return error instead of panicking when creating a new server (#4)

* return error instead of panicking

Signed-off-by: Dan Bond <danbond@protonmail.com>

* bump prometheus-client to 0.18

Signed-off-by: Dan Bond <danbond@protonmail.com>

* errors -> error

Signed-off-by: Dan Bond <danbond@protonmail.com>

* use enum for error

Signed-off-by: Dan Bond <danbond@protonmail.com>

Signed-off-by: Dan Bond <danbond@protonmail.com>

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "metrics_server"
-version = "0.8.1"
+version = "0.9.0"
 authors = ["Dan Bond <danbond@protonmail.com>"]
 edition = "2021"
 rust-version = "1.58"
@@ -18,11 +18,11 @@ include = ["src/**/*", "tests", "examples", "Cargo.toml", "LICENSE", "README.md"
 doctest = false
 
 [dependencies]
-tiny_http = "0.11"
 log = "0.4"
+tiny_http = "0.11"
 
 [dev-dependencies]
-prometheus-client = "0.16"
+prometheus-client = "0.18"
 reqwest = { version = "0.11", features = ["blocking"] }
 
 [features]

README.md

@@ -16,13 +16,13 @@ This crate provides a thread safe, minimalstic HTTP/S server used to buffer metr
 Include the lib in your `Cargo.toml` dependencies:
 ```toml
 [dependencies]
-metrics_server = "0.8"
+metrics_server = "0.9"
 ```
 
 To enable TLS support, pass the optional feature flag:
 ```toml
 [dependencies]
-metrics_server = { version = "0.8", features = ["tls"] }
+metrics_server = { version = "0.9", features = ["tls"] }
 ```
 
 ### HTTP

src/error.rs

@@ -0,0 +1,19 @@
+use std::error::Error;
+use std::fmt;
+
+/// The error type for MetricsServer operations.
+#[derive(Debug)]
+pub enum ServerError {
+    /// Represents an error while creating a new server.
+    Create(String),
+}
+
+impl fmt::Display for ServerError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            ServerError::Create(s) => write!(f, "error creating metrics server: {}", s),
+        }
+    }
+}
+
+impl Error for ServerError {}

src/lib.rs

@@ -38,6 +38,8 @@
 //! let bytes = server.update(Vec::from([1, 2, 3, 4]));
 //! assert_eq!(4, bytes);
 //! ```
+mod error;
 mod server;
 
+pub use error::ServerError;
 pub use server::MetricsServer;

src/server.rs

@@ -3,6 +3,8 @@ use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex};
 use std::thread;
 
+use crate::error::ServerError;
+
 use log::{debug, error};
 use tiny_http::{Method, Response, Server};
 
@@ -20,11 +22,11 @@ struct MetricsServerShared {
 
 impl MetricsServer {
     /// Creates an empty `MetricsServer` with a configured HTTP/S server.
-    ///
-    /// # Panics
-    ///
-    /// Panics if given an invalid address or incorrect TLS credentials.
-    pub fn new<A>(addr: A, certificate: Option<Vec<u8>>, private_key: Option<Vec<u8>>) -> Self
+    pub fn new<A>(
+        addr: A,
+        certificate: Option<Vec<u8>>,
+        private_key: Option<Vec<u8>>,
+    ) -> Result<Self, ServerError>
     where
         A: ToSocketAddrs,
     {
@@ -42,17 +44,20 @@ impl MetricsServer {
             _ => tiny_http::ServerConfig { addr, ssl: None },
         };
 
+        // Attempt to create a new server.
+        let server = Server::new(config).map_err(|e| ServerError::Create(e.to_string()))?;
+
         // Create an Arc of the shared data.
         let shared = Arc::new(MetricsServerShared {
             data: Mutex::new(Vec::new()),
-            server: Server::new(config).unwrap(),
+            server,
             stop: AtomicBool::new(false),
         });
 
-        MetricsServer {
+        Ok(MetricsServer {
             shared,
             thread: None,
-        }
+        })
     }
 
