Flare (Spark for 1.12.2)

Performance and Diagnostics for Minecraft 1.12.2

Flare is a powerful toolkit for performance analysis and debugging, specifically designed for Minecraft version 1.12.2 with support for Forge and Cleanroom. This mod is an evolution of the Spark project and offers extended functionality for server monitoring.

Key Features

CPU Profiling

The profiling system helps identify performance issues such as lag, low tick rate, and high CPU usage. Main advantages:

• Minimal impact - can be used on a running server without significant performance degradation
• Easy to use - requires no additional configuration, just install the mod
• Quick results - even 30 seconds of operation is enough to obtain useful data
• Flexible configuration - ability to target specific threads, select sampling interval, and record only problematic periods
• Easy analysis - tree structure of data simplifies result interpretation with deobfuscation support

Profiling works by collecting statistical data about system activity and building a call graph, which is then analyzed in an online viewer.

Two profiling mechanisms are available:

• Native AsyncGetCallTrace + perf_events based on async-profiler (Linux x86_64 only)
• Built-in Java ThreadMXBean - improved version of the popular WarmRoast profiler

Memory Analysis

Toolkit for diagnosing memory usage problems:

• Heap summary - basic server memory snapshot with information about memory usage and instance counts of classes
• Full memory dump - creation of HPROF snapshot of entire JVM memory with compression capability for subsequent analysis
• Garbage collection monitoring - tracking GC activity with correlation to server hangs and analysis of memory freeing efficiency

Server Health Monitoring

Flare tracks key metrics for assessing overall server health:

• TPS - precise measurement of ticks per second
• Tick durations - minimum, maximum, and average execution time
• CPU usage - processor load by the process and the entire system
• Memory usage - RAM consumption
• Disk usage - free and occupied space

Additionally, the system can monitor individual ticks and send reports when a specified duration threshold is exceeded, helping to identify patterns in performance issues.

Usage

All Flare functions are accessible through Minecraft's standard command system, making the tool intuitive for users.

License

The project is distributed freely with open source under GNU GPLv3 license. The API module is released under the more permissive MIT license. Flare is a fork of the spark project, which also used GPLv3 license.