Log4j2 Benchmark Tool

A minimal Java tool to benchmark Log4j2 logging throughput with configurable concurrent threads and various logging configurations.

Features

• Configurable number of concurrent logging threads
• Duration-based or event-count-based test modes
• Configurable message size (~100 chars default)
• Multiple Log4j2 configurations to compare:
  • sync-immediate - Synchronous with immediateFlush=true
  • sync-buffered - Synchronous with immediateFlush=false (8KB buffer)
  • async-1k - AsyncLogger with 1024 ring buffer size
  • async-4k - AsyncLogger with 4096 ring buffer size
  • async-10k - AsyncLogger with 10240 ring buffer size
• CSV output support for further analysis

Requirements

• Java 17+
• Maven 3.6+

Build

mvn clean package

This creates an executable fat JAR at target/log4jbench-1.0-SNAPSHOT.jar (~2.7MB).

Usage

Basic Run (all configs, 100 threads, 10s duration)

# With Maven
mvn exec:java

# With standalone JAR
java -jar target/log4jbench-1.0-SNAPSHOT.jar

With Custom Options

java -jar target/log4jbench-1.0-SNAPSHOT.jar --threads=8 --duration=30 --warmup=5

Event-Count Mode

java -jar target/log4jbench-1.0-SNAPSHOT.jar --mode=events --events=500000 --threads=2

Test Specific Configs Only

java -jar target/log4jbench-1.0-SNAPSHOT.jar --configs=sync-immediate,async-4k

Custom Message Size

java -jar target/log4jbench-1.0-SNAPSHOT.jar --msg-size=200 --threads=4

Export to CSV

java -jar target/log4jbench-1.0-SNAPSHOT.jar --output=results.csv

Command Line Options

Option	Description	Default
-t, --threads=N	Number of concurrent threads	100
-m, --mode=MODE	Test mode: duration or events	duration
-d, --duration=N	Test duration in seconds	10
-e, --events=N	Total events (events mode)	1000000
-w, --warmup=N	Warmup duration in seconds	3
-s, --msg-size=N	Message size in characters	100
-c, --configs=LIST	Comma-separated config names	all
-o, --output=FILE	Output CSV file	stdout only

Example Output

=== Log4j2 Benchmark ===
Threads: 4 | Mode: DURATION | Message size: 100 chars
Duration: 10s | Warmup: 3s
Configs: [sync-immediate, sync-buffered, async-1k, async-4k, async-10k]

Running: sync-immediate ...
sync-immediate   |   4 threads |    1,234,567 events | 10.00s | 123,456 events/s | 12.34 MB/s

Running: async-4k ...
async-4k         |   4 threads |    5,678,901 events | 10.00s | 567,890 events/s | 56.78 MB/s

Log Configurations

sync-immediate

Standard synchronous file appender with immediateFlush="true". Every log event is flushed to disk immediately.

sync-buffered

Synchronous file appender with immediateFlush="false" and 8KB buffer. Events are batched before writing.

async-1k / async-4k / async-10k

Async loggers using LMAX Disruptor with ring buffer sizes of 1024, 4096, and 10240 respectively. Logging threads hand off events to a background thread for I/O.

Notes

• Cache dropping: Before each test, the tool attempts to drop Linux filesystem caches (sync; echo 3 > /proc/sys/vm/drop_caches) for consistent results. Run with sudo for this to work.
• Async loggers: Use the LMAX Disruptor for high-throughput async logging.

License

MIT