Struct IdPool 

pub(crate) struct IdPool {
    next: u64,
    upper: u64,
}

A pool of pre-allocated user IDs to avoid per-DDL persist writes.

IDs in the range [next, upper) are available for allocation. When exhausted, the pool must be refilled via the catalog.

Correctness

The pool is owned by Coordinator, which processes all requests on a single-threaded event loop. Because every access requires &mut self on the coordinator, there is no concurrent access to the pool — no additional synchronization is needed.

Global ID uniqueness is guaranteed because each refill calls Catalog::allocate_user_ids, which performs a durable persist write that atomically reserves the entire batch before any IDs from it are handed out. If the process crashes after a refill but before all pre-allocated IDs are consumed, the unused IDs form harmless gaps in the sequence — user IDs are not required to be contiguous.

This guarantee holds even if multiple environmentd processes run concurrently. Each process has its own independent pool, but every refill goes through the shared persist-backed catalog, which serializes allocations across all callers. Two processes will therefore never receive overlapping ID ranges, for the same reason they could not before this pool existed.

Fields

next: u64

upper: u64

Implementations

impl IdPool

pub fn empty() -> Self

Creates an empty pool.

pub fn allocate(&mut self) -> Option<u64>

Allocates a single ID from the pool, returning None if exhausted.

pub fn allocate_many(&mut self, n: u64) -> Option<Vec<u64>>

Allocates n consecutive IDs from the pool, returning None if insufficient IDs remain.

pub fn remaining(&self) -> u64

Returns the number of IDs remaining in the pool.

pub fn refill(&mut self, next: u64, upper: u64)

Refills the pool with the given range [next, upper).

Trait Implementations

impl Debug for IdPool

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.