feat: Integrate lurk-metrics package into project workspace (PoC)

- Added `lurk-metrics` package to the project and updated `metrics` package to version `0.21.1` in workspace
- Modified `lurk-metrics` project to use workspace `metrics` dependency instead of previous external version
- Integrated `lurk_metrics::MetricsSink` initialization into the main function, displaying metrics in the log.

Cargo.toml

@@ -29,6 +29,8 @@ indexmap = { version = "1.9.3", features = ["rayon"] }
 itertools = "0.9"
 log = { workspace = true }
 lurk-macros = { path = "lurk-macros" }
+lurk-metrics = { path = "lurk-metrics" }
+metrics = { workspace = true }
 neptune = { workspace = true, features = ["arity2","arity4","arity8","arity16","pasta","bls"] }
 nom = "7.1.3"
 nom_locate = "4.1.0"
@@ -105,6 +107,7 @@ blstrs = "0.7.0"
 clap = "4.3.17"
 ff = "0.13"
 log = "0.4.19"
+metrics = "0.21.1"
 neptune = { version = "10.0.0" }
 nova = { package = "nova-snark", version = "0.22", default-features = false }
 once_cell = "1.18.0"

lurk-metrics/Cargo.toml

@@ -8,7 +8,7 @@ description = "Metrics Sink for lurk"
 repository = "https://github.com/lurk-lab/lurk-rs"
 
 [dependencies]
-metrics = "0.18"
+metrics = { workspace = true }
 once_cell = { workspace = true }
 log = { workspace = true }
 hdrhistogram = { version = "7.5.2", default-features = false }

lurk-metrics/src/data.rs

@@ -77,7 +77,7 @@ pub enum MetricType {
 pub enum Metric {
     Counter(ValueAndCount<u64>),
     Gauge(ValueAndCount<f64>),
-    // We currently have a fixed scaling configuration for histograms that is tuned for
+    // Fixed scaling configuration for histograms, tuned for
     // microsecond-scale latency timers. It saturates at 60 seconds.
     Histogram(hdrhistogram::Histogram<u64>),
 }

src/eval/reduction.rs

@@ -67,6 +67,9 @@ fn reduce_with_witness_inner<F: LurkField, C: Coprocessor<F>>(
     c: &NamedConstants<F>,
     lang: &Lang<F, C>,
 ) -> Result<(Control<F>, Option<Ptr<F>>), ReductionError> {
+    // sanity-check: this should return the number of iterations 
+    // of the last 5s of computation
+    metrics::counter!("evaluation", 1, "type" => "step");
     let mut closure_to_extend = None;
 
     Ok((
@@ -105,6 +108,8 @@ fn reduce_with_witness_inner<F: LurkField, C: Coprocessor<F>>(
                         // CIRCUIT: sym_is_self_evaluating
                         Control::ApplyContinuation(expr, env, cont)
                     } else {
+                        // Register a symbol lookup
+                        metrics::counter!("evaluation", 1, "type" => "sym lookup step");
                         // Otherwise, look for a matching binding in env.
 
                         // CIRCUIT: sym_otherwise
@@ -161,6 +166,7 @@ fn reduce_with_witness_inner<F: LurkField, C: Coprocessor<F>>(
 
                                                 // CIRCUIT: with_sym_binding_unmatched_new_lookup
                                                 {
+                                                    metrics::counter!("evaluation", 1, "type" => "push lookup continuation");
                                                     Control::Return(
                                                         expr,
                                                         smaller_env,
@@ -1190,16 +1196,19 @@ fn apply_continuation<F: LurkField>(
             }
             _ => unreachable!(),
         },
-        ContTag::Lookup => match cont_witness
-            .fetch_named_cont(ContName::ApplyContinuation, store, &cont)
-            .ok_or_else(|| store::Error("Fetch failed".into()))?
-        {
-            Continuation::Lookup {
-                saved_env,
-                continuation,
-            } => Control::MakeThunk(result, saved_env, continuation),
-            _ => unreachable!(),
-        },
+        ContTag::Lookup => {
+            metrics::counter!("evaluation", 1,  "type" => "pop lookup continuation");
+            match cont_witness
+                .fetch_named_cont(ContName::ApplyContinuation, store, &cont)
+                .ok_or_else(|| store::Error("Fetch failed".into()))?
+            {
+                Continuation::Lookup {
+                    saved_env,
+                    continuation,
+                } => Control::MakeThunk(result, saved_env, continuation),
+                _ => unreachable!(),
+            }
+        }
         ContTag::Tail => match cont_witness
             .fetch_named_cont(ContName::ApplyContinuation, store, &cont)
             .ok_or_else(|| store::Error("Fetch failed".into()))?

src/main.rs

@@ -3,6 +3,9 @@ mod cli;
 use anyhow::Result;
 
 fn main() -> Result<()> {
+    // this handle should be held until the end of the program,
+    // do not replace by let _ = ...
+    let _metrics_handle = lurk_metrics::MetricsSink::init();
     pretty_env_logger::init();
     cli::parse_and_run()
 }