fix: restart router when there is no nodes (openobserve#728)

fix openobserve#720 

When router not found other nodes, just reload nodes from etcd maybe
won't fix the problem. maybe the router disconnect from etcd. we need
reconnect it and load everything again.

The better solution is, just let it `exit` and then `k8s` will restart
it.

Author: hengfeiyang

src/service/router/mod.rs

@@ -18,7 +18,7 @@ use awc::Client;
 use rand::seq::SliceRandom;
 use rand::thread_rng;
 
-use crate::infra::cluster::{self, is_ingester, is_querier, list_nodes, Node, NodeStatus};
+use crate::infra::cluster;
 use crate::infra::config::CONFIG;
 
 const QUERIER_ROUTES: [&str; 9] = [
@@ -89,33 +89,20 @@ async fn dispatch(
         return Ok(HttpResponse::ServiceUnavailable().body("No online nodes"));
     }
 
-    // random nodes
+    // checking nodes
     let mut nodes = nodes.unwrap();
-    let mut rng = thread_rng();
-    nodes.shuffle(&mut rng);
-
     if nodes.is_empty() {
-        nodes = list_nodes().await.unwrap_or_else(|_| vec![]);
-        let filter_fn = if check_querier_route(path) {
-            |node: &Node| node.status == NodeStatus::Online && is_querier(&node.role)
-        } else {
-            |node: &Node| node.status == NodeStatus::Online && is_ingester(&node.role)
-        };
-
-        nodes.retain(filter_fn);
-
-        if nodes.is_empty() {
-            log::error!("No online querier or ingestor nodes");
-            return Ok(
-                HttpResponse::ServiceUnavailable().body("Please wait for other nodes to be online")
-            );
-        }
+        log::error!("Not found online nodes, restaring...");
+        std::process::exit(1);
     }
 
-    let node = nodes.first().unwrap();
-    let new_url = format!("{}{}", node.http_addr, path);
+    // random nodes
+    let mut rng = thread_rng();
+    nodes.shuffle(&mut rng);
 
     // send query
+    let node = nodes.first().unwrap();
+    let new_url = format!("{}{}", node.http_addr, path);
     let resp = client
         .request_from(new_url.clone(), req.head())
         .send_stream(payload)