Enum FlushPolicy 

#[non_exhaustive]
pub enum FlushPolicy {
    Batch(usize),
    Interval(Duration),
    BatchOrInterval {
        batch_size: usize,
        interval: Duration,
    },
    BatchOrIntervalMin {
        batch_size: usize,
        min_batch: usize,
        interval: Duration,
        max_interval: Duration,
    },
    Manual,
}

When to auto-flush pending items from memory to a segment file.

Passed to SegmentConfig via its flush_policy field. Replaces the pre-v0.4.0 silent combination of two separate fields (max_batch_events and flush_interval_secs) that OR’d together without telling the caller which trigger fired.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Batch(usize)

Flush as soon as batch_size items are buffered. No interval trigger.

Interval(Duration)

Flush as soon as interval has elapsed since the last flush. No batch trigger.

Timing note: the interval clock starts at open(), not at the first append(). If the buffer sits idle after construction, the first append will immediately trigger a flush.

BatchOrInterval

Flush when EITHER batch_size items are buffered OR interval has elapsed since the last flush — whichever fires first. This is the pre-v0.4.0 default behavior.

Caution: during low-throughput periods this policy creates tiny segment files (as small as 1 event) every interval. Use BatchOrIntervalMin to suppress interval flushes below a minimum batch threshold.

Timing note: the interval clock starts at open(), not at the first append().

Fields

batch_size: usize

In-memory item count threshold.

interval: Duration

Max time between flushes.

BatchOrIntervalMin

Flush when batch_size items are buffered, OR when interval has elapsed AND at least min_batch items are pending, OR when max_interval has elapsed regardless of pending count.

This policy prevents tiny segment files during low-throughput periods: the interval timer only triggers a flush if enough events have accumulated to be worth writing. The max_interval safety valve ensures events don’t sit in memory indefinitely during idle periods (protecting crash-recovery latency).

Example: batch_size=256, min_batch=10, interval=5s, max_interval=60s means: flush immediately at 256 events; every 5s, flush only if 10+ events are pending; every 60s, flush everything regardless.

Fields

batch_size: usize

In-memory item count threshold for immediate flush.

min_batch: usize

Minimum pending items before an interval-triggered flush fires. Prevents writing tiny segments during low-throughput periods.

interval: Duration

Interval after which to flush if at least min_batch items accumulated.

max_interval: Duration

Absolute maximum time between flushes, regardless of pending count. Ensures events don’t sit in memory indefinitely during idle periods.

Manual

Never auto-flush. The caller must call SegmentBuffer::flush explicitly to make appends durable. Useful for tests and for callers that want absolute control over write amplification.

Implementations

impl FlushPolicy

pub fn validate(&self)

Check internal constraints that, if violated, make the policy behave incorrectly (e.g. an interval trigger that can never fire).

Currently validates:

• BatchOrIntervalMin: min_batch <= batch_size and interval <= max_interval.

In debug builds, violations panic via debug_assert!. In release builds this method is a no-op — the policy is still usable but may behave surprisingly if the constraints are violated. Call this from any construction path that receives caller-supplied values.

Panics

Panics in debug builds if a constraint is violated.

Trait Implementations

impl Clone for FlushPolicy

fn clone(&self) -> FlushPolicy

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for FlushPolicy

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

Formats the value using the given formatter.

impl Default for FlushPolicy

fn default() -> Self

Returns the “default value” for a type.

impl Display for FlushPolicy

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

Human-readable representation suitable for logging and diagnostics.

The format is intentionally compact and stable across releases so operators can parse it in log-scraping tools without breakage.

impl Eq for FlushPolicy

impl PartialEq for FlushPolicy

fn eq(&self, other: &FlushPolicy) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for FlushPolicy