Logging

Overview
@marblejs/core defines a pluggable Logger dependency registered by default to the context of every server factory. Having that you can inspect things like, registered context dependencies, mapped HTTP routes, request/response logs, I/O event traces, etc.
Logger
The interface allows you to define the log tag, type, main message and an optional level, which if not defined defaults to LoggerLevel.INFO.
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{
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  tag: 'event_bus',
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  type: 'saveOfferDocument#x27;,
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  message: 'Saving offer document...',
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  level: LoggerLevel.INFO
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}
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enum LoggerLevel { INFO, WARN, ERROR, DEBUG, VERBOSE };
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​
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interface LoggerOptions = {
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  tag: string;
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  type: string;
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  message: string;
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  level?: LoggerLevel;
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};
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Marble.js logger is an instance of IO monad which represents a synchronous effectful computation. In order to execute the logger you have to "run the IO action".
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Logger :: LoggerOptions -> IO<void>;
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import { LoggerTag, LoggerToken, LoggerLevel, useContext } from '@marblejs/core';
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import { r } from '@marblejs/http';
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import { requestValidator$, t } from '@marblejs/middleware-io';
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import { tap } from 'rxjs/operators';
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import { UserDto } from './user.dto';
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​
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const foo$ = r.pipe(
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  r.matchPath('/foo'),
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  r.matchType('GET'),
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  r.useEffect((req$, ctx) => {
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    const logger = useContext(LoggerToken)(ctx.ask);
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​
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    const logMagic = logger({
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      tag: LoggerTag.HTTP
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      level: LoggerLevel.INFO,
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      type: 'foo#x27;,
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      message: 'Here the magic happens...',
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    });
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    return req$.pipe(
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      tap(logMagic),
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      // ..
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    ));
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  });
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Custom logger
You can override the binding and map the stdout IO operations to a different destination (e.g. file or external service) when needed.
logger.reader.ts
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import * as O from 'fp-ts/lib/Option';
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import { pipe } from 'fp-ts/lib/function';
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import { Logger, LoggerLevel, createReader } from '@marblejs/core';
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import { CustomLogger } from './customLogger';
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​
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export const CustomLoggerReader = createReader<Logger>(() => opts => {
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  const tag = opts.tag;
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  const level = opts.level ?? LoggerLevel.INFO;
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  const message = `${opts.type} ${opts.message}`;
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  const log = pipe(
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    O.fromNullable({
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      [LoggerLevel.ERROR]: CustomLogger.error,
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      [LoggerLevel.INFO]: CustomLogger.log,
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      [LoggerLevel.WARN]: CustomLogger.warn,
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    }[level),
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    O.getOrElse(() => CustomLogger.log),
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  );
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​
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  return () => log({ tag, message });
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});
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Then in your server definition you have to override the binding.
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import { bindTo, LoggerToken } from '@marblejs/core';
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import { createServer } from '@marblejs/http';
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import { CustomeLoggerReader } from './logger.reader.ts';
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​
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const server = createServer({
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  // ...
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  dependencies: [
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    bindTo(LoggerToken)(CustomLoggerReader),
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  ],
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});
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Contents

Overview

Logger

Custom logger