Introduction
Logging levels
You can globally set the minimum logging level with Memento.config.
julia>Memento.config("debug")Will log all messages for all loggers at or above "debug".
julia>Memento.config("warn")Will only log message at or above the "warn" level.
We can also set the logging level for specific loggers or collections of loggers if we explicitly set the level on an existing logger.
julia>set_level(get_logger("Main"), "info")Will only set the logging level to "info" for the "Main" logger and any future children of the "Main" logger.
By default Memento has 9 logging levels.
| Level | Number | Description |
|---|---|---|
| not_set | 0 | Will not log anything, but may still propagate messages to its parents. |
| debug | 10 | Log verbose message used for debugging. |
| info | 20 | Log general information about a program. |
| notice | 30 | Log important events that are still part of normal execution. |
| warn | 40 | Log warning that may cause the program to fail. |
| error | 50 | Log errors and throw or rethrow an error. |
| critical | 60 | Entire application has crashed. |
| alert | 70 | The entire application crashed and is not recoverable. Probably need to wake up the sysadmin. |
| emergency | 80 | System is unusable. Applications shouldn't need to call this so it may be removed in the future. |
Formatting logs
Unless explicitly changed Memento will use a DefaultFormatter for handlers. This Formatter takes a format string for mapping log record fields into each log message. Desired fields are wrapped in curly brackets (ie: "{msg}")
The default format string is "[{level} | {name}]: {msg}", which produces messages that look like
[info | root]: my info message.
[warn | root]: my warning message.
...However, you could change this string to just "{level}: {msg}", which would produce messages that look like
info: my info message.
warn: my warning message.
...The simplest way to globally change the log format is with Memento.config
julia> Memento.config("debug"; fmt="[{level} | {name}]: {msg}")The following fields are available via the DefaultRecord.
| Field | Description |
|---|---|
| date | The log event date rounded to seconds |
| level | The log event level as a string |
| levelnum | The integer value for the log event level |
| msg | The source log event message |
| name | The name of the source logger |
| pid | The pid where the log event occured |
| lookup | The top StackFrame of the stacktrace for the log event |
| stacktrace | A StackTrace for the log event |
For more details on the DefaultFormatter and DefaultRecord please see the API docs. More general information on Formatters and Records will be discussed later in this manual.
Architecture
There are five main components of Memento.jl that you can manipulate:
Loggers
Handlers
Formatters
Records
IO
The remainder of this manual will discuss how you can use these components to customize Memento to you particular application.