ulog

ulog

ulog is the antidote to modern loggers.

• ULog only logs JSON formatted output. Structured logging is the only good logging.
• ULog does not have log levels. If you don't want something logged, don't log it.
• ULog supports setting fields in context. This is useful for building a log context over the course of an operation.
• ULog has no dependencies. Using ulog only brings in what it needs, and that isn't much!
• ULog always uses RFC3339 formatted UTC timestamps, for sanity.

Basic Usage

    ulog.Print("a message")

{ "ts": "2019-11-18T14:00:32Z", "msg": "a message" }

With Fields

    ulog.Print("a message",
        "field", "value",
        "a_number", 123,
        "a_bool", false,
    )

{ "ts": "2019-11-18T14:00:32Z", "msg": "a message", "field": "value", "a_number": 123, "a_bool": false }

With Context

    logger := ulog.With(
        "request_id", "12345",
        "user_id": "big_jim_mcdonald",
    )

    logger.Print("a message",
        "field", "value",
        "a_number", 123,
        "a_bool", false)

{ "ts": "2019-11-18T14:00:32Z", "msg": "a message", "request_id": "12345", "user_id": "big_jim_mcdonald", "field": "value", "a_number": 123, "a_bool": false }

With More Complex Data Types

    ulog.Print("something complex!",
        "array", []string{"this", "is", "an", "array"},
        "map", map[string]string{
            "key": "value",
            "just": "like that",
        },
        "the_ulog_struct_itself", ulog.With("hello", "world"),
    )

{ "ts": "2019-11-18T13:41:56Z", "msg": "something complex!", "array": [ "this", "is", "an", "array" ], "map": { "key": "value", "just": "like that" }, "the_ulog_struct_itself": { "Fields": [ "hello", "world" ] } }

Output To Somewhere Other Than STDOUT

    var sb strings.Builder
    logger := ulog.WithWriter(sb)

    logger.Print("a message",
        "field", "value",
        "a_number", 123,
        "a_bool", false)

    fmt.Println(sb.String())

{ "ts": "2019-11-18T14:00:32Z", "msg": "a message", "field": "value", "a_number": 123, "a_bool": false }

Output to systemd-journald

import "github.com/UNO-SOFT/ulog/ulogjournal"

logger := ulog.WithWriter(ulogjournal.Maybe(os.Stderr))

This will log to /var/run/systemd/journal/socket if exists and os.Stderr is the same as file as $JOURNAL_STREAM says, os.Stderr otherwise.

For more information, see journald and JOURNAL_STREAM.