feat: add log output destinations (--log-outputs) and file rotation

[nelson-parente]

Adds two independent, opt-in capabilities to log output. All new flags default to off/empty, so behaviour with no new flags is unchanged.

1. --log-outputs — a list of log destinations

Per review, destinations are a list rather than a tee bool: --log-outputs takes a comma-separated list of stdout, stderr, or file paths. --log-file merges into that list, so the two flags compose and existing behaviour is unchanged; the tee use case is --log-outputs=stdout,/path/to/file.

Destinations are deduplicated (two writers on one path would double every line and corrupt rotation), and console destinations order before files — io.MultiWriter stops at the first failing writer, so this keeps console output alive when file writes start failing (a full disk, for example). Rotation and compression apply to every file destination.

2. --log-file-max-* / --log-file-compression — rotation

--log-file opens the file O_APPEND and never rolls it, so long-lived components grow it without bound. Rotation is delegated to lumberjack:

flag	meaning
--log-file-max-size	megabytes before rotation
--log-file-max-backups	rotated files to keep
--log-file-max-age	days to retain rotated files
--log-file-compression	none (default) or gzip for rotated files

When none is set, newFileWriter returns a plain append-mode *os.File — the existing code path, unchanged.

File permissions are kept identical with rotation on or off

lumberjack creates missing files as 0600 (and preserves the mode of existing ones), where the plain path creates 0644. Left alone, enabling rotation would silently change new log-file permissions and break log shippers tailing the file as a non-owner user. newFileWriter therefore pre-creates the file with the same flags and mode as the plain path; rotated archives and post-rotation files inherit that mode. A test asserts mode parity between the two paths (comparing them to each other, so it is immune to umask and Windows permission semantics).

Misconfiguration warns instead of silently no-opping

Rotation or compression flags with no file destination configured (neither --log-file nor a file entry in --log-outputs) now log a warning through a dapr.kit.logger logger. Warn rather than error: an error here would turn a harmless misconfiguration into a startup failure for every binary that attaches these flags. The logger is fetched at the top of ApplyOptionsToLoggers, before the registry snapshot, so the warning follows the configured format, level and output of that apply.

Typed fields behind separate flag receivers

Per review: the optional fields are properly typed and unexported — *uint rotation limits (nil = flag not provided) and a none|gzip compression enum — with the CLI flags attached to separate unexported string receivers that validate() parses at apply time, mirroring the pattern in dapr/dapr cmd/daprd/options. AttachCmdFlags keeps its (stringVar, boolVar) signature, so no caller changes anywhere. Invalid values fail validation with a clear error naming the flag, before any logger is mutated.

On lumberjack

gopkg.in/natefinch/lumberjack.v2 is MIT-licensed and the de-facto Go rotation library (it is what the zap ecosystem uses). It is low-activity because it is feature-complete rather than unmaintained. Behaviours worth knowing, documented alongside the flags:

• when only --log-file-max-age or --log-file-compression is set, lumberjack applies its own 100MB default MaxSize
• cleanup runs at rotation time, not at process start
• rotation renames files, so the log path must be on a per-pod volume — pointing multiple replicas at one shared RWX path will lose data

Notes

• setLogOutput now takes *Options rather than a bare path, since it needs more than the path. logOutputFile *os.File becomes logOutputCloser io.Closer so it can close either writer type. The redirect-before-close ordering is preserved.
• consoleWriter is introduced as a package-level io.Writer (defaulting to os.Stdout) purely so tests can capture console output.
• The exported Logger interface is untouched.
• History note: the branch evolved through review (tee bool → destinations list; string fields → typed fields behind separate receivers); happy to squash on merge.

Test plan

• go test -race ./logger/... passes, including -count=2 for order-independence; logger package coverage ~90%
• Behavioural rotation test: drives ~3MB at max-size=1MB and asserts on disk that an archive appeared and the active file rolled (deliberately size-based only — compression and MaxBackups pruning run on a background goroutine and would be timing-flaky in CI)
• Full flag-set registration asserted (add/remove/rename fails the test deliberately), destination union/dedupe/stderr, outputs+rotation combined, permission parity, misconfiguration warning, invalid values rejected
• golangci-lint run ./logger/... adds zero new findings versus main (the 9 remaining goconst hits are pre-existing)
• Existing file-output tests unchanged and passing, confirming defaults are untouched
• Note: concurrency and events/ratelimiting fail to build on main today, unrelated to this change

[JoshVanL]

@nelson-parente please resolve conflicts

[codecov-commenter]

Codecov Report

❌ Patch coverage is 93.63636% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.80%. Comparing base (1bef456) to head (23ea94d).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
logger/options.go	93.63%	5 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #166      +/-   ##
==========================================
+ Coverage   72.37%   72.80%   +0.42%     
==========================================
  Files          92       92              
  Lines        6537     6666     +129     
==========================================
+ Hits         4731     4853     +122     
- Misses       1617     1622       +5     
- Partials      189      191       +2     

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