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• About
• Status
• Support packages
• Related packages
• Installation
• Dependencies
• API
• Authors
• License

About

Structured, multilevel & hierarchical loggers based on @thi.ng/rstream.

This package provides extensible, multi-level & multi-hierarchy logging infrastructure, with logged values transformable via @thi.ng/transducers. Several built-in transformers are provided.

The Logger class in this package implements the @thi.ng/logger ILogger interface and uses LogLevel enums to configure levels / filtering. See that package for more details.

Status

STABLE - used in production

Search or submit any issues for this package

Support packages

• @thi.ng/rstream-log-file - File output handler for structured, multilevel & hierarchical loggers based on @thi.ng/rstream

Related packages

• @thi.ng/logger - Basis types for arbitrary & hierarchical logging

Installation

yarn add @thi.ng/rstream-log

ESM import:

import * as rslog from "@thi.ng/rstream-log";

Browser ESM import:

<script type="module" src="https://esm.run/@thi.ng/rstream-log"></script>

JSDelivr documentation

For Node.js REPL:

const rslog = await import("@thi.ng/rstream-log");

Package sizes (brotli'd, pre-treeshake): ESM: 749 bytes

Dependencies

• @thi.ng/api
• @thi.ng/checks
• @thi.ng/logger
• @thi.ng/rstream
• @thi.ng/strings
• @thi.ng/transducers

Note: @thi.ng/api is in most cases a type-only import (not used at runtime)

API

Generated API docs

import { LogLevel } from "@thi.ng/logger";
import { Logger, formatString, writeConsole } from "@thi.ng/rstream-log";

const logger = new Logger("main");
// or with min level
const logger = new Logger("main", LogLevel.DEBUG);
// or min level given as string
const logger = new Logger("main", "DEBUG");

// add console output w/ string formatter (a transducer)
// each logger instance has a rstream Stream instance
// allowing for downstream processing
logger.stream.transform(formatString()).subscribe(writeConsole());

logger.debug("hello world");
// [DEBUG] main: 2024-02-16T20:38:11.143Z hello world

logger.warn("eek");
// [WARN] main: 2024-02-16T20:38:11.144Z eek

// loggers can form hierarchies by creating/attaching child loggers
const child = logger.childLogger("child", LogLevel.INFO);

import { postWorker } from "@thi.ng/rstream";
// additionally send messages from this logger to worker
child.stream.subscribe(postWorker("log-worker.js"));

child.info("hi from submodule");
// [INFO] child: 2024-02-16T20:38:11.145Z hi from submodule

Authors

• Karsten Schmidt

If this project contributes to an academic publication, please cite it as:

@misc{thing-rstream-log,
  title = "@thi.ng/rstream-log",
  author = "Karsten Schmidt",
  note = "https://thi.ng/rstream-log",
  year = 2017
}

License

© 2017 - 2026 Karsten Schmidt // Apache License 2.0