From c30958a32dbdc85244ddac563245b06ed0af8e71 Mon Sep 17 00:00:00 2001
From: phil <uniphil@gmail.com>
Date: Tue, 5 Aug 2025 16:11:44 -0400
Subject: [PATCH] healthcheck

---
 slingshot/src/error.rs       |  8 ++++++++
 slingshot/src/healthcheck.rs | 32 ++++++++++++++++++++++++++++++++
 slingshot/src/lib.rs         |  2 ++
 slingshot/src/main.rs        | 15 ++++++++++++++-
 slingshot/src/server.rs      |  3 ++-
 5 files changed, 58 insertions(+), 2 deletions(-)
 create mode 100644 slingshot/src/healthcheck.rs

diff --git a/slingshot/src/error.rs b/slingshot/src/error.rs
index 17eb0ee..67b3e07 100644
--- a/slingshot/src/error.rs
+++ b/slingshot/src/error.rs
@@ -46,6 +46,12 @@ pub enum IdentityError {
     RefreshQueueKeyError(&'static str),
 }
 
+#[derive(Debug, Error)]
+pub enum HealthCheckError {
+    #[error("failed to send checkin: {0}")]
+    HealthCheckError(#[from] reqwest::Error),
+}
+
 #[derive(Debug, Error)]
 pub enum MainTaskError {
     #[error(transparent)]
@@ -54,6 +60,8 @@ pub enum MainTaskError {
     ServerTaskError(#[from] ServerError),
     #[error(transparent)]
     IdentityTaskError(#[from] IdentityError),
+    #[error(transparent)]
+    HealthCheckError(#[from] HealthCheckError),
     #[error("firehose cache failed to close: {0}")]
     FirehoseCacheCloseError(foyer::Error),
 }
diff --git a/slingshot/src/healthcheck.rs b/slingshot/src/healthcheck.rs
new file mode 100644
index 0000000..fd60758
--- /dev/null
+++ b/slingshot/src/healthcheck.rs
@@ -0,0 +1,32 @@
+use crate::error::HealthCheckError;
+use reqwest::Client;
+use std::time::Duration;
+use tokio::time::sleep;
+use tokio_util::sync::CancellationToken;
+
+pub async fn healthcheck(
+    endpoint: String,
+    shutdown: CancellationToken,
+) -> Result<(), HealthCheckError> {
+    let client = Client::builder()
+        .user_agent(format!(
+            "microcosm slingshot v{} (dev: @bad-example.com)",
+            env!("CARGO_PKG_VERSION")
+        ))
+        .no_proxy()
+        .timeout(Duration::from_secs(10))
+        .build()?;
+
+    loop {
+        tokio::select! {
+            res = client.get(&endpoint).send() => {
+                let _ = res
+                    .and_then(|r| r.error_for_status())
+                    .inspect_err(|e| log::error!("failed to send healthcheck: {e}"));
+            },
+            _ = shutdown.cancelled() => break,
+        }
+        sleep(Duration::from_secs(51)).await;
+    }
+    Ok(())
+}
diff --git a/slingshot/src/lib.rs b/slingshot/src/lib.rs
index 2e5e687..7737374 100644
--- a/slingshot/src/lib.rs
+++ b/slingshot/src/lib.rs
@@ -1,12 +1,14 @@
 mod consumer;
 pub mod error;
 mod firehose_cache;
+mod healthcheck;
 mod identity;
 mod record;
 mod server;
 
 pub use consumer::consume;
 pub use firehose_cache::firehose_cache;
+pub use healthcheck::healthcheck;
 pub use identity::Identity;
 pub use record::{CachedRecord, ErrorResponseObject, Repo};
 pub use server::serve;
diff --git a/slingshot/src/main.rs b/slingshot/src/main.rs
index a02d02e..ae5fdbb 100644
--- a/slingshot/src/main.rs
+++ b/slingshot/src/main.rs
@@ -1,7 +1,9 @@
 // use foyer::HybridCache;
 // use foyer::{Engine, DirectFsDeviceOptions, HybridCacheBuilder};
 use metrics_exporter_prometheus::PrometheusBuilder;
-use slingshot::{Identity, Repo, consume, error::MainTaskError, firehose_cache, serve};
+use slingshot::{
+    Identity, Repo, consume, error::MainTaskError, firehose_cache, healthcheck, serve,
+};
 use std::path::PathBuf;
 
 use clap::Parser;
@@ -44,6 +46,9 @@ struct Args {
     /// recommended in production, but mind the file permissions.
     #[arg(long)]
     certs: Option<PathBuf>,
+    /// an web address to send healtcheck pings to every ~51s or so
+    #[arg(long)]
+    healthcheck: Option<String>,
 }
 
 #[tokio::main]
@@ -127,6 +132,14 @@ async fn main() -> Result<(), String> {
         Ok(())
     });
 
+    if let Some(hc) = args.healthcheck {
+        let healthcheck_shutdown = shutdown.clone();
+        tasks.spawn(async move {
+            healthcheck(hc, healthcheck_shutdown).await?;
+            Ok(())
+        });
+    }
+
     tokio::select! {
         _ = shutdown.cancelled() => log::warn!("shutdown requested"),
         Some(r) = tasks.join_next() => {
diff --git a/slingshot/src/server.rs b/slingshot/src/server.rs
index db198a4..9066da1 100644
--- a/slingshot/src/server.rs
+++ b/slingshot/src/server.rs
@@ -19,7 +19,7 @@ use poem::{
         Listener, TcpListener,
         acme::{AutoCert, LETS_ENCRYPT_PRODUCTION},
     },
-    middleware::{Cors, Tracing},
+    middleware::{CatchPanic, Cors, Tracing},
 };
 use poem_openapi::{
     ApiResponse, ContactObject, ExternalDocumentObject, Object, OpenApi, OpenApiService, Tags,
@@ -758,6 +758,7 @@ where
                 .allow_methods([Method::GET])
                 .allow_credentials(false),
         )
+        .with(CatchPanic::new())
         .with(Tracing);
     Server::new(listener)
         .name("slingshot")
-- 
2.51.2