

  • Commonly used across all components
  • Authentication middleware
  • Logging middleware
  • Error handling middleware

• configs/ - Configuration management utilities

  • Configuration processing commonly used internally
  • Configuration file parsing (TOML, YAML)
  • Environment variable processing
  • Configuration validation

Other Components

• contexts/ - Context management utilities

  • ContextVar-based request and user tracking
  • Current request ID tracking
  • Current user information management
  • Context propagation

• data/ - Common data utilities

  • Data-based value processing used in internal logic
  • Data transformation and validation
  • Common data type handling

• exception.py - Common exception classes

  • Base exceptions for all Backend.AI services
  • Exception definitions must inherit from BackendAIError
  • Domain-specific exception classes
  • Communicate error situations externally

• utils.py - Other utility functions

  • String processing
  • Time conversion
  • Other helper functions

Installation

$ pip install backend.ai-common

For development

$ pip install -U pip setuptools
$ pip install -U -r requirements/dev.txt

Running test suite

$ python -m pytest

With the default halfstack setup, you may need to set the environment variable BACKEND_ETCD_ADDR to specify the non-standard etcd service port (e.g., localhost:8110).

The tests for common.redis module requires availability of local TCP ports 16379, 16380, 16381, 26379, 26380, and 26381 to launch a temporary Redis sentinel cluster via docker compose.

In macOS, they require a local redis-server executable to be installed, preferably via brew, because docker compose in macOS does not support host-mode networking and Redis cannot be configured to use different self IP addresses to announce to the cluster nodes and clients.

Related Documentation

• Event Dispatcher System
• Background Task Handler System
• Manager Component
• Agent Component
• Storage Proxy Component