Logger v1.0.5 Logger.Formatter
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:
$time
- time the log message was sent$date
- 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
- set 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
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 chose
which metadata it wants to print and it will replace the $metadata
value.
Summary
Types
Functions
Specs
compile(binary | nil) :: [pattern | binary]
compile({atom, atom}) :: {atom, atom}
Compiles a format string into an array that the format/5
can handle.
Check the module doc for documentation on the valid parameters. If you
pass nil
, it defaults to: $time $metadata [$level] $levelpad$message\n
If you would like to make your own custom formatter simply pass
{module, function}
to compile/1
and the rest is handled.
iex> Logger.Formatter.compile("$time $metadata [$level] $message\n")
[:time, " ", :metadata, " [", :level, "] ", :message, "\n"]
Specs
format({atom, atom} | [pattern | binary], Logger.level, Logger.message, time, Keyword.t) :: IO.chardata
Takes a compiled format and injects the, level, timestamp, message and metadata listdict and returns a properly formatted string.