Struct CounterSet 

pub struct CounterSet { /* private fields */ }

A grouped set of related sharded counters.

Use CounterSet when one hot-path operation commonly updates several counters together, such as request count, bytes processed, and cache hits. The counters share the same shard row, so updates by the same thread touch a compact row while rows for different shards remain padded apart to avoid false sharing.

CounterSet still supports individual counter updates by index. Resolve those indexes once during construction and keep direct handles/indexes on the hot path.

use fast_telemetry::CounterSet;

const REQUESTS: usize = 0;
const BYTES: usize = 1;
const HITS: usize = 2;

let counters = CounterSet::new(4, 3);
counters.inc(REQUESTS);
counters.add(BYTES, 4096);
counters.inc(HITS);

assert_eq!(counters.sum(REQUESTS), 1);
assert_eq!(counters.sum(BYTES), 4096);
assert_eq!(counters.sum(HITS), 1);

Implementations

impl CounterSet

pub fn new(shards: usize, counters: usize) -> Self

Creates a grouped counter set with counters counters per shard.

Shards are padded by row instead of by cell, so related counters updated by the same thread sit contiguously while adjacent shard rows remain separated enough to avoid false sharing.

pub fn len(&self) -> usize

Returns the number of counters in each shard row.

pub fn is_empty(&self) -> bool

Returns true if there are no counters in the set.

pub fn inc(&self, counter_idx: usize)

Increments one counter in the current thread’s shard row.

pub fn add(&self, counter_idx: usize, value: isize)

Adds a value to one counter in the current thread’s shard row.

pub fn inc_all(&self)

Increments all counters in the current thread’s shard row.

pub fn add_all(&self, value: isize)

Adds the same value to all counters in the current thread’s shard row.

pub fn add_indices(&self, indexes: &[usize], value: isize)

Adds the same value to selected counters in the current thread’s shard row.

pub fn add_index_values(&self, updates: &[(usize, isize)])

Adds one value per selected counter in the current thread’s shard row.

pub fn add_all_indexed(&self, value: isize)

Adds the same value to all counters in the current thread’s shard row.

pub fn add_values(&self, values: &[isize])

Adds one value per counter in the current thread’s shard row.

pub fn sum(&self, counter_idx: usize) -> isize

Returns the sum for one counter across all shards.

pub fn sum_all(&self) -> isize

Returns the sum of all counters across all shards.

pub fn snapshot(&self) -> Vec<isize>

Returns one value per counter in index order.

pub fn sum_and_reset(&self, counter_idx: usize) -> isize

Resets one counter to zero and returns its previous sum.

Eventual Consistency

Writes that occur concurrently with sum_and_reset() may be attributed to the next window rather than the current one. No counts are lost; they simply shift to the next export window.

pub fn snapshot_and_reset(&self) -> Vec<isize>

Returns one value per counter in index order, then resets all counters.

Eventual Consistency

Writes that occur concurrently with snapshot_and_reset() may be attributed to the next window rather than the current one. No counts are lost; they simply shift to the next export window.