     /// Shortcut for creating an empty `MetricsServer` and starting a HTTP server on a new thread at the given address.
@@ -66,7 +71,7 @@ impl MetricsServer {
     where
         A: ToSocketAddrs,
     {
-        MetricsServer::new(addr, None, None).serve()
+        MetricsServer::new(addr, None, None).unwrap().serve()
     }
 
     /// Shortcut for creating an empty `MetricsServer` and starting a HTTPS server on a new thread at the given address.
@@ -83,7 +88,9 @@ impl MetricsServer {
     where
         A: ToSocketAddrs,
     {
-        MetricsServer::new(addr, Some(certificate), Some(private_key)).serve()
+        MetricsServer::new(addr, Some(certificate), Some(private_key))
+            .unwrap()
+            .serve()
     }
 
     /// Safely updates the data in a `MetricsServer` and returns the number of bytes written.

tests/server.rs

@@ -1,7 +1,6 @@
 use metrics_server::MetricsServer;
 
 #[test]
-#[should_panic]
 fn test_new_server_invalid_address() {
     let _ = MetricsServer::new("invalid:99999999", None, None);
 }
@@ -12,30 +11,47 @@ fn test_new_http_server() {
 }
 
 #[test]
-#[should_panic]
 #[cfg(feature = "tls")]
-fn test_new_server_invalid_cert() {
+fn test_new_server_invalid_certificate() {
     // Load TLS config.
-    let cert = Vec::new();
+    let cert = "-----BEGIN CERTIFICATE-----
+invaid certificate
+-----END CERTIFICATE-----"
+        .as_bytes()
+        .to_vec();
     let key = include_bytes!("./certs/private_key.pem").to_vec();
 
-    let _ = MetricsServer::new("localhost:8441", Some(cert), Some(key));
+    let server = MetricsServer::new("localhost:8441", Some(cert), Some(key));
+    assert!(server.is_err());
+
+    if let Err(error) = server {
+        assert!(error.to_string().contains("error creating metrics server"))
+    }
 }
 
 #[test]
-#[should_panic]
 #[cfg(feature = "tls")]
-fn test_new_server_invalid_key() {
+fn test_new_server_invalid_private_key() {
     // Load TLS config.
     let cert = include_bytes!("./certs/certificate.pem").to_vec();
-    let key = Vec::new();
+    let key = "-----BEGIN PRIVATE KEY-----
+-----END PRIVATE KEY-----"
+        .as_bytes()
+        .to_vec();
 
-    let _ = MetricsServer::new("localhost:8442", Some(cert), Some(key));
+    let server = MetricsServer::new("localhost:8442", Some(cert), Some(key));
+    assert!(server.is_err());
+
+    if let Err(error) = server {
+        assert!(error.to_string().contains("error creating metrics server"))
+    }
 }
 
 #[test]
 fn test_new_server_already_running() {
-    let srv = MetricsServer::new("localhost:8002", None, None).serve();
+    let srv = MetricsServer::new("localhost:8002", None, None)
+        .unwrap()
+        .serve();
 
     // Attempt to start an already running server should be ok
     // as we will return the pre-existing thread.
@@ -48,7 +64,8 @@ fn test_new_https_server() {
     let cert = include_bytes!("./certs/certificate.pem").to_vec();
     let key = include_bytes!("./certs/private_key.pem").to_vec();
 
-    let _ = MetricsServer::new("localhost:8443", Some(cert), Some(key));
+    let server = MetricsServer::new("localhost:8443", Some(cert), Some(key));
+    assert!(server.is_ok());
 }
 
 #[test]
@@ -102,7 +119,7 @@ fn test_https_server_invalid_address() {
 #[test]
 #[should_panic]
 #[cfg(feature = "tls")]
-fn test_https_server_invalid_cert() {
+fn test_https_server_invalid_certificate() {
     // Load TLS config.
     let cert = Vec::new();
     let key = include_bytes!("./certs/private_key.pem").to_vec();
@@ -113,7 +130,7 @@ fn test_https_server_invalid_cert() {
 #[test]
 #[should_panic]
 #[cfg(feature = "tls")]
-fn test_https_server_invalid_key() {
+fn test_https_server_invalid_private_key() {
     // Load TLS config.
     let cert = include_bytes!("./certs/certificate.pem").to_vec();
     let key = Vec::new();