Struct PoolPressureMonitorConfig 

pub struct PoolPressureMonitorConfig {
    pub enabled: bool,
    pub min_pool_size: u32,
    pub max_pool_size: u32,
    pub target_queue_depth: u32,
    pub scale_up_step: u32,
    pub scale_down_step: u32,
    pub scale_down_idle_ratio: f64,
    pub tuning_interval_ms: u64,
    pub samples_before_action: u32,
}

Configuration for connection pool pressure monitoring with scaling recommendations.

This monitor samples PoolMetrics at a configurable interval and emits scaling recommendations via fraiseql_pool_tuning_* Prometheus metrics and log lines. It does not resize the pool at runtime — the underlying deadpool-postgres library does not expose a resize() API.

To act on recommendations: adjust max_connections in fraiseql.toml and restart the server. Active pool resizing is tracked as future work (migration to bb8 with resize() support).

Recommendation mode

All scaling decisions are advisory. When a recommendation fires, the monitor:

• Updates fraiseql_pool_tuning_adjustments_total (Prometheus counter)
• Logs the recommendation at WARN level
• Updates recommended_size() for external inspection

To suppress the WARN noise in environments that already tune the pool manually, set enabled = false in [pool_tuning].

Fields

enabled: bool

Enable adaptive pool sizing. Default: false.

min_pool_size: u32

Minimum pool size. The tuner never shrinks below this value. Default: 5.

max_pool_size: u32

Maximum pool size. The tuner never grows above this value. Default: 50.

target_queue_depth: u32

Maximum acceptable queue depth before scaling up. Default: 3.

scale_up_step: u32

Connections to add per scale-up step. Default: 5.

scale_down_step: u32

Connections to remove per scale-down step. Default: 2.

scale_down_idle_ratio: f64

Minimum idle ratio (idle / total) before considering a scale-down. Default: 0.5 (50% idle connections triggers potential shrink).

tuning_interval_ms: u64

Polling interval in milliseconds. Default: 30 000 (30 s).

samples_before_action: u32

Consecutive samples above threshold required before acting. Default: 3.

Implementations

impl PoolPressureMonitorConfig

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

Validate configuration invariants.

Errors

Returns an error string if:

• min_pool_size >= max_pool_size
• scale_up_step == 0 or scale_down_step == 0
• scale_down_idle_ratio is outside [0.0, 1.0]
• tuning_interval_ms < 100

Trait Implementations

impl Clone for PoolPressureMonitorConfig

fn clone(&self) -> PoolPressureMonitorConfig

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for PoolPressureMonitorConfig

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

Formats the value using the given formatter.

impl Default for PoolPressureMonitorConfig

fn default() -> Self

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for PoolPressureMonitorConfig

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for PoolPressureMonitorConfig

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

where __S: Serializer,

Serialize this value into the given Serde serializer.