About

Tjahzi is a set of Java
tools and appenders for sending logs
to Grafana Loki.

Latest releases:

If you find the project useful (or not useful for some reason) please
let me know to encourage further development. ⭐ Stars are also welcome
⭐ ;).

Features

Tjahzi allows pushing log data to Loki. It uses a protobuf format to
push log lines with timestamps and labels. On top of that we
built appenders for log4j2, Logback, and log4j1.x/reload4j.
These feature:

Logging does not allocate objects nor take any locks.
Sending data to Loki in batches allocates as little as possible.
We also provide a no-dependency version of these appenders.
Includes in-house implementation of protobuf wire format for Loki to
reduce dependencies and improve performance.

These points apply to log4j2 appender. Logback and log4j1.x
designs do not allow allocation-free operation, but we go to great
lengths to reduce allocations and even provide an optimized version of
the pattern layout for Logback.

Getting started

Log4j2

For log4j2 appender quick start guide and detailed discussions see
this README.md.

Logback

For Logback appender quick start guide and detailed discussions see
this README.md.

Log4j1.x / Reload4j

For appender quick start guide and detailed discussions see
this README.md.

The log4j1.x was discontinued by the Apache Foundation and is no
longer updated.
The Reload4j project is a drop
in replacement for log4j1.x which fixes "the most pressing security
issues".

The log4j.jar is interchangeable with reload4j.jar and you can
freely use reload4j
appender even if you use old log4j1.x.

Core design principles

Logging should be lightweight and not interfere with the main business
tasks of threads that happen to log a message.
Asking the logging subsystem to log a message should be as CPU efficient
as possible.
That's a truism. Apart from computation itself, there are many other
causes of jitter (varying speed of code execution).
Thread can be slowed down by excessive allocations, by initialization
code running in constructors of unnecessarily allocated objects,
by garbage collector activity that is triggered by it. There can be
configuration refresh checks on logging path, inter-thread signaling,
etc.

To avoid these effects, we strive to adhere to the following
principles (and document any violations):

Lock free and wait free API
Allocation free in a steady state

You can compare this
with design principles of Aeron
which are close to our hearts.

Architecture

                [via 10kB thread local buffer]
                           │                                          
┌─────────────┐    Log  ←──┘                                                
│ Application │----------------┐                                          
│  Thread 1   │                │                                          
└─────────────┘                │                                          
                               │                                          
       .                       ▼                                          
                          ┌────────────────────┐         ┌─────────┐         ┌─────────┐
       .      Log         │                    │         │ Log     │         │  I/O    │
         ----------------▶│     Log buffer     ├--→---→--┤ shipper ├--→---→--┤ thread  │      
       .                  │                    │         │ agent   │         │ (Netty) │    
                          └────────────────────┘         └─────────┘         └─────────┘    
       .                             ▲                                    
                                     │                                    
┌─────────────┐      Log             │                                    
│ Application │----------------------┘                                    
│  Thread N   │                                                           
└─────────────┘

For those interested, the wiki contains some information
on log buffer sizing.

Monitoring

Check
out this wiki article.

LICENSE

This work is released under MIT license. Feel free to use, copy and
modify this work as long as you credit original authors.
Pull and feature requests are welcome.

tkowalcz/tjahzi