Struct PoolSnapshot 

#[non_exhaustive]
pub struct PoolSnapshot {
    pub read_cache_entries: usize,
    pub read_cache_tombstones: usize,
    pub read_cache_hits: usize,
    pub read_cache_misses: usize,
    pub read_cache_capped: usize,
    pub read_cache_evictions: usize,
    pub read_cache_open_fails: usize,
    pub read_cache_max_entries: usize,
    pub ledger_writer_inits: usize,
}

Read-cache + ledger-writer snapshot.

Returned by crate::Engine::pool. All counters are monotonic since process start.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

read_cache_entries: usize

Active read-cache entries (open SQLite connections currently parked).

read_cache_tombstones: usize

Tombstoned entries waiting on in-flight reads to drain.

read_cache_hits: usize

Cache hits since process start.

A hit means a Phase 1 cached slot returned a definitive answer: Some from a Ready slot, or None from Tombstone. Opening and Evicted retry signals are not hits.

read_cache_misses: usize

Cache misses since process start.

Counted at most once per external read, even if internal retry loops run more than once. Under races, one external read may independently count a miss and later a hit if another reader installs the target slot first.

read_cache_capped: usize

Times a read saw the cache at cap after a miss.

Counted at most once per external read. The read may still evict a sampled cold slot instead of falling back to a transient slot.

read_cache_evictions: usize

Successful cap-full read-cache evictions since process start. Failed eviction attempts fall back to transient reads and are not counted.

read_cache_open_fails: usize

Read-cache slot open failures (SQLite open errors).

read_cache_max_entries: usize

Configured maximum cache entries.

ledger_writer_inits: usize

Ledger writer (re)initializations since process start.