Memory Assault

The memory-assault module in light-chaos-monkey allows you to inject memory pressure into your application. When triggered, it allocates memory in increments until a target threshold is reached, holds that memory for a specified duration, and then releases it. This is useful for testing how your application behaves under low-memory conditions and identifying potential memory-related issues.

Core Components

MemoryAssaultHandler

The middleware handler responsible for consuming memory.

• Behavior: When enabled and triggered (based on the level configuration), it starts an asynchronous process to “eat” free memory. It incrementally allocates byte arrays until the total memory usage reaches the memoryFillTargetFraction of the maximum heap size.
• Safety: The handler includes logic to prevent immediate OutOfMemoryErrors by controlling the increment size and respecting the maximum target fraction. It also performs a System.gc() after releasing the allocated memory to encourage the JVM to reclaim the space.

MemoryAssaultConfig

Configuration class that loads settings from memory-assault.yml.

Configuration

The module is configured via memory-assault.yml.

Key Settings:

• enabled: Enable or disable the handler (default: false).
• bypass: If true, the assault is skipped even if enabled (default: true).
• level: The probability of an attack, defined as “1 out of N requests”.
  • level: 10 means approximately 1 in 10 requests (10%) will trigger the memory assault.
  • level: 1 means every request can trigger it (though typically it runs until finished once started).
• memoryMillisecondsHoldFilledMemory: Duration (in ms) to hold the allocated memory once the target fraction is reached (default: 90000).
• memoryMillisecondsWaitNextIncrease: Time (in ms) between allocation increments (default: 1000).
• memoryFillIncrementFraction: Fraction of available free memory to allocate in each increment (default: 0.15).
• memoryFillTargetFraction: The target fraction of maximum heap memory to occupy (default: 0.25).

Example Configuration:

enabled: true
bypass: false
level: 10
memoryFillTargetFraction: 0.5
memoryMillisecondsHoldFilledMemory: 60000