feat: full async implementation of DatabaseSessionService

[GitMarco27]

Implement Full async DatabaseSessionService

Target Issue: #1005

Overview

This PR introduces an asynchronous implementation of the DatabaseSessionService with minimal breaking changes. The primary goal is to enable effective use of ADK in fully async environments and API endpoints while avoiding event loop blocking during database I/O operations.

Changes

• Converted DatabaseSessionService to use async/await patterns throughout

Testing Plan

The implementation has been tested following the project's contribution guidelines:

Unit Tests

• All existing unit tests pass successfully
• Minor update to test requirements added to support aiosqlite

Manual End-to-End Testing

• E2E tests performed using:
  • LLM Provider: LiteLLM
  • Database: PostgreSQL with asyncpg driver

from google.adk.sessions.database_session_service import DatabaseSessionService

connection_string: str = (
   "postgresql+asyncpg://PG_USER:PG_PSWD@PG_HOST:5432/PG_DB"
)
session_service: DatabaseSessionService = DatabaseSessionService(
   db_url=connection_string
)

session = await session_service.create_session(
   app_name="test_app", session_id="test_session", user_id="test_user"
)
assert session is not None

sessions = await session_service.list_sessions(app_name="test_app", user_id="test_user")
assert len(sessions.sessions) > 0


session = await session_service.get_session(
   app_name="test_app", session_id="test_session", user_id="test_user"
)
assert session is not None

await session_service.delete_session(
   app_name="test_app", session_id="test_session", user_id="test_user"
)
assert (
   await session_service.get_session(
       app_name="test_app", session_id="test_session", user_id="test_user"
   )
   is None
)

The implementation have been also tested using the following configurations for llm provider and Runner:

def get_azure_openai_model(deployment_id: str | None = None) -> LiteLlm:
    ...

    if not deployment_id:
        deployment_id = os.getenv("AZURE_OPENAI_DEPLOYMENT_ID")

    logger.info(f"Using Azure OpenAI deployment ID: {deployment_id}")

    return LiteLlm(
        model=f"azure/{os.getenv('AZURE_OPENAI_DEPLOYMENT_ID')}",
        stream=True,
    )

...

    @staticmethod
    def _get_runner(agent: Agent) -> Runner:
        storage=DatabaseSessionService(db_url=get_pg_connection_string())
        return Runner(
            agent=agent,
            app_name=APP_NAME,
            session_service=storage,
        )

...

async for event in self.runner.run_async(
    user_id=user_id,
    session_id=session_id,
    new_message=content,
    run_config=(
        RunConfig(
            streaming_mode=StreamingMode.SSE, response_modalities=["TEXT"]
        )
        if stream
        else RunConfig()
    ),
):
    last_event = event
    if stream:
        yield event

...

Breaking Changes

• Database connection string format may need updates for async drivers

[gemini-code-assist]

Summary of Changes

Hello @GitMarco27, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a comprehensive asynchronous implementation for the DatabaseSessionService. The primary motivation is to facilitate the effective use of the ADK in fully asynchronous environments and API endpoints, specifically by preventing event loop blocking during database I/O operations. This change significantly enhances the service's compatibility and performance in modern async Python applications.

Highlights

• Asynchronous DatabaseSessionService: The DatabaseSessionService has been fully converted to use asynchronous patterns, enabling non-blocking database I/O operations in async environments.
• Lazy Table Creation: Database tables are now created lazily upon the first database interaction, rather than during service initialization, improving startup performance.
• Dependency Update: The aiosqlite library has been added as a test dependency to support asynchronous SQLite connections.
• Minimal Breaking Changes: The implementation aims for minimal breaking changes, primarily affecting database connection string formats for async drivers.

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[gemini-code-assist]

Code Review

This pull request does a great job of converting the DatabaseSessionService to a fully asynchronous implementation. The changes correctly adopt async/await patterns and modern SQLAlchemy 2.0 style for async operations, which will significantly benefit applications running in an async environment. The code is clean and the approach of lazy table creation is sound. I've found one potential race condition in the table creation logic and provided a detailed suggestion to resolve it using an asyncio.Lock. With that fix, this will be a solid enhancement.

[GitMarco27]

@gemini-code-assist review

[gemini-code-assist]

Code Review

This pull request does an excellent job of converting the DatabaseSessionService to a fully asynchronous implementation. The changes correctly adopt sqlalchemy.ext.asyncio patterns, including the use of an async engine, async sessions, and the modern select statement syntax. The introduction of lazy, thread-safe table creation via _ensure_tables_created is a robust addition. My review focuses on performance optimizations, suggesting the use of asyncio.gather to run independent database queries concurrently, which should reduce latency in several key methods. Overall, this is a high-quality and well-executed feature implementation.