From 7171f0e94dd9225b50e66b1b8ff173e1ced6d966 Mon Sep 17 00:00:00 2001
From: Andy Nogueira <me@andynogueira.dev>
Date: Thu, 3 Jun 2021 07:41:24 -0400
Subject: [PATCH] Add `host` parameter to `telemetry` config (#1033)

* Fixing telemetry server listen host (#1032)

* Add `host` parameter for the telemetry server

* Gracefully exit when telemetry service fails to start

Co-authored-by: Romain Ruetschi <romain@informal.systems>
---
 config.toml                       |  1 +
 relayer-cli/src/commands/start.rs | 30 ++++++++++++++++++++++--------
 relayer/src/config.rs             |  2 ++
 telemetry/src/lib.rs              | 27 ++++++++++++++++++++++++---
 telemetry/src/server.rs           | 15 ++++++++++-----
 5 files changed, 59 insertions(+), 16 deletions(-)

diff --git a/config.toml b/config.toml
index b8aa553f4d..ae996198e9 100644
--- a/config.toml
+++ b/config.toml
@@ -7,6 +7,7 @@ log_level = 'info'
 
 [telemetry]
 enabled = true
+host = '127.0.0.1'
 port = 3001
 
 [[chains]]
diff --git a/relayer-cli/src/commands/start.rs b/relayer-cli/src/commands/start.rs
index 8190b776d6..72a780f4f8 100644
--- a/relayer-cli/src/commands/start.rs
+++ b/relayer-cli/src/commands/start.rs
@@ -1,3 +1,5 @@
+use std::error::Error;
+
 use abscissa_core::{Command, Options, Runnable};
 
 use ibc_relayer::config::Config;
@@ -13,27 +15,39 @@ impl Runnable for StartCmd {
     fn run(&self) {
         let config = app_config();
 
-        let supervisor = spawn_supervisor(config.clone());
-        match supervisor.run() {
+        match spawn_supervisor(config.clone()).and_then(|s| s.run()) {
             Ok(()) => Output::success_msg("done").exit(),
-            Err(e) => Output::error(e).exit(),
+            Err(e) => Output::error(format!("Hermes failed to start, last error: {}", e)).exit(),
         }
     }
 }
 
 #[cfg(feature = "telemetry")]
-fn spawn_supervisor(config: Config) -> Supervisor {
+fn spawn_supervisor(config: Config) -> Result<Supervisor, Box<dyn Error + Send + Sync>> {
     let state = ibc_telemetry::new_state();
 
     if config.telemetry.enabled {
-        ibc_telemetry::spawn(config.telemetry.port, state.clone());
+        let address = (config.telemetry.host.clone(), config.telemetry.port);
+
+        match ibc_telemetry::spawn(address, state.clone()) {
+            Ok((addr, _)) => {
+                info!(
+                    "telemetry service running, exposing metrics at {}/metrics",
+                    addr
+                );
+            }
+            Err(e) => {
+                error!("telemetry service failed to start: {}", e);
+                return Err(e);
+            }
+        }
     }
 
-    Supervisor::spawn(config, state)
+    Ok(Supervisor::spawn(config, state))
 }
 
 #[cfg(not(feature = "telemetry"))]
-fn spawn_supervisor(config: Config) -> Supervisor {
+fn spawn_supervisor(config: Config) -> Result<Supervisor, Box<dyn Error + Send + Sync>> {
     if config.telemetry.enabled {
         warn!(
             "telemetry enabled in the config but Hermes was built without telemetry support, \
@@ -42,5 +56,5 @@ fn spawn_supervisor(config: Config) -> Supervisor {
     }
 
     let telemetry = ibc_relayer::telemetry::TelemetryDisabled;
-    Supervisor::spawn(config, telemetry)
+    Ok(Supervisor::spawn(config, telemetry))
 }
diff --git a/relayer/src/config.rs b/relayer/src/config.rs
index bd5e9c40a0..b756eaab06 100644
--- a/relayer/src/config.rs
+++ b/relayer/src/config.rs
@@ -92,6 +92,7 @@ impl Default for GlobalConfig {
 #[derive(Clone, Debug, Deserialize, Serialize)]
 pub struct TelemetryConfig {
     pub enabled: bool,
+    pub host: String,
     pub port: u16,
 }
 
@@ -99,6 +100,7 @@ impl Default for TelemetryConfig {
     fn default() -> Self {
         Self {
             enabled: false,
+            host: "127.0.0.1".to_string(),
             port: 3001,
         }
     }
diff --git a/telemetry/src/lib.rs b/telemetry/src/lib.rs
index 446d566761..593901475c 100644
--- a/telemetry/src/lib.rs
+++ b/telemetry/src/lib.rs
@@ -1,7 +1,12 @@
 pub mod server;
 pub mod state;
 
-use std::{sync::Arc, thread::JoinHandle};
+use std::{
+    error::Error,
+    net::{SocketAddr, ToSocketAddrs},
+    sync::Arc,
+    thread::JoinHandle,
+};
 
 pub use crate::state::TelemetryState;
 
@@ -9,6 +14,22 @@ pub fn new_state() -> Arc<TelemetryState> {
     Arc::new(TelemetryState::default())
 }
 
-pub fn spawn(port: u16, state: Arc<TelemetryState>) -> JoinHandle<()> {
-    std::thread::spawn(move || server::run(state, port))
+pub fn spawn<A>(
+    address: A,
+    state: Arc<TelemetryState>,
+) -> Result<(SocketAddr, JoinHandle<()>), Box<dyn Error + Send + Sync>>
+where
+    A: ToSocketAddrs + Send + 'static,
+{
+    let server = server::listen(address, state);
+
+    match server {
+        Ok(server) => {
+            let address = server.server_addr();
+            let handle = std::thread::spawn(move || server.run());
+
+            Ok((address, handle))
+        }
+        Err(e) => Err(e),
+    }
 }
diff --git a/telemetry/src/server.rs b/telemetry/src/server.rs
index a0fc153e9d..31adcf2338 100644
--- a/telemetry/src/server.rs
+++ b/telemetry/src/server.rs
@@ -1,7 +1,7 @@
-use std::sync::Arc;
+use std::{error::Error, net::ToSocketAddrs, sync::Arc};
 
 use prometheus::{Encoder, TextEncoder};
-use rouille::Request;
+use rouille::{Request, Response, Server};
 
 use crate::state::TelemetryState;
 
@@ -20,8 +20,11 @@ impl Route {
     }
 }
 
-pub fn run(telemetry_state: Arc<TelemetryState>, port: u16) {
-    rouille::start_server(("localhost", port), move |request| {
+pub fn listen(
+    address: impl ToSocketAddrs,
+    telemetry_state: Arc<TelemetryState>,
+) -> Result<Server<impl Fn(&Request) -> Response>, Box<dyn Error + Send + Sync>> {
+    let server = Server::new(address, move |request| {
         match Route::from_request(request) {
             // The prometheus endpoint
             Route::Metrics => {
@@ -37,5 +40,7 @@ pub fn run(telemetry_state: Arc<TelemetryState>, port: u16) {
             // Return an empty response with a 404 status code.
             Route::Other => rouille::Response::empty_404(),
         }
-    })
+    })?;
+
+    Ok(server)
 }