[log] log(envutil): add debug logging to env var parse fallbacks

[github-actions]

Summary

Adds debug logging to internal/envutil/envutil.go to surface misconfiguration earlier.

What changed

Added var logEnvUtil = logger.New("envutil:envutil") and three targeted logEnvUtil.Printf calls — one in each type-converting function — that fire only when an environment variable is set but unusable:

Function	Log condition
GetEnvInt	Value is set but not a valid positive integer
GetEnvDuration	Value is set but not a valid positive duration
GetEnvBool	Value is set but not a recognised boolean (1/true/yes/on / 0/false/no/off)

The GetEnvString function is intentionally not logged — it has no parse step and adding a log there would be too noisy.

Why

When an operator sets e.g. MCP_GATEWAY_PAYLOAD_SIZE_THRESHOLD=512k (an invalid integer), the gateway silently falls back to the default with no indication of what happened. With this change, enabling DEBUG=envutil:* reveals the problem immediately:

envutil:envutil GetEnvInt: MCP_GATEWAY_PAYLOAD_SIZE_THRESHOLD="512k" is not a valid positive integer, using default=524288

Quality checklist

• Exactly 1 file modified
• No test files modified
• Logger declaration added (var logEnvUtil = logger.New("envutil:envutil"))
• Logger naming follows pkg:filename convention (matches logGitHub/logExpand in the same package)
• Logger arguments use only in-scope variables — no side effects
• Log messages are meaningful and actionable
• No duplication of existing logs
• Import statements follow Go formatting conventions

Generated by Go Logger Enhancement · ● 4.8M · ◷

[Copilot]

Pull request overview

Adds targeted debug logging in internal/envutil to surface invalid environment variable values (set-but-unusable) when parsing ints, durations, and booleans, helping operators detect misconfiguration earlier.

Changes:

• Introduce a package-level envutil:envutil debug logger.
• Emit debug logs when GetEnvInt, GetEnvDuration, or GetEnvBool fall back due to invalid (or non-positive) values.

Show a summary per file

File	Description
internal/envutil/envutil.go	Adds a logger and fallback debug logs for type-converting env helpers.

Copilot's findings

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Comments suppressed due to low confidence (2)

internal/envutil/envutil.go:46

• These debug logs include the full env var value in the message. To avoid leaking secrets into stderr/log files, consider sanitizing/truncating envValue before logging (the repo already uses internal/logger/sanitize for env vars in other places).

		}
		logEnvUtil.Printf("GetEnvDuration: %s=%q is not a valid positive duration, using default=%v", envKey, envValue, defaultValue)
	}

internal/envutil/envutil.go:64

• This log line emits the raw environment variable value. To reduce the risk of secret exposure (and because debug logs are also written to the file logger), consider sanitizing/truncating envValue before including it in the log message.

		}
		logEnvUtil.Printf("GetEnvBool: %s=%q is not a recognized boolean value, using default=%v", envKey, envValue, defaultValue)
	}

• Files reviewed: 1/1 changed files
• Comments generated: 2

[Copilot]

These debug logs print the raw environment variable value (%q). Since Logger.Printf also forwards to the file logger, this can persist potentially sensitive values if a secret-like env var is accidentally parsed via GetEnvInt. Consider sanitizing/truncating the value before logging (e.g., using internal/logger/sanitize helpers).

This issue also appears in the following locations of the same file:

• line 44
• line 62

[Copilot]

The doc comment says GetEnvDuration falls back only when unset/empty or ParseDuration fails, but the implementation also requires d > 0 (and the new log message refers to a “positive duration”). Update the comment to mention that zero/negative durations also fall back to defaultValue.

[lpcox]

Review + Fixes

Evaluated the Copilot review and pushed fixes in 9def5d0:

Addressed

1. Sanitize env values in debug logs — All 3 log lines now use sanitize.TruncateSecret(envValue) instead of raw envValue. Env vars could contain secrets (API keys, tokens), and since debug logs also write to the file logger, full values should never be persisted. Output now shows e.g. ghp_... instead of the full token.

2. Fix GetEnvDuration doc comment — Added mention that zero/negative durations also fall back to defaultValue, matching the d > 0 condition in the code and aligning with the existing GetEnvInt doc pattern.

Own review notes

The PR itself is clean and well-targeted:

• Logger naming logEnvUtil follows the pkg:filename convention correctly
• Logs fire only on the set-but-unusable path (not on unset/empty) — good signal-to-noise ratio
• No unnecessary logging added to GetEnvString (which has no validation to fail)