Struct Metrics 

pub struct Metrics {

    pub http_requests: Family<HttpRequestLabels, Counter>,
    pub http_duration: Histogram,
    pub retrieve_latency: Histogram,
    pub commit_duration: Histogram,
    pub ingest_duration: Histogram,
    pub ingest_chunks: Counter,
    pub remote_fetch_blocks: Counter,
    pub remote_push_blocks: Counter,
    pub remote_advance_head: Family<AdvanceHeadLabels, Counter>,
    pub leiden_mode: Family<LeidenModeLabels, Counter>,
    pub leiden_debounce_effective: Gauge,
    pub leiden_storm_cap_effective: Gauge,
    pub leiden_delta_ratio_effective: Gauge,
    pub leiden_mode_current: Gauge,
    pub traverse_answer_hard_wall_ms_effective: Gauge,
    pub traverse_answer_max_hops_effective: Gauge,
    pub traverse_answer_hard_wall_exceeded: Counter,
    pub ppr_size_gate_skipped: Family<PprSizeGateLabels, Counter>,
    pub ppr_size_gate_threshold: Gauge,
    /* private fields */
}

Server-wide Prometheus metric registry.

Cloned into AppState behind an Arc so every handler gets a cheap reference. All metrics are registered up-front at construction time; there is no per-request registry mutation.

Fields

http_requests: Family<HttpRequestLabels, Counter>

Per-request counter keyed on (method, route, status).

http_duration: Histogram

Request-duration histogram (seconds). Buckets cover 1ms to 10s, which matches the typical range for local-first HTTP calls.

retrieve_latency: Histogram

Retrieve-handler latency histogram (seconds). Separate from http_duration so operators can track hybrid-retrieval cost without the embed / ingest traffic skewing the distribution.

commit_duration: Histogram

Commit-duration histogram (seconds). Covers the end-to-end write path including vector cache invalidation and redb fsync.

ingest_duration: Histogram

Ingest-pipeline duration histogram (seconds). Measured around the full POST /v1/ingest run: parse + chunk + extract + commit. Separate from http_duration + commit_duration so operators can see where the time went inside a single ingest.

ingest_chunks: Counter

Total chunks produced across every successful /v1/ingest call. Monotonic counter; divide by ingest_duration’s sample count for an average-chunks-per-ingest view.

remote_fetch_blocks: Counter

/remote/v1/fetch-blocks invocation counter.

remote_push_blocks: Counter

/remote/v1/push-blocks invocation counter (counts successful imports; auth and body-decode failures short-circuit earlier).

remote_advance_head: Family<AdvanceHeadLabels, Counter>

/remote/v1/advance-head invocation counter, bucketed by result (success | cas_mismatch | auth_fail).

leiden_mode: Family<LeidenModeLabels, Counter>

Gap 10 R3: Leiden recompute-mode counter, one increment per community_for_head serve. Labelled full | full_debounced | fallback_stale.

leiden_debounce_effective: Gauge

Gap 10 R6 (floor-a runtime): effective debounce window in ms.

leiden_storm_cap_effective: Gauge

Gap 10 R6 (floor-c, default 60): effective commit-storm cap.

leiden_delta_ratio_effective: Gauge

Gap 10 R6 (floor-c, default 0.5): effective delta-ratio force- full fraction, encoded as parts-per-ten-thousand.

leiden_mode_current: Gauge

Gap 10 current-mode indicator. 0=full, 1=full_debounced, 2=fallback_stale.

traverse_answer_hard_wall_ms_effective: Gauge

Gap 09 traverse_answer effective hard-wall ms (tunable mirror).

traverse_answer_max_hops_effective: Gauge

Gap 09 traverse_answer effective max-hops (tunable mirror).

traverse_answer_hard_wall_exceeded: Counter

Gap 09 traverse_answer hard-wall breach counter.

ppr_size_gate_skipped: Family<PprSizeGateLabels, Counter>

Gap 02 #17: PPR size-gate skipped count, labeled by reason. Closed vocabulary above_threshold | opted_out.

ppr_size_gate_threshold: Gauge

Gap 02 #17: effective threshold (mirrors mnem_core::ppr::PPR_DEFAULT_MAX_NODES tunable).

Implementations

impl Metrics

pub fn new() -> Self

Build a fresh registry with all four metric families registered.

Exponential buckets are used so the histograms cover several orders of magnitude with a constant bucket count. The first bucket (1ms for requests, 100us for retrieves/commits) matches the fastest plausible path; the last caps at 10s which is the operator-visible ceiling before a caller typically gives up.

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

Encode the current metrics as Prometheus text-exposition format.

Errors

Returns an std::fmt::Error only if the in-memory writer rejects a write, which cannot happen for String under normal conditions. Surfaces the error so callers can turn it into a 500 rather than panic.

Trait Implementations

impl Clone for Metrics

fn clone(&self) -> Metrics

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Default for Metrics

fn default() -> Self

Returns the “default value” for a type.