Stats - a runtime statistics endpoint

Layer: L7 Application · Build flags: PC_ENABLE_STATS

What this example teaches

server.stats(slot_id) writes a JSON snapshot of the server's live state - uptime, request and error counts, connection-pool usage, and free heap - straight to the response. Wire it to a route and you have a zero-effort health/diagnostics endpoint. The same counters back the Prometheus exporter in PrometheusMetrics; this one emits plain JSON.

One call renders the snapshot:

server.on("/stats", HttpMethod::HTTP_GET, [](uint8_t id, HttpReq *) { server.stats(id); });

The JSON is written directly into the response buffer (no heap), so it is safe to poll frequently.

Build and run

pio ci --board=esp32dev --project-option="framework=arduino" \
  --project-option="build_flags=-DPC_ENABLE_STATS=1" \
  --lib="." examples/L7-Application/Stats/Stats.ino

curl http://<ip>/stats   # JSON: uptime, requests, errors, pool usage, free heap

Annotated source

The complete sketch (Stats.ino), reproduced verbatim with added explanatory comments:

// Copyright (C) 2026 Douglas Quigg (dstroy0) <dquigg123@gmail.com>
// SPDX-License-Identifier: AGPL-3.0-or-later
 
#define PC_ENABLE_STATS 1
 
#include "protocore.h"
#include "network_drivers/physical/physical.h"
 
static const char *SSID = "YOUR_SSID";
static const char *PASSWORD = "YOUR_PASSWORD";
 
PC server;
 
void setup()
{
    Serial.begin(115200);
    init_wifi_physical(SSID, PASSWORD);
    Serial.print("Connecting to WiFi");
    while (!wifi_ready())
    {
        delay(250);
        Serial.print('.');
    }
    uint32_t ip = pc_net_egress_ip(); // library egress IP (network byte order), no Arduino WiFi
    Serial.printf("IP: %u.%u.%u.%u\n", (unsigned)(ip & 0xFF), (unsigned)((ip >> 8) & 0xFF),
                  (unsigned)((ip >> 16) & 0xFF), (unsigned)((ip >> 24) & 0xFF));
 
    // Serve a live JSON snapshot of the server's counters.
    server.on("/stats", HttpMethod::HTTP_GET, [](uint8_t id, HttpReq *) { server.stats(id); });
    server.begin(80);
}
 
void loop()
{
    server.handle();
}