Add test to verify default node filter function (#2756)

(cherry picked from commit 98b3802)

Author: JoshMock

src/client.ts

@@ -135,7 +135,7 @@ export interface ClientOptions {
     * @defaultValue null */
   agent?: HttpAgentOptions | UndiciAgentOptions | agentFn | false
   /** @property nodeFilter A custom function used by the connection pool to determine which nodes are qualified to receive a request
-    * @defaultValue () => true */
+    * @defaultValue A function that uses the Connection `roles` property to avoid master-only nodes */
   nodeFilter?: nodeFilterFn
   /** @property nodeSelector A custom function used by the connection pool to determine which node should receive the next request
     * @defaultValue A "round robin" function that loops sequentially through each node in the pool. */

test/unit/client.test.ts

@@ -77,6 +77,31 @@ test('Missing node(s)', t => {
   t.end()
 })
 
+test('multi nodes with roles, using default node filter', async t => {
+  const client = new Client({
+    nodes: [
+      {
+        url: new URL('http://node1:9200'),
+        roles: { master: true, data: false, ingest: false, ml: false }
+      },
+      {
+        url: new URL('http://node2:9200'),
+        roles: { master: true, data: true, ingest: false, ml: false }
+      },
+    ]
+  })
+  const conn = client.connectionPool.getConnection({
+    now: Date.now() + 1000 * 60 * 3,
+    requestId: 1,
+    name: 'elasticsearch-js',
+    context: null
+  })
+
+  t.equal(conn?.url.hostname, 'node2')
+
+  t.end()
+})
+
 test('Custom headers', t => {
   const client = new Client({
     node: 'http://localhost:9200',