firestore session service added for session management

[Hariharan0309]

Link to Issue or Description of Change

1. Link to an existing issue (if applicable):

• N/A (This is a new feature contribution)

2. Or, if no issue exists, describe the change:
This change adds a new FirestoreSessionService to the ADK.
It's designed to solve a key problem: the default in-memory session manager loses all data on serverless platforms like Cloud Run. This new service uses Google Firestore to persistently save session history, making it possible to build reliable, stateful agents that don't lose their memory on a container restart.

Problem:
While the ADK includes persistent session services for specific platforms (like VertexAISessionService or SQLSessionService), it lacks a simple, serverless, and persistent session manager ideal for deployments on Google Cloud Run.
The SQLSessionService requires developers to manage a separate SQL database, which adds significant operational overhead. The default InMemorySessionService is unsuitable for production on Cloud Run, as all session history is lost on container restarts or scaling events.
This leaves a gap for developers wanting to build stateful agents on a serverless, NoSQL stack.

Solution:
This pull request bridges that gap by introducing FirestoreSessionService, a new session service implementation that uses Google Cloud Firestore as a persistent, serverless, and highly-scalable backend.
This service is a drop-in replacement that perfectly complements a Cloud Run deployment, allowing developers to maintain session state with zero database management overhead.
This implementation has been field-tested across multiple projects (including the VentureAI agent) and is confirmed to work perfectly in a containerized production environment, managing complex session states and history.

Testing Plan

Please describe the tests that you ran to verify your changes. This is required
for all PRs that are not small documentation or typo fixes.

Testing Plan

Unit Tests:

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

(Unit tests for this service would require mocking the Google Cloud Firestore client. The primary validation relies on live, end-to-end integration testing as described below.)

Manual End-to-End (E2E) Tests:

This test plan verifies that the FirestoreSessionService can successfully authenticate with Google Cloud, create a new session in Firestore using an app_name, and then retrieve that same session.

1. Environment Setup

1. Install Dependencies:

   pip install google-cloud-firestore

2. Authenticate with Google Cloud:
   Run the following gcloud command to set up Application Default Credentials (ADC). The Firestore client library will automatically find and use these credentials.

   gcloud auth application-default login

3. Enable Firestore API:
   Ensure the Cloud Firestore API is enabled on your project (replace YOUR_PROJECT_ID):

   gcloud services enable firestore.googleapis.com --project="YOUR_PROJECT_ID"

2. Manual Test Script

Create a Python file (e.g., test_session_service.py) and paste the following code. You must update the import path to match your new service's location.

import asyncio
import os
import uuid

# --- IMPORTANT ---
# Change this import to match the path to your new service
from agent_base.sessions.firestore_session_service import FirestoreSessionService 
from agent_base.sessions.abc import Session # Also import Session

# --- CONFIGURE YOUR TEST ---
PROJECT_ID = "your-gcp-project-id"  # CHANGE THIS
DATABASE_ID = "ventureai"         # CHANGE THIS (or use '(default)')
APP_NAME = "my_test_app"          # The app_name to test multi-tenancy
# ---------------------------

async def run_test():
    print(f"Testing with Project ID: {PROJECT_ID}, App: {APP_NAME}")
    session_service = FirestoreSessionService(project=PROJECT_ID, database=DATABASE_ID)
    
    # Test data
    test_user_id = "test-user-123"
    new_session_id = str(uuid.uuid4())
    session_data = {"history": [{"role": "user", "content": "Hello!"}]}

    # 1. Test create_session
    print("Step 1: Creating a new session...")
    
    created_session = await session_service.create_session(
        app_name=APP_NAME,
        user_id=test_user_id,
        session_id=new_session_id,
        state=session_data
    )
    
    assert created_session.session_id == new_session_id
    assert created_session.state["history"][0]["content"] == "Hello!"
    print(f"✅ Success: Session '{new_session_id}' created in Firestore.")
    print("--------------------")

    # 2. Test get_session
    print(f"Step 2: Retrieving session '{new_session_id}'...")
    retrieved_session = await session_service.get_session(
        app_name=APP_NAME,
        user_id=test_user_id,
        session_id=new_session_id
    )
    
    assert retrieved_session.session_id == new_session_id
    assert retrieved_session.state["history"][0]["content"] == "Hello!"
    print("✅ Success: Session correctly retrieved from Firestore.")
    print("--------------------")
    
    # 3. Test get_session (Non-existent)
    print("Step 3: Testing for a non-existent session...")
    try:
        await session_service.get_session(
            app_name=APP_NAME, 
            user_id="another-user",
            session_id="non-existent-id"
        )
    except Exception as e:
        print(f"✅ Success: Correctly raised an error for a missing session: {e}")
    
    print("\n🎉 All tests passed!")

if __name__ == "__main__":
    asyncio.run(run_test())

####3. Execution

1. Set your PROJECT_ID and DATABASE_ID in the test_session_service.py script.
2. Run the script from your terminal:

   python test_session_service.py

4. Verification

Check the script output: The script will print success messages for each step (✅ Success: Session '...' created in Firestore.).
Check your Firestore Console: Log in to your Google Cloud project and navigate to Firestore. You will see a new top-level collection named my_test_app (or your APP_NAME). Inside that collection, you will find a document with the session_id from the test.

Checklist

• [✅ ] I have read the CONTRIBUTING.md document.
• [ ✅ ] I have performed a self-review of my own code.
• [ ✅ ] I have commented my code, particularly in hard-to-understand areas.
• [ ✅ ] I have added tests that prove my fix is effective or that my feature works.
• [ ✅ ] New and existing unit tests pass locally with my changes.
• [ ✅ ] I have manually tested my changes end-to-end.
• [✅ ] Any dependent changes have been merged and published in downstream modules.

[google-cla]

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View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[gemini-code-assist]

Summary of Changes

Hello @Hariharan0309, 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 new FirestoreSessionService to the ADK, designed to provide robust and persistent session management for applications deployed on serverless platforms such as Google Cloud Run. By leveraging Google Cloud Firestore, this service effectively solves the critical issue of session data loss that occurs with in-memory session managers during container restarts or scaling events. It offers a scalable, serverless, and low-overhead alternative for maintaining session state, making it an ideal solution for building stateful agents in a cloud-native, NoSQL environment.

Highlights

• New Firestore Session Service: Introduces a FirestoreSessionService to the ADK, providing persistent session management capabilities using Google Cloud Firestore.
• Serverless Persistence: Addresses the problem of session data loss on serverless platforms like Cloud Run by storing session history persistently in Firestore, enabling reliable stateful agents.
• Asynchronous Operations: The implementation uses the synchronous Firestore client, with all database operations wrapped in asyncio.to_thread to prevent blocking the asynchronous event loop.
• Comprehensive Session Management: Provides full CRUD operations for sessions (create, get, list, delete), along with functionality to update session state and append events to a session's history.
• Event Serialization: Includes robust serialization and deserialization logic for Event objects, with a specific feature to omit large PDF content from history during serialization to prevent oversized documents.

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[gemini-code-assist]

Code Review

This pull request introduces a new FirestoreSessionService to provide persistent session management using Google Cloud Firestore. This is a valuable addition, especially for serverless deployments like Cloud Run, addressing the limitations of in-memory session services. The implementation correctly leverages asyncio.to_thread for synchronous Firestore client calls within an asynchronous environment and uses batch operations for efficiency.

However, there are several critical and high-severity issues identified related to data consistency, adherence to the base class contract, and correct deserialization of event data. These issues should be addressed to ensure the service functions reliably and correctly persists all session data.

[ryanaiagent]

Hi @Hariharan0309 , Thank you for your contribution!
Can you fix the failing unit tests and lint errors.

[Hariharan0309]

Hi @Hariharan0309 , Thank you for your contribution! Can you fix the failing unit tests and lint errors.

Hi @ryanaiagent I have resolved all the failing unit test cases . Can you please check

[Hariharan0309]

Hi @ryanaiagent can you check the PR

[Hariharan0309]

Hi @ryanaiagent can you now check the PR

[Hariharan0309]

Hi @ryanaiagent updated the PR .

[Hariharan0309]

Hi @ryanaiagent can you check the PR

[ryanaiagent]

Hi @Hariharan0309 , Your PR has been received by the team and is currently under review. We will provide feedback as soon as we have an update to share.

[ryanaiagent]

Hi @ankursharmas , can you please review this.

[Hariharan0309]

Hi @ankursharmas Could you please review this

[Hariharan0309]

Hi @Hariharan0309 , Your PR has been received by the team and is currently under review. We will provide feedback as soon as we have an update to share.

Okay @ryanaiagent

[Hariharan0309]

Hi @ankursharmas @ryanaiagent Could you please review this

[blacksmithop]

I'm honestly surprised there is no native support for Fire Store