Struct WriteBufferManager 

pub struct WriteBufferManager { /* private fields */ }

Write Buffer Manager for coordinating memory across memtables

Implements jj.md Task 2: Write Buffer Manager with Global Memory Coordination

Algorithm

total_buffer_memory = active_memtable.size + Σ(immutable_memtables[i].size)

on_write(bytes):
    if total_buffer_memory + bytes > hard_limit:
        block_until(total_buffer_memory < soft_limit)
    if total_buffer_memory > soft_limit:
        trigger_flush(largest_immutable_memtable)
    total_buffer_memory += bytes

on_flush_complete(memtable):
    total_buffer_memory -= memtable.size
    signal_blocked_writers()

Implementations

impl WriteBufferManager

pub fn new(buffer_limit: u64) -> Self

Create a new write buffer manager

Arguments

• buffer_limit - Maximum total memory for write buffers (bytes)

pub fn with_limits( buffer_limit: u64, soft_limit_ratio: f64, hard_limit_ratio: f64, ) -> Self

Create with custom soft/hard limits

pub fn reserve_memory(&self, bytes: u64) -> bool

Reserve memory for a write operation

May block if hard limit is exceeded, waiting for flushes to complete. Returns true if flush should be triggered (soft limit exceeded).

pub fn release_memory(&self, bytes: u64)

Release memory after flush completes

Signals any blocked writers to retry.

pub fn memory_usage(&self) -> u64

Get current buffer memory usage

pub fn usage_percent(&self) -> f64

Get usage as percentage of limit

pub fn is_under_pressure(&self) -> bool

Check if under soft limit pressure

pub fn stats(&self) -> &WriteBufferStats

Get statistics