1 files changed, 115 insertions, 1 deletions
diff --git a/src/main.rs b/src/main.rs
index e7a11a9..44bd651 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,117 @@
+use std::io::{self, Read, Write};
+use std::net::{SocketAddr, TcpStream};
+use std::time::Duration;
+
+const MAGIC: [u8; 4] = [0x32, 0x7f, 0xfe, 0x4c];
+const RESP_OK: [u8; 5] = [0x32, 0x7f, 0xfe, 0x4c, 0x00];
+const RESP_NORMAL: [u8; 5] = [0x32, 0x7f, 0xfe, 0x4c, 0x01];
+const PING_INTERVAL: Duration = Duration::from_secs(12);
+const TCP_TIMEOUT: Duration = Duration::from_secs(8);
+const MAX_RETRY: i32 = 30;
+
+const EXIT_SUCCESS: i32 = 0;
+const EXIT_USAGE: i32 = 1;
+const EXIT_PING: i32 = 2;
+const EXIT_BUG: i32 = 3;
+const EXIT_IO: i32 = 4;
+
 fn main() {
-    println!("Hello, world!");
+    let mut args = std::env::args().skip(1);
+
+    let addr = match args.next() {
+        Some(addr) => addr,
+        None => {
+            eprintln!("Usage: rsdsl_healthping host:port");
+            std::process::exit(EXIT_USAGE);
+        }
+    };
+    let addr: SocketAddr = match addr.parse() {
+        Ok(addr) => addr,
+        Err(e) => {
+            eprintln!("invalid address: {}", e);
+            std::process::exit(EXIT_USAGE);
+        }
+    };
+
+    let mut lasterr = None;
+
+    print!("Pinging");
+    for _ in 0..MAX_RETRY {
+        print!(".");
+        match io::stdout().flush() {
+            Ok(_) => {}
+            Err(e) => {
+                eprintln!("flush stdout: {}", e);
+
+                std::thread::sleep(PING_INTERVAL);
+                std::process::exit(EXIT_IO);
+            }
+        }
+
+        let mut conn = match TcpStream::connect_timeout(&addr, TCP_TIMEOUT) {
+            Ok(conn) => conn,
+            Err(e) => {
+                lasterr = Some(e);
+
+                std::thread::sleep(PING_INTERVAL);
+                continue;
+            }
+        };
+
+        match conn.write_all(&MAGIC) {
+            Ok(_) => {}
+            Err(e) => {
+                lasterr = Some(e);
+
+                std::thread::sleep(PING_INTERVAL);
+                continue;
+            }
+        }
+
+        let mut buf = [0; 5];
+        match conn.read_exact(&mut buf) {
+            Ok(_) => {}
+            Err(e) => {
+                lasterr = Some(e);
+
+                std::thread::sleep(PING_INTERVAL);
+                continue;
+            }
+        }
+
+        match buf {
+            RESP_OK => success(),
+            RESP_NORMAL => success_unexpected(),
+            _ => eprintln!("got invalid response {:?}", buf),
+        }
+
+        std::thread::sleep(PING_INTERVAL);
+    }
+
+    println!();
+
+    match lasterr {
+        Some(e) => {
+            eprintln!("{}", e);
+            std::process::exit(EXIT_PING)
+        }
+        None => {
+            eprintln!("max retries exceeded without error");
+            std::process::exit(EXIT_BUG)
+        }
+    }
+}
+
+fn success() {
+    println!();
+    println!("Success");
+
+    std::process::exit(EXIT_SUCCESS);
+}
+
+fn success_unexpected() {
+    println!();
+    println!("Host is not waiting for healthcheck ping");
+
+    std::process::exit(EXIT_SUCCESS);
 }