LogDog: designed to work out of the box, you can use the pre-configured logger anytime

by iOS Example

LogDog

Usage

LogDog is designed to work out of the box, you can use the pre-configured logger anytime, anywhere:

sugar.debug("hi")

sugar.error("somethings went wrong")

Or, make a local copy and do some changes:

var logger = suggar
logger["path"] = "/me"

logger.debug("hi")

You can quickly create a logger with just a label, it will use the predefined log handler:

var logger = Logger.sugar("worker:a")
logger.level = .info

logger.info("hi")

SugarLogHandler

The core component that makes this all work is SugarLogHandler.

The following code snippet shows how to create a SugarLogHandler and use it to bootstrap the logging system.

LoggingSystem.bootstrap { label in

    // ! to create your own `SugarLogHandler`, you need a `sink`, an `appender` and an optional `errorHandler`. 
    let sink = LogSinks.Builtin.short
    let appender = TextLogAppender.stdout
    let errorHandler = { error: Error in
        print("LogError: \(error)")
    }

    var handler = SugarLogHandler(label: label, sink: sink, appender: appender, errorHandler: errorHandler)

    // ! use dynamicMetadata to register values that are evaluted on logging.
    handler.dynamicMetadata["currentUserId"] = {
        AuthService.shared.userId
    }   
    
    return handler
}

let logger = Logger(label: "app")
logger.error("Something went wrong")

Sink

Sinks process log records.

A sink can be a formatter, or a filter, a hook, or a chain of other sinks.

Formatter

You can create a formatter sink with just a closure.

let sink = LogSinks.firstly
    .format {
        "\($0.entry.level.uppercased) \($0.entry.message)\n"
    }
    
// Output:
//
//     DEBUG hello

Or use the built-in neat formatters directly.

let short = LogSinks.BuiltIn.short

// Output:
//
//     E: bad response
//     C: can not connect to db


let medium = LogSinks.BuiltIn.medium  // default sink for sugar loggers

// Output:
//
//     20:40:56.850 E/App main.swift.39: bad response url=/me, status_code=404
//     20:40:56.850 C/App main.swift.41: can not connect to db


let long = LogSinks.BuiltIn.long

// Output:
//
//     ╔════════════════════════════════════════════════════════════════════════════════
//     ║ 2020-11-15 20:46:31.157  App  ERROR     (main.swift:39  run(_:))
//     ╟────────────────────────────────────────────────────────────────────────────────
//     ║ bad response
//     ╟────────────────────────────────────────────────────────────────────────────────
//     ║ url=/me
//     ║ status_code=404
//     ╚════════════════════════════════════════════════════════════════════════════════

Filter

You can create a filter sink with just a closure.

let sink = LogSinks.firstly
    .filter {
        $0.entry.source != "LogDog"
    }
    
// logs from `LogDog` will not be output.

DSL

Or use the built-in expressive dsl to create one.

let sink = LogSinks.BuiltIn.short
    .when(.path)
    .contains("private")
    .deny
    
let sink = LogSinks.BuiltIn.short
    .when(.level)
    .greaterThanOrEqualTo(.error)
    .allow

Concat

Sinks are chainable, a sink can concatenate another sink.

let sink = sinkA + sinkB + sinkC // + sinkD + ...

// or
let sink = sinkA
    .concat(sinkB)
    .concat(sinkC)
    // .concat(sinkD) ...

LogDog ships with many commonly used operators.

Prefix & Suffix

let sink = LogSinks.BuiltIn.short
    .prefix("? ")
    
// Output:
//
//     ? E: bad response


let sink = LogSinks.BuiltIn.short
    .suffix(" ?")
    
// Output:
//
//     E: bad response ?

Encode

let sink = LogSinks.firstly
    .encode(JSONEncoder())

Crypto

let sink = LogSinks.firstly
    .encode(JSONEncoder())
    .encrypt(using: key, cipher: .ChaChaPoly)

Compress

let sink = LogSinks.firstly
    .encode(JSONEncoder())
    .compress(.COMPRESSION_LZFSE)

Schedule

Sinks's processing can be time-consuming, if you don't want it to slow down your work, you can using Scheduler to make logging asynchronous.

let sink = LogSinks.firstly
    .sink(on: dispatchQueue) // or an operationQueue, or some other custom schedulers, for example, an eventLoop.
    .encode(JSONEncoder()) // time-consuming processing begins.
    .encrypt(using: key, cipher: .ChaChaPoly)
    .compress(.COMPRESSION_LZFSE)

Hook

Because of Scheduler, the logging may be asynchronous.

It means that the sinking may be in a different context,

You can use hook with entry.parameters to capture and pass the context.

private struct CustomSinkContext: LogParameterKey {
    typealias Value = CustomSinkContext

    let date = Date()
    let thread = LogHelper.thread
}

let customSink: AnyLogSink<Void, String> = AnyLogSink {

    // ! beforeSink: in the same context as the log generation.
    
    $0.parameters[CustomSinkContext.self] = .init()
} sink: { record, next in

    // ! sink: may not be in the same context as the log generation.

    record.sink(next: next) { (record) -> String? in
        guard let context = record.entry.parameters[CustomSinkContext.self] else {
            return nil
        }

        let time = LogHelper.format(context.date, using: "HH:mm:ss.SSS")
        let thread = context.thread
        
        // ...
    }
}

Please note, when using encode, parameters with string as key will also be encoded.

LogSinks.firstly
  .hook { 
     $0.parameters["currentUserId"] = AuthService.shared.userId
  }
  .hook(.appName, .appVersion, .date) /* , ..., a lot of built-in hooks */
  .encode(JSONEncoder())
  
/*
{
  "label": "app",
  "level": "debug",
  "metadata": {
    // ...
  }
  // ...
  "currentUserId": "1",
  "appName": "LogDog",
  "appVersion": "0.0.1",
  "date": "2020-11-19T01:12:37.001Z"
}
 */

Appender

Appenders are destinations of log records.

Built-in Appenders

OSLogAppender

Append strings to the underlying OSLog.

let appender = OSLogAppender(osLog)

TextLogAppender

Append strings to the underlying TextOutputStream.

let appender = TextLogAppender(stream)

let stdout = TextLogAppender.stdout
let stderr = TextLogAppender.stderr

MultiplexLogAppender

Append outputs to the underlying appenders.

// when `concurrent` is `true`, a dispatch group is used to make the appending of all appenders parallel. 
let appender = MultiplexLogAppender(concurrent: true, a, b, c, d/*, ...*/)

FileLogAppender

WIP

  • [ ] async
  • [ ] auto rotate
  • [ ] ...

Community

In addition to the sinks/appenders mentioned above, you can also find more integrations at LogDogCommunity!

LogDogChalk

Color the output of LogDog.

LogDogCryptoSwift

Encrypt the output of LogDog.

LogDogCocoaLumberjack

Append the output of LogDog to CocoaLumberjack.

Don't have the sink/appender you want? Contributions are welcome!

Installation

Swift Package Manager

.package(url: "https://github.com/luoxiu/LogDog.git", from: "0.2.0"),

CocoaPods

pod 'LogDog', '~> 0.2.0'

GitHub

https://github.com/luoxiu/LogDog