Access Log improved for common Istio operators

[awgn]

Enable the following access-log operators: ROUTE_NAME, REQUESTED_SERVER_NAME, UPSTREAM_TRANSPORT_FAILURE_REASON, RESPONSE_CODE_DETAILS, and CONNECTION_TERMINATION_DETAILS.

Specifically, perform the following refactoring:

• Track upstream transport errors in FinishContext and access logs
• Refactor error handling to propagate EventKind/Error through SyntheticHttpResponse
• Update BodyWithMetrics to pass EventError to completion callback
• Simplify Context trait implementations using map_or
• Move EventError from retry_policy to event_error module
• Update synthetic response constructors to accept EventKind/EventError
• Pass upstream_failure to access log contexts in TCP and HTTP handlers
• Add response_code_details to FinishContext
• Include ConnectionTerminationDetails in FinishContext, access logs, and log formatting
• Apply other minor improvements and bug fixes

[gemini-code-assist]

Summary of Changes

Hello @awgn, 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 significantly enhances the access logging capabilities by introducing several new operators that provide more detailed insights into request processing, upstream failures, and connection terminations. It centralizes error handling logic into a dedicated module, allowing for a more structured and informative propagation of event-specific errors throughout the system. These changes collectively aim to provide richer, more actionable data for monitoring and troubleshooting, particularly beneficial for operators managing services with Istio.

Highlights

• Enhanced Access Log Operators: Enabled new access log operators including ROUTE_NAME, REQUESTED_SERVER_NAME, UPSTREAM_TRANSPORT_FAILURE_REASON, RESPONSE_CODE_DETAILS, and CONNECTION_TERMINATION_DETAILS to provide more granular and comprehensive logging for Istio operators.
• Refactored Error Handling: Introduced a new event_error module to centralize EventError and EventKind definitions, improving error propagation and allowing for more specific error details to be captured in access logs and synthetic responses.
• Improved Contextual Information: Updated various context structs (FinishContext, UpstreamContext, DownstreamContext, InitHttpContext) to include new fields like upstream_failure, response_code_details, connection_termination_details, route_name, and server_name, enriching the data available for logging and metrics.
• Simplified Code with map_or: Refactored Context trait implementations, particularly in TcpContext and DownstreamContext, to leverage map_or for more concise and idiomatic handling of optional values.
• Updated Synthetic HTTP Responses: Modified SyntheticHttpResponse constructors to accept EventKind, ensuring that internally generated responses carry specific event information for better debugging and logging.

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[gemini-code-assist]

Code Review

This pull request introduces significant improvements to access logging by enabling several new Istio-compatible operators. The refactoring to propagate detailed error and event information via EventKind and SyntheticHttpResponse is well-executed and enhances observability. The code is also cleaner with the move of error-related logic to a dedicated event_error module and the consistent use of map_or for conciseness. I've found one potential issue with error chain traversal that should be addressed. Otherwise, this is a great set of changes.

[kmesh-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dawid-nowak

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[hzxuzhonghu]

/lgtm