flash

Types

Attr

Collection of typed attributes to add data to loggers.

pub type Attr {
  BoolAttr(key: String, value: Bool)
  FloatAttr(key: String, value: Float)
  GroupAttr(key: String, value: List(Attr))
  IntAttr(key: String, value: Int)
  StringAttr(key: String, value: String)
}

Constructors

```
BoolAttr(key: String, value: Bool)
```
```
FloatAttr(key: String, value: Float)
```

GroupAttr(key: String, value: List(Attr))

```
IntAttr(key: String, value: Int)
```
```
StringAttr(key: String, value: String)
```

Level

</>

Available log levels, where debug is the lowest level and error is the highest level.

pub type Level {
  DebugLevel
  InfoLevel
  WarnLevel
  ErrorLevel
}

Constructors

```
DebugLevel
```
```
InfoLevel
```
```
WarnLevel
```
```
ErrorLevel
```

Logger

</>

pub opaque type Logger

Writer

</>

Function type for custom writer implementations.

pub type Writer =
  fn(Level, String, List(Attr)) -> Nil

Constants

default

</>

pub const default: Logger = Logger(InfoLevel, text_writer, [])

Default logger that omits debug level logs and outputs a text format.

Functions

debug

</>

pub fn debug(logger: Logger, message: String) -> Nil

Logs the message and any attributes at the debug level.

error

</>

pub fn error(logger: Logger, message: String) -> Nil

Logs the message and any attributes at the error level.

info

</>

pub fn info(logger: Logger, message: String) -> Nil

Logs the message and any attributes at the info level.

json_writer

</>

pub fn json_writer(
  level: Level,
  message: String,
  attrs: List(Attr),
) -> Nil

A writer that writes to standard out using a JSON representation. Here’s some example code and the associated JSON output:

let logger = with_attr(logger, StringAttr("request_id", "foobar"))
info(logger, "/health")

{"level":"info","time":"2024-03-09T12:52:43.657-05:00","message":"/health","request_id":"foobar"}

The level, time, and message attributes are added automatically and will be ordered before other attributes. Other attributes are sorted lexicographically with groups being sorted after non group attributes. If multiple attributes in the same group share a key, the last attribute with the key is chosen.

level_to_string

</>

pub fn level_to_string(level: Level) -> String

Converts a level variant to an equivalent string representation.

log

</>

pub fn log(logger: Logger, level: Level, message: String) -> Nil

Logs the message and any attributes if the logger is enabled to log at the given log level.

new

</>

pub fn new(
  level: Level,
  writer: fn(Level, String, List(Attr)) -> Nil,
) -> Logger

Creates a logger that logs for levels greater than or equal to the given level and writes using the given writer.

parse_level

</>

pub fn parse_level(level: String) -> Result(Level, Nil)

Parses a string representation of a level to the equivalent level variant.

text_writer

</>

pub fn text_writer(
  level: Level,
  message: String,
  attrs: List(Attr),
) -> Nil

A writer that writes to standard out using a text representation. Here’s some example code and the associated text output:

let logger = with_attr(logger, StringAttr("request_id", "foobar"))
info(logger, "/health")

12:59:37 INFO  /health                                       request_id=foobar

Attributes are sorted lexicographically with groups being sorted after non group attributes. If multiple attributes in the same group share a key, the last attribute with the key is chosen.

warn

</>

pub fn warn(logger: Logger, message: String) -> Nil

Logs the message and any attributes at the warn level.

with_attr

</>

pub fn with_attr(logger: Logger, attr: Attr) -> Logger

Adds the given attribute to the logger.

with_attrs

</>

pub fn with_attrs(logger: Logger, attrs: List(Attr)) -> Logger

Adds the list of attributes to the logger.