@seda-protocol/rotating-file-logger

Effect-based rotating file logger. Writes logs to date-named files (e.g. yyyy-MM-dd.log), batches writes, and prunes old files.

Usage

Wrap your program with provideRotatingFileLogger to replace the default logger with one that logs to both console (with colors) and rotating files:

import { Effect } from "effect";
import { provideRotatingFileLogger } from "@seda-protocol/rotating-file-logger";

const program = Effect.log("Hello");

Effect.runPromise(program.pipe(provideRotatingFileLogger));

For custom configuration, use provideRotatingFileLoggerWithOptions:

import { Effect } from "effect";
import { provideRotatingFileLoggerWithOptions } from "@seda-protocol/rotating-file-logger";

// JSON to stdout only, no files (e.g. containerized deployment)
const program = Effect.log("Hello");

Effect.runPromise(
	program.pipe(
		provideRotatingFileLoggerWithOptions({
			stdoutFormat: "json",
			fileLogging: false,
		}),
	),
);

Configuration

| Env var | Default | Description | |----------------------|-----------|-----------------------------------------------------------------------------| | LOG_LEVEL | Info | Minimum log level (None, Fatal, Error, Warning, Info, Debug, Trace) | | LOG_DIR | logs | Directory for log files | | LOG_MAX_FILES | 14 | Max number of date-based log files to keep | | LOG_STDOUT_FORMAT | pretty | Stdout format: pretty (colored) or json (one JSON object per line) | | LOG_FILE_ENABLED | true | When false, disables rotating file logging entirely |

Programmatic options passed to provideRotatingFileLoggerWithOptions override environment variables:

| Option | Default | Description | |-----------------|-----------|--------------------------------------------------| | stdoutFormat | env | Stdout format: pretty or json | | fileLogging | env | When false, skips file I/O and rotation | | logLevel | env | Minimum log level | | batchWindow | 1 second | Duration to batch file log writes | | mapOutput | none | Transform final log strings before output. This is also applied to JSON output, so preserve valid JSON if downstream parsers expect it |

Log files are named by date (e.g. 2025-03-17.log). When the date changes, a new file is created and files older than LOG_MAX_FILES are removed. A small config file (rotating-logger.json) in the log directory tracks active files.