Logging for MoonBit: plain text and JSONL appenders with timestamps, and size-triggered log rotation

log

logging

jsonl

rotate

append

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Author

chensuiyi

Version

0.3.0

License

MIT

Repository

github.com/chenbimo/moonbit

Last updated

7 hours ago

Downloads

Dependencies

#chensuiyi/logfly

Logging for MoonBit: plain text / JSONL line formats with automatic ISO timestamps, plus size-triggered rotation in rename or copytruncate mode.

#Install

moon add chensuiyi/logfly

#Features

plain: one timestamp-prefixed text line — crash records, human-read logs
event: a JSONL management event; values arrive as pre-encoded fragments, so fields the caller omits never appear on the wire
maybe_rotate: rotate past a size limit in rename or copytruncate mode; a missing file is not an error
Depends on chensuiyi/fsx + chensuiyi/dateku + chensuiyi/fndash

#Scenarios

Daemon event logs: JSONL, machine-parseable, dedupe-friendly
Crash records: plain text, human-read
Long-running services: size-triggered rotation keeps disk usage bounded

#API

Function	Description
plain(path, text)	Timestamp-prefixed text line
event(path, event, fields)	JSONL event line
maybe_rotate(path, max_bytes, copytruncate?)	Rotate past limit, returns rotated

// Management event: omitted optional fields never appear on the wire
@logfly.event("/var/lib/app/events.jsonl", "spawn_failed", [
  ("app", @fndash.jstr("api")),
  ("pid", "42"),
])

// Crash record: plain text with automatic timestamp
@logfly.plain("/var/log/app/crash.log", "app=api reason=exit_1")

// Rotate past 10 MB
@logfly.maybe_rotate("/var/log/app/events.jsonl", 10485760)

#Author

陈随易 (@chenbimo) · mooncakes: chensuiyi

#License

MIT

#chensuiyi/logfly

MoonBit 日志库:纯文本 / JSONL 两种行格式,自动 ISO 时间戳,按大小触发轮转(rename 与 copytruncate 双模式)。

#安装

moon add chensuiyi/logfly

#功能

plain:一行时间戳前缀文本——崩溃记录、人读日志
event:JSONL 管理事件,值传已编码片段——调用方省略的字段就不会出现在线上
maybe_rotate:超限轮转;文件不存在不算错
依赖:chensuiyi/fsx + chensuiyi/dateku + chensuiyi/fndash

#场景

守护进程事件日志(JSONL,机器可解析)
崩溃记录与人读日志(纯文本)
长驻服务:按大小轮转控制磁盘占用

#API

函数	说明
plain(path, text)	时间戳前缀文本行
event(path, event, fields)	JSONL 事件行
maybe_rotate(path, max_bytes, copytruncate?)	超限轮转,返回是否轮转

#用法示例

// 管理事件:省略的可选字段不会以 null 出现在线上
@logfly.event("/var/lib/app/events.jsonl", "spawn_failed", [
  ("app", @fndash.jstr("api")),
  ("pid", "42"),
])

// 崩溃记录:纯文本,自动时间戳
@logfly.plain("/var/log/app/crash.log", "app=api reason=exit_1")

// 超过 10 MB 轮转
@logfly.maybe_rotate("/var/log/app/events.jsonl", 10485760)

#作者

陈随易 (@chenbimo)

#协议

MIT

event

source

fn event(path : String, event : String, fields : Array[(String, String)]) -> Unit raise @chensuiyi/fsx.FileError
FileError

Append one JSONL management event: {"ts":"...","event":"...","<key>":<value>...}. Keys are quoted by the library; values must arrive as already-encoded JSON fragments — pass @fndash.jstr(text) for strings and raw digits for numbers, so a field the caller omits simply does not appear on the wire.

maybe_rotate

source

fn maybe_rotate(path : String, max_bytes : Int64, copytruncate? : Bool) -> Bool raise @chensuiyi/fsx.FileError
FileError

Rotate path once it exceeds max_bytes: copytruncate for logs held open by app processes (they keep writing to the old inode), rename for logs written by the caller itself. Returns true when a rotation ran. Raises FileError when a needed rotation failed; a missing file is not an error (nothing to rotate).

plain

source

fn plain(path : String, text : String) -> Unit raise @chensuiyi/fsx.FileError
FileError

Append one plain text line, prefixed with the current ISO timestamp: 2026-10-03T08:15:30.123Z <text>. Failures raise so the caller stays in charge of best-effort handling.