Implement Coordinator

src/runner.rs

@@ -1,3 +1,5 @@
+mod coordinator;
+
 use tracing::error;
 
 use crate::config::Config;

src/runner/coordinator.rs

@@ -0,0 +1,26 @@
+//! Coordinate performing runs across servers.
+
+pub struct Coordinator {
+    names: Vec<String>,
+    current: usize,
+}
+
+impl Coordinator {
+    pub fn new(mut names: Vec<String>) -> Self {
+        assert!(!names.is_empty());
+        names.sort_unstable();
+        Self { names, current: 0 }
+    }
+
+    pub fn active(&self, name: &str) -> bool {
+        self.names[self.current] == name
+    }
+
+    pub fn next(&mut self, name: &str) {
+        // Check just to prevent weird shenanigans
+        if self.active(name) {
+            self.current += 1;
+            self.current %= self.names.len();
+        }
+    }
+}