Fix duplicate challenge containers on server restart

Clean up old challenge containers with different suffixes when starting
a new challenge. This handles the case where the server restarts with
a new container ID, which would previously leave orphaned containers.

Author: echobt

crates/challenge-orchestrator/src/docker.rs

@@ -437,9 +437,17 @@ impl DockerClient {
             "Generated challenge container name"
         );
 
-        // Remove existing container if any
+        // Remove existing container if any (same name)
         let _ = self.remove_container(&container_name).await;
 
+        // Clean up old challenge containers with different suffixes (from previous server restarts)
+        let challenge_prefix = format!(
+            "challenge-{}-",
+            config.name.to_lowercase().replace(' ', "-")
+        );
+        self.cleanup_old_challenge_containers(&challenge_prefix, &container_name)
+            .await;
+
         // Build port bindings - expose on a dynamic port
         let mut port_bindings = HashMap::new();
         port_bindings.insert(
@@ -732,6 +740,44 @@ impl DockerClient {
         Ok(output)
     }
 
+    /// Clean up old challenge containers with different suffixes
+    /// This handles the case where the server restarts with a new container ID
+    async fn cleanup_old_challenge_containers(&self, prefix: &str, exclude_name: &str) {
+        let options = ListContainersOptions::<String> {
+            all: true,
+            ..Default::default()
+        };
+
+        let containers = match self.docker.list_containers(Some(options)).await {
+            Ok(c) => c,
+            Err(e) => {
+                warn!(error = %e, "Failed to list containers for cleanup");
+                return;
+            }
+        };
+
+        for container in containers {
+            let names = container.names.unwrap_or_default();
+            let container_id = match container.id.as_ref() {
+                Some(id) => id.clone(),
+                None => continue,
+            };
+
+            // Check if container name matches prefix but is not the current container
+            let should_remove = names.iter().any(|name| {
+                let clean_name = name.trim_start_matches('/');
+                clean_name.starts_with(prefix) && clean_name != exclude_name
+            });
+
+            if should_remove {
+                info!(container = ?names, "Removing old challenge container from previous server instance");
+                if let Err(e) = self.remove_container(&container_id).await {
+                    warn!(container = ?names, error = %e, "Failed to remove old container");
+                }
+            }
+        }
+    }
+
     /// Clean up stale task containers created by challenge evaluations
     ///
     /// This removes containers that match the pattern but excludes: