gelf-pretty

CLI to pretty-print GELF log lines

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Introduction

CLI tool to read Graylog Extended Log Format (GELF) log lines from stdin, such as:

{"version":"1.1","host":"my-server","short_message":"Starting server","timestamp":1555690413.839,"level":6,"_app":"my-app","_logger":"api","_port":"3000"}
{"version":"1.1","host":"my-server","short_message":"Listening for requests","timestamp":1555690413.903,"level":6,"_app":"my-app","_logger":"api","_endpoint":"locahost:3000/v1"}
{"version":"1.1","host":"my-server","short_message":"Request received","timestamp":155569049.540,"level":6,"_app":"my-app","_logger":"api","_method":"GET","_path":"/todos/1","_request_id":"0c4c165d"}
{"version":"1.1","host":"my-server","short_message":"Response","full_message":"{\n\t\"user_id\": 1,\n\t\"id\": 1,\n\t\"title\": \"fix /users/:id/todos route\",\n\t\"completed\": false\n}","timestamp":155569049.584,"level":7,"_app":"my-app","_logger":"api","_request_id":"0c4c165d","_status":200}
{"version":"1.1","host":"my-server","short_message":"Request received","timestamp":155569349.236,"level":6,"_app":"my-app","_logger":"api","_method":"GET","_path":"/users/1/todos","_request_id":"0c4c165d"}
{"version":"1.1","host":"my-server","short_message":"Unexpected error","full_message":"runtime error: index out of range\ngoroutine 1 [running]:\nmain.main()\n\t/app/api/main.go: 9 +0x20","timestamp":155569349.563,"level":3,"_app":"my-app","_logger":"api","_request_id":"0c4c165d"}
{"version":"1.1","host":"my-server","short_message":"Server shutting down","timestamp":155569349.571,"level":4,"_app":"my-app","_logger":"api"}

And pretty-print them to stdout like:

Installation

You can install gelf-pretty using one of the following options:

• Pre-built packages for macOS and Linux (easiest);
• Pre-compiled binaries for macOS, Linux and Windows;
• From source.

Pre-built packages

macOS

Install via Homebrew:

$ brew install joaodrp/tap/gelf-pretty

Linux

Install via Snapcraft:

$ snap install gelf-pretty

You can also download .deb or .rpm packages from the releases page and install with dpkg -i or rpm -i respectively.

Pre-compiled binaries

Download the correct archive for your platform from the releases page and extract the gelf-pretty binary to a directory included in your $PATH/Path.

From source

$ go install github.com/joaodrp/gelf-pretty@latest

Make sure that $GOPATH/bin is in your $PATH.

Output Format

GELF messages are pretty-printed in the following format:

[<timestamp>] <level>: <_app>/<_logger> on <host>: <short_message> <_*>=<value>\n
    <full_message>

Description

• <timestamp> is the value of the standard GELF unix timestamp field, formatted as 2006-01-02 15:04:05.000;

• <level> is the value of the standard GELF log level field, formatted in a human-readable form (e.g. DEBUG instead of 7);

• <_app> is an optional reserved additional field. It can be used to identify the name of the application emitting the logs. If not provided, the forward slash that follows it is omitted;

• <_logger> is an optional reserved additional field. It can be used to identify the specific application module or logger instance that is emitting a given log line;

• <host> is the value of the standard GELF host field;

• <short_message> is the value of the standard GELF short_message field;

• <_*>=<value> is any number of GELF additional fields (_*), formatted as key=value pairs separated by a whitespace. The keys leading underscore is omitted for readability;

• <full_message> is the value of the standard GELF full_message field (usually used for exception backtraces). It is preceded by a new line and indented with four spaces.

Colors

gelf-pretty automatically detects if the output stream is a TTY or not. If (and only if) it is, the output will be formatted by default with ANSI colors for improved readability.

Usage

To pretty-print GELF logs from your application simply pipe its output to gelf-pretty:

$ app | gelf-pretty

Run gelf-pretty --help for a list of available options:

$ gelf-pretty --help
Usage of gelf-pretty:
  --no-color
        Disable color output
  --version
        Show version information

Capture stderr

If your application writes to the stderr stream you will need to pipe it along with stdout:

$ app 2>&1 | gelf-pretty

Disable colors

To disable colored output (even if the output stream is a TTY) use the --no-color option:

$ app | gelf-pretty --no-color

FAQ

My logs are not formatted, why?

gelf-pretty validates each input line. If a line (delimited by \n) is not a valid JSON string or is invalid according to the GELF specification, gelf-pretty will simply echo it back to the stdout without any modification (silently, with no error messages).

If you believe that your log messages are valid, please open a new issue and let us know.

Contributions

This project adheres to the Contributor Covenant code of conduct. By participating, you are expected to uphold this code. Please refer to our contributing guide for further information.