From 4c6c44a2ea1bf5e8c0fdb2a8c0a7be676a9096f0 Mon Sep 17 00:00:00 2001
From: Christopher Roddy <76755988+cjrkoa@users.noreply.github.com>
Date: Wed, 18 Oct 2023 23:06:23 -0400
Subject: [PATCH] prometheus metrics

fixes #1094
in progress
---
 Cargo.lock                             | 22 ++++++++++++++++++++++
 Cargo.toml                             |  1 +
 crates/ott-balancer-bin/Cargo.toml     |  1 +
 crates/ott-balancer-bin/src/service.rs | 22 +++++++++++++++++++++-
 4 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/Cargo.lock b/Cargo.lock
index 9fc05055e..fe63f9b29 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1595,6 +1595,7 @@ dependencies = [
  "ott-balancer-protocol",
  "ott-common",
  "pin-project",
+ "prometheus",
  "rand 0.8.5",
  "reqwest",
  "route-recognizer",
@@ -1795,6 +1796,21 @@ dependencies = [
  "yansi",
 ]
 
+[[package]]
+name = "prometheus"
+version = "0.13.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "449811d15fbdf5ceb5c1144416066429cf82316e2ec8ce0c1f6f8a02e7bbcf8c"
+dependencies = [
+ "cfg-if 1.0.0",
+ "fnv",
+ "lazy_static",
+ "memchr",
+ "parking_lot 0.12.1",
+ "protobuf",
+ "thiserror",
+]
+
 [[package]]
 name = "prost"
 version = "0.11.9"
@@ -1827,6 +1843,12 @@ dependencies = [
  "prost",
 ]
 
+[[package]]
+name = "protobuf"
+version = "2.28.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "106dd99e98437432fed6519dedecfade6a06a73bb7b2a1e019fdd2bee5778d94"
+
 [[package]]
 name = "quick-error"
 version = "1.2.3"
diff --git a/Cargo.toml b/Cargo.toml
index 87eaba1f5..715b6e8d3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -19,6 +19,7 @@ once_cell = "1.17.1"
 ott-common = { path = "crates/ott-common" }
 ott-balancer-protocol = { path = "crates/ott-balancer-protocol" }
 pin-project = "1.0.12"
+prometheus = "0.13.3"
 rand = "0.8.5"
 reqwest = { version = "0.11.17", features = ["json", "stream", "rustls-tls"] }
 serde = { version = "1", features = ["derive", "rc"] }
diff --git a/crates/ott-balancer-bin/Cargo.toml b/crates/ott-balancer-bin/Cargo.toml
index b514c9c47..8456b4a2c 100644
--- a/crates/ott-balancer-bin/Cargo.toml
+++ b/crates/ott-balancer-bin/Cargo.toml
@@ -33,4 +33,5 @@ ott-balancer-protocol.workspace = true
 route-recognizer = "0.3.1"
 once_cell.workspace = true
 pin-project.workspace = true
+prometheus.workspace = true
 trust-dns-resolver = { version = "0.22.0", features = ["system-config"] }
diff --git a/crates/ott-balancer-bin/src/service.rs b/crates/ott-balancer-bin/src/service.rs
index a6a6e5aec..abfc0f96f 100644
--- a/crates/ott-balancer-bin/src/service.rs
+++ b/crates/ott-balancer-bin/src/service.rs
@@ -15,6 +15,7 @@ use reqwest::Url;
 use route_recognizer::Router;
 use tokio::sync::RwLock;
 use tracing::{debug, error, info, warn};
+use prometheus::{Opts, Registry, Counter, TextEncoder, Encoder};
 
 use crate::balancer::{BalancerContext, BalancerLink};
 use crate::client::client_entry;
@@ -83,7 +84,26 @@ impl Service<Request<IncomingBody>> for BalancerService {
                     .join("\n");
                     mk_response(rendered)
                 }
-                "metrics" => mk_response("TODO: prometheus metrics".to_owned()),
+                "metrics" => {
+                    // Create a Counter.
+                    let counter_opts = Opts::new("test_counter", "test counter help");
+                    let counter = Counter::with_opts(counter_opts).unwrap();
+
+                    // Create a Registry and register Counter.
+                    let r = Registry::new();
+                    r.register(Box::new(counter.clone())).unwrap();
+
+                    // Inc.
+                    counter.inc();
+
+                    // Gather the metrics.
+                    let mut buffer = vec![];
+                    let encoder = TextEncoder::new();
+                    let metric_families = r.gather();
+                    encoder.encode(&metric_families, &mut buffer).unwrap();
+
+                    mk_response(String::from_utf8(buffer).unwrap().to_owned())
+                },
                 "room" => {
                     let Some(room_name) = route.params().find("room_name") else {
                         return Ok(not_found());