Station Manager: logging package

A thin, concurrency-safe wrapper around rs/zerolog with a structured-first API, safe lifecycle (Initialize/Close), file rotation via lumberjack, and rich error history enrichment.

Highlights

• Structured logs only: compose fields with typed helpers
• Context loggers via With() for request/job scoping
• Graceful shutdown: waits for in-flight logs with a bounded timeout
• File rotation (size/age/backups) and optional console formatting
• Error history enrichment: automatically logs full error chains and operations

Quick start

svc := &logging.Service{ConfigService: cfgSvc}
if err := svc.Initialize(); err != nil { panic(err) }
defer svc.Close()

svc.InfoWith().Str("user_id", id).Int("count", 3).Msg("processed")

req := svc.With().Str("request_id", reqID).Logger()
req.DebugWith().Str("path", path).Msg("incoming request")

// Error history enrichment
if err != nil {
    svc.ErrorWith().Err(err).Msg("operation failed")
}

Error history enrichment

When you attach an error with Err/AnErr, the logger emits:

• error: the standard zerolog error field (string)
• error_chain: array of messages from outermost -> root
• error_root: the root cause message
• error_history: the joined chain string (outer -> ... -> root)
• error_ops: array of operation identifiers per chain element (if using DetailedError; empty strings for non-DetailedError links)
• error_root_op: the root operation identifier (if available)

For AnErr("db_err", err), the keys are prefixed accordingly (db_err_chain, db_err_root, db_err_history, db_err_ops, db_err_root_op).

Example output (JSON, abbreviated):

{
  "level":"error",
  "msg":"operation failed",
  "error":"startup failed",
  "error_chain":[
    "startup failed",
    "failed to connect to database",
    "dial tcp 127.0.0.1:5432: connect: connection refused"
  ],
  "error_ops":["server.Start","db.Open","db.Connect"],
  "error_root":"dial tcp 127.0.0.1:5432: connect: connection refused",
  "error_root_op":"db.Connect",
  "error_history":"startup failed -> failed to connect to database -> dial tcp 127.0.0.1:5432: connect: connection refused"
}

Configuration (types.LoggingConfig)

Relevant fields (non-exhaustive):

• Level: trace|debug|info|warn|error|fatal|panic
• WithTimestamp: include timestamp field
• SkipFrameCount: enable caller info with given skip frames when > 0
• ConsoleLogging / FileLogging: enable writers; if both false, file logging is enabled by default
• RelLogFileDir: relative directory for log files (validated for safety; created on init)
• LogFileMaxBackups, LogFileMaxAgeDays, LogFileMaxSizeMB, LogFileCompress
• ConsoleNoColor, ConsoleTimeFormat
• ShutdownTimeoutMS, ShutdownTimeoutWarning

Lifecycle and concurrency

• Initialize(): validates config, ensures directory, sets up writers, applies level, timestamp/caller, stores logger
• Close(): stops accepting new logs, waits up to ShutdownTimeoutMS for in-flight events, optionally warns, closes file writer
• All event builders use internal reference counting to avoid races during Close()

Context loggers

req := svc.With().Str("request_id", id).Logger()
req.InfoWith().Str("route", "/v1/items").Int("count", 10).Msg("processed")

Dump helper

svc.Dump(struct{ A int; B string }{A:1, B:"x"})

Safely logs nested structures at Debug level with cycle protection and depth limits.

Testing

• Unit tests cover lifecycle, concurrent usage, event builders, Dump, and error history enrichment.

Notes

• Error ops are included when errors are created via github.com/Station-Manager/errors.DetailedError.
• Standard library wrapped errors (errors.Unwrap / fmt.Errorf("%w")) are traversed for messages, but have empty ops.