slingshot: add configurable cache sizes, host, and ports

- Add --cache-memory-mb and --cache-disk-gb flags
- Add --host and --port for HTTP server
- Add --metrics-port for prometheus metrics server

slingshot/src/firehose_cache.rs

···
 
 pub async fn firehose_cache(
     cache_dir: impl AsRef<Path>,
+    memory_mb: usize,
+    disk_gb: usize,
 ) -> Result<HybridCache<String, CachedRecord>, String> {
     let cache = HybridCacheBuilder::new()
         .with_name("firehose")
-        .memory(64 * 2_usize.pow(20))
+        .memory(memory_mb * 2_usize.pow(20))
         .with_weighter(|k: &String, v| k.len() + std::mem::size_of_val(v))
         .storage(Engine::large())
         .with_device_options(
             DirectFsDeviceOptions::new(cache_dir)
-                .with_capacity(2_usize.pow(30)) // TODO: configurable (1GB to have something)
+                .with_capacity(disk_gb * 2_usize.pow(30))
                 .with_file_size(16 * 2_usize.pow(20)), // note: this does limit the max cached item size, warning jumbo records
         )
         .build()

slingshot/src/main.rs

···
     /// where to keep disk caches
     #[arg(long)]
     cache_dir: PathBuf,
+    /// memory cache size in MB
+    #[arg(long, default_value_t = 64)]
+    cache_memory_mb: usize,
+    /// disk cache size in GB
+    #[arg(long, default_value_t = 1)]
+    cache_disk_gb: usize,
+    /// port for HTTP server (when not using --domain)
+    #[arg(long, default_value_t = 3000)]
+    port: u16,
+    /// port for metrics/prometheus server
+    #[arg(long, default_value_t = 8765)]
+    metrics_port: u16,
     /// the domain pointing to this server
     ///
     /// if present:
···
 
     let args = Args::parse();
 
-    if let Err(e) = install_metrics_server() {
+    if let Err(e) = install_metrics_server(args.metrics_port) {
         log::error!("failed to install metrics server: {e:?}");
     } else {
-        log::info!("metrics listening at http://0.0.0.0:8765");
+        log::info!("metrics listening at http://0.0.0.0:{}", args.metrics_port);
     }
 
     std::fs::create_dir_all(&args.cache_dir).map_err(|e| {
···
     log::info!("cache dir ready at at {cache_dir:?}.");
 
     log::info!("setting up firehose cache...");
-    let cache = firehose_cache(cache_dir.join("./firehose")).await?;
+    let cache = firehose_cache(
+        cache_dir.join("./firehose"),
+        args.cache_memory_mb,
+        args.cache_disk_gb,
+    )
+    .await?;
     log::info!("firehose cache ready.");
 
     let mut tasks: tokio::task::JoinSet<Result<(), MainTaskError>> = tokio::task::JoinSet::new();
···
             args.domain,
             args.acme_contact,
             args.certs,
+            args.port,
             server_shutdown,
         )
         .await?;
···
     Ok(())
 }
 
-fn install_metrics_server() -> Result<(), metrics_exporter_prometheus::BuildError> {
+fn install_metrics_server(port: u16) -> Result<(), metrics_exporter_prometheus::BuildError> {
     log::info!("installing metrics server...");
     let host = [0, 0, 0, 0];
-    let port = 8765;
     PrometheusBuilder::new()
         .set_quantiles(&[0.5, 0.9, 0.99, 1.0])?
         .set_bucket_duration(std::time::Duration::from_secs(300))?

slingshot/src/server.rs

···
     domain: Option<String>,
     acme_contact: Option<String>,
     certs: Option<PathBuf>,
+    port: u16,
     shutdown: CancellationToken,
 ) -> Result<(), ServerError> {
     let repo = Arc::new(repo);
···
         )
         .await
     } else {
-        run(TcpListener::bind("127.0.0.1:3000"), app, shutdown).await
+        run(
+            TcpListener::bind(format!("127.0.0.1:{port}")),
+            app,
+            shutdown,
+        )
+        .await
     }
 }