Add node/fork endpoint to HTTP API, tidy

beacon_node/http_server/src/metrics.rs

@@ -0,0 +1,57 @@
+use crate::key::BeaconChainKey;
+use beacon_chain::{BeaconChain, BeaconChainTypes};
+use iron::prelude::*;
+use iron::{status::Status, Handler, IronResult, Request, Response};
+use persistent::Read;
+use prometheus::{Encoder, IntCounter, Opts, Registry, TextEncoder};
+use slot_clock::SlotClock;
+use std::sync::Arc;
+use types::Slot;
+
+pub fn build_handler<T: BeaconChainTypes + 'static>(
+    beacon_chain: Arc<BeaconChain<T>>,
+) -> impl Handler {
+    let mut chain = Chain::new(handle_metrics::<T>);
+
+    chain.link(Read::<BeaconChainKey<T>>::both(beacon_chain));
+
+    chain
+}
+
+/// Handle a request for Prometheus metrics.
+///
+/// Returns a text string containing all metrics.
+fn handle_metrics<T: BeaconChainTypes + 'static>(req: &mut Request) -> IronResult<Response> {
+    let beacon_chain = req.get::<Read<BeaconChainKey<T>>>().unwrap();
+
+    let r = Registry::new();
+
+    let present_slot = if let Ok(Some(slot)) = beacon_chain.slot_clock.present_slot() {
+        slot
+    } else {
+        Slot::new(0)
+    };
+    register_and_set_slot(
+        &r,
+        "present_slot",
+        "direct_slock_clock_reading",
+        present_slot,
+    );
+
+    // Gather the metrics.
+    let mut buffer = vec![];
+    let encoder = TextEncoder::new();
+    let metric_families = r.gather();
+    encoder.encode(&metric_families, &mut buffer).unwrap();
+
+    let prom_string = String::from_utf8(buffer).unwrap();
+
+    Ok(Response::with((Status::Ok, prom_string)))
+}
+
+fn register_and_set_slot(registry: &Registry, name: &str, help: &str, slot: Slot) {
+    let counter_opts = Opts::new(name, help);
+    let counter = IntCounter::with_opts(counter_opts).unwrap();
+    registry.register(Box::new(counter.clone())).unwrap();
+    counter.inc_by(slot.as_u64() as i64);
+}