Typewriter

This repository provides a GoLang logging package, which are inspired by some Log4j features like package specific enablement

:warning: :construction: Unstable release v0.0.2 (See also Module version numbering)

Nevertheless, pre-release versions can already be tested: typewriter at pkg.go.dev

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Usage

Logging

Access

The logger can be accessed via importing github.com/ma-vin/typewriter/logger and using the Log() method at logger package. This will return a struct implementing the Logger interface. There are also the same methods directly in the logger package, but without returning an interface.

Log Methods

There are permutations of the following categories for each severity

• log without additional parameters, e.g. Information(args ...any)
• log with correlation, e.g. InformationWithCorrelation(correlationId string, args ...any)
• log with custom values map, e.g. InformationCustom(customValues map[string]any, args ...any)
• message format with args, e.g. Informationf(format string, args ...any)
• panic (only for warning, error and fatal) e.g. ErrorWithPanic(args ...any)
• exit (only for fatal) e.g. FatalWithExit(args ...any)

Arguments are handled in the manner of fmt.Sprint/fmt.Sprintf

In addition, there exists an indicator if the severity is enabled or not.

Configuration

Configuration is currently possible via environment variables or an properties file.

Configauration by file

To use a configuration file by setting an environment variable TYPEWRITER_CONFIG_FILE with a path to a properties file. If this environment variable is set, all others will be ignored. Nevertheless, the same property names are used by both. It is possible to use single line comments #,// or -- and multiline commets with begin at /* and end at */.

Log levels

The log level can be set via TYPEWRITER_LOG_LEVEL with one of the following values:

• DEBUG
• INFO or INFORMATION
• WARN or WARNING
• ERROR
• FATAL

The default log level is ERROR

Appender

There are two types of appender at the moment. They can be configured by setting TYPEWRITER_LOG_APPENDER_TYPE with one of the following values:

• STDOUT: Standard output appender
• FILE: File appender which writes to a file
  • The target file of the appender has to be configured by setting the path to TYPEWRITER_LOG_APPENDER_PARAMETER

The default appender is the standard output one

Formatter

There are three types of formatter which provides the texts to log for the appender. They can be configured by setting TYPEWRITER_LOG_FORMATTER_TYPE with one of the following values:

• DELIMITER: The record information will be appended and delimited with a given sign. They can be set TYPEWRITER_LOG_FORMATTER_PARAMETER_<x> where <x> has to be replaced by the following values:

  1. DELIMITER the delimiting signs. The default value of the delimiter is -.
  2. TIME_LAYOUT time layout. Default value of time.RFC3339

• TEMPLATE: The records will be derived from three templates and time layout. They can be set TYPEWRITER_LOG_FORMATTER_PARAMETER_<x> where <x> has to be replaced by the following values:

  1. TEMPLATE template for writing time, severity and the message. Default [%s] %s: %s
  2. TEMPLATE_CORRELATION template for writing time, severity, correlationID and the message. Default [%s] %s %s: %s
  3. TEMPLATE_CUSTOM template for writing time, severity, message and custom value map. Default [%s] %s: %s
  4. TIME_LAYOUT time layout. Default value of time.RFC3339
  5. TEMPLATE_TRIM_SEVERITY indicator whether to trim severity text or to add space at warn and info to algin following elements. Default false
  6. TEMPLATE_CALLER like 1. with caller function, file and line placed in front of message. Default [%s] %s %s(%s.%d): %s
  7. TEMPLATE_CALLER_CORRELATION like 2. with caller function, file and line placed in front of message. Default [%s] %s %s %s(%s.%d): %s
  8. TEMPLATEE_CALLER_CUSTOM like 3. with caller function, file and line placed in front of message. Default [%s] %s %s(%s.%d): %s

  It is possible to reorder parameter by argument indices. The custom value map at 3 will be appended as key-value-pairs sorted by key (e.g. a custom map with three entries of string, number and boolean format at indices from 4 to 9: severity: %[2]s message: %[3]s %[4]s: %[5]s %[6]s: %[7]d %[8]s: %[9]t time: %[1]s)

• JSON: The records will be logged as JSON. It is possible to define key names, the time layout and if the custom value map should be a sub element or not. The keys of the custom value map will be used 1:1. The properties can be set via TYPEWRITER_LOG_FORMATTER_PARAMETER_<x> where <x> has to be replaced by the following values:

  1. JSON_TIME_KEY key of time. Default time
  2. JSON_SEVERITY_KEY key of severity. Default: severity
  3. JSON_CORRELATION_KEY key of correlationID. Default: correlation
  4. JSON_MESSAGE_KEY key of message. Default: message
  5. JSON_CUSTOM_VALUES_KEY key of custom values if used as sub elements. Default: custom
  6. JSON_CUSTOM_VALUES_SUB indicator to add custom value map as sub element: Default: false
  7. TIME_LAYOUT time layout. Default value of time.RFC3339
  8. JSON_CALLER_FUNCTIOM_KEY key of the caller function. Default: caller
  9. JSON_CALLER_FILE_KEY key of the caller file. Default: file
  10. JSON_CALLER_LINE_KEY key of the caller file line. Default: line

The default formatter is the delimiter one.

Caller

The logging of the caller function, file and line can be activated by setting true at TYPEWRITER_LOG_CALLER. The default is false.

Package specific configuration

Each configuration element can be declared package specific by replacing TYPEWRITER with TYPEWRITER_PACKAGE and adding the package as postfix at environment variable names.

The table shows the corresponding variable names for the example package logger

general	package specific
TYPEWRITER_LOG_LEVEL	TYPEWRITER_PACKAGE_LOG_LEVEL_LOGGER
TYPEWRITER_LOG_APPENDER_TYPE	TYPEWRITER_PACKAGE_LOG_APPENDER_TYPE_LOGGER
TYPEWRITER_LOG_APPENDER_PARAMETER	TYPEWRITER_PACKAGE_LOG_APPENDER_PARAMETER_LOGGER
TYPEWRITER_LOG_FORMATTER_TYPE	TYPEWRITER_PACKAGE_LOG_FORMATTER_TYPE_LOGGER
TYPEWRITER_LOG_FORMATTER_PARAMETER	TYPEWRITER_PACKAGE_LOG_FORMATTER_PARAMETER_LOGGER
TYPEWRITER_LOG_FORMATTER_PARAMETER_DELIMITER	TYPEWRITER_PACKAGE_LOG_FORMATTER_PARAMETER_LOGGER_DELIMITER

Examples

Examples are avialable at godoc logger/example_test.go