feat(stress test): improve the amount of routers

stress-test/target_data/scenario.js

 import tarantool from "k6/x/tarantool";
 import {randomItem} from 'https://jslib.k6.io/k6-utils/1.1.0/index.js';
 
-const client = tarantool.connect("localhost:3301", {"user": "admin", pass: "app-cluster-cookie"})
+const clients = [
+    tarantool.connect("localhost:3301", {"user": "admin", pass: "app-cluster-cookie"}),
+    tarantool.connect("localhost:3306", {"user": "admin", pass: "app-cluster-cookie"}),
+    tarantool.connect("localhost:3307", {"user": "admin", pass: "app-cluster-cookie"}),
+    tarantool.connect("localhost:3308", {"user": "admin", pass: "app-cluster-cookie"})
+]
+
+export let current_server = 0
+
+function get_client() {
+    let c = clients[current_server]
+    current_server += 1
+    if (current_server >= clients.length) {
+        current_server = 0
+    }
+    return c
+}
 
 let ids = Array.from(
     {
@@ -21,5 +37,5 @@ const pattern = `SELECT *
     WHERE "reestrid" = ?`
 
 export default () => {
-    tarantool.call(client, "query", [pattern, [randomItem(ids)]]);
+    tarantool.call(get_client(), "query", [pattern, [randomItem(ids)]]);
 }
\ No newline at end of file

test_app/instances.yml

 ---
-test_app.router:
+test_app.router-1:
   advertise_uri: localhost:3301
   http_port: 8081
+  readahead: 16711680
+
+test_app.router-2:
+  advertise_uri: localhost:3306
+  http_port: 8086
+  readahead: 16711680
+
+test_app.router-3:
+  advertise_uri: localhost:3307
+  http_port: 8087
+  readahead: 16711680
+
+test_app.router-4:
+  advertise_uri: localhost:3308
+  http_port: 8088
+  readahead: 16711680
 
 test_app.s1-master:
   advertise_uri: localhost:3302
   http_port: 8082
+  readahead: 16711680
 
 test_app.s1-replica:
   advertise_uri: localhost:3303
   http_port: 8083
+  readahead: 16711680
 
 test_app.s2-master:
   advertise_uri: localhost:3304
   http_port: 8084
+  readahead: 16711680
 
 test_app.s2-replica:
   advertise_uri: localhost:3305
   http_port: 8085
+  readahead: 16711680
 
 test_app-stateboard:
   listen: localhost:4401

test_app/replicasets.yml

-router:
+router-1:
   instances:
-  - router
+  - router-1
+  roles:
+  - failover-coordinator
+  - vshard-router
+  - app.roles.api
+  all_rw: false
+router-2:
+  instances:
+  - router-2
+  roles:
+  - failover-coordinator
+  - vshard-router
+  - app.roles.api
+  all_rw: false
+router-3:
+  instances:
+  - router-3
+  roles:
+  - failover-coordinator
+  - vshard-router
+  - app.roles.api
+  all_rw: false
+router-4:
+  instances:
+  - router-4
   roles:
   - failover-coordinator
   - vshard-router