tracing_cache/
config.rs

1//! Tunable knobs for the cache + driver.
2
3/// Default number of in-flight slab shards (must be a power of two).
4pub const DEFAULT_LANE_COUNT: usize = 16;
5
6/// Optional knobs for the cache + driver.  Pass to
7/// [`crate::SpanCache::with_config`] /
8/// [`crate::SpanCache::with_predicate_and_config`]; the no-config
9/// constructors use [`CacheConfig::default`].
10#[derive(Debug, Clone)]
11pub struct CacheConfig {
12    /// Number of in-flight slab shards.  Silently clamped to `[1, 256]` and
13    /// rounded up to the next power of two (so `3` becomes `4`, `200`
14    /// becomes `256`, `1000` is capped at `256`).  More lanes = more
15    /// concurrent writers without contention; each lane adds a
16    /// `Mutex<Slab<SpanRecord>>` plus consumes one more bit of the encoded
17    /// `tracing::span::Id` for shard selection.
18    /// Default: [`DEFAULT_LANE_COUNT`].
19    pub lane_count: usize,
20    /// Flush the thread-local PENDING buffer to the spillway after this many
21    /// span closures on a single thread.  Smaller = lower visibility latency
22    /// for low-traffic threads at the cost of more spillway sends.  Default: 8.
23    pub pending_batch: usize,
24    /// Flush the driver's accumulated batch into the shared map after this
25    /// many spans have been received.  Smaller = lower visibility latency at
26    /// the cost of more map write-lock acquisitions.  Default: 600.
27    pub driver_batch: usize,
28    /// Upper bound on how long the driver will wait before flushing whatever
29    /// it has, even if `driver_batch` hasn't been reached.  Default: 1 second.
30    pub driver_interval: std::time::Duration,
31    /// Soft upper bound on each spillway channel (span + event) that moves
32    /// closed records from producer threads to the driver.  When producers
33    /// outrun the driver (e.g. many cores + few async workers), this caps
34    /// spillway's internal buffers so the producer can't grow process
35    /// memory unboundedly.  `send_many` rejects whole batches when the
36    /// limit is hit and `flush_pending` drops the rejected drain (logging
37    /// at DEBUG).  Decoupled from the user-facing `capacity` (the
38    /// BTreeMap bound): the channel is intermediate buffering and only
39    /// needs enough headroom for normal bursts.  Default: 65536.
40    pub channel_capacity: u64,
41}
42
43impl Default for CacheConfig {
44    fn default() -> Self {
45        Self {
46            lane_count: DEFAULT_LANE_COUNT,
47            pending_batch: 8,
48            driver_batch: 600,
49            driver_interval: std::time::Duration::from_secs(1),
50            channel_capacity: 65536,
51        }
52    }
53}
tracing_cache/config.rs

tracing_cache/
config.rs
