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Module

std/log/handlers.ts

Deno standard library
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// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.import { getLevelByName, LevelName, LogLevels } from "./levels.ts";import type { LogRecord } from "./logger.ts";import { red, yellow, blue, bold } from "../fmt/colors.ts";import { existsSync, exists } from "../fs/exists.ts";import { BufWriterSync } from "../io/bufio.ts";
const DEFAULT_FORMATTER = "{levelName} {msg}";type FormatterFunction = (logRecord: LogRecord) => string;type LogMode = "a" | "w" | "x";
interface HandlerOptions { formatter?: string | FormatterFunction;}
export class BaseHandler { level: number; levelName: LevelName; formatter: string | FormatterFunction;
constructor(levelName: LevelName, options: HandlerOptions = {}) { this.level = getLevelByName(levelName); this.levelName = levelName;
this.formatter = options.formatter || DEFAULT_FORMATTER; }
handle(logRecord: LogRecord): void { if (this.level > logRecord.level) return;
const msg = this.format(logRecord); return this.log(msg); }
format(logRecord: LogRecord): string { if (this.formatter instanceof Function) { return this.formatter(logRecord); }
return this.formatter.replace(/{(\S+)}/g, (match, p1): string => { const value = logRecord[p1 as keyof LogRecord];
// do not interpolate missing values if (value == null) { return match; }
return String(value); }); }
log(_msg: string): void {} async setup(): Promise<void> {} async destroy(): Promise<void> {}}
export class ConsoleHandler extends BaseHandler { format(logRecord: LogRecord): string { let msg = super.format(logRecord);
switch (logRecord.level) { case LogLevels.INFO: msg = blue(msg); break; case LogLevels.WARNING: msg = yellow(msg); break; case LogLevels.ERROR: msg = red(msg); break; case LogLevels.CRITICAL: msg = bold(red(msg)); break; default: break; }
return msg; }
log(msg: string): void { console.log(msg); }}
export abstract class WriterHandler extends BaseHandler { protected _writer!: Deno.Writer; #encoder = new TextEncoder();
abstract log(msg: string): void;}
interface FileHandlerOptions extends HandlerOptions { filename: string; mode?: LogMode;}
export class FileHandler extends WriterHandler { protected _file: Deno.File | undefined; protected _buf!: BufWriterSync; protected _filename: string; protected _mode: LogMode; protected _openOptions: Deno.OpenOptions; protected _encoder = new TextEncoder(); #unloadCallback = (): Promise<void> => this.destroy();
constructor(levelName: LevelName, options: FileHandlerOptions) { super(levelName, options); this._filename = options.filename; // default to append mode, write only this._mode = options.mode ? options.mode : "a"; this._openOptions = { createNew: this._mode === "x", create: this._mode !== "x", append: this._mode === "a", truncate: this._mode !== "a", write: true, }; }
async setup(): Promise<void> { this._file = await Deno.open(this._filename, this._openOptions); this._writer = this._file; this._buf = new BufWriterSync(this._file);
addEventListener("unload", this.#unloadCallback); }
handle(logRecord: LogRecord): void { super.handle(logRecord);
// Immediately flush if log level is higher than ERROR if (logRecord.level > LogLevels.ERROR) { this.flush(); } }
log(msg: string): void { this._buf.writeSync(this._encoder.encode(msg + "\n")); }
flush(): void { if (this._buf?.buffered() > 0) { this._buf.flush(); } }
destroy(): Promise<void> { this.flush(); this._file?.close(); this._file = undefined; removeEventListener("unload", this.#unloadCallback); return Promise.resolve(); }}
interface RotatingFileHandlerOptions extends FileHandlerOptions { maxBytes: number; maxBackupCount: number;}
export class RotatingFileHandler extends FileHandler { #maxBytes: number; #maxBackupCount: number; #currentFileSize = 0;
constructor(levelName: LevelName, options: RotatingFileHandlerOptions) { super(levelName, options); this.#maxBytes = options.maxBytes; this.#maxBackupCount = options.maxBackupCount; }
async setup(): Promise<void> { if (this.#maxBytes < 1) { this.destroy(); throw new Error("maxBytes cannot be less than 1"); } if (this.#maxBackupCount < 1) { this.destroy(); throw new Error("maxBackupCount cannot be less than 1"); } await super.setup();
if (this._mode === "w") { // Remove old backups too as it doesn't make sense to start with a clean // log file, but old backups for (let i = 1; i <= this.#maxBackupCount; i++) { if (await exists(this._filename + "." + i)) { await Deno.remove(this._filename + "." + i); } } } else if (this._mode === "x") { // Throw if any backups also exist for (let i = 1; i <= this.#maxBackupCount; i++) { if (await exists(this._filename + "." + i)) { this.destroy(); throw new Deno.errors.AlreadyExists( "Backup log file " + this._filename + "." + i + " already exists", ); } } } else { this.#currentFileSize = (await Deno.stat(this._filename)).size; } }
log(msg: string): void { const msgByteLength = this._encoder.encode(msg).byteLength + 1;
if (this.#currentFileSize + msgByteLength > this.#maxBytes) { this.rotateLogFiles(); this.#currentFileSize = 0; }
this._buf.writeSync(this._encoder.encode(msg + "\n")); this.#currentFileSize += msgByteLength; }
rotateLogFiles(): void { this._buf.flush(); Deno.close(this._file!.rid);
for (let i = this.#maxBackupCount - 1; i >= 0; i--) { const source = this._filename + (i === 0 ? "" : "." + i); const dest = this._filename + "." + (i + 1);
if (existsSync(source)) { Deno.renameSync(source, dest); } }
this._file = Deno.openSync(this._filename, this._openOptions); this._writer = this._file; this._buf = new BufWriterSync(this._file); }}