Metrics API ​
Thread-safe, allocation-free request/response metrics using atomic operations.
Located in src/web/metrics/ (registry.zig, snapshot.zig).
Registry ​
httpx.metrics.Registry (aliased as httpx.Metrics) holds atomic counters, gauges, and a latency histogram. The server owns one (server.metricsRegistry) and records automatically; use the API below for custom instrumentation.
| Method | Description |
|---|---|
recordRequest() | Increment total requests (+1 in-flight) |
recordRequestMethod(method) | Count by method (GET, POST, …) |
recordResponse(bytes) | Increment responses, decrement in-flight, add bytes out |
recordResponseFull(status, durationNs, bytes) | Response + status class + latency sample |
recordStatus(status) | Bucket a status code (status2xx…status5xx) |
recordError() | Increment errors (decrements in-flight) |
recordBytesIn(n) / recordBytesOut(n) | Byte counters |
recordTimeout() | Increment timeouts |
connectionOpened() / connectionClosed() | Active-connection gauge (underflow-safe) |
reset() | Reset all counters to zero |
snapshot() | Return an immutable MetricsSnapshot |
render(writer) / renderPrometheus(writer) | Prometheus 0.0.4 text exposition |
Root-level aliases: httpx.Metrics, httpx.MetricsSnapshot, httpx.ServerSnapshot, httpx.ClientSnapshot, httpx.Counter, httpx.Gauge, httpx.Histogram.
MetricsSnapshot ​
Immutable point-in-time copy. All multi-word fields are camelCase:
| Field | Type | Description |
|---|---|---|
requestsTotal | u64 | Total requests recorded |
responsesTotal | u64 | Total responses recorded |
errorsTotal | u64 | Total errors |
timeoutsTotal | u64 | Total timeouts |
bytesIn / bytesOut | u64 | Byte counters |
activeConnections / activeRequests | u64 | Current gauges |
status2xx / status3xx / status4xx / status5xx | u64 | Status class counts |
methodGet / methodPost / methodPut / methodDelete / methodPatch / methodHead / methodOptions / methodOther | u64 | Per-method counts |
durationCount | u64 | Latency sample count |
durationSumSeconds | f64 | Latency sum in seconds |
durationBuckets | [11]u64 | Cumulative histogram buckets |
| Method | Returns | Description |
|---|---|---|
errorRate() | f64 | errorsTotal / requestsTotal (0.0 when empty) |
averageLatencySeconds() | f64 | Mean latency in seconds |
averageLatencyMs() | f64 | Mean latency in milliseconds |
ServerSnapshot ​
server.snapshot() returns uptime, gauges, totals, and the embedded metrics: MetricsSnapshot. errorRate() and requestsPerSecond() are computed from the snapshot (no duplicated stored state).
Prometheus exposition ​
renderPrometheus emits standard snake_case wire names (http_requests_total, http_requests_by_method_total{method="GET"}, http_responses_by_status_total, http_request_duration_seconds_bucket/count/sum). Wire names follow the Prometheus convention; Zig identifiers stay camelCase.