Fix broker stats

app/src/components/helper/usePollingToFetchTreeNode.tsx

@@ -0,0 +1,38 @@
+import * as q from '../../../../backend/src/Model'
+import { useState, useEffect } from 'react'
+
+/**
+ * If a node is not available when the plot is shown, keep polling until it has been created
+ */
+export function usePollingToFetchTreeNode(tree: q.Tree<any> | undefined, path: string) {
+  const [treeNode, setTreeNode] = useState<q.TreeNode<any> | undefined>()
+
+  function pollUntilTreeNodeHasBeenFound() {
+    if (!tree) {
+      return
+    }
+
+    const initialTreeNode = tree.findNode(path)
+    if (initialTreeNode) {
+      setTreeNode(initialTreeNode)
+      return
+    }
+
+    let intervalTimer: any
+    if (!treeNode) {
+      intervalTimer = setInterval(() => {
+        const node = tree.findNode(path)
+        if (node) {
+          setTreeNode(node)
+          clearInterval(intervalTimer)
+        }
+      }, 500)
+    }
+    return function cleanup() {
+      intervalTimer && clearInterval(intervalTimer)
+    }
+  }
+
+  useEffect(pollUntilTreeNodeHasBeenFound, [tree])
+  return treeNode
+}