Struct WatchConfig 

pub struct WatchConfig {
    pub event_queue_size: usize,
    pub watcher_buffer_size: usize,
    pub enable_metrics: bool,
}

Configuration for the Watch mechanism that monitors key changes

The watch system allows clients to monitor specific keys for changes with minimal overhead on the write path. It uses a lock-free event queue and configurable buffer sizes to balance performance and memory usage.

Performance Characteristics

• Write path overhead: < 0.01% with 100+ watchers
• Event notification latency: typically < 100μs end-to-end
• Memory per watcher: ~2.4KB with default buffer size

Configuration Example

[raft.watch]
event_queue_size = 1000
watcher_buffer_size = 10
enable_metrics = false

Fields

event_queue_size: usize

Buffer size for the global event queue shared across all watchers

This queue sits between the write path and the dispatcher thread. A larger queue reduces the chance of dropped events under burst load, but increases memory usage.

Performance Impact:

• Memory: ~24 bytes per slot (key + value pointers + event type)
• Default 1000 slots ≈ 24KB memory

Tuning Guidelines:

• Low traffic (< 1K writes/sec): 500-1000
• Medium traffic (1K-10K writes/sec): 1000-2000
• High traffic (> 10K writes/sec): 2000-5000

Default: 1000

watcher_buffer_size: usize

Buffer size for each individual watcher’s channel

Each registered watcher gets its own channel to receive events. Smaller buffers reduce memory usage but increase the risk of dropping events for slow consumers.

Performance Impact:

• Memory: ~240 bytes per slot per watcher
• 10 slots × 100 watchers = ~240KB total

Tuning Guidelines:

• Fast consumers (< 1ms processing): 5-10
• Normal consumers (1-10ms processing): 10-20
• Slow consumers (> 10ms processing): 20-50

Default: 10

enable_metrics: bool

Enable detailed metrics and logging for watch operations

When enabled, logs warnings for dropped events and tracks watch performance metrics. Adds minimal overhead (~0.001%) but useful for debugging and monitoring.

Default: false (minimal overhead in production)

Implementations

impl WatchConfig

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

Validates watch configuration parameters

Trait Implementations

impl Clone for WatchConfig

fn clone(&self) -> WatchConfig

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for WatchConfig

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

Formats the value using the given formatter.

impl Default for WatchConfig

fn default() -> Self

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for WatchConfig

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for WatchConfig

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.