From 1ca42fe92ed513b149765e37a1b778e39eb15d40 Mon Sep 17 00:00:00 2001
From: Denis Carriere <carriere.denis@gmail.com>
Date: Tue, 7 Nov 2023 22:44:34 -0500
Subject: [PATCH] add 1s cache to `/health`

---
 src/fetch/health.ts | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/fetch/health.ts b/src/fetch/health.ts
index 35e12a5..8a82b40 100644
--- a/src/fetch/health.ts
+++ b/src/fetch/health.ts
@@ -2,16 +2,32 @@ import client from "../clickhouse/createClient.js";
 import { logger } from "../logger.js";
 import { BadRequest, toText } from "./cors.js";
 
+function now() {
+  return Math.floor(Date.now() / 1000); // seconds
+}
+
+// cache the timestamp and value for 1 seconds
+let timestamp = now();
+let value = true; // true = OK, false = ERROR
+
 export default async function () {
+  // return cached response if timestamp is less than 1 second old
+  if ( now() - timestamp < 1 ) {
+    return value ? toText("OK") : BadRequest;
+  }
+
   try {
     const response = await client.ping();
     if (!response.success) {
       throw new Error(response.error.message);
     }
-
+    timestamp = now();
+    value = true;
     return toText("OK");
   } catch (e) {
     logger.error(e);
+    timestamp = now();
+    value = false;
     return BadRequest;
   }
 }