Conveniences for formatting data for logs.
This module allows developers to specify a string that serves as template for log messages, for example:
$time $metadata[$level] $message\n
Will print error messages as:
18:43:12.439 user_id=13 [error] Hello\n
The valid parameters you can use are:
$time - the time the log message was sent$date - the date the log message was sent$message - the log message$level - the log level$node - the node that prints the message$metadata - user controlled data presented in "key=val key2=val2 " format$levelpad - sets to a single space if level is 4 characters long, otherwise set to the empty space. Used to align the message after level.Backends typically allow developers to supply such control strings via configuration files. This module provides compile/1, which compiles the string into a format for fast operations at runtime and format/5 to format the compiled pattern into an actual IO data.
Metadata to be sent to the logger can be read and written with the Logger.metadata/0 and Logger.metadata/1 functions. For example, you can set Logger.metadata([user_id: 13]) to add user_id metadata to the current process. The user can configure the backend to choose which metadata it wants to print and it will replace the $metadata value.
Compiles a format string into a data structure that format/5 can handle.
Takes a compiled format and injects the level, timestamp, message, and metadata keyword list and returns a properly formatted string.
Formats date as chardata.
Formats time as chardata.
Prunes invalid Unicode code points from lists and invalid UTF-8 bytes.
pattern() :: :date | :level | :levelpad | :message | :metadata | :node | :time
time() :: {{1970..10000, 1..12, 1..31}, {0..23, 0..59, 0..59, 0..999}} compile(binary() | nil) :: [pattern() | binary()]
compile(pattern) :: pattern when pattern: {module(), function :: atom()} Compiles a format string into a data structure that format/5 can handle.
Check the module doc for documentation on the valid parameters that will be interpolated in the pattern. If you pass nil as the pattern, the pattern defaults to:
"\n$time $metadata[$level] $levelpad$message\n"
If you want to customize formatting through a custom formatter, you can pass a {module, function} tuple as the pattern.
iex> Logger.Formatter.compile("$time $metadata [$level] $message\n")
[:time, " ", :metadata, " [", :level, "] ", :message, "\n"]
iex> Logger.Formatter.compile({MyLoggerFormatter, :format})
{MyLoggerFormatter, :format} format(
{atom(), atom()} | [pattern() | binary()],
Logger.level(),
Logger.message(),
time(),
keyword()
) :: IO.chardata() Takes a compiled format and injects the level, timestamp, message, and metadata keyword list and returns a properly formatted string.
iex> pattern = Logger.Formatter.compile("[$level] $message")
iex> timestamp = {{1977, 01, 28}, {13, 29, 00, 000}}
iex> formatted = Logger.Formatter.format(pattern, :info, "hello", timestamp, [])
iex> IO.chardata_to_string(formatted)
"[info] hello" format_date({1970..10000, 1..12, 1..31}) :: IO.chardata() Formats date as chardata.
format_time({0..23, 0..59, 0..59, 0..999}) :: IO.chardata() Formats time as chardata.
prune(IO.chardata()) :: IO.chardata()
Prunes invalid Unicode code points from lists and invalid UTF-8 bytes.
Typically called after formatting when the data cannot be printed.
© 2012 Plataformatec
Licensed under the Apache License, Version 2.0.
https://hexdocs.pm/logger/1.11.2/Logger.Formatter.html