Add support for JSON format in LoggerService

[MiniMarker]

Is there an existing issue that is already proposing this?

• [X] I have searched the existing issues

Is your feature request related to a problem? Please describe it

Not related to a problem

Describe the solution you'd like

When instantiating a new LoggerService, a new option property for format can be added. Based on the setting either an ConsoleLogger or possibly a new JsonConsoleLogger will be used.

the resulting log message would be splitted up into an object looking like this:

{
  "pid": 1,
  "timestamp": "XXX",
  "level": "info",
  "message": "hello",
  ...otherProps
}

Teachability, documentation, adoption, migration strategy

No migration neccesary, since regular text logger should be default

What is the motivation / use case for changing the behavior?

External log collection tools (like elasticsearch) have the ability to parse objects and split them into separate data rows for better filtration and querying.

[MiniMarker]

I can contribute with an implementation if feature request is ok 😸

[kamilmysliwiec]

I can contribute with an implementation if feature request is ok 😸

That would be great! PRs are more than welcome

[MiniMarker]

For future questions, which channel in discord is most suitable for questions related to core nest features?

[Tony133]

For future questions, which channel in discord is most suitable for questions related to core nest features?

Hi @MiniMarker use nestjs forum (see screenshot) that what regarding NestJS framework topics such as core, cli, express, fastify, etc.

[armujahid]

I created my own JsonConsoleLogger by extending ConsoleLogger

import { ConsoleLogger, LogLevel } from '@nestjs/common';

export class JsonConsoleLogger extends ConsoleLogger {

  protected formatPid(pid: number) {
    return `${pid}`;
  }

  protected colorize(message: string, logLevel: LogLevel) {
    return message;
  }

  protected formatMessage(logLevel: LogLevel, message: unknown, pidMessage: string, formattedLogLevel: string, contextMessage: string, timestampDiff: string): string {
    const output = this.stringifyMessage(message, logLevel);
    return `${JSON.stringify({
      pidMessage,
      timestamp: this.getTimestamp(),
      logLevel,
      contextMessage,
      output,
      timestampDiff,
    })}\n`
  }
}

Output:

{"pidMessage":"43457","timestamp":"10/05/2022, 4:07:52 PM","logLevel":"log","contextMessage":"\u001b[38;5;3m[NestFactory] \u001b[39m","output":"Starting Nest application...","timestampDiff":""}

Goal was to get json without any colorize formating. Issue is currently we cannot override contextMessage and timestampDiff formatting. That's why I have created two PRs (already linked with this issue) to resolve this issue.

[MiniMarker]

Hi @armujahid great job! You beat me to it 😅

One small detail is the naming of the keys which can be shortened a bit?

pidMessage -> pid
contextMessage -> context
output -> message

Also what do you do with optional context objects provided as the second parameter in the log functions?

[armujahid]

@MiniMarker yes I will use short keys in final implementation.

Also what do you do with optional context objects provided as the second parameter in the log functions?

I didn't change context behavior so it will propagate as it is via 2nd string argument or via global setting of context via constructor.

logger.error('Hello world', "2nd string argument");

{"pid":"16973","timestamp":"10/06/2022, 10:56:03 AM","logLevel":"error","context":"\u001b[38;5;3m[2nd string argument] \u001b[39m","message":"Hello world","timestampDiff":""}

[kamilmysliwiec]

Thanks for sharing @armujahid!

[MiniMarker]

@armujahid have you finished the final implementation? I can't find the pull request for the json logger