feature/auto-create-new-session

[lwangverizon]

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Link to Issue or Description of Change

2. Or, if no issue exists, describe the change:

Problem:

When building frontend applications with ADK, there's a limitation where frontends cannot always guarantee that create_session is called before initiating a conversation. This creates friction in the user experience because:

• Users may refresh the page or navigate directly to a conversation URL with a specific session_id
• Frontend state management may lose track of whether a session was already created
• Mobile apps or single-page applications have complex lifecycle management where ensuring create_session is called first adds unnecessary complexity
• This forces developers to implement additional logic to check session existence before every conversation

Currently, if get_session is called with a non-existent session_id, it returns None, requiring the frontend to explicitly handle this case and call create_session separately.

Solution:

Modified the get_session method in DatabaseSessionService to automatically create a session if it doesn't exist in the database. This "get or create" pattern is common in many frameworks and provides a more developer-friendly API.

The implementation:

1. Attempts to fetch the session from the database
2. If the session doesn't exist (returns None), automatically calls create_session with the provided parameters
3. Retrieves and returns the newly created session
4. Maintains backward compatibility - existing code continues to work without changes

This allows frontends to simply call get_session with a session_id and be confident that the session will be available, regardless of whether it was previously created.

Benefits:

• Simplifies frontend integration by removing the need to track session creation state
• Reduces API calls (no need to check existence before calling get_session)
• Follows the principle of least surprise - getting a session with an ID should work reliably
• No breaking changes to existing code that checks for None return values

Testing Plan

Unit Tests:

• I have added or updated unit tests for my change.
• All unit tests pass locally.

pytest results:

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[gemini-code-assist]

Summary of Changes

Hello @lwangverizon, 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 enhances the DatabaseSessionService by introducing an automatic session creation mechanism within the get_session method. Previously, frontends had to explicitly handle cases where a session might not exist, leading to increased complexity. With this change, get_session will now create a session if it's not found, streamlining frontend integration and ensuring sessions are always available when requested, without requiring additional logic.

Highlights

• Automatic Session Creation: The get_session method in DatabaseSessionService now automatically creates a new session if one doesn't already exist for the given app_name, user_id, and session_id. This implements a 'get or create' pattern.
• Simplified Frontend Integration: This change simplifies frontend development by removing the need for explicit checks and calls to create_session before attempting to retrieve a session, reducing complexity and API calls.
• Backward Compatibility: The modification maintains full backward compatibility, ensuring existing code that checks for None returns from get_session will continue to function as expected.

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[adk-bot]

Response from ADK Triaging Agent

Hello @lwangverizon, thank you for your contribution!

Before we can review your PR, you will need to sign the Contributor License Agreement (CLA). It looks like the CLA check is currently failing. Please visit https://cla.developers.google.com/ to sign the agreement.

Thanks!

[gemini-code-assist]

Code Review

This pull request introduces a "get or create" pattern for get_session, which is a useful feature. However, the current implementation in DatabaseSessionService is inefficient, as it creates a session and then immediately re-fetches it, leading to redundant database calls. A more efficient approach would be to return the result of create_session directly. Furthermore, this change introduces a behavioral inconsistency: get_session will now always return a Session for DatabaseSessionService, while the base class and other implementations still allow for a None return. This should be addressed by either making the behavior consistent across all implementations and updating the base class contract, or by introducing a new method for this functionality. The unit tests also need to be updated to reflect this new behavior, as some will likely fail.

[ryanaiagent]

Hi @lwangverizon, Thank you for your contribution! We appreciate you taking the time to submit this pull request.
Can you please fix the failing unit tests and lint errors before we proceed with the review.