spark 1.5.2

Useful Links

• Website - browse the project homepage
• Documentation - read documentation and usage guides
• Downloads - latest development builds

What does it do?
spark is made up of a number of components, each detailed separately below.

• CPU Profiler: Diagnose performance issues.
• Memory Inspection: Diagnose memory issues.
• Server Health Reporting: Keep track of overall server health.

CPU Profiler
spark's profiler can be used to diagnose performance issues: "lag", low tick rate, high CPU usage, etc.

It is:

• Lightweight - can be ran in production with minimal impact.
• Easy to use - no configuration or setup necessary, just install the plugin/mod.
• Quick to produce results - running for just ~30 seconds is enough to produce useful insights into problematic areas for performance.
• Customisable - can be tuned to target specific threads, sample at a specific interval, record only "laggy" periods, etc
• Highly readable - simple tree structure lends itself to easy analysis and interpretation. The viewer can also apply deobfuscation mappings.

It works by sampling statistical data about the systems activity, and constructing a call graph based on this data. The call graph is then displayed in an online viewer for further analysis by the user.

There are two different profiler engines:

• Native AsyncGetCallTrace + perf_events - uses async-profiler (only available on Linux x86_64 systems)
• Built-in Java ThreadMXBean - an improved version of the popular WarmRoast profiler by sk89q.

Memory Inspection
spark includes a number of tools which are useful for diagnosing memory issues with a server.

• Heap Summary- take & analyse a basic snapshot of the servers memory
  • A simple view of the JVM's heap, see memory usage and instance counts for each class
  • Not intended to be a full replacement of proper memory analysis tools. (see below)
• Heap Dump- take a full (HPROF) snapshot of the servers memory
  • Dumps (& optionally compresses) a full snapshot of JVM's heap.
  • This snapshot can then be inspected using conventional analysis tools.
• GC Monitoring- monitor garbage collection activity on the server
  • Allows the user to relate GC activity to game server hangs, and easily see how long they are taking & how much memory is being free'd.
  • Observe frequency/duration of young/old generation garbage collections to inform which GC tuning flags to use

Server Health Reporting
spark can report a number of metrics summarising the servers overall health.

These metrics include:

• TPS - ticks per second, to a more accurate degree indicated by the /tps command
• Tick Durations - how long each tick is taking (min, max and average)
• CPU Usage - how much of the CPU is being used by the server process, and by the overall system
• Memory Usage - how much memory is being used by the process
• Disk Usage - how much disk space is free/being used by the system

As well as providing tick rate averages, spark can also monitor individual ticks - sending a report whenever a single tick's duration exceeds a certain threshold. This can be used to identify trends and the nature of performance issues, relative to other system or game events.


Usage
To install, just add the spark-nukkit.jar file to your servers plugins directory.

Information about how to use commands can be found in the docs.

If you’d like help analysing a profiling report, or just want to chat, feel free to join us on Discord.

Guides
There are a few small "guides" available in the docs, covering the following topics.

• The tick loop
• Finding the cause of lag spikes