Header augmentation

[sreya-guha]

This PR implements a configurable header system that allows administrators to include custom headers in all API responses. Headers are sent before any other content, providing important information about licensing, data retention policies, and UI components to API consumers.

Changes Made
Configuration System:

• Added headers field to NLWebConfig dataclass in config.py
• Enhanced load_nlweb_config() method to load headers from YAML configuration
• Added get_headers() method to access configured headers

Response Handler:

• Modified send_message() method in baseHandler.py to inject headers before all content
• Added headersSent flag to ensure headers are sent only once per session
• Supports both streaming and non-streaming response modes
• Headers are sent immediately after API version but before "asking_sites" messages

Configuration File:

• Updated config_nlweb.yaml with sample headers section including:
  • License information (MIT License is given as an example)
  • Specifies how long the data can be retained by the API caller
  • UI components that may be used to display the data
    More headers may be added for a specific instance of NLWeb.

Message Flow

1. API version message (existing)
2. Headers (new - sent as individual messages with message_type matching header key)
3. "asking_sites" message (existing)
4. Results and other content (existing)

Tests that were performed with the installation on hello-world

• Test non-streaming mode: curl "http://localhost:8000/ask?query={test_query}&streaming=false"
• Verify headers appear at top level of JSON response before other content
• Confirm headers are sent only once per query session
  Test query that was used: "Give me episodes about foundation model differences"

[Copilot]

Pull Request Overview

This PR implements a configurable header system to include custom headers in all API responses. Key changes include:

• Integration of header sending logic in both streaming and non-streaming response modes in baseHandler.py.
• Updates to config_nlweb.yaml to include a new headers section.
• Modifications in config.py to load and retrieve header configurations.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
code/core/baseHandler.py	Added header injection logic and a headersSent flag to guard against duplicate header sends.
code/config/config_nlweb.yaml	Added a headers section with sample header entries.
code/config/config.py	Extended NLWebConfig to load header configurations and provide a get_headers method.

[Copilot]

Consider setting the headersSent flag only after successfully sending all header messages. As it stands, if an exception occurs during header transmission, headersSent remains true, preventing a retry.

Suggested change

self.headersSent = True

[Copilot]

The string value for the ui_component header is missing a closing quote, which may lead to YAML parsing errors. Please ensure the string is properly enclosed in quotes.

Suggested change

	ui_component: "This field may be used to provide a link to the web components that can be used to display the results.
	ui_component: "This field may be used to provide a link to the web components that can be used to display the results."

[sreya-guha]

@microsoft-github-policy-service agree

…

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