Struct ReplicationConfig 

pub struct ReplicationConfig {
    pub factor: u8,
    pub placement: PlacementStrategy,
    pub heartbeat_ms: u64,
    pub leader_pinned: Option<NodeId>,
    pub on_under_capacity: UnderCapacity,
    pub replication_budget_fraction: f32,
    pub default_bandwidth_class: BandwidthClass,
    pub background_fraction: f32,
}

Per-channel replication opt-in. The default-when-set ReplicationConfig::new gives sensible values (factor 3, 500 ms heartbeat, standard placement, withdraw-under-capacity, 0.5 NIC peak budget); the with_* builders adjust individual fields.

validate() runs the full set of invariants pinned at module top — callers should invoke it before committing the config to a Redex so a malformed config can’t leak into the coordinator’s hot loop.

Fields

factor: u8

Replication factor — number of replicas (including the leader) maintained. Must satisfy REPLICATION_FACTOR_MIN <= factor <= REPLICATION_FACTOR_MAX. Default REPLICATION_FACTOR_DEFAULT.

placement: PlacementStrategy

How replicas are chosen when first instantiated and on roster change. Default PlacementStrategy::Standard.

heartbeat_ms: u64

Heartbeat interval between leader and replicas, in milliseconds. Must satisfy heartbeat_ms >= HEARTBEAT_MS_MIN. Default HEARTBEAT_MS_DEFAULT.

leader_pinned: Option<NodeId>

Optional override pinning the leader to a specific node. None = leader is the channel’s natural publisher (the ChannelPublisher home). When Some(node), the override applies on every leader election; the deterministic nearest-RTT election picks node whenever it’s healthy.

on_under_capacity: UnderCapacity

Behavior when a replica falls below the channel’s retention requirement due to local disk pressure. Default UnderCapacity::Withdraw.

replication_budget_fraction: f32

Bandwidth budget for replication-sync I/O, as a fraction of measured NIC peak. Must lie in (0.0, 1.0] and be finite. Default REPLICATION_BUDGET_FRACTION_DEFAULT.

default_bandwidth_class: BandwidthClass

v0.3 Phase D2: per-channel default BandwidthClass the runtime stamps on every emitted SyncRequest unless the caller explicitly overrides it. Receivers honor the per-request value in preference to this default. Default BandwidthClass::Foreground.

background_fraction: f32

v0.3 Phase D2: admission-gate parameter — the fraction of the bandwidth bucket reserved against Background requests. A Background request is admitted only when available >= (1 - background_fraction) * capacity. Operators tune per channel: hot channels set this low (tight Background bound, more Foreground headroom); archival channels set it high (give Background more room). Must lie in [0.0, 1.0) and be finite (1.0 would deny every Background request unconditionally and is rejected; the v0.3 Phase D4 anti-starvation hatch one- shot bypasses the gate after 60 s starve regardless of the configured value). Default BACKGROUND_FRACTION_DEFAULT.

Implementations

impl ReplicationConfig

pub fn new() -> Self

Construct a ReplicationConfig with all defaults — factor 3, 500 ms heartbeat, standard placement, withdraw-under- capacity, 0.5 NIC peak budget, leader = natural publisher.

pub fn with_factor(self, factor: u8) -> Self

Set the replication factor. Validate via Self::validate before committing the config to a Redex.

pub fn with_placement(self, placement: PlacementStrategy) -> Self

Set the placement strategy.

pub fn with_heartbeat_ms(self, heartbeat_ms: u64) -> Self

Set the heartbeat cadence in milliseconds.

pub fn with_leader_pinned(self, leader: Option<NodeId>) -> Self

Pin the leader to a specific NodeId. Pass None to fall back to “leader = natural publisher.”

pub fn with_on_under_capacity(self, on_under_capacity: UnderCapacity) -> Self

Set the under-capacity policy.

pub fn with_replication_budget_fraction(self, fraction: f32) -> Self

Set the replication-sync I/O budget as a fraction of measured NIC peak.

pub fn with_default_bandwidth_class(self, class: BandwidthClass) -> Self

Set the per-channel default BandwidthClass the runtime stamps on emitted SyncRequest frames. v0.3 Phase D2 — defaults to Foreground.

pub fn with_background_fraction(self, fraction: f32) -> Self

Set the per-channel background_fraction — the share of the bandwidth bucket reserved against Background admission. Must lie in [0.0, 1.0) and be finite (1.0 is rejected as it would deny every Background request unconditionally). Default BACKGROUND_FRACTION_DEFAULT (0.3).

pub fn effective_factor(&self) -> u8

Effective replica count — placement may override factor: PlacementStrategy::Pinned pins the count to the length of its Vec<NodeId> regardless of the configured factor (the operator’s explicit list wins over the numeric hint). All other strategies honor factor.

pub fn validate(&self) -> Result<(), ReplicationConfigError>

Run every documented invariant. Returns Ok(()) when the config is safe to commit; otherwise a typed ReplicationConfigError naming the first violation. Pin in tests; surface to operators on Redex::open_file.

Trait Implementations

impl Clone for ReplicationConfig

fn clone(&self) -> ReplicationConfig

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ReplicationConfig

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

Formats the value using the given formatter.

impl Default for ReplicationConfig

fn default() -> Self

Returns the “default value” for a type.

impl PartialEq for ReplicationConfig

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for ReplicationConfig