Keep full-logging alive in granian workers after post-fork dictConfig

[masenf]

Type of change

• Bug fix (non-breaking change which fixes an issue)

Changes To Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully ran tests with your changes locally?

Defect

FINDING-005 from 0.9.9a1 pre-release testing (logging_cli cluster, verifier-confirmed): with REFLEX_ENABLE_FULL_LOGGING, granian's worker startup (granian/server/mp.py::WorkerProcess.wrap_target) runs granian.log.configure_logging -> logging.config.dictConfig before loading the app. Stdlib dictConfig unconditionally runs _clearExistingHandlers(), which closes every handler in the process — including the fork-inherited reflex full-logging FileHandler. Since the handler was opened with mode="w", Python 3.10+ FileHandler.emit refuses to reopen it once closed (it would truncate), so every worker-side record was silently dropped from the log file — precisely the records full logging exists to capture.

Worse, log_file_stream() then returned the closed handler's None stream (despite its comment claiming that could never happen), and the legacy console.print_to_log_file writer's rich.Console(file=None) falls back to stdout: every legacy console call in a worker leaked a duplicated [YYYY-mm-dd HH:MM:SS.ffffff] ... plain-text line, breaking the machine-readable --json output contract (11 non-JSON lines interleaved with JSON records in the repro). Regression introduced by #6863, which routed the legacy file console through the logging FileHandler's stream (0.9.8's file console opened its own append-mode file that dictConfig could not touch).

Fix

All in reflex_base/utils/log.py (+ one line in console.py), no post-fork hook needed — the pipeline now self-heals lazily, which also protects against any application-side dictConfig:

• _file_handler() truncates the log file explicitly at creation and opens the handler in append mode. The stdlib then reopens a closed mode="a" handler on the next emit, so fork-inherited worker handlers resume writing instead of dropping records; appends are atomic (O_APPEND), letting the CLI parent and the reopened worker copies safely share one file. Per-run truncation semantics are unchanged.
• log_file_stream() reopens a closed stream under the handler lock instead of handing writers a dead one.
• The legacy console file writer now holds a stable proxy file object (log_file_proxy()) that resolves the live stream on every write — it can neither fall back to stdout (the --json leak) nor crash with ValueError on a stale closed stream captured before the fork.

Test plan

• New unit tests in tests/units/reflex_base/utils/test_log.py, written first and shown failing on unfixed main with the exact three failure modes: test_file_handler_survives_external_dictconfig (post-dictConfig record missing from the file), test_log_file_console_targets_file_after_external_close (timestamped line leaked to captured stdout), test_cached_log_file_console_survives_external_close (ValueError: I/O operation on closed file), plus test_file_handler_truncates_previous_run guarding the truncate-then-append semantics. All 52 tests in the module pass with the fix.
• Real repro: scratch app with an api_transformer route emitting console.info/console.warn/reflex_base.* logger records, REFLEX_ENABLE_FULL_LOGGING=1 REFLEX_LOG_FILE=... reflex run --backend-only under granian with the fork start method (the default on Python <= 3.13; forced via multiprocessing.set_start_method("fork") on this 3.14 dev env, where granian otherwise coerces forkserver to spawn and the bug cannot trigger). Before: 0 worker records in the log file, 6 leaked timestamped stdout lines, and with --json 11 non-JSON lines interleaved. After: all worker records (legacy shim + pipeline) land in the same file as the parent's, 0 leaked lines, and --json stdout is 14/14 valid JSON lines.
• uv run ruff check . / uv run ruff format . clean; uv run pyright reflex tests and pyright on the touched reflex-base files: 0 errors.

🤖 Generated with Claude Code

https://claude.ai/code/session_01EMjBXPozsNeQNSBZecNH8x

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Generated by Claude Code

[greptile-apps]

Greptile Summary

The PR makes full-file logging recover after Granian closes inherited handlers during worker logging reconfiguration.

• Opens the handler in append mode after explicitly truncating the file at initial creation.
• Adds a stable stream proxy that resolves and locks the current handler stream for each write or flush.
• Routes the legacy Rich console through that proxy and adds regression coverage for handler closure and truncation behavior.

Confidence Score: 5/5

The PR appears safe to merge because no blocking failure remains in the eligible follow-up review scope.

No blocking failure remains.

Important Files Changed

Filename	Overview
packages/reflex-base/src/reflex_base/utils/log.py	Changes file-handler initialization to truncate then append and adds a lock-protected, lazily reopening stream proxy.
packages/reflex-base/src/reflex_base/utils/console.py	Routes the cached Rich file console through the stable logging-stream proxy.
tests/units/reflex_base/utils/test_log.py	Adds regression tests for external handler closure, cached consoles, stdout isolation, and per-run truncation.
packages/reflex-base/news/+full-logging-worker.bugfix.md	Documents restored worker logging and prevention of plain-text leakage into JSON output.

_{Reviews (3): Last reviewed commit: "Merge remote-tracking branch 'origin/mai..." | Re-trigger Greptile}

[codspeed-hq]

Merging this PR will not alter performance

✅ 32 untouched benchmarks
⏩ 8 skipped benchmarks¹

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_{Comparing claude/rel-fix-full-logging-worker (dd5272e) with main (7427617)}

Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[cubic-dev-ai]

All reported issues were addressed across 4 files

